Looking for a 1967 Vox Jaguar schematic

[DrGonz78]

Got to just add one more post... Sorry

So anyway I got looking at the board fully and can clearly say, that even though there is some drift of almost all the resistors, still I don't think any resistor here is the problem. I tried to look at all the caps on the board and did some tests on them with batteries to see if they would hold juice, they did. Also, I noticed that there even might be problems on the B tone generator card or something related between A# and B. You see the lowest B right above the A# (White Bass Keys) sounds like it is missing part of it's sound. All the other B notes sound find but it is only the one on the lowest B, and not so noticeable. So, I saw this ad for a Vox Jaguar for sale...

VOX Jaguar Combo Organ - $450 (Candler Park) : music instr : Atlanta Classified :: ListLux.Com

"The only problem with this Jaguar are in the C notes. All C keys across the board play the same tone (high C). This can be remedied by replacing the Germanium transistors on the clearly labeled C-key "Tone Generator Card" inside the organ, as well as on the divide down card. "

So I am assuming the "Tone Generator Card" and the "divide down card" are the same thing, or did I miss something that divide the bass key to higher keys that might be just a small part of my problem here?? I guess I am so new to this thing that I am not sure if there if a bass divider circuit before/between the Bass keys and the higher keys. Please steer me in the right direction here as of less than a week ago I would have never touched this thing!! lol!

Anyway I was also reading on Nate's Vox Continental web page I came across something there too...

http://www.theamericannight.com/voxproject/project.html

"The correct pin order is: emitter (nearest to edge of board), collecter (middle), base (nearest center of board)."

That statement there is completely opposite between base and collector on my post from before, isn't it? I would assume these germanium transistors are the same being such closely related. Either that or the SFT351 are EBC and the SFT353 (the one's I think he was using) are ECB pin layout. I guess I will have to research that some more as I still think it could be something transistor related, yet again. lol.

Well I don't see any difference between the 351 & 353 pin layout...
SFT351(B,C) Semiconductor (Transistor, diode, IC) Cross reference

SFT353(B,C,D) Semiconductor (Transistor, diode, IC) Cross reference

So I guess it might have been 322's that he was using?? Nope!! Basically, I think he mistyped by saying the Collector was the middle pin... Makes no sense, but I will stop rambling now.

Edit: I truly think that the ceramic caps are really hard to fail parts and just don't think they are the problem. However, I can't say for sure. Either way I can totally rebuild this board as an experiment. My thought is to order transistors and not mix and match them on one board at all if I can help it. Nate's page made mention of that it is wise to keep matching transistors on the tone/divider boards. Also, once I am done fixing the A# board then I will apply that knowledge to the B board... So I might be ordering quite a few parts just to get this thing back to normal. Still it will be budget conscience to order a good amount rather than a few at a time, "just in case parts."

Double Edit: I know I know... Well I guess part of the problem might be related to this part of the schematic... I just feel that maybe the bass divider circuit having an effect on the A# and B tones. Now that is not saying there is nothing wrong with A# and B tone generators & divider circuits there... Just saying that maybe I need to focus on this a bit to get the whole perspective. Earlier today when I showed the organ to my brother it (for the first time) would not play the low C note. A few hours later I turned it on and cannot get the Low C note to fail now... So is this what Nate meant by saying the divide down circuit card... Being something different than the divider circuit attached to each individual tone generator. What do you guys think?

[Steve Conner]

The divider circuits are nothing but flip-flops. The transistors are indeed non-critical, you might even get away with using silicon ones, far cheaper than germaniums. The MPSA92 is in a similar gain range to the SFT351.

[DrGonz78]

Thanks Steve I will give that some thought and I might actually have some already. So, that might be interesting to try out.

[Jazz P Bass]

You still have not found where the circuit is failing.
I see a lot of assumptions & no data.
I would try to focus on one card.
Time to break out the scope?

[DrGonz78]

I just got a Hitachi scope waiting to go, but I need to buy some probes. However, I have yet to use a scope up to this point so I have a steep learning curve ahead. Also, got to learn how to use it and make sure it is working good. This might take a little time...

Edit: I hate to say this might be out of my scope of repair at the moment, but it is. I might bring the card over to Matthew at field services if it comes down to it. Thanks for all the help thus far

Double Edit: So I also hate to throw in the towel too!! lol! Anyway this is the more complex divider circuit on the Continental 302e and it shows some info on what I need to do. So, I guess with this as a starting point guide it seems feasible that I should give this a shot!

[DrGonz78]

Funny that the vid clip involves the A# board just as a coincidence here. So you take a 9 volt battery connect it to the associated parts on the generator board. Then connect (-) terminal clip on the battery to ground on the scope. Then check the pulse wave from each appropriate pin in the divider circuit. This looks a lot better now, but still got to get some parts. Gives me a little time to research the scope and practice on something. This will be a great new lesson to further my learning... Hopefully I won't forget it later and claim that I only have education. (Enzo's quote broken to bits)

[Jazz P Bass]

A scope in it's simplest form is a voltmeter with a screen.
You have a ground probe & a signal probe.
The screen can be stretched/ shrunk in amplitude & in time.
That's it.
From what I have read on these keyboards, the pin connector on each tone card is a bit fragile.
So the less they are removed, the better chance you have of them working.
You aleady have the voltage coming to the board, so why take it out?

[DrGonz78]

Good point on pulling the board in and out... I have been very careful with the board, but yeah got to minimize removing it.

I just watched a clip where he measures the resistance of what is essentially a bad cap. I noticed that after the lowest tones disappears on my organ there is a popping noise present on the lowest key and tiny pops on the higher A# keys. I should have measured for DC coming into the signal path as video shows. However since the board was out already I measured the resistance between C1 in circuit and it was 29k. I also measured the resistance of C2 in circuit and it was 284ohms. Out of circuit I get only a OL on my meter and no measurable readings of resistance. I tried two different meters and got the same result OL or (I)nfinite on the other one. So does that mean the resistance is ultra high? What does that tell us or does it make sense? I measured capacitance of both 22000pf caps and both read 22.90nf (meter was reading nf) = 22960pf. Basically, just needed to learn better how to test these little caps if nothing more. I will practice with some good caps to get more experience dealing with this in general. Watch about 2mins into this video for what I am referencing.

VOX Continental Organ 302E Key Clicks and DC Bias Repair - YouTube

Edit: I guess I was really confused about how he read resistance on those caps... My main question is really about what type of caps are these listed below.

Also, what is this type of Ducati brand capacitor? It is 22000pf and 125 V- is what is written on it. Here is a picture since I might need to order these parts to have on hand just in case. What are ones to replace this one and is this a polarized cap? Thanks...

[52 Bill]

Edit: I guess I was really confused about how he read resistance on those caps... My main question is really about what type of caps are these listed below.[/U][/B]

Also, what is this type of Ducati brand capacitor? It is 22000pf and 125 V- is what is written on it. Here is a picture since I might need to order these parts to have on hand just in case. What are ones to replace this one and is this a polarized cap? Thanks

There should be no resistance reading across the cap, period. If there is, then it is shorted and needs to be replaced. That's why the guy in the video is saying they need to be replaced, because they are leaking dc voltage into the audio path. When you first put your meter on the leads, there might be a slight low reading until the meter charges the cap. Then it should read the same as if the leads were not connected to anything.

The caps are mylar film caps and the 22000pf equals 0.022uF. If the meter reads close to that then they are ok.

The Jaguar does not have the same single note output connections that the Continental does. The lower octave notes are mixed together through a series of resistors so it will be harder to figure out which, if any divider cap is leaking dc voltage. Don't expect the same results as the video because the board designs are entirely different.

[Enzo]

There should be no resistance reading across the cap, period.

BZZZZZZT!!

I think you mean infinite resistance? Not the dead short "no resistance" implies?

[52 Bill]

BZZZZZZT!!

I think you mean infinite resistance? Not the dead short "no resistance" implies?

Yes, what I should have said was there should not be a resistance reading across any cap.

[DrGonz78]

I will start with checking for DC voltage on any of the board pins, attached is pic of the pins and their function.

Well I started off testing the A generator card instead of the A#... whoops. Just to note: Pin 4 on the A card had 3.62vDC on it.

======================================================== =================================
As for the A# pin DC voltages in respect to playing the A# keys... As Bill said this card is different than the Continental, but still here are the voltages gathered.

Pin2 resting voltage at 0.4mv then while playing highest key it goes to 6.50v -- All other keys did made no change to resting 0.4mv voltage

Pin3 resting voltage at 0.4mv while playing 2nd highest key it goes to 5.81v -- All other keys did made no change to resting 0.4mv voltage

Pin4 resting voltage was 214.2mv playing lowest key makes voltage drop to 66.2mv -- Playing through all the keys results in voltage sitting at 6.71v. Then play 3 lowest keys in succession results in the voltage then resting at 210.7mv.

Pin 5 resting voltage at 0.4mv then playing lowest key it goes to 5.79v

Pin6 resting voltage at 0.4mv then playing 3rd highest key it goes to 5.79v
======================================================== =================================

Okay so I finally have used a scope for the first time, so be easy on me. Or should I say that I am learning how to hook it up and just flip all sorts of switches to look at the wave form. I think this scope needs some work but it might help give us some test data.

Anyway, what I have are a bunch of picture of wave forms and explanations for each one. I will try not to be drag this out too long or be too brief. Also, if after reading this>>> if anyone has some ideas what to scope next that would be the goal as I am starting to see the light.

When I refer to pin 2-6 that is the pin scoped and then the associated waveform picture. Sometimes the waveform was moving too fast and could not get it stand still as to take the pictures, probably something need work on this scope.

[52 Bill]

I think that you are confused about the way the generator card works. The top octave oscillator is always running. This note is fed to the first divider, which runs as long as there is a signal coming into it. The same is true for the lower octave dividers.

When you scope each of the card's output pins you should see the square wave mixtures constantly on the screen. You do not need to press any key for the notes to be generated, they are always being generated. The key only connects the audio output from the generator cards to the audio output buss.

To get the most out of your scope, you should connect the scope to the output of the top octave note oscillator and then to each of the individual dividers. That way you will see what each section is doing, not looking at a mixture of octaves.

I've had to edit myself here as I forgot that the keys on a Jaguar are normally grounded, so any voltage that appears on the output pins will normally be grounded when no key is pressed.

[DrGonz78]

Thank you Bill for making sure I look in the right places. I know you had mentioned it twice but I was just trying to analyze some silly stuff really. I was just getting connected with the scope and looking at stuff. I see the light now and have a way better understanding of the circuit at hand.

Actually, I traced out the board so I could figure which transistor was Q2-Q8. Took a little patience just getting that done as to make sure I could understand each divider circuit better. I have included a picture so other people online might find it easier to reference the board layout in relation to the the tone generator schematic.


I was able to see the DC pulses coming off each transistor. I even went and scoped the other working tone generator card as a reference point to look at each transistor in the divider circuits. What I found on the A# card was that Q2 must be failing and there was no steady DC pulse detected. I could detect other pulses in the other transistors but they too looked that they were getting shunted off a bit by Q2. So, I have ordered some transistors for replacement parts and will follow up later on my repairs. Thanks so much for all the help on this one!

Edit: Just have to state that cleaning of the board to get solder rosin off is a good idea. This pic show lots of solder rosin before cleaned it up a bit. The Solder Rosin can be a conductive path on the circuit board and is just one tiny thing to look at on both side of the circuit board.

[52 Bill]

A quick test would be to swap Q2 with another transistor lower in the circuit, like Q8. This may or may not work, but it would be a fast test of the theory that Q2 is the problem.