[Bill Thomas]

January 3rd, 2009 - Mini-update:  "Houston, We Have a Problem!"

     Well, it seems that the earlier reports of problems when using metal-film resistors are NOT without merit!  (I will be covering the details of our initial "power-up" on the tuner in a MUCH more detailed update, but I wanted to pass this information on IMMEDIATELY to those who are getting ready to start a rebuild.)

     The GOOD news is, our first tuner is actually up and running and sounding *quite* nice.  The BAD news is that the "STEREO" indicator is constantly on.  The REALLY bad news is that the problem appears to be oscillation *somewhere* on the IF board.

     I will be HEAVILY involved in troubleshooting the problem for the rest of the weekend.  Once the dust settles (and things are operating properly), I will follow up this "mini-update" with a complete report on my findings.

     If anyone has any experiences that might shed some light on this, I would LOVE to hear about it!  I have until about 3 PM on Monday to get this completed and shipped!

Sincerely,

Bill Thomas

[justin_122]

Bill,
I had the same problem with the Stereo Indicator being on all the time when I rebuilt my FM-3.  It was not an error in wiring, it was due to something I did when I rebuilt my multiplex board. When I rebuilt my Multiplex board, the C-73 cap was physically damaged, and since this is an odd value cap (.012uf) I replace it with a .015 orange drop, thinking that this was close enough for it to work.  Well, I was wrong,  because after I did this the Stereo Indicator was on all the time.   Lucky for me I had a "spare parts" FM-3 that I stole an original (good) .012uf cap out of, and when I installed that on my multiplex board, the Stereo Indicator worked properly.   

My assumption is that the value of the C-73 cap needs to be very tight, it has to be a value of .012uf.

Regards,

Chuck

[Bill Thomas]

Hi, Chuck!

     Thanks for the information.  As it turns out, I was "chasing my tail" over a problem that wasn't really a problem.  This tuner has turned out to be one of the most sensitive FM-3's I have ever come across.  The inter-station hiss had enough energy in the 19 kHz region to make the "STEREO" indicator close.  Part of *my* problem was that I have no FM modulator that doesn't supply a Stereo subcarrier - or so I thought!

     After replacing metal-film resistors in the IF strip, and noticing ZERO change.  I started putting a little more "gray-matter" to the situation.  I had an old B&K 1077B television analyst in storage.  Not much good for FM servicing, but *just* good enough.  It WILL Output a signal on Channel 6.  This also means that it will generate a modulated Sound Carrier at 87.5 MHz!  A little "tweaking" of the FM-3's local oscillator allowed it to tune to the Sound Carrier.  Here's a picture of the EMM801 with a MONO signal:

                                                 

     It was coupled *just* enough to allow *almost* full closure of the tuning indicator.  The top is fully UN-CLOSED!  No Stereo light!  Not a TRACE of ANY movement!  On Stereo signals, full closure!

     When I originally suspected a problem, I began replacing ALL of the capacitors on the multiplex board, one-by-one and observing the results.  NONE of them made ANY sort of change.  I even went back and swapped out the .012 uF capacitor *again* after your post.  Again, no change.  This is just a VERY sensitive tuner.

     With an 18" piece of wire, I am picking up a station 70 miles away in Stereo with FULL quieting!  With NO antenna, it pulled in a station 35 miles away with only the faintest "trace" of hiss in Stereo, NONE in Mono.  All this before a full alignment.

     I have been chasing a problem that simply isn't there.  Dynaco mentions that it is normal for the Stereo light to close due to inter-station hiss, but in almost every other tuner I have seen, there was *some* opening of the "STEREO" portion.  But again, this is one of the most sensitive FM-3's I have run across.  The inter-station hiss is enough to trigger the light.  With a Mono signal (and no 19 kHz pilot), the STEREO light is totally out!

     Again, I will have a full update on the results in the next couple of days.  I have been working almost 22 hours a day for the past three days trying to troubleshoot a "non-problem", so I'm going to need a couple of days to recover once the tuner is aligned, cosmetically completed and packed up for shipping.

     I *should* mention that other than the two "slightly used" Telefunken 12AX7's, every tube in this tuner is NOS - including the EMM801.  With a completely fresh set of tubes, this thing actually operates quite well down to less than 60 Volts AC from a Variac!  Go much below that and the B+ and filament Voltages are too low to sustain meaningful electron flow.

     Get ready, England!  There's a Dynaco FM-3 that's about to make music back in the "Mother Country!"  More to come from THIS side of the pond, soon!

Sincerely,

Bill Thomas

[smbrown]

Wow, Bill, what a great detail of the restoration. I've been following a number of your projects - really inspiring! Maybe I should tackle that Scott 222c I've got in the closet. Unfortunately, since it wasn't a kit, I don't have detailed instructions for putting it back together, but I guess I could work from the schematic and photos. Anyway, keep up the great work!

[rlee8394]

I have stripped my FM-3 down as well, but, this is what I want:

http://home.comcast.net/~netminer/MOTHERBOARD.html

Chauncey has designed a nice new single motherboard for the FM-3. This looks like a nicer alternative to stripping and reusing the three original boards. I believe he needs a few more orders prior to ordering a new batch of boards. May some of you will want to go this route and maybe Chauncey will get the few orders he needs. Not that Bill hasn't done  wonderful job with the original boards, but as he has even mentioned, you may need a parts unit or two to get a workable solution. I think that this new motherboard would fill the bill (pun intended  ) quite nicely.

Thanks,
Ron

[Bill Thomas]

January 7th, 2009 - Update:  "Let's Get Wired!"

     While this update *may* be a bit "anti-climactic" due to my previous post, there's still some "big doin's" to show you, as well as a promised "fix" for a *teensy* little "goof" Dynaco made in the original wiring.   In our last "Full Update", we stopped after installing the Printed Circuit boards.  Now, "Let's Get Wired!"

     There is a method to Dynaco's (and any other "Kit" Manufacturer's units.)  No matter what the kit, you're generally instructed to do the mechanical assembly of various sub-sections, then the mechanical assembly of the Main Chassis, and THEN you start wiring of each sub-assembly.  Then, it's a (relatively) simple matter of wiring in the various sub-assemblies.

     In the case of the FM-3 Tuner, there are only four sub-assemblies:  The RF Printed Circuit board, The IF Printed Circuit Board, the Multiplex Decoder Printed Circuit Board and the Front Panel sub-assembly.  We've covered the assembly of the Printed Circuit boards and the "Magic Eye" indicator on the Front Panel.  Dynaco's next step is the pre-wiring of the Volume Control - Stereo/Mono Switch assembly.  Here's a picture of the completely pre-wired assembly:

                             

     The twisted pair of red wires will be routed through a slot in the chassis and connect to T-73's secondary.  These wires are part of the "Stereo/Mono" switch wiring.  The trio of Black, Red and Green wires on the right will actually be routed to the left and soldered to eyelets near the PEC modules.  These three wires contain the signal from the Output of the decoded Multiplex diode matrix and feed the Input to the Volume Control.  Red is Right - Green is Left - and Black is the common audio ground.  They don't have far to go, so I stuck with Dynaco's individual "twisted-trio" of wiring.  The two shielded wires are a deviation from Dynaco's original wiring.  Originally, Dynaco also used two "twisted-pairs" for these wires.  These are the Output Wires from the Volume Control and they go all the way to the back of the Multiplex Board.  But these wires are at a pretty high Impedance - 470,000 Ohms.  They route around a tube with AC on the filaments.  Just to make SURE we keep hum at a minimum, let's just shield them and forget about hum pickup.  The shields are connected at the Ground connection to the Volume Control.  The shields float at the other end.  We mounted the assembly (temporarily) to the Front Panel, per Dynaco's original instructions.

     One thing I haven't covered yet has to do with the type of wire being used for *most* of the FM-3 rebuild project.  For most of my rebuilds, I have been using stranded wire.  But due to the frequencies involved in a tuner, a LOT of the wiring must be routed in a specific manner, mainly; VERY close to the surface of the chassis.  Also, the eyelets used in the FM-3 tuner are VERY small.  Trying to slip a tinned-stranded wire into one of them would make me suicidal!  By using solid wire, we can bend it like a Barbie Doll (TM) and get it to "hold a pose" for us.  The downside of using solid wire is that it is MUCH easier to "nick" the insulation on a sharp edge of the chassis, so extra care is necessary.  DYNACO used solid wire when they furnished the original wire!  Who are WE to disagree?

     With that final sub-assembly out of the way, it's time to get to the HEART of the project - the Main Chassis.  The absolute FIRST thing to do is to break out your biggest and baddest Soldering GUN!  You know, the one used to solder gutters and car radiators?  THAT'S the one!  You're gonna NEED it for *this* tuner.  Here's why:

                                  

     Dynaco says it isn't necessary to solder the ground lugs from the main Tuning Capacitor to the chassis.  No, it may not be necessary, but THEY did it when they manufactured a factory-wired unit.  There are good reasons to go ahead and DO it!  Mechanically, it makes the tuning assembly much more rigid.  Electrically, the ground connection is VERY important.  The better the ground, the more stable and less noisy our tuner will be during tuning operations.  It'll take that big Soldering Gun to develop enough heat to make a good, soldered connection to the chassis itself.  (I even went back later and made these connections a little more solid as well.)

     But don't put that soldering gun away *quite* yet.  We need it again right here:

                   

     This is the central ground point for the FM-3 tuner!  The center-tap of the High Voltage Secondary of the Power Transformer is connected here.  That small black wire connects to lug #3 of the terminal strip, which is also grounded to the chassis.  Ground Loop? Yes, it is.  But the distance is SO small that there is little chance of it causing a problem.

     Here is a picture of the wiring at the Main Filter Capacitor.  This is NOT "by the book" because I was *originally* going to use our good ol' 80-40-30-20 uF quad capacitor here.  This picture shows that capacitor installed:

                                                           

     Nice and neat!  But only temporary, as it would turn out!  (I'll "spill the beans" about *MY* truly *brilliant* stupidity a bit later!)  Yeah, things were shaping up *quite* nicely (I thought):

                   

     The Power Supply is the absolute HEART of any unit.  "If it ain't right, EVERYTHING will wind up WRONG!"  This *would* have been a GREAT start.  (I even got a chance to HEAR how it would sound.  It was REALLY nice!)  But let's not delve into that right now.  Let's go ahead and "wire up a tuner!"

     Dynaco followed a fairly organized procedure in wiring up the Main Chassis.  First the Filament Wiring to the RF and IF Circuit Boards is done, then the B+ (High Voltage) wiring is done to the same units.  When finished, this is what we have:

                             

     Notice that the filament and the B+ wiring are all routed right against the chassis?  This is VERY important, so our solid wire choice keeps things where they belong!  You can also see another area where you need to solder the Printed Circuit Board ground-place to the chassis.  It's in the upper right-hand corner of the picture, just to the right of the antenna coil.  DON'T skip this step!  It's IMPORTANT!

     With the RF board wired-in, let's move on to the IF board.  Here's a picture of the Left third of the IF board:

                         

     Green for filament Voltage and Red for High Voltage.  Now here's the middle-third of the IF board - more of the same:

                         

     You might notice that I DID use stranded wire to wire the Power Switch.  Since it goes through the grommet, it is well-supported in the proper position.  Now, here's the right-third of the IF board:

                         

     Make SURE you solder the board to the chassis with your Soldering Gun.  THIS joint will determine the integrity of the audio ground connection for the Multiplex Board, so make it REALLY good!  (While this joint was ok, I went back later and improved the quality of the final solder joint - just to be SURE!)

     The Multiplex board is wired-in the same way.  Here's a picture of the completed Main Chassis wiring:

                         

     All we have left is to add our "special" PEC modules, add a Power Cord and wire in the Front Panel - (or so I thought!)  We'll cover all this and more in our next update, coming SOON!  Stay Tuned!

Sincerely,

Bill Thomas 

[Bill Thomas]

January 8th, 2009 - Update:  "My, Those Are Some NICE Lookin' PECS!"

     Let's start this update with our modified PEC modules.  In an original FM-3 Multiplex board, the PEC modules provide filtering of the 38 KHz subcarrier, but their most *important* function is to provide the correct "de-emphasis" of the recovered audio signal.  Most folks here probably know what I'm talking about, but just in case, let's go over the concept of "pre-emphasis" and corresponding "de-emphasis."

     When our current FM broadcasting band was created, part of the specification called for boosting the high frequencies at the Transmitter.  At each receiver, a simple R-C filter is used to provide a complementary "cut" of the high frequencies.  The result is *supposed* to be a flat response.  Why did they do this?  To reduce high-frequency noise and hiss.  And it really DOES work!  (Phonograph records use a similar, but more complicated "pre-emphasis" - "de-emphasis" system for exactly the same reasons.)

     In the United States, we use a 75 microsecond pre-emphasis/de-emphasis value.  In practical terms, this means that for a 1 KHz signal at 0 dB, changing the audio frequency to 10 KHz will increase the amplitude of the signal to almost 13 dB!  (If I recall correctly, it's something like 12.72 dB.)  That's a pretty big boost!

     In Great Britain, the FM standard was modified to use a 50 microsecond pre-emphasis/de-emphasis curve.  This reduces the amount of boost at the Transmitter, and requires less rolloff of the high frequencies at the receivers.  This all means we need to change the value of the capacitors in the PEC modules, since this tuner will be used in England.

     Since the time-constants in Great Britain are two-thirds of those in the US, we need to reduce the capacitor values by a corresponding amount.  In the "upgraded" PEC modules for the FM-3, the three de-emphasis capacitors are 510 pF.  All we need to do is change them to 340 pF and we're done!  The only problem is, 340 pF is a non-standard value - NOBODY makes 'em!  In order to come up with the correct value, we need to parallel two capacitors to replace each 510 pF value in the original circuit.  Here's a picture of the result:

                             

     To make 340 pF, we used a 100 pF and a 240 pF capacitor in parallel.  Yes, our revised PEC modules are "widebodies" compared with a "normal" version of the module, but there's enough room for it all to work out just fine.

     Since these modules are located pretty close to the 6V4/EZ80 rectifier, a little protection helps.  Here's a picture of our completed, and encased PEC modules - ready for installation:

                                                 

     Believe it or not, that is heat-shrink tubing providing the "extra protection" for our modules.  While we could have used a heat gun to shrink it, a MUCH better way is to simply use the eye of an electric stove.  You can control the amount of heat applied by raising or lowering the assembly.  It also applies heat over the entire assembly, so shrinkage happens all at once.  This keeps things in place a LOT better than shrinking the module "jackets" in sections.  While the tubing was still warm, I crimped the ends with long-nose pliers.  With all that in mind, here's a picture of our installed PEC modules on the Multiplex board:

                   

     Kinda looks like a couple of pieces of black Ravioli, doesn't it?  But, instead of "good eatin'" we'll have some "good listenin'" when we're done.  Here's another picture that shows the "extra protection" we used on the wires that have to deal with the sharp edges on the "slots" puched in the chassis:

                   

     You can also see the trio of twisted wires that feed from the Output of the PEC modules to the Volume Control.  That means it's time to show you our next step - installation and wiring of the Front Panel.  Here's the wiring from the Volume Control - Stereo/Mono Switch assembly to the Multiplex Board:

                               

     Now you can see why I chose to shield the wires from the Volume Control to the Output section of the Multiplex board.  The Input Impedance of the 12AX7 is set at 470,000 Ohms.  With such a high Input Impedance, shielding the wiring is a no-brainer, in order to keep hum pickup to a bare minimum.

     Now, here's a picture of the tuning indicator tube area of the installed Front Panel:

                   

     Now you can see why I "pre-wired" the tuning indicator socket.  There simply isn't a whole lot of room to do a "neat and tidy" job with the Front Panel installed.  By the way, there's one *teensy* little detail to remember BEFORE you install the Front Panel - THIS:

                             

     Make SURE you install your "Tuning Dial" BEFORE you mount the Front Panel to the Main Chassis.  Make CERTAIN it is completely seated on the shaft of the Tuning Capacitor, but don't apply TOO much force.  These things break VERY easily.  (This one happens to be a brand new NOS part.)  When you're done, things should look something like this:

                   

     When properly installed, the tuning dial will not scrape or rub against the Front Panel, but there *isn't* a lot of clearance - *just* enough, see:

                   

     One more "Construction Update" to follow.  Then, we'll get into the alignment of our tuner.  Yes, I'll also go over a couple of "goofs" in the next "Update", following VERY soon.  More FINE TUNING to come.  Stay with us!

Sincerely,

Bill Thomas

[Bill Thomas]

January 8th, 2009 - Update:  "Let's FINISH This Thing!"

     OK, it's time to "Fess Up!"  I mentioned my little *goof* previously.  Here's the whole story!  First, take a look at the initial picture of the Main Chassis with the circuit boards installed:

                   

     Now, here's a picture of the completely wired Tuner:

                   

     Look VERY closely at the top of the main Filter Capacitor.  Notice a change?  Yep!  I had *originally* planned to use our familiar 80-40-30-20 uF filter capacitor.  The only problem is - it's about one-half inch TALLER than the cover for the tuner!  That certainly didn't even enter my mind - at first!  Of course, it was immediately OBVIOUS once I attached the Front Panel to the Main Chassis.  Rather than punch a hole in the perforated cover (just kidding!), I replaced it with a "less towering" capacitor.

     I know the camera angle makes it nearly impossible to see the difference.  Fortunately, (for my pride) I didn't snap a picture of the original capacitor choice, TOWERING over the top edge of the Front Panel.  But UNfortunately for my pride,  I truly believe in "full disclosure" - warts and all!  Besides, I *knew* everybody would get a kick out of my stupidity, right?  Of course, discovering this little "catastrophe" at the "Eleventh Hour" didn't do much to improve my outlook for the weekend, but it only took about an hour and a half to "correct" my little "faux pas."  I *did* get a chance to hear the tuner with the "wrong capacitor" installed.  The funny thing is, there was virtually no difference between it and the replacement capacitor.  The replacement is a 40-40-20-20 uF capacitor - the original values Dynaco used.  When Dynaco got it right, they really got it RIGHT!

     But that brings us to *one* area where Dynaco got it wrong.  I also mentioned previously that we were going to "correct" Dynaco's *teensy* little goof.  Well, this is it!  Take a look at the wiring to the two RCA jacks on the Rear Panel of the tuner:

                   

     This is NOT the way Dynaco wired things.  Dynaco used small RCA Jacks that grounded the shell to the chassis.  They used the chassis as the low side of the RCA's.  No wire, no nuttin'!  But the chassis is *also* used as one side of the filament wiring for the RF and IF Circuit Boards!  ANY resistance ANYWHERE can lead to hum from the Output Jacks.  If your tuner has a mysterious case of hum that you simply cannot eliminate, *this* is the most likely cause.  In this particular tuner, I decided to insulate the RCA jacks from the chassis and ground them to the ground point for the 12AX7 Output amplifier V72 - the center pin of the tube socket.  This point is wired directly to the Main Ground at the terminal strip.  The result?  Not a TRACE of any hum.  Nothing!  Nada!

     By the way, it probably isn't necessary to use insulated RCA jacks, but it IS necessary to run the ground for the jacks back to the Multiplex Board's ground point.  Don't just leave the ground side of the RCA's connected to the chassis alone.  Your tuner might not hum NOW, but it is almost GUARANTEED to hum sooner or later.  You'll think your quad cap is bad, but it isn't.  You'll think the last 12AX7 has developed a Heater-to-Cathode short, but it hasn't.  You'll imagine all SORTS of probable causes for the hum, but you'll overlook THIS one - the REAL reason!  It wasn't a HUGE goof, but it WAS a goof on Dynaco's part.  This fixes it, once and for all!  If you have a tuner that hums a little, try this fix FIRST!

     So, now all we have to do is complete the "cosmetic" portion of our tuner build and align the beast.  You already saw a picture of the Front Panel and the Main Chassis.  Here's a picture from the rear of the unit:

                   

     Sorry about cutting off the right side of the image.  The thick rubber band that is currently holding the battery door closed on my camera covered up that portion of the viewfinder screen, so I had to *guesstimate* the width of the tuner.  I just guessed a little *under*!  Anyway, here' an overall shot of the tuner from the rear:

                   

     Yep!  Looks like a tuner!  But not a *finished* one.  For that, we need just a FEW more parts, like the Bottom Panel:

                   

     Other than a few fingerprints from the "cleanup phase", this panel looks pretty good.  Now, here's another item you won't see every day - a NEW (NOS) insert for the window in the Face Plate:

                                       

     Speaking of the Face Plate, here is our cleaned up Face Plate, along with the knobs and hardware used to attach it:

                   

     Dynaco NEVER issued a tuner with these knobs.  They used the original style die-cast knobs.  The FM-3 was discontinued before these machined aluminum knobs were ever used on a Dynaco product.  *I* used them because this tuner is going to be paired with "The Last of the Dinosaurs" PAS-3X preamplifier and I wanted them to match.  Here's how the tuner looks with the Face Plate and knobs installed:

                   

     I kinda like that "glint" of sunbeams that danced across the face plate in this picture.  But here's a shot of the completed tuner, ready to be packed up and shipped:

                   

     Compare that with the picture of "The Last of the Dinosaurs" PAS-3X preamplifier:

                   

     That's a match made in heaven!  And that wraps up the construction of our first FM-3 tuner!  But, we have one more update to go - namely, the alignment of our tuner.  I'll cover that in our final update, coming up shortly.  If you were wondering how tough it is to align an FM-3, take heart.  It's a piece of cake!  Honest!

Sincerely,

Bill Thomas

[Bill Thomas]

Hi, fellow Dyna-Nuts!

     When I goof, I think it's important to "set the record straight."  In our Final update on the construction of the FM-3 tuner, I mentioned that Dynaco never issued an FM-3 tuner with the aluminum knobs, rather than the die-cast knobs.  This is apparently a totally WRONG statement.  While I don't have anything in writing to confirm it, apparently some of the final tuners issued by Dynaco did indeed feature the aluminum knobs.  The evidence is pretty strong that this is the case.

     While it is a simple matter to "swap" knobs (as *I* did in the rebuild project), our good friend Mike (Flyquail 56) informed me of some tuners he has seen with aluminum knobs with no "pointer notch."  In other words, the knobs HAD to be for use with a tuner, since tuners are the only items in the Dynaco catalog that don't need a pointer on the large knob.  I can't imagine *anyone* "robbing" the knobs from an FM-5 or an AF-6 tuner, just to "harvest" knobs to replace the old die-cast knobs on their FM-3 with more "modern" parts.

     On top of that, this past week I repaired a late-model FM-3 for a WONDERFUL gentleman who uses his FM-3 on a daily basis in his office.  He walked out of his office for a moment, and when he walked back in, it was making an INCREDIBLE buzzing hum!  Not a trace of music, just BUZZZZZZZZ!  His tuner also featured aluminum knobs, however; the tuning knob on his tuner DID have a notch in it for a pointer.  In his case, I suspect that a previous owner DID swap the knobs.

     By the way, his tuner is on the way back to him as we speak.  I'm afraid that our second tuner in the "Double Dose of Fine Tuning" will have to wait for awhile.  I had to use my last NEW can capacitor to repair his tuner, and it is unclear whether any others will be available soon.  While A.E.S. DOES offer a can capacitor with the correct values, it is 3" tall.  Because of my *last* experience with capacitors that are a *bit* too tall, I'm a little wary of trying to use one of these.  By my "reckoning", a 3" tall capacitor is about 1/4" too tall for the FM-3.  I'm not absolutely POSITIVE about this yet, but it sure *looks* like this is the case.

     Not to worry!  I'm working out the details of an "alternate solution" for our next FM-3 rebuild.  I'll keep you posted on the results.

Sincerely,

Bill Thomas

P.S. We'll be covering alignment of an FM-3 tuner shortly.  I just need to set up the lighting for the necessary "indoor photography" to detail the process properly.  Sorry about the delay.

Bill

[Bill Baker]

Beautiful work Bill. Just goes to show what a little patience will do.

[Bill Thomas]

     You are MOST kind, Bill, but next to YOUR work, I'm restoring a Volkswagen compared to a gullwing SL300!  THAT is some really GORGEOUS stuff!

MOST Sincerely,

Bill

[avahifi]

Dyna did indeed supply FM-3 tuners with machined knobs and no "notch" in the big knob.  I built many of them like that.

By the way I hope you have a frequency counter to start the alignment process.  The Dyna kit manual alignment process tuned the other IF transformers to the first pre-set one.  When realigning an old one, you cannot assume that the first IF transformer is still accurately on 10.7 meg.

Regards,

Frank Van Alstine

By the way, we soldered the ground foil to the chassis at several places around the IF board for good contact.

[rlee8394]

Any reason why the ceramic disc capacitors couldn't be replaced by more temperature stable and tighter tolerance parts such as dipped mica or other film based units?

Ron

[Bill Thomas]

     Frank is absolutely right with all of his information.  It is CRUCIAL to make sure the Primary of the 1st IF transformer is set "dead-on" at 10.7 MHz, since the rest of the transformers are peaked to that transformer.  You might not be lucky enough to have a signal generator and a frequency counter available, but the solution *might* be as close as your nearest Truck Stop that has a CB shop!  (Many of them do!)  For a few bucks, you can *probably* get the fellow there to check the setting of that first transformer.  If not, it'll probably cost a bit more, but any two-way communication shop *should* be able to handle it.  It isn't necessary to go any further than that because YOU will be doing the rest of the alignment yourself.

     I appreciate the confirmation regarding the machined aluminum knobs and I stand corrected on my original statement.  Thanks, Frank!  Frank also makes a VERY good point about soldering the IF strip to the chassis in several places.  Even though I didn't show it, I did do just that when I was looking for what I *thought* was a problem with oscillation on the IF board.

     Ron, due to the complex nature of the tuner, I would stick with original disc capacitors for the RF and IF bypass functions (ceramic discs are IDEAL for RF bypass applications).  You could certainly use micas for coupling capacitors on the IF board.  But due to the heat involved in this unit, I don't see a big reason to change to other types of capacitors.  I hope to have more definitive information on this very issue soon.

Sincerely,

Bill Thomas

[katabatic]

I had to use my last NEW can capacitor to repair his tuner, and it is unclear whether any others will be available soon.  While A.E.S. DOES offer a can capacitor with the correct values, it is 3" tall.  Because of my *last* experience with capacitors that are a *bit* too tall, I'm a little wary of trying to use one of these.  By my "reckoning", a 3" tall capacitor is about 1/4" too tall for the FM-3.  I'm not absolutely POSITIVE about this yet, but it sure *looks* like this is the case.

Bill--

Many thanks for this wonderful thread -- I just finished grounding the RCA jacks of my FM-3 per your advice.  On the can capacitor front, these folks -- http://www.die-wuestens.de/dindex.htm?/k8.htm   -- have a can capacitor (the KTL 14) that looks like what the FM-3 needs - 40-40-20-20, and the specs show a height of 2.4 inches, which, by my measurement, should fit.  All for about 30 Euros.  Do you know offhand if this would work (like, are there limitations on the diameter of a can cap to fit the slots in the chassis)?  If it would fit, it would be a solution to the 'too-tall-can' problem....

George

[Bill Thomas]

Dear George,

     Thanks for the VERY kind words.  (You forgot to mention if the change in grounding made a difference in your particular tuner.  Did it help?)

     It certainly *looks* like this capacitor *might* be a solution to the problem.  Unfortunately, the site does not seem to indicate the diameter of the can.  It's pretty close quarters next to the Power Transformer with only a little over 1/4" of additional space.  Any possibility that you might know the diameter of this capacitor?  The original is *just* under 1 3/8" wide at the widest part (the base.)  The rest of the can is 1 1/4" in diameter.  Other than that, the actual mounting is the standard "twist-loc" design, so there shouldn't be a problem with that.

     While I was aware that "Ask Jan First" had some electrolytics, I really hadn't researched the site completely.  GREAT detective work, George!

Sincerely,

Bill Thomas

[katabatic]

Bill--

There's a secondary data sheet on the site that shows the diameter as 40mm, or 1.575 in., which is wider than the stock unit  I checked my tuner and you're right, it is very tight around the cap, but it looks like a 40mm can would just clear everything, and the listed 60mm height is actually a bit smaller than the can that is in there.  I'm going to bite the bullet an order one...I was going to try to make the SDS Labs cap board myself (I've never made a pc board before--whoa, toxic chemicals and even more chances to electocute myself) but this alternative seems easier and safer (hey, I can send an email to Germany; I can do THAT)  I'll let you know when the thingie arrives in the mail.

George

[katabatic]

Bill--

I've now received the can cap from AskJanFirst (link above), and it fits, both in height and width.  The new cap is shorter but wider (40mm wide) than the stock Dynaco part:




But, it clears the power transformer, the tuning shield, and the front circuit board (and fits the slots in the chassis perfectly)...Sorry about the rust spots on the chassis; I'm working on it....




Hooked everything up, flipped on the power, and WETA-FM came up loud and clear!  It's been part of a broader upgrade with new output caps, PEC modules, and those nasty resistors on the front board that caused you such grief.

Hey, no smoke, no flames, no need to call 911; it's a good day.



Cost of the cap can, with shipping, was 39.70 Euros, or about $51.00.  Not the cheapest alternative, but one that looks right and drops right in.

Only issue now is that when I tap the tuning knob, I can hear the tap through the speakers.  Didn't do that before.  Oh well, something to track down...

George

[Speedskater]

I was up in the attic the other day and came across the 10.7MHz crystal (XTAL) oscillator that I had used to align my FM-3. 30 some years ago.

[Speedskater]

I was up in the attic the other day and came across the 10.7MHz crystal (XTAL) oscillator that I had used to align my FM-3. 30 some years ago.

The temperature outside just went above freezing and I got back into the attic and while doing to other stuff, I found two  Telefunken EM84/6FG6 eye tubes.