[Brett Buck]

               

     FINALLY!  Now THIS is a Rear Panel that is truly *worthy* of our "Really SUPER Preamplifier!"

     Bill, are you doing anything to cover up the bare metal when you are done?  My experience has been that they look great when you first do it, but pretty quickly corrode again once you have the plating off from fingerprints, humidity in the air, etc. That's how the originals got corroded, even with cad plating. I have used various lacquers (clear model airplane dope was the best) with some success, but I would be very concerned about it corroding with nothing at all.

      Brett

[bregez]

Another trick in cleaning contacts on those Dynaco selector switches is to use a drafting eraser (the soft white vinyl small diameter cylindrical ones that Staedtler makes).  They do a good job in removing any residual buildup and don’t leave any eraser particulates behind.

Brad

[Bill Thomas]

Friday, March 5th, 2010 - Update:  "Step By Step"

     With apologies to The Crests, it's time to FINALLY make some REAL progress with our "Really SUPER Preamplifier" build.  Now, you might wonder what ever happened to our original plans to update you over a week ago.  Sadly, real life, a real job and continuing "issues" with my recent move have all conspired to delay my "updates" a bit.  That *doesn't* mean that no progress has been made, as you'll soon see.  But first, let's talk about the recent questions and tips that have been raised above.

     Brett raises a VERY good point regarding the protection of our newly-cleaned metal parts.  The short answer is that I don't apply any extra protective layer to the cleaned metal pieces.  There are several reasons for this.

     The first reason is that the original finish was bare metal and just like a "Thoroughbred" Mustang car restoration, I prefer to leave "unfinished" metalwork in a natural state.  I have found that the metal parts will gradually develop a "patina" due to atmospheric causes, but this is a natural and normal state of affairs.

     The second reason I leave the metal in a natural state is that almost *everybody* has a "favorite compound" they swear by that is used to clean or polish the metal parts.  If I encased the metal in a clearcoat, it would be impossible to improve its appearance in the future.

     The third reason is a bit more practical.  Any clearcoat will have insulating properties.  While this can be dealt with using "selective removal" wherever metal-to-metal contact is necessary, it reduces the overall electrical integrity of the "box structure" created by all the metal parts solidly touching each other.

     An easy solution would be to use a CAREFUL application of an automotive-type paste wax, but MY personal preference is to "go commando" with the bare metalwork.

     Regarding Brad's suggested use of a drafting eraser, I see nothing wrong with the idea, however; there is always the danger that a contact might become bent and there is NO way to get that eraser between the contact "fingers" to make SURE the cleaning operation is complete.  I have had really GOOD success using chemical means and a good, stiff bristle brush.  Yes, you can still bend contacts if you aren't very careful, but it's a LOT harder to totally WRECK things.  (Then again, *some* people can break a crowbar in a sandbox!)

     I prefer to let people choose their OWN method to preserve the appearance of one of these units.  As an aside, I have units approaching the two year mark that show relatively little degradation, even with NO additional protection.  Of course, as with ALL things, NOTHING lasts forever, but I feel quite confident that these units will last for MANY years without *too* much visual degradation.  Now, let's get back to "the build!"

     First, I NEED to mention that Frank sent replacement RCA jacks out IMMEDIATELY after I destroyed two of them while attempting to tighten them "firmly."  They arrived just a few days after our last "update" was posted.  This allowed me to complete the "upgrade" RCA jack field and install it on the rear panel of the preamp.  Here's how it looks after mounting in the panel:

               

     Notice that we now have a nice, convenient binding post between the Phono Input jacks so we can easily connect the ground wire from most turntables.  Also notice that there is an additional mounting screw in the middle of the RCA jack field.  This means we don't have to worry that the new jack field will "flex" excessively when inserting interconnects in the central area of the jack field.  These are little details that help to make this a "complete" solution.  Along with the RCA jack field, I have also mounted four new AC "convenience outlets" to the rear panel.  Remember:  These AC outlets are NON-polarized.  NEVER attempt to insert a polarized plug into one of these sockets or you will destroy the socket.  Since these are not being manufactured by Kulka anymore and my stock of original sockets isn't unlimited, protect them at ALL cost!

     Once the "upgrade jack field" has been mounted, we actually have some wiring to do!  Take a look at the Phono Jacks from the inside of the Back Panel:

                   

     It's amazing how much satisfaction you can get from just four little wires and two capacitors!  But, at least we're getting to hang some wires on SOMETHING!  Since these wires carry VERY low-level signals, it is VERY important to twist the four wires into two twisted pairs.

     Take a closer look at the two little capacitors:

             

     These capacitors provide DC isolation of the Phono Input ground connections while allowing a path for AC signals (RF, noise, etc.) to be grounded to the audio ground point in the preamplifier.  Notice that the leads on these capacitors are kept quite short and the bodies are positioned VERY close to the ground-plane.  Again, this is to keep hum and noise to as low a level as possible.

     It's *almost* time to mount the Rear Panel to the Main Chassis.  But first, we need to mount two of the three "modules" we previously constructed.  (The Power Supply module will be mounted a *bit* later.)  Here's a picture of the Phono Preamp module and the Line Stage module after mounting them to the chassis:

               

     The Power Supply module will sit on top of the five stand-offs.  At this stage, the stand-offs are only "finger-tight" to allow for adjustment when mounting the Power Supply module.  We've also installed the rubber grommet supplied with the kit.  Wires from the Power Supply module will pass through this grommet.  Since some Voltages in those wires run as high as 400 Volts, it would be a pretty nasty thing if a wire were to become "chafed" by a sharp edge on a chassis hole.

     We've also installed an important NEW safety item:  The new fuse holder:

               

     While I have NEVER heard of any PAS preamplifier catching fire, a shorted Power Transformer is NOT that unusual.  Why tempt fate?  A fuse in the Primary side of the Power Transformer is a welcome safety addition.  The new (NOS) Tube Socket is not included in the Super PAS Three kit.  In almost every case, the original socket can be re-used.  I just wanted to "start fresh."

     It's almost time to mate the Rear Panel back to the Main Chassis, but first, we need to connect the Power Transformer wires to the terminal strips like this:

                         

     The high Voltage Secondary winding wires go to the top terminal strip, while the Primary and Filament windings are connected to the bottom terminal strip.  Since the high Voltage Secondary wires route through the cooling slots, I thought it would be a good idea to add some heat-shrink tubing over the wires for extra protection from sharp edges.  Notice anything unusual?  Two of the high Voltage Secondary wires are cloth-covered.  The rest of the transformer wires are PVC covered.  (I dunno about THAT one!)  I added little "collars" of heat-shrink tubing to the cloth covered wires to prevent fraying of the cloth covering.

     We're going to take a BIG step in our next photo:

               

     We've attached the Rear Panel to the Main Chassis and FINALLY, we get to actually complete our FIRST wiring connections - two twisted pairs from the Output of the Line Stage module to the Main Out jacks on the Rear Panel.  These two pairs are routed underneath the Power Supply module, so these pairs are run first.  THEN we mount the Power Supply module, routing the right side wires through the rubber grommet, align the mounting holes with the standoffs and tighten all the screws.

     Here's a look underneath the Main Chassis showing how the wires that pass through the grommet connect to their respective locations:

               

     All wires are connected except the red/black pair that is routed towards the front of the Main Chassis.  This pair will feed the light emitting diode on the Front Face Plate when our unit is finished.

     Now, let's move back topside.  The next step is to connect the heavy black ground wires to the various locations around the preamplifier.  Trim each wire to the correct length for a neat, clean installation.  Once the heavy black ground wires are connected, then the four small red wires are connected to the Phono and the Line Stage boards.  Again, tirm them for a neat installation.  Here's a picture of the result:

                             

     Next, we add a heavy black ground wire from the center-tap of the high Voltage secondary terminal of the upper terminal strip, to the tubular ground terminal on the Power Supply module.  Then, connect two small wires from the filament winding terminals on the lower terminal strip, to the two tubular terminals for the incoming filament supply.  Here's the result:

                     

     This completes the wiring for the Power Supply module, but we still have a little more to take care of before we get to a convenient stopping point.  First, we need to connect the rest of the wiring to the terminal strips on the rear panel.  A twisted pair of red wires connects from the top terminal strip and routes through an existing hole in the chassis to be connected to the plate terminals of the rectifier tube.  Since the Voltage through these wires is over 700 Volts, it's a good idea to add a little heat-shrink tubing for extra protection to those wires where they pass through the hole in the chassis.  Here's a picture:

                             

     We've also added a wire from the lower terminal strip to the fuse holder.  And with that, the wiring on the top side of the Main Chassis is at our stopping point.

     Now, let's finish this stage of wiring underneath the chassis.  Here's the final area we need to tackle:

               

     Remember, these wires carry full AC Line Voltage so make SURE they can't short to the chassis.  You'll notice two wires that haven't been twisted together yet.  These two wires will route to the On-Off Switch on the Front Panel.  We'll also add the new Line Cord during our next phase of assembly.

     Well!  We've made a LOT of progress!  We started with empty metal parts and have gotten through more than half of the wiring!  Up next, we'll pre-wire the Front Panel and then re-assemble it to the Main Chassis.  But that will have to wait for our next update, coming VERY soon.  Until then, stay SUPER!

Sincerely,

Bill Thomas

[Bill Thomas]

Tuesday, March 9th, 2010 - Update:  "Get Together"

     No, it's not time to drag out the Youngblood's greatest hit; it's time to get everything together to complete our Front Panel.  We begin all that by mounting the slide switches and the new Noble stepped potentiometers to the panel.  Here's a picture of the parts installed in the panel, ready for wiring:

           

     Let's take a closer look at the noble potentiometers:

           

     These are truly high-quality pieces.  In our initial description, I mentioned that the balance control has a detent.  Actually, BOTH controls have detents.  That's because they are detented controls! (well, Duh!)  In fact, this is the easy way to tell them apart when it comes time to install them.  The Volume Control has smaller "steps" between positions than the balance control.  It should be noted that you CAN set the controls "between steps" for finer control of the Volume or Balance.  Mount the controls as shown in the pictorial (the same as they are shown in the picture above.)

     Before we can actually wire the Front Panel, we need to do some pre-assembly of the Blend Switch.  We start by adding the two new resistors that actually do the "blending" (when selected) of the Left and Right channels.  Here's a picture:

                 

     I decided to begin at the left side of the "gap" between terminals in order to make SURE I didn't forget anything.  Wonder of wonders, I actually DID remember it all!  Here's a picture of the completed pre-assembly of the Blend Switch:

                       

     Actually, there are two more wires to be installed on the right side that will route to the Tape Monitor Switch when the Blend Switch is installed on the Front Panel.  We'll add them before we install the switch to the panel.  When installing the parts and the wires on the Blend Switch, make SURE they don't interfere in the operation of the switch itself.  Here's a picture from the side:

           

     None of the parts or wires make ANY contact with the "workings" of the Blend Switch (even though it *appears* that the black wire is touching the shaft, it too has plenty of clearance.)

     Let's add those two wires and mount the Blend Switch on the Front Panel now.  Here's a picture showing the result:

           

     The black wire from the Blend Switch will connect to the Line Stage module once the Front Panel has been mated to the Main Chassis.  Take a look at the red and green wires coming from the right side of the Blend Switch.  You'll notice that they are separated from each other.  Also notice that they are positioned against the inside of the Front Panel.  These are the Left and Right channel audio signal wires that connect to the Tape Monitor switch.  At this point, the Impedance of these wires is 100,000 Ohms, so we want to route them as *close* to the panel as possible to keep any potential hum pickup to an absolute minimum.  They are separated from each other in order to avoid any high-frequency crosstalk between them.  At this stage, we have also connected the wires from the balance control to the Blend Switch and we have also connected the ground wires from the Volume Control to the Balance Control.

     Let's finish the Front Panel wiring.  Here's a close-up picture of the finished wiring:

           

     Notice that we have arranged things to keep the Left and Right channel wiring as separated as possible.  Where a red wire simply MUST cross a green wire, we do so at a 90 degree angle for the absolute MINIMUM crosstalk.  (You'll NEVER hear any!)  The two twisted pairs of wires will connect to the Line Stage module when we mate the Front Panel back to the Main Chassis.

     And THAT is where we'll leave things for now.  We'll cover the installation and wiring of the Front Panel in our next "update" which will leave us with a nearly completed preamplifier - that is, if we were only interested in using it with ONE Line Level source.  But, we'll "expand our possibilities" with the installation and wiring of the Main Selector Switch too!  And THAT will complete the electronic assembly of our "Really SUPER Preamplifier!"  But we still have a few "aesthetic details" left to cover.  We'll get into ALL of it, VERY shortly!  Stay with us!

Sincerely,

Bill Thomas

[ArthurDent]

Bill -

I'm sure this is a (well Duh ?) question, but is the use of the noted non-polarized AC outlets because no one makes a polarized replacement of the same size ? Just curious. Things are looking sweet, am looking forward to the next installment, "as the Selector turns".   

Hope the pile of boxes is decreasing, and you are getting better situated post move. After much testing & consideration I passed on the tuner. Thought I had a donor unit available, but missed the boat. Until I get a few more existing projects completed figured it was wiser not to add to the list. Thanks again for the input.

JD

[Bill Thomas]

Hi, Arthur and thanks for the kind comments.

     Regarding the AC outlets, you're correct.  There are no polarized replacements available that fit in the existing opening.  There's a real-world reason for this.  The wider "blade" would not allow enough "plastic" material to provide a proper "safety margin."  By the same token, the original outlets and Line Cord are non-polarized.  If I were to find a source of polarized outlets that DID fit the openings in the chassis, I would also have to replace the Line Cord with a polarized cord.  It is ABSOLUTELY against the "rules" to use a non-polarized cord to feed polarized outlets since it is all too easy to reverse the "hot" and "neutral" connections at the outlets by simply reversing the non-polarized Line Cord in the wall.  Sure, I *could* have enlarged the AC outlet openings and used polarized outlets, but I haven't seen any polarized convenience outlets that would actually fit the available mounting space between the Bottom Panel and the surface of the Main Chassis.  The BEST solution is to use the original outlets with a non-polarized Line Cord.

Sincerely,

Bill Thomas

[Bill Thomas]

Wednesday, March 17th, 2010 - Update:  "What's Goin' On?"

     With apologies to the late Marvin Gaye, the answer is:  "A LOT!"  So without further ado, let's get down to business!

     We had completed our wiring of the Front Panel in our last "update," so now it's time to re-acquaint the Front Panel with the Main Chassis.  Here's a picture:

           

     This angle shows how close to the panel the wires to the Tape Monitor switch are routed.  It also shows that the two twisted pairs of wires from the balance control are separated to keep inter-channel crosstalk to a minimum.  These wires route under the Balance Control and connect to the Line Stage module.  Here's a picture showing how the Left Channel pair connects to the module:

           

     And here's a picture that shows how the Right Channel pair connects to the module:

           

     You can also see how the black ground wire from the Blend Switch connects next to the Right Channel pair's ground wire.  Here's a picture of the attached Front Panel from a different angle:

           

     If you look *closely* you can see the routing of the black ground wire from the Blend Switch.

     The two twisted pairs and the black ground wire are the only wires that need to be connected from the Front Panel to the top of the chassis, but we DO have other little "details" to take care of underneath the chassis.  Let's flip the chassis over and take a look at our next little "detail" - wiring the Power Switch.  Here's our next "victim":

           

     Looks simple enough, right?  Well, before we can wire the Power Switch, I thought it *might* be a good idea to add a bit of "protection" to the twisted pair of black wires carrying 120 Volts since they are routed along the side of the chassis where the sharp-pointed cover screws just *might* cause "issues."  Confused?  Well, a picture should help:

           

     We've covered the black twisted pair with some black heat-shrink tubing.  If you look closely, you can see the two holes on the bottom of the picture where the cover screws will protrude.  There's actually a good deal of room between the pair of wires and the screw holes, but the heat-shrink adds a little "insurance," - just in case.

     Since we're protecting the wires to the Power Switch, it just makes sense to do the same for the black and red twisted pair that will connect to the LED on the Face Plate when our preamplifier is completely finished.  Here's a picture of our heat-shrink tubing prior to "shrinkage":

           

     With our wires to the Front Panel "protected," let's connect the Power Switch.  Here's a (blurry) picture of the final result:

                             

     (Sorry about the focus problem.)  Notice the added .01 uF capacitor.  It's there to absorb the "spike" created when the switch is turned off and the magnetic field collapses in the Power Transformer.  This accomplishes two things:  First, it GREATLY extends the life of the slide switch and second, it reduces the likelihood of a loud "Pop" making it into the audio when the preamplifier is turned off.  If you look VERY closely, you'll see some clear heat-shrink tubing covering the leads of the capacitor; again, "just in case."

     We have just two more areas to cover before we can call the Front Panel wiring completed:  The Face Plate LED wiring (which we'll cover when we install our Face Plate) and the four wires that will complete the wiring of the Tape Monitor Switch:

           

     We'll take care of the Tape Monitor switch wiring when we install the main Selector Switch and we'll cover THAT in our next "update."  I'll be posting the next update VERY shortly.  Then, we'll fill THIS space with a big switch and lots of wires:

                                         

     We'll also FINALLY connect the Input connections to the Phono Preamplifier module.  If you'll remember, I delayed the connection of these wires in order to route them away from the Line Level wiring.  Don't worry.  It'll all make sense when we sort it out in the next update.

     Let's close for now, but don't stray too far.  Our next update really WILL follow in short order.  We'll cover the final electrical assembly (except for the wiring to the LED on the Face Plate).  Once *that* is done, we'll go ahead and give the preamplifier the "Smoke Test" to see how things sound.  I have a feeling it'll be something TRULY special!  Until then, "Stay Tuned!"

Sincerely,

Bill Thomas

[JerryM]

That's the prettiest work I have ever seen on anything electrical, anywhere. 

Beautiful work, Bill! 

[Bill Thomas]

Thursday, March 18th, 2010 - Update:  "Life Gits Tee-jus Don't It?"

     I *think* you'll understand why I pulled that old Carson Robison song out of my foggy memory bank after we finish this update.  This is the most time-consuming part of our "project."  In this update, we're going to wire the Main Selector Switch and the rest of the RCA jacks in the ground-plane jack field.

     Before we get started, I just wanted to sincerely THANK YOU, Jerry.  I'm afraid that I'm a bit of a "throwback" because I TRULY believe in trying to do my VERY best to achieve a QUALITY result.  Personally, I believe that people are getting tired of poor quality, shoddy workmanship and "kludges" of all kinds.  It would be all too easy to throw a kit like this together in a couple of evenings and chances are, it'd work *ok* for awhile.  But to achieve the goal of building a unit that will have a long, trouble-free "second life-span" requires a different level of care and consideration.  But don't make the mistake of giving me too much credit.  ANYONE can achieve the same results.  It takes TIME to take care of the "little things," but it is the attention to detail that makes all the difference between an "ok" unit and an OUTSTANDING one.  Start with a solid foundation and take it one step at a time.  Break it down to sub-sections and complete the sub-sections in a logical order.

     For example, in EVERY total rebuild project, our "solid foundation" ALWAYS begins with a blank, CLEAN chassis.  I *do* have an added advantage of being able to select from several "donor" units, but even the "less than perfect" units can be cleaned up in one way or another.  In a future "project," I *hope* to take a REALLY trashed Stereo 70 and return it to service.  The chassis is REALLY sad with LOTS of pitting and some rust as well.  But when we finish with it, it *should* be nice enough to display *proudly* in ANY Hi-Fi System.  But, I'm getting ahead of myself.  Let's get back to business!

     We're down to the final stage of electrical assembly:  The Main Selector Switch and the associated wiring to the RCA Jack Field.  Here's a picture from Frank Van Alstine's website.  It's the same picture on the front of the "Super PAS Three" Construction manual, but it's a little clearer than the photo of the cover shot:

                     

     I'm posting this because this gives us a good idea of the wire routing for the Selector Switch and the RCA jacks.  The photo shows the optional fiberglass selector switch, but we can still follow the "general" wire routing with the original Dynaco switch (manufactured by Centralab).  In general, you'll notice that the red Right Channel wires are routed so they will be near the Main Chassis and the side of the metal cover.  The green Left Channel wires are routed so they will be near the side and top of the metal cover.  They are separated from each other by several inches to minimize inter-channel crosstalk.  Of course, it would be nice to have something to wire TO, so let's reinstall the Main Selector Switch with the red dot pointing UP at the 12 o'clock position.  Here's how it sits in "the grand scheme of things":

           

     You'll notice a red and a green wire connected from the front and rear wafers to the middle wafer.  These two wires will allow us to convert the two original (and now, no longer needed) Low-level Inputs, into additional Line-level Inputs.  These two NEW Line-level Inputs are best suited for audio sources that are not active all the time, like a CD player or an I-pod.  In the original Dynaco Switch, unused sources are grounded unless they are selected.  This reduced crosstalk between sources.  But our two NEW Inputs are NOT grounded when they are not selected, so they should not be supplied with audio at all times in order to minimize crosstalk.  It's not really a BIG deal, but it pays to know the "best-case" and the "worst-case" scenarios.

     So, let's get "down and dirty" and begin wiring the lower RCA jacks to the Selector Switch, as well as the other places they need to go.  The BEST way to accomplish all this is to route ONE wire properly, and then form each additional wire so it is neatly routed next to it's "kissin' cousin."

     Here's a picture of a pre-formed wire that will be installed between an RCA jack and the Main Selector Switch:

                 

     Looks kinda *silly* "out-of-context" like this, doesn't it?  But pre-forming each wire pays off with BIG dividends.  Here's a picture of the completed Right Channel wiring:

           

     It takes TIME to do all this.  Each wire probably took an average of around 20 to 25 minutes to properly cut, form and then install.  You'll also notice that we have FINALLY connected the red and black twisted pair from the Phono Input.  Notice that we've routed the pair AWAY from the Line-level wiring.  Again, this is to minimize any crosstalk in the Phono Input from a Line-level source.

     Here's a look at the Selector Switch wiring of the Right Channel from a different angle:

           

     Now, with the Right Channel wiring out of the way, let's move on the Left Channel.  Here's one of the pre-formed Left Channel wires:

           

     Here's what it looks like when installed with a "mate":

             

     Here's a *partially* pre-formed wire.  We still have to "final measure" the left end of the wire for proper length and "bending-path" at the Selector Switch:

           
       
     There's enough wire included in the kit to allow us to be "generous" with the wire lengths prior to *final* cutting.  "Better too long than too short."  Trimming is easy.  Wire-stretching?  Not so much.

     Here's a shot of the *almost* completed Selector Switch wiring:

           

     We still have two more jacks to wire, but things are progressing nicely.  (I REALLY liked the "look" of this shot with the light source illuminating the circuit boards.)

     Our second-to-last wire has some of the most *interesting* routing:

           

     Our goal is to route this wire against the side while still maintaining separation from the corresponding Right Channel wire.  This wire goes from the RCA jack to the Tape Monitor Switch.  Unless you're "Edward Tweezerhands," you can FORGET about bending this wire "in-place."

     Finally, let's connect the wires from the Left Channel Phono Input.  We're routing them away from the Line-level wires as well as the Right Channel Phono Input wires.  Here's a picture of the FINAL results:

           

     We'll do a "final straightening" when we're ready to install the top cover, but each wire will wind up nice and straight when all is said and done.

     With the exception of the wiring to the LED on our Face Plate, all wiring has now been completed!  Here's the *electrically* finished unit:

                         

     Here's the Front Panel:

           

     And here's the "view from the rear":

           

     Ahh, but we *still* have some "aesthetic details" to tend to.  We'll get to all that in a later "update," but here's a "hint" of things to come:

           

     This might *look* like the shaft of a Volume Control, but this little piece of metal is eight inches from Left to Right!  That makes the diameter of the thing about 1.5 inches!  As a further "hint," take a look at the same "metal" with a *teensy* application of "Wright's Brass Polish":

           

     Mull that over for awhile.  I'll explain it all in a later "update," but FIRST, we have the "Smoke Test" to come in our very next update.  Yep, it's "Tube Stuffin' Time at the Rodeo!"  We'll cover the results in short order.  Don't miss it!

Sincerely,

Bill Thomas

[nunhgrader]

This is an incredible project - learning so much!

[Bill Thomas]

     Thanks for the kind words.  They are deeply appreciated.  We'll be covering the "smoke test" within the next 24 hours, along with the first of several "aesthetic updates" as we *inch* closer and closer to a finished unit that *should* make a very nice addition to any "Vintage Hi-Fi" collection.

Sincerely,

Bill Thomas

[ratso]

i think you're going to have to put everything else in your life on hold from now on. cuz i'm not sure we can wait 24 hours anymore  . just really great stuff, even though, as i said once before i have no idea what is going on half the time. but still just amazing.

[Bill Thomas]

Saturday, March 27th, 2010 - Update:  "Smokey Places"

     Anyone else remember the "Corsairs?"  I think it's safe to call "Smokey Places" one of the really FUN Do-Wop songs (especially considering that the subject matter had to do with "cheating!")  Of course, in OUR case, I'm talking about our "Smoke Test" of the "Really SUPER Preamplifier!'

     Yes, it's *that* time!  We're going to delve into a fairly extensive electrical "checkout" of our preamplifier.  We'll divide our checkout into three "stages."  First, we're going to check out the wiring of the Main Selector Switch and the Input Jack wiring.  Second, we'll check out the Line Stage board.  Third, we'll give the equalized Phono Preamplifier module a workout.

     First, here's a picture of the new label supplied with our "Super PAS Three" kit:

           

      We'll be referring to this label to verify that ALL of our Line-level RCA Inputs (except the "Tape Amp" input) are wired correctly.

     The first stage of our testing can be accomplished without plugging the preamplifier into the wall!  We can do this because we're going to connect our Power Amplifier to the "Tape Output" RCA jacks.  This Output is an "un-buffered" Output.  In other words, there are no amplification stages involved with this Output.  The Main Selector Switch simply routes the selected Input to the "Tape Output" RCA jacks.  Of course, it *also* routes the selected source to the following amplified stages, but for our initial checkout, we don't need to be concerned with that just yet.

     Of course, we need a signal source.  Here's my "preferred" audio signal source:

                 

     As you might guess, there's nothing at all "fancy" about this CD player.  It's a portable Sony "Walkman" CD player.  Why do I like to use it as a source?  The MAIN reason is simple:  It is totally and completely isolated from any possible ground loop situation!  It is battery operated and can be programmed to repeat a CD until the batteries die.  It has a Line-level Output, but it actually delivers about half of the nominal 2 Volt Output of most CD players.  While in many cases this might be considered a "negative," in the case of our preamplifier, this allows us to see how much gain can be supplied by the Line Stage module (when we actually get the opportunity to apply power to the unit).  By the way, battery drain is amazingly low.  With a fresh set of batteries, this little CD player can operate continuously for over 36 hours!

     So, let's get crackin'!  We begin by plugging the Left and Right audio connections from the "Tape Output" jacks into our "test" power amplifier.  (I'm using a really *dinky* Radio Shack amplifier because I'm using a pair of Sony MDR-7506 headphones to listen to the audio, rather than speakers.)  Now, connect the Output of the CD player to the Left and Right "Tape Head" input jacks:

           

     Hit the "Play" button on the CD player and switch the Main Selector Switch to the "Tape Head" position.  If all is well, you *should* hear the audio from the CD player in your headphones.  Now, switch the Selector Switch through all the other positions and verify that audio is ONLY heard when the Selector Switch is in the "Tape Head" position.  (You'll probably hear a *teensy* bit of crosstalk when the switch is in other positions, but this is normal.)

     You can get a good idea of how quiet or noisy the Main Selector Switch is during this test.  As it turns out, our Selector Switch operates without an excessive amount of "scratchiness."  In fact, it actually broke both connections at the exact same point of rotation.  This shows that the alignment of the Front and Rear sections of the Selector Switch is right "on the money!"  (I got lucky!)  So far, so good!

     Now, move the Input Connections to the "Special" input:

           

     Move the Main Selector Switch to the "Special" position and listen again.  All good?  Great!  (It was in our case.)  I should mention that it's a good idea to pull one of the Input connections to make SURE Left is Left and Right is Right.  Plug it back in and pull the opposite channel's connection.  You'll notice that inter-channel crosstalk is nearly zero.  That's because of the separation between the green and the red wires inside our preamplifier.

     Now, move the Input connections to the "AM-FM" Input:

           

     You'll probably notice that when you move the Selector Switch AWAY from the "AM-FM" Input, there will be significantly less crosstalk heard.  The remaining Inputs are all grounded *except* for the one that is selected to be "active."  It *does* make a difference.  As before, check the integrity of the Selector Switch and to make SURE the channels aren't transposed.

     Now, move the CD player connections to the "FM MPX" Input:

           

     Test this Inpu in the same manner as the previous Inputs.  Again, you'll find that crosstalk between source Inputs will be very low.  This Input and the following Input are again, inputs that are grounded when not selected.

     And finally, move the connections from the CD player to the "Spare" Input:

           

     Move the Main Selector Switch to the "Spare" Input setting and again, check the audio the same way you did for the previous Inputs.  If everything checks out ok, (as it did with our unit), then the first "stage" of testing is now complete.

     By the way, if you are restoring a "stock" PAS preamplifier, you can use the exact same method to test the function of the Main Selector Switch and the associated RCA jack Input wiring.

     And that's it!  We have managed to test the wiring of twelve of the eighteen RCA jacks; all without even applying any power to the unit!  We can't check the "Tape Amp" Input because it doesn't feed the "Tape Out" jacks at all.  Of course, the "Phono Input" jacks are wired directly to the Phono Preamplifier module, so we'll need power to test that function.  That only leaves the "Audio Output" jacks, which we'll test during the next "stage" of testing.

     All this preliminary testing will take you less than an hour to perform.  In our case, everything checked out beautifully, but if you discover a problem, NOW would be the time to fix it - BEFORE you apply any Power to the unit.

     I can honestly say that in the case of our "Super PAS Three" unit, the biggest surprise was that there were NO surprises!  Everything worked well right "out of the box" with truly SOLID connections at each position of the Main Selector Switch.  All RCA jacks made good, solid connections to the plugs and none of them were troubled by excessive solder on the terminals that could block insertion of the center pin of the RCA plugs.

     And with "Phase One" under our belts, we'll drag out our variable AC Transformer and a Voltmeter, and prepare to embark on "Phase Two" of our testing.  We'll cover *that* part of the testing in our next "update," coming up later today.  Until then, stay with us!

Sincerely,

Bill Thomas

[Bill Thomas]

     Sorry for the delay.  Some computer problems slowed things down a bit.  The next update will follow later this evening.

Sincerely,

Bill Thomas

[Bill Thomas]

     Just a quick note to first, apologize for the LONG delay in posting any further updates, and second, to let you know that another update is DEFINITELY "in the pipeline" for posting very soon.  There have been quite a few "interruptions" to my plans during the past two weeks, but there will be quite a bit of GOOD that will *eventually* come from it.  (At least, for any folks who might be hankering for more restored Dynaco units.)

     I lost my lease for my warehouse storage space this past week and had to *quickly* retrieve ALL of my Dynaco parts and equipment.  While that might not sound like much, we are actually talking about MILLIONS of resistors, capacitors, sockets, connectors and the like.  During the transfer of all this stuff, I located more original Dynaco units, as well as even more NOS Dynaco parts.  (Most of the newly discovered parts are for the FM-1 and FM-3 tuners.)  I also FINALLY found my box of brand NEW tuning capacitors for the FM-3 and FM-1.  These were produced by a different manufacturer than the original parts (the original manufacturer is LONG gone), and the planetary drive mechanism is EXTREMELY stiff when compared with the original parts, but they WILL loosen up during use and *should* function with similar smoothness to the original units fairly rapidly.  That's some of the GOOD news.

     The NOT so good news is that I now have a HUGE mass of parts that are now clogging up every room here.  It will take a bit of time to gradually return the inventory to an "organized" situation, but I WILL take care of it as we go along.

     If I happen to live long enough, I *should* be able to supply quite a few more tuners, amplifiers and preamplifiers over the next few years, as well as have the ability to help repair or restore MANY units that are currently "in the wild" now.

     We will be wrapping up our "Really SUPER Preamplifier" article during the next week or so and I promise a few surprises (nice ones, REALLY) along the way.

     I'm "on the mend" after a DISASTROUS bout with the flu while all this was happening.  As soon as I can get a *bit* more energy back in my poor ol' tired body, I'll be back in the saddle again and we'll get back "down to business!"

     Thanks to EVERYONE for their patience.

Sincerely,

Bill Thomas

[ArthurDent]

Bill -

Just a quick wish for a speedy completion to the mending process. The flu is a bummer anytime, but late spring when things are getting nice outdoors just doesn't seem fair.

Oh yes, and good luck on the sorting process.

Best Regards,
JD

[Listens2tubes]

Yes Bill I hope you re-gain strength quickly to continue your excellent Updates and sorting /organizing chores. Your efforts are a real inspiration to all of us who enjoy the DIY part of HiFi.

[dyna70]

All the very best for a speedy recover Bill and look forward to the next installement in this restoration epic!

Cheers,

- John

[PeterCapo]

Hang in there, Bill.  We're rooting for you!

Peter

[Indiansprings]

Has anyone heard from Bill? Is he OK?