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[Bill Thomas]

September 23, 2008 - "Frankly Speaking!" - Our Audio by Van Alstine "Ultimate Stereo 70" Build!

     "Modding", "Tweaking", "Hot-Rodding", "Upgrading".  Whatever you call it, it is a HUGE part of the "Hi-Fi Experience" for many people.  Since the very beginning of the "High Fidelity Era", aficionados have spent untold amounts of time and money trying to "improve" existing audio equipment in the never-ending quest to achieve PERFECT fidelity.  Of course, there is no such thing as PERFECT fidelity.  But, there is also no such thing in the audio community as "Good Enough!"

     The term "legendary" gets thrown around a LOT in the audio community too.  Some names have become so well known that they have achieved fame (and sometimes fortune) outside the audio community.  Avery Fisher, Ray Dolby, Dr. Amar Bose, Bing Crosby, (OK, Bing achieved "legendary status" BEFORE he got involved with audio and video recording, but you get the idea.)

     Then there are the people who, while not as well known outside the audio world, certainly are considered legendary within the audio community.  Names like Edgar Villchur of Acoustic Research, Henry Kloss; also originally with AR and later with KLH, Advent, and others; David Hafler; founder of Dynaco and Hafler; and MANY other names you are probably VERY familiar with.

     Now that we've mentioned Dynaco, this brings us to the field of "aftermarket upgraders" who have taken the lowly, inexpensive Dynaco products, and elevated them to "new heights of sonic transparency."  (OK, I'm laying it on a *little* thick here, but again, you get the idea.)  Their idea was pretty simple: Take a Dynaco amplifier like a Stereo 70, or a Dynaco preamplifier like a PAS preamp, replace the electronic circuitry with something less "compromised" for cost considerations, and Voila!  Reliable, high-quality sound!  I think it's pretty safe to say that ONE name has achieved "legendary status" in this particular area, namely: Frank Van Alstine.  Frank was the one who STARTED the whole "Dynaco Upgrade" merry-go-round, and he's still doing it today!  (Along with a FABULOUS line of other VERY high-quality audio equipment.  See for yourself at: www.avahifi.com).

     Since the 1970's, Audio by Van Alstine has delivered TREMENDOUS "bang for the buck" equipment, and Frank's status as "legendary" is well-deserved.  But not just for his audio equipment.  It's a little difficult trying to "pigeonhole" Frank.  He is a "straight-shooter", extremely gracious, helpful and SO much more.  But a fan of "purple prose", he is NOT!  If you tell Frank your product sounds better than anything on the market, you'd better be ready to PROVE it against EVERYTHING else on the market!  From 1982 through 1994, Frank published his "Audio Basics Newsletter" and then made them available online at no charge.  They're STILL available online for free and contain more HONEST information than you are likely to find anywhere else.  His articles on "Complete Stereo 70 Rebuild Plans" and "Keeping the dyna FM-3 working" are considered "Bibles" to scores of Dynaco fans.  I consider them both "Must Reading!"  I'm telling you all this because a little background is in order for our next Dynaco "rebuild": Audio by Van Alstine's "Ultimate Stereo 70!"  This is a picture of the COMPREHENSIVE Assembly Manual for the "Ultimate Stereo 70." 

                                             

     Before building ANY electronic kit, it is EXTREMELY important to "RTFM" (Read the Freakin' Manual) COMPLETELY.  EVERY page - EVERY word - EVERY picture and drawing!  NO exceptions!  If you don't, you can't POSSIBLY get an idea of the scope of the project.  You will waste more time searching for that ONE instruction you overlooked if you don't.  Your chances of success will increase DRAMATICALLY if you'll just take the time to READ THE MANUAL FIRST!  Did you get that?  Then DO it!

     OK, now that I've gotten that out of the way, let's take a look at the contents of the "Ultimate Stereo 70" rebuild kit:

                               

     This kit contains EVERYTHING you need to transform your old Stereo 70 into something truly SPECTACULAR!  (Yes, even the wire and the SOLDER!)  Speaking of solder, as you notice in the picture above, this is NOT a pre-constructed circuit board that you simply "drop-in" and wire up.  This isn't a criticism in any way, but if you are not familiar with good soldering practices, take some time to perfect your soldering technique with some "junk" parts and terminals BEFORE you tackle this kit.  ALWAYS keep a clean tip on your soldering iron and tin it before making your solder joints.  If you have the budget for it, purchase a Weller "controlled temperature" soldering station, rather than a Radio Shack el-cheapo!  You will spend less time, and get MUCH better results - results that will last and last!  Keep a damp sponge handy to clean the tip of your iron.  If you are using the Weller "controlled-temperature" soldering station, they make it easy by including a good sponge, and the tray to put it in.  USE it - OFTEN.  Then "tin" the tip after it's clean.  Over the years, I have "standardized" on this procedure:

1.     Turn on the iron and bring it up to temperature.
2.     As it warms up, clean the tip against the sponge until it shines!
3.     "Tin" the tip by applying solder.  Place the iron in the holder.
4.     When it's time to make your solder joint, clean the tip against the sponge.
5.     Re-tin the tip of the iron.
6.     Apply the tip of the iron to the work.
7.     Place the solder against the opposite side of the work from the tip of the iron.
8.     Allow the solder to flow over the joint and remove the solder.
9.     THEN remove the iron from the work.
10.    Clean the tip of the iron.
11.    Re-tin the tip of the iron and place it in the holder.

     Repeat steps 4 through 11 as necessary.  When your "soldering session" is completed, clean the tip of the iron again.  Re-tin the tip of the iron and place it in the holder.  THEN turn the soldering station off and allow it to cool.  If you do all this, you'll stand a MUCH better chance of winding up with solder joints that are clean and shiny, not crystalline and dirty.  If you DO wind up with a crystalline appearance to a solder joint, do it again!  "Cold" solder joints are the most common reasons why a project like this fails.  I'm stressing all this because the quality of the "Ultimate Stereo 70" kit is SO high, you'll want the quality of YOUR work to be just as high.

     I hope you haven't considered this "update" a waste of space or time.  It really IS important to properly prepare BEFORE the first component is soldered in.  In our next update, we'll actually BUILD the "Ultimate Stereo 70" printed circuit board!  Honest!

Sincerely,

Bill Thomas

[Opus Flatus]

Be prepared to be blown away when you complete the rebuild. I rebuilt my modded (popular upgrade driver and quad cap replacement) after it became annoyingly noisy. With the exception of the hum it sounded great -nice soundstage. I am not an expert DIYer. I took my time rebuilding it. After smoke testing it -it would have been wiser to send back to AVA for a free checkup-I was in near tears it sounded so sweet. I was up to the wee hours shuffling my IPOD through it. It is a spectacular amp that I will never part with.
Enjoy!

[acwd1950]

I see your at it again, Bill. Keep up the great work! I need to fine me a Dynaco 70 to mod. And experience they great sound everyones talking about, but I think the better half might have something to say about it She thinks I have too much stuff now

Steve

[Bill Thomas]

September 24, 2008 - Update  "Resistance is Futile!"

     Seriously, there really IS an order to the Universe.  YOU should put YOUR Universe in order as well.  Here is where the process begins:  Take the parts list and check the supplied resistors against the list of resistors.  DON'T just begin "stuffing" resistors in the PC board.  While Frank has made the kit as simple as possible, there IS room for confusion.  You could EASILY solder a 270K 1/2 Watt resistor where a 270K 2 Watt resistor should go.  Or, you might install a 1K 2 Watt resistor where one of the 1K 1/2 Watt resistors belongs, and then wonder why you're missing one of the required 1K 2 Watters.  Start by laying out the resistors IN ORDER.  Check them CAREFULLY against the parts list.

                   

     Once you are SURE you have all the resistors in the parts list, and have laid them out in order, here is a tip from the old Heathkit and Dynaco Kit building days:  Get a corrugated cardboard box and slide the resistors, IN ORDER, into the corrugations, like this:

                   

     But be careful!  Those little tiny 1/2 Watt metal film resistors can EASILY slide down into the corrugations and wind up trapped inside the wall of the box.

     OK, NOW we are ready to begin "stuffing and soldering."  But don't just "stuff" the resistors into the PC board "any old way."  Take the time to make sure the values of the resistors are visible from the top, so you can read them after the board is finished.  It's also nice to orient them in the same direction so you can read them from left to right, or from top to bottom.  The resistors should be installed flush against the circuit board.  Make SURE you use the solder Frank has supplied with the kit.  Resist the temptation to use some sort of "exotic" solder of you own.  I prefer the "solder as you go" approach.  This simply means, first you bend the leads and install the resistor.  Next you solder the two leads of the resistor to the Printed Circuit pads.  Then move on to the next resistor.  Here's a picture of the installation of our first four resistors:

                         

     Sorry that the photo is a bit blurry, but you can see that the values of the resistors can be easily read from the top of the board.  Here's a close-up of one of the solder joints on the under side of the printed circuit board:

                                                 

     Notice that the solder is clean and shiny.  You don't need a big blob of solder - just enough to flow completely around the resistor lead.  I prefer to cut the resistor leads after all of them have been installed and soldered.  This just tends to make the cut-length more uniform for a neater finished appearance.  Now, following the instructions in the manual, "stuff and solder" the rest of the resistors.  Make SURE to ALWAYS carefully check the values of the resistors as you go.  Take your time and work slowly.  After all, you want the "Ultimate Stereo 70" to work properly when you power it up, don't you?  Here's a picture of the Printed circuit board with all the resistors installed:

                             

     You can read the value of EVERY resistor without difficulty.  (There are four more resistors located outside the visible area of this picture.)  All resistors are oriented so you can read them from left to right, or from top to bottom.  You won't have to rotate the board more than 90 degrees to verify the installed resistor values.  There are four 1K resistors left over.  They are the "grid stopper" resistors and will be used when we install the completed circuit board in the Stereo 70 chassis.

     Next, it's time to install the ten diodes.  We're using the same "box method" to keep track of the different diode types.  Here's a picture:

                             

     Diodes are directional devices.  Therefore, make certain they are oriented properly on the Printed Circuit Board.  If you install just ONE of them backwards, the results can be catastrophic.  Check the parts placement diagram CAREFULLY before you solder them in.  When soldering the diodes onto the Printed Circuit Board, it is of the UTMOST importance to use as little heat as possible.  Excessive heat can melt the "innards" of a diode before you can say "Oops!"  Yes, you want a good solder joint, but don't keep the soldering iron on the Printed Circuit "pad" any longer than absolutely necessary.  You can increase the chance of a diode's survival by using a "heat sink clip" (or even a simple alligator clip) on the diode lead you are soldering.  It should be clipped onto the lead as close to the body of the diode as possible.  Solder that lead onto the printed circuit pad.  Allow the connection (and the diode) to cool.  Then move the clip to the other side of the diode and solder that lead to the circuit pad.  Once again, allow it to cool completely.  Then move on to the next diode using the same method.  Clip, solder, cool.  It's CHEAP insurance and you'll be happy you took the extra time and trouble to keep your diodes safe and sound.

     I'll begin our next update with a picture of the installed diodes.  Then, it's on to the final round - Installing the tube sockets and finishing up with the capacitors.  Stay with us!!

Sincerely,

Bill Thomas

[Bill Thomas]

September 28, 1008 - Update:  "I Feel STUFFED!"

     As promised, here's the picture of our installed diodes.

                                       

     Because of the way the part numbers are printed on the diodes, it isn't possible to orient them in a way that allows you to read the part numbers from above the board, but it still should be possible to see much of the part numbers; enough to allow checking to make SURE you have the correct diodes installed in the proper locations.  With the diodes installed, checked and DOUBLE-checked, it's time to move on to the next stage of assembly: Installing the two tube sockets.

     The tube sockets supplied with the "Ultimate Stereo 70" kit are high-quality parts.  The contacts make a VERY secure connection with the tube pins, BUT this makes the tubes a little harder to insert or remove.  Therefore, it is of the UTMOST importance to make certain they are soldered in correctly and completely.  Also, it is REALLY easy to install them at an angle, rather than EXACTLY parallel to the surface of the Printed Circuit board.  It is TRULY depressing to finish soldering all nine pins to the Printed Circuit board only to realize that the socket is crooked, and will have to be UN-soldered, and RE-soldered properly.  Unless you have rather expensive de-soldering equipment, the chances of harming the sockets and the Printed Circuit board are pretty high, so take the time to make SURE both sockets are inserted into the Printed Circuit board holes completely.  Then CAREFULLY turn the board upside-down and place the surface of the tube sockets (now underneath the board) against a flat surface.  Apply a *little* pressure to make sure they are completely seated.  Now, "wobble" the Printed Circuit board a bit.  If the sockets are crooked, you will find it easy to do this "wobbling."  If they are parallel to the surface of the Printed Circuit board, attempting to "wobble" the board will be much more difficult.  Now, without moving the PC board, look underneath the board to make SURE the tube sockets are flush against the work surface, rather than "cocked" one way or another.  Once you are satisfied that everything is properly positioned, you can BEGIN soldering them in.  But don't just start at Pin 1 or Pin 9 and go around the circle of pins.  Instead, "tack" solder Pin 5  of both sockets first.  Then, look under the board again and check to make sure the sockets are still parallel to the surface of the PC board and the work surface.  If the socket is now "cocked", you only have to unsolder ONE pin, instead of NINE!  If everything looks nice and parallel, "tack-solder" Pin 1 and Pin 9 of both sockets.  Now, "wobble" the Printed Circuit board again, and again, look under the board to make SURE the sockets are parallel to the Printed Circuit board, and flush with the work surface.  If everything looks good, GREAT!  NOW you can begin soldering the rest of the pins permanently.  But again, don't just go around the circle.  Instead, solder Pin 3 next, and then solder Pin 7.  Look under the board and check it AGAIN for parallelism.  If everything looks good now, go back and PERMANENTLY solder Pin 5 and check it AGAIN!  Then go back and PERMANENTLY solder Pin 1, and then Pin 9.  Look under the board and check it AGAIN!  At this point, every other Pin should be permanently soldered and the sockets should be flat against the work surface.  Now solder Pin 2, followed by Pin 6.  Then  finish off by soldering Pin 4 and Pin 8.  Once both sockets are completely soldered in, look under the board AGAIN to make CERTAIN everything still looks straight.  Here's a picture of a properly installed tube socket:

                             

     Although the picture is a bit "fuzzy", you can tell that the socket is parallel to the surface of the Printed Circuit board.  (It's hard to get any depth of field using the macro settings on the camera.)

     Now, one more point concerning soldering in the tube sockets.  You OBVIOUSLY want the solder connection to last the life of the amplifier, right?  But inserting and removing tubes will cause a great deal of mechanical "stress" to the solder joints.  Therefore, you want to make SURE solder COMPLETELY surround each pin of the socket.  There should be no "holes" or "voids".  The solder should COMPLETELY join each socket pin to the Printed Circuit pad.  When applying your soldering iron, make certain it contacts both the Printed Circuit board "pad" AND the tube socket Pin.  Apply solder *gradually* to the Printed Circuit board pad.  As it *gradually* fills the area around the pin, it will "wick over" to the tube socket pin and completely encircle the pin, securely joining the pin to the Printed Circuit pad.  The finished result should look something like this:

                         

     Notice that there are no solder "blobs".  Instead, each pin is completely surrounded by a firmly soldered connection for maximum mechanical strength.  If you apply your soldering iron tip to only the pins, solder will wick over the the pin and flow down the hole and build up between the top of the board, and the bottom of the tube socket.  Needless to say, this is NOT what you want to happen.  Take the time to do it right the FIRST time, if possible. 

     I realize we have spent a LOT of time checking and re-checking.  YOU should do the same!  If you take the EXTRA time to properly prepare, you'll SAVE time in the long run.  We have spent MUCH more time discussing "soldering technique", than we have discussing "installing parts."  Doing things correctly the FIRST time will save you TREMENDOUS amounts of time "fixing" what you goofed up.  Check what you are GOING to do carefully, DO what you are attempting to do carefully, then RE-check what you have DONE carefully.  Once you are SURE both sockets are properly soldered in, you can move on to the FINAL assembly stage:  Installing the capacitors.

     Here is a picture of all the new capacitors supplied with the Audio by Van Alstine "Ultimate Stereo 70" rebuild kit, laid-out in "parts-list" order:

                                   

     The top row of capacitors are film and dipped mica capacitors.  The second row of light blue "box-style" capacitors are the coupling capacitors.  The row of black cylinders are the various electrolytic capacitors and the tan disc capacitor will be used when we re-wire the Stereo 70 chassis.  We'll use our familiar "box method" to keep the small capacitors in order like this:

                             

     Install and solder the ten C1 through C5 capacitors, again making sure they are installed so you can read the part values from left to right, or from top to bottom.  Next, install the 8 "box-style" coupling capacitors.  Solder one side of each one, and then check to make certain they are flush  against the circuit board and parallel to each other.  THEN solder in the other side.  Install one pair at a time and don't rush.  Keeping them nice and even will ensure you have an amplifier you can be "visually" proud of.  Next, install the two small electrolytics for the bias supply, followed by the two "snap-in" electrolytics, and FINALLY, the last four electrolytics.  They should all be flush against the Printed Circuit board.  Make SURE you observe the proper polarity of ALL electrolytics.  Installing one backwards will destroy it VIOLENTLY upon application of power.  Exploding capacitors are no fun to clean up, and you'll have to buy a replacement part before you can continue.

     Once you have installed all the capacitors, you're *almost* finished with the Driver Board.  If you have all the components installed correctly, it *should* look something like this!:

                             

     But we have two little "details" remaining before we can call our Driver Board assembly complete.

[Bill Thomas]

September 27, 2008 - Addendum

     Here's our FIRST little detail:

                             

     Looks a little like a forest, doesn't it?  But, before you start clipping all the component leads as close to the circuit board as possible, here's a little tip:  I like to leave approximately 1/16th of an inch of the component lead remaining.  Here's why:  If something should ever go wrong with one of the components on the Printed Circuit board,  that tiny bit of remaining component lead will act as a "guide" or "locating pin" for your "solder-sucker" or vacuum de-soldering gun.  It will help to minimize your chance of messing up the "solder-mask" if you ever have to remove a part.  It will also reduce the amount of time you need to apply heat when de-soldering a component.  Don't get CRAZY if you should happen to clip a lead flush with the board, but try to leave a *teensy* bit of component lead left.  (This is just *MY* opinion, but it has always served me well.)

     Once you have clipped the excess component leads, there is only one step remaining.  The soldering process deposits a bit of rosin-flux on each connection.  This is ESSENTIAL for a reliable connection, but once that connection is made, the flux that remains is a bit of an eyesore.  MANY solvents will remove the flux, but many of those solvents can also dissolve the solder mask - NOT a good thing.  The solution is as close as your nearest convenience store.  Purchase a bottle or can of common "Lighter Fluid."  Lighter fluid is actually 100% Naptha.  It will dissolve the flux without harming the circuit board, or the solder mask.  You can use cotton swabs, but there is a potential for a LOT of remaining cotton fibers to "catch" on those remaining component lead "stubs."  I prefer to use those blue automotive store "paper towels" to do the job.  While they too can "catch" on the component lead "stubs" the fibers are a LOT easier to clean off.  You may find that a toothbrush (NOT the one you use on your teeth, please) may work better, followed by "blotting" the board with one of those blue paper "shop towels."  Either way, once you have cleaned off the flux, you'll get a clear view to check for solder "bridges" or little TINY "solder balls."  Use the toothbrush to remove any "solder balls" and be SURE to correct any "solder bridges" you might find.  Fortunately, the "solder mask" reduces the chance of creating a solder bridge IMMENSELY!

     I hope I haven't bored you to death regarding "soldering technique" or the importance of checking and re-checking your work.  As the old expression goes: "The devil is in the details."  If you take care of the details as you go along, you will be rewarded with a unit that will likely work correctly the FIRST time, and will operate consistently and reliably for YEARS to come.

     We're *almost* ready to start tearing our original Stereo 70 apart in preparation for the installation of our "Ultimate Stereo 70" Driver Board, but we have one other area to cover first.  We're also going to install the optional "Upgraded" Input and Output connectors.  That will follow in our next installment, coming soon!  Stay tuned!  The BEST is yet to come!

Sincerely,

Bill Thomas

[Bill Thomas]

September 29, 2008 - Update - "It's GREAT to have Connections!"

     Back when the Stereo 70 was originally designed, the Input and Output connectors were pretty much "state of the art."  But we've come a long way since 1959.  Back then, when you were connecting your speakers, you'd go to the neighborhood Hardware store and buy 50 feet of Lamp Cord, strip the ends, twist the wires and wrap them around the screw terminals, tighten the screws, and HOPE a strand didn't short out to the adjacent screw terminal.  If you were REALLY "high-falootin'", you'd buy some uninsulated spade lugs and crimp or solder them onto the bare wires.  Ahhh, CONVENIENCE!

     These days, a shorted strand *might* just destroy a $250.00 pair of Output tubes!  5-way binding posts are SO much easier to use AND they are a LOT safer!  The optional "Upgraded Connector Kit" allows us to replace the original screw-type speaker terminals with Pomona 5-way binding posts - MUCH nicer!  In order to make this a "drop-in" replacement, the binding posts have to be mounted on a substrate.  Here's a picture of the supplied substrates for two sets of Output connectors:

                       

     The mounting substrate is made from high-grade copper-clad Printed Circuit board material.  Of course, the exposed copper oxidizes easily which is why our two little boards look "less than optimal."  Let's take care of that with a household SOS steel wool pad.  A little bit of work produces THIS result:

                         

     Is it really necessary to clean these boards?  Not really.  After all, the copper will be INSIDE the amplifier where no one will see it.  But YOU'LL know it's there.  Besides, the copper is there to provide shielding, so let's make sure the mounting screws contact nice, CLEAN copper for the lowest resistance connection.  Makes sense doesn't it?  Now, let's mount the three 5-way binding posts.  The actual posts have a "D" shaped base that secures the plastic insulating collar so it won't rotate.  Make certain the post is completely seated in the insulating collar.  Just rotate the collar until the post drops into the "D" shaped recess.  Then insert this assembly through the hole in the "green" side of the substrate and put the corresponding rear washer on the mounting screw from the other, "copper" side.  Add a lock washer and a nut and tighten the nut "finger-tight" so you can still align the binding post properly.  You want the holes that go through the binding post to be aligned vertically like this:

                         

     Now, tighten the nuts securely.  You really want these pretty tight, but be careful not to strip the threads.  Check your alignment again and readjust if necessary.  When you're finished, here's what the assembly will look like from the "business end":

                         

     And here's what the assembly looks like from the back:

                         

     Unlike the original "screw-type" terminal board, this assembly will be mounted from inside the chassis.  You probably noticed that we are "one binding post short."  There simply isn't enough room to accommodate four binding posts, so we'll sacrifice the 16 Ohm terminal. After all, there aren't very many 16 Ohm speakers in use these days.  Since the 16 Ohm connection is used to provide a feedback point, we'll mount two little one-terminal strips (supplied with the kit) inside the chassis on one of the mounting screws for our new binding post assemblies.  Neat, convenient and reliable!  Now, let's move on to the Input Connectors.

     The original Input Connectors on the Stereo 70 "work", but they are too closely spaced for many of today's interconnect cables.  The fact that they are tin-plated doesn't help either.  Our "Upgrade Connectors" are gold-plated and are spaced *slightly* father apart to allow the use of "fatter" RCA plugs.  We will mount them on another piece of "Circuit Board" material, cut for the purpose.  This material is not copper clad because we want the two RCA jacks to remain insulated from each other, and from the chassis.  This substrate is also designed to cover the hole left by the removal of the obsolete Stereo/Mono Switch.  Here's a picture of the completed assembly from the front:

                         

     And here is a picture of the completed assembly from the rear:

                         

     We'll bend the ground lugs back before we mount the completed assembly inside the chassis.  Notice that the RCA Jacks are color-coded.  Black for the Left Channel, and Red for the Right Channel.

     That completes our assembly of the Upgraded Input and Output Connectors.  All we have to do now is "gut" a Stereo 70 and install our brand new goodies.  We'll cover THAT process in our next update, coming soon.  Don't miss it!

Sincerely,

Bill Thomas

     

[Boscodude]

I like Otis's idea as well. Welbourne does it with their Mod so why not!?

[Bill Thomas]

Hi, Otis!

     Thanks for the kind words.  I appreciate it!

     Regarding your question, "Can it be done?"  The answer is:  "Sure!"  But the more important question is, "SHOULD it be done?"  Before I get into that question, let me preface my statements with the comment that I tend to be more of a "traditionalist" when it comes to "modding" Stereo 70's.  (My current "Construction Chronicles" on the "Ultimate Stereo 70 notwithstanding.)  I tend to treat "modding" a Stereo 70 the way most people today modify "classic cars."  In other words, I try to make sure that any change I might make could be EASILY reversed at a later date, without having to resort to welding, or replacing the chassis.  Obviously, drilling holes in a good Stereo 70 chassis doesn't rank high on my list of "good ideas."  Trying to "put things right" after drilling holes in the back of the chassis would be a VERY expensive and difficult proposition.  Also, while you certainly CAN make such a change, (and I've seen my share of units that have been modified this way), the potential for hum pickup is VERY high.  NO shielding is perfectly effective, and we're dealing with a VERY high Input Impedance of 470,000 Ohms.  Plug a preamp with a low Output Impedance into it and things might be fine.  Plug a PAS preamp into it and it might hum like a forgetful Tenor!

     Of course, it is YOUR amplifier so I want you to know that I support your right to do whatever you want to do to it.  (You'd be AMAZED what I have seen done to these things!)  I personally don't think it's a great idea, but if it will serve you better that way, why not?  But then, what happens if you find that it doesn't work to your satisfaction?  You'll wind up with the Input connections back in front, and two extra "ventilation holes" in the back.  Decisions, decisions...

     All I can say is, "*I* wouldn't do it, but I'm pretty opinionated about these things."  Just remember, if you DO decide to try it, the Input jacks MUST be insulated from the chassis somehow.

     I wish I could give you a truly definitive answer.  I'm pretty sure that most "authorities" on upgrading a Stereo 70 would recommend against the idea.  But hey, if you simply can't LIVE without a Raspberry-colored 1968 Shelby 500KR with tubbed wheel wells and a Mustang II suspension in front supporting a Cadillac GMC-blown engine, it's YOUR 250,000.00, so GO for it! (lol)

     I guess I'm not much help, am I Otis?   In the final analysis, it's really YOUR decision.

Sincerely,

Bill Thomas

     

[Bill Thomas]

October 7, 2008 - Update:  "Time Out!"

     I was hoping to wrap up our build by now, but due to a serious case of the "Stupids", the Stereo 70 I grabbed from my storage unit turned out to be a completely unmolested original *factory wired* Stereo 70.  The problem is, nearly everything is riveted to the chassis.  That makes this a LOUSY candidate for our completed "Ultimate Stereo 70" Driver Board.

     I'll be heading to my (out of town) storage unit next weekend to pick up a better candidate for our build.  I don't know about you, but I'd really like to be able to replace those unreliable tube sockets with some NOS Mil-spec ceramics.  (But then, I'm a "belt AND suspenders" kinda guy!)

     More to come!  This weekend, I promise!

Sincerely,

Bill Thomas

[Bill Thomas]

October 12, 2008 - Update:  "And now, a word from our 'Donor'..."

     Well, as promised, I actually DID make it to my out-of-town storage unit and retrieved some additional Dynaco "goodies."  (We'll talk about THEM later!)  First, here's a look at a pretty mixed-bag of a Stereo 70.  Let's start out with a "View From the Top":

                             

     It remains to be seen whether this chassis is going to be salvageable.  This one has gone well beyond just "pitting", But, on the Positive side, the Transformers are in good shape.  You're probably wondering why I would select *this* chassis, right?  Well, this particular amplifier has already been "upgraded" by a previous owner.  Let's look a little deeper at the *supposed* "upgrades."

     Here's a picture of the front of the amplifier:

                               

     Notice that our previous "upgrader" has put this amp on stilts!  Those two wood pieces are screwed to the bottom plate of the Stereo 70!  But there's something about his rebuild of the Driver Board that doesn't look too good:

                             

     Yeah, he used better quality components, but what sort of construction technique is THAT???  While it's true that none of the components' lead wires are under much "stress", the components themselves are not very solidly mounted.  Perhaps that is to assist them in achieving a better "synchronicity" with the music, because they will be more inclined to vibrate at their OWN individual rates...

     Bah - Loney!  This type of assembly can only be called ONE thing: "Sloppy!"  Yes, it's possible our previous "upgrader" wanted to be able to make changes quickly and easily, but I don't think so.  Let's take a look under the hood:

                             

     There is just SO much that is SO wrong under here!  Notice the nice Cardas shielded wire?  Then notice the little "chain" of resistors that are totally UN-shielded.  Not good!  And one MORE little detail:  The shield of the Cardas wire?  It's not connected to anything.  Nada.   NOTHING - at either end!  So much for shielding!

     Here's ANOTHER problem just waiting to literally EXPLODE:

                             

     When the Stereo 70 is *first* turned on, the peak Voltage can often exceed 500 Volts!  THIS capacitor is on "borrowed time!"  When it fails, it WON'T be a pretty sight.  Most likely, the can will physically explode!

     Here's a look at the "upgraded" bias supply:

                             

     NONE of this circuitry should be retained!  But the GOOD thing is, our Audio by Van Alstine Driver Board module will replace ALL of this amplifier's "problem areas" - Except one:  The condition of the chassis itself!

     So, here's our donor in its present condition:

                             

     What should we do with this chassis?  Try to have it re-plated?  Strip it, sand it and then powder-coat it?  What would YOU do with this?  Feel free to reply to this post with your suggestions.  But don't worry, I WON'T paint it Pink!  In our next update, this chassis will be totally NAKED!  Perhaps that will help us decide what to do with it.  One thing's for sure, it probably WON'T be pretty!  Stay tuned for ALL the gory details!  MUCH more to come!

Sincerely,

Bill Thomas

[Bill Thomas]

Thursday October 23, 2008 - Update:  "The Prodigal Chassis Comes Home!"

     This will be a brief update.  They say one picture is worth a thousand words, so here's a thousand word's worth.  Draw your own conclusions!

               

     NOW we can get down to BUSINESS!  More to come VERY soon!

Sincerely,

Bill Thomas

[BradJudy]

Wow - that replated chassis looks stellar. 

[Bill Thomas]

October 26, 2008 - Update:  "Assembly Time!"

     Well, the *beginnings* of the assembly, anyway.  Under "normal" circumstances, (whatever THAT is), I wouldn't be "juggling" two projects at the same time, but we've had a few "hitches" in BOTH projects that have served to keep both projects "on the table" for now.  Our "Ultimate Stereo 70" project was slowed down by a "less than stellar" chassis, so we had to wait for a re-plating job before we could continue.  You've seen the result of that in our last update.  I think it was worth the wait!  Now, we can concentrate on "putting it all together!"

     Here's a picture of our Initial Mechanical Assembly:

                   

     While I had originally planned to use NOS ceramic tube sockets, I decided to use these NOS Eby sockets instead.  These are very high-quality tube sockets.  As a matter of fact, Western Electric used these sockets in their equipment because they were EXTREMELY reliable!  The reason *I* decided to use them was because they elevate the tubes just a *smidge* in order to keep the base of the tubes from rubbing on our re-plated chassis.  As usual, I decided to use the "normal" tube sockets for the "Biaset Sockets" on the front panel for aesthetic reasons.

     In our next update, we'll mount the transformers and wire the Main Chassis in preparation for our Driver Board.  It'll look quite a bit simpler than the usual chassis wiring because the Power Supply is now on the Driver Board, as is the Bias Supply.  Our next update will follow tomorrow, so don't take that extended vacation *quite* yet.  We'll have some pretty pictures to show you tomorrow.  With any luck, we'll have this amplifier making BEAUTIFUL music by the end of the week.  Stay tuned!

Sincerely,

Bill Thomas

[Bill Thomas]

November 23rd, 2008 - Update:  "Paint It Black!"

     Well!  At LONG last, we're back on our "Ultimate Stereo 70" project.  (THAT'LL teach me to work on more than one project at a time!)  It just goes to show that when you're planning a rebuild or build project, it pays to budget at *least* TWICE the time you might *expect* a project to take!  (And probably *twice* the MONEY as well, but that's a story for another day!)  I started the SCA-35 project while waiting for the chassis to return for our "Ultimate Stereo 70" build.  As it turned out, the chassis arrived a LOT quicker than expected and the SCA-35 took a LOT longer than expected.  But now that it's complete (see the story at: http://www.audiocircle.com/circles/index.php?topic=60578.0), it's time to get "back to business" on the "Ultimate Stereo 70."

     We were getting ready to mount our transformers and begin wiring the Main Chassis, but an "aesthetic problem" cropped up!  Once it became apparent just how BEAUTIFUL the re-plated chassis turned out, our discolored Transformer bells simply wouldn't suffice.  After all, if this is going to be an "Ultimate Stereo 70", then it ought to LOOK the part, right?  With that in mind, let's take a look at what it takes to "pretty things up" a bit.

     If you forgot what our original "donor" Power Transformer looked like, this picture tells the story:

              

     Dented, rusty and ugly AREN'T going to win any "beauty prizes" on our "Ultimate Stereo 70", so we disassembled the top "bell" from a shorted Power Transformer so our "donor" transformer would have a "donor" top bell of its own!  As it turned out, the shorted transformer had been re-painted, but it was a VERY "slapdash" job.  The metal itself was in pretty good condition, but someone decided to just hit it with a spray bomb; covering the bell, the bolts and the fiber washers with a coat of black paint.  TOTALLY unacceptable!  Using some 220 grit sandpaper to remove the paint, followed by some 600 grade to smooth out the sanding marks, followed by some 1000 grit to smooth things even further, we wound up with a bare metal top bell.  Completely cleaning the result with lacquer thinner and waiting for a fairly warm day, we applied a coat of "ruddy brown primer" to assure adhesion of the color coat later on.  Here's how that turned out:

                   

     Surface preparation is EVERYTHING when it comes to painting.  That includes primering.  The final wipedown with lacquer thinner removed any leftover oils from handling the part and left a surface that the primer should adhere to very well.  When applying the primer, make SURE you follow the manufacturer's recommendations regarding temperature, distance and coverage.  It is MUCH better to lay down several *light* coats, rather than one thick, heavy one.  Allow the proper drying interval between coats in order to assure maximum adhesion.

     Once the part is completely primered, resist the temptation to simply spray on the color coat.  Instead, allow the primer coat to harden for several days (at LEAST).  Then, get out that fine sandpaper again and smooth out the surface.  The idea is to cut the surface of the primer, but avoid going THROUGH the primer down to bare metal.  If you DO sand to bare metal, wipe down the bell with lacquer thinner and primer it again!  Once again, wait a few days and sand down the imperfections.  Once the surface is smooth and even, wipe it down with lacquer thinner again, allow it to dry and lay down a color coat.  Here's a picture of the result after laying down a complete color coat:

                   

     This picture was taken when the color coat was still wet.  Doesn't really look all that great does it?  But laying down the color coat is only the BEGINNING of the painting process.  Here's another picture of the first color coat on the end bell, taken from a different angle:

                   

     This is where most people would "call it a day" and bolt the Power Transformer back together.  Sorry, but that is TOTALLY premature.  We've still got a LONG way to go before this paint job will be worthy of our "Ultimate Stereo 70."  But for now, we've got a little "drying time" ahead of us before we can get rid of the "orange peel" and REALLY make it shine!

     While we're waiting, let's see what we can do to make the transformer "bolts" look a little nicer.  Here's why:

                   

     Notice how grungy these bolts were when we found them?  Dull, discolored and painted - NOT the way we want our transformer to wind up.  How about something a little more like THIS?

                   

     Well, Yeah!  THAT'S more *like* it!  All it takes to get there is a little work with an SOS pad and water to clean the surface of the screw head, but to get down into the slot, we use some sandpaper to eradicate all traces of the black paint.

     While it's a LOT harder to get good results from your typical "spray-bomb" application of paint, it CAN be done!  We'll show you the *next* phase of our "refinishing job" as soon as we've let this color coat "cure" for awhile.  Until then, we'll take care of some "pre-wiring" on our Main Chassis and get another update ready.  Our updates *should* be coming a *little* quicker now (but you know how THAT goes - let's just remain "hopeful" until then!)

     We've got another "cold snap" coming which *may* affect our "painting schedule" a bit.  We'll hope for the best and show you the results in our next update, coming soon.  (I can feel the "adrenaline rush" building in anticipation!)  Stay tuned!

Sincerely,

Bill Thomas

[Bill Thomas]

November 28th, 2008 - Update:  "Transforming the Transformers"

     Let's start out by taking a look at the "intermediate stage" of our Power Transformer "bell."  Our color coat has cured sufficiently to begin "cutting" that "orange peel" a bit.  It'll take a bit of CLOSE observation to notice the difference between this picture and our "just painted" picture in the last post.

                   

     We'll give it a little more effort and show you the finished results in our next update.  But we have quite a bit more refinishing work to do before ALL of the transformers are more "cosmetically acceptable."

     Let's turn our attention to the Output Transformers.  They need substantially more help to look nicer.  First, here's a shot of one of the two Output Transformers in "as found" condition:

                         

     At first glance, it doesn't really look TOO bad, but upon closer inspection, you'll notice that things aren't *quite* so "rosy."  Here's a picture of the same transformer from underneath:

                                   

     It's pretty obvious that our "donor" was stored in a "less than ideal" location.  Rust is NEVER a good sign on the bells of any transformer.  Here's a picture of the non-numbered end bell on this (the prettier) of our two Output Transformers:

                                   

     Do you notice anything "interesting" about this end bell?  (Besides the rust and flaking paint.)  If you guessed "Gee, it *looks* like this has been repainted once before!"  You're right on target!  Our previous "caretaker" of this Stereo 70 decided to hit the transformers with a slapdash paint job.  But he apparently did ZERO surface preparation.  He didn't remove any previous rust or scale.  Nor did he prime the bare metal.  His goal was to just make it all black - not PRETTY, just black!  Sorry, this will NEVER do!

     We'll be alternating photos between the two Output Transformers, so don't get TOO excited if our pictures don't always match up.  The same procedure will be used on BOTH transformers.  Let's go ahead and dis-assemble the bells from the transformers.  Here's a picture of one of the transformers after our initial dis-assembly:

                             

     Fortunately, the "guts" of the two transformers are in great condition:

                               

     The rust on the laminations is just surface rust and can be removed with a little bit of care using one of the many fine "rust neutralizing" products on the market.  Naval Jelly (tm) is one product that works quite well, but remember: these products contain phosphoric acid.  Always use gloves when using these products.  Common disposable gloves from the auto parts store (I like the blue ones) will protect your skin quite well.  Always remember to neutralize the rust neutralizing agent after getting rid of the rust.  It's a little more difficult in this case, because we don't want a lot of water getting into the insulating paper between the windings.  Use common sense and a lot of care when doing your de-rusting, an you should be fine.

     The end bells themselves are going to need a more "aggressive" plan of attack.  Here's why:

                   

     While it was a rather simple matter to sand off the paint on the top bell of our Power Transformer, the end bells on our Output Transformers have WAY too many "nooks and crannies" to deal with.  There are two solutions to this problem.  We can use a "paint remover" to get rid of the old paint (which will do NOTHING to remove the rust), OR we can go the MUCH easier route.  Taking a tip from the "old car hobby", we're going to "farm out" the job!  (We'll get into the specifics of THAT procedure in our next update.)

     Let's just take a look at the rest of the pieces we're going to have to deal with in our "beautification process."  Here's a picture of one of the screws that hold the transformer together:

                             

     Not too pretty, is it?  Now, here's a picture of the "prettiest" of our four end bells:

                                       

     It's pretty obvious, we have a LOT of work to do to.  But if there was any doubt, take a look at the INSIDE of one of our end bells:

                                       

     Even with a blurry photo, it's pretty easy to see the rust that's been allowed to form on our end bells.  Ahh, but there IS hope!  By "farming out" our paint removal and rust removal process, for a total of $10.00, we'll get back four end bells that are clean, de-rusted and ready to prep for painting.  Talk about a DEAL!

     We'll examine the results in our next update.  (I'm leaving to pick up the end bells right after this update!)  Plus, we'll "gussie-up" the "guts" of our Output Transformers as well.  Pretty soon, we'll be puttin' them all back together so we can get back to the final assembly on our "Ultimate Stereo 70."  THIS one is REALLY going to be a "stunner!"  Stay with us!

Sincerely,

Bill Thomas

[avahifi]

Note that you can use a heat gun or hair dryer to pre- soften the old lacquer (or whatever it is) impregnated in the cloth insulation of the transformer leads so you can manipulate them without cracking these old wires.

Regards,

Frank Van Alstine

[Bill Thomas]

November 28th, 2008 - Update Two:  "Goodbye, Old Paint!"

     First, I want to thank Frank for a tip that I *should* have mentioned.  As it turned out, I didn't need to "manipulate" the transformer leads very much and they were a bit more "supple" than *most* of the Dynaco Transformers with cloth-covered leads.  But, Frank's "tip" is right on the MONEY!  Your Dynaco transformers are HIGHLY likely to harbor wires that are VERY stiff, and the insulation (and the cloth covering) may crack or shed easily.  The hair dryer tip will allow you to safely (up to a point) manipulate the wires on your old transformers WITHOUT destroying the wire's insulation.

     Now, let's take a look at our "farmed out" end bells.  First, take a look at the inside of the four bells:

                             

     Notice that every TRACE of rust is a thing of the past!  That "matte finish" is absolutely bare metal.  There is no coating whatsoever!  Now, here's a look at the outside of the bells:

                             

     Once again, every TRACE of rust is completely gone!  Is it worth ten bucks to "farm out" this kind of work?  You BET it is!  Oh!  I almost forgot!  Remember the rusty bolts and nuts?  Take a look NOW:

                   

     Do you have a *clue* how many hours you would spend to get these parts in THIS kind of condition using any "home-brew" paint removal method?  BELIEVE me, ten bucks is absolutely "dirt cheap!"  And the BEST part is, these parts are *almost* ready to primer!  All we have to do is blow 'em off with some compressed air (a can of "computer dust remover works just fine!), a thorough wipe down with lacquer thinner, and we can hit 'em with a "high-build" primer.  (Our "ruddy brown" primer is ideal for this!)  The reason we use a "high-build" primer is this:

               

     That is one *little* area where the rust damage was a *bit* more than just "surface rust."  The "high-build" primer will help "smooth things out" a little and give us a MUCH nicer result when we're done!

     Okay, I haven't mentioned our "miracle technique" that *only* cost ten bucks!  Here it is, and it's as close as your neighborhood automotive machine shop.  Have the parts glass-bead blasted!  The same technique that machine shops use to make cylinder heads and engine blocks look like they have *just* been manufactured, also makes our transformer parts clean, COMPLETELY de-rusted, and ready to clean and paint!

     Now, I'm sure that MANY people who are involved with rebuilding our beloved Vintage Hi-Fi gear *possibly* have an interest in the "old car hobby" as well.  If so, glass-bead blasting is "old hat" to them.  But if you aren't familiar with this paint and rust removal technique, here are the basics:

     Little *teensy* glass beads are shot through a nozzle at VERY high speed using compressed, clean, DRY air.  When they strike the metal, they hit with enough force to abrade the rust and paint.  It's almost like "infinitely conformable sandpaper."  The spent glass beads fall to the bottom of a hopper where they are collected, filtered and recycled through the nozzle.  It only took about 15 minutes to get ALL of these parts TOTALLY clean, de-rusted and left with a surface that will accept primer BEAUTIFULLY!  It is very similar to sandblasting, but it is MUCH gentler on the parts.  And with parts made out of such thin sheet metal, gentle is a GOOD idea!

     Well, that ought to wrap up this installment quite nicely.  Next, we'll take a look at the priming of these parts, as well as the polishing of the bolt heads.  It'll take several days before we can get to the color coat, but weather permitting, we'll show you how THAT goes next week.  Until then, keep that "thermionic emission" well controlled!  MUCH more to come!

Sincerely,

Bill Thomas

[TONEPUB]

Man, this stuff is a work of art...

You are a master!!!

[planet10]

                         

Is there any reason why these couldn't be installed with the black in the middle so that both the 4 and 8 ohm connections could be used with a standard set of dual banana plugs (i assume this is standard 3/4" spacing)

dave