Looking for a 1967 Vox Jaguar schematic

[DrGonz78]

Well thank you Bill for that great recommendation. So I pulled Q2 and swapped it out with Q8. Nothing changed... Anyway as I was pulling the transistors I did some checks on them too. Q2 is bad... It measured continuity between the can of the transistor and the collector, so something is off there. I tested the HFE on Q8, it was like 150 then I test the HFE on Q2 and is started around 300 then kept on rising up to about 600-900, crazy. So Q2 definitely has issues here.

So I got this silly idea... I took a working boards transistors and put them in the the A# card. Now I was very careful doing this and I just had to know. Well nothing changed. So, I learned better how to scope between parts in the circuit and saw working cards pulses compared to the not working cards. This helped but still I was at a loss still. I then got into looking how the voltage goes through the board and that is when I stopped right at the 1st divider circuit, again. There is R7 100k resistor dropping about 15v to 8.4v and then it leads over to R8 and R15. R8 drops down to 6.2v on the the collector side, but R15 drops down to 180mv. Looking all over the circuit the story remains the same here: Q2, Q4 and Q6 have 6.2 where the the other ones have about the same 180mv on the collector side of the circuit. Hence the voltage drop across R11 is the same as across R7 15v to about 8.4v or so. I will keep observing more until I make the connection. I was looking at the drift of the circuit as far as the resistors are concerned and it does concern me that some of the resistors have drifted. For example, R15 is supposed to be 4.7k but it measure out of circuit as 5.33k, which about 13% tolerance(R8 is measured 5.24k). The other 33k resistors R9 & R13 measure 36.5k and 35.7k, which is 10% tolerance right on the line. Still something has boggled me on this one and any ideas where to look would be greatly appreciated.



Edit: I must note that when I first used the scope to see the pulses on the transistors that I was not doing it the right way. I found a way to use the scope out circuit and hold it close to the can of the transistor to detect the dc pulse. Then I started looking at the scope correctly!! I then saw pulses traveling through the circuit while touching each individual resistor or what not. It made me understand things much better. Then I got realizing the voltages are just wrong and the circuit is lopsided right now. I know that I did not need to take out all of the transistors but I just had to be sure. At least at this point it is making more sense for me as a result.

[Jazz P Bass]

I do not have a clue what you just said
My first thought is where is the 15.5 Vdc (shouldn't that be Minus 15.5?) coming from on R7.
It appears that C3 is leaking.
How about taking some meaningful readings.
Like from a working board.
Notate them as you did.
Then compare them to the non-working board.
Notate these voltages as well.

[DrGonz78]

Yeah it is all in Negative voltages on this board... Sorry I know I should finish this post by saying that I intend to show better what I just discovered. I really just saw this at the very end of a long night. It was 119 for the high here and my shop was horrible to work in tonight even. Maybe the heat is cooking my brain! lol! Either way I think it just might be C3 too. However I replaced C1-C3 to be on the safe side with Mylar film caps to just to make sure...

I will follow through more tomorrow in getting all the voltages on the working board down pat. It is a lot of information and just tad overwhelming really. Hard to convey here online, but bare with me as eventually I might get it right. Still I understand your complaint and I agree completely. Thanks.

Edit: Actually just to note that on all the collectors there should be about -3.1v present. I will be more detailed with contrasting the working board to the non-working board in further posts.

[Jazz P Bass]

119 degrees, huh.
Ah, but it's a dry heat Mr Pinette.
John Pinette - Las Vegas: All You Can Eat - YouTube

[52 Bill]

The transistor with the rising gain is showing signs of leakage. Some germanium transistors are manufactured with one of the elements connected to the case. I've seen some with the Emitter and some with the Base connected. Test another matching transistor and see if the case is connected to the Collector of that one.

Don't get caught up in the out of tolerance resistor thing. I'll bet if you measure the resistors on the working boards, the resistors will be just as out of tolerance. If they are way out, then deal with it. If they are close then they probably aren't the cause of your problems.

If you look at the schematic the output of the oscillator comes from the collector of Q1. From there it is sent to the first divider. The output of the first divider comes from the collector of Q3. So use the scope to look at the signal at the collectors of Q1 and Q3 and so on. If the oscillator is working, you should see a square wave at Q1, then you should see a square wave at 1/2 the frequency at Q3, and 1/4 the frequency at the output of the next divider.

I will try and pull out my Jaguar and pull a generator board to get some direct readings to give you, but in the mean time try and stay cool.

[DrGonz78]

So I got it!! I was so concerned that the voltage was dropping due to the 2200pf and 4700pk capacitors that I just pulled them all out. I replaced them with some new ones to rule out the concern. At that point I started to see each square wave generating it's proper signal. However, it was just like the other times that it worked and it died out again. So, the only component on the board the entire time that I did not look at closely was Q1. So I pulled Q1 out of circuit for some testing, figuring it might be leaking. The whole time though it seemed like it was the only one working correctly too. It measured 400+ HFE and it seemed to me to be quite high. To answer your question Bill only Q2 measured continuity between the collector and the can, it too had a very high leakage. No other legs on any of these SFT351 transistor measured continuity between any of the legs and the cans.

I pulled the Q1 on the A board and measured it to around 200 HFE and it seemed way better comparably. After installing the new Q1 I have a fully functional A# card. Still got to do some matching of transistor HFE readings to get it just right I think. I will follow up here with more voltage readings and fully document this troubleshooting experience. I was trying the whole time to not just start pulling parts and when I did it had to be for a good reason. So far I have learned quite a bit from the preliminary troubleshooting of this organ. I still have some issues with the B and C card but they are at least functioning.

At this point I will be back later to really document this whole experience as I do think somebody later on will find some of this useful. Not too much info online when working on this specific model and I intend on creating as much as I can here on this thread for others to reference. Thanks so much to Bill and Jazz for all the feedback and help!! I will post more later... It is just too hot right now and I need a bit of a break. Still it's nice to take the rest of the night off and have a nice cold beer.

Edit: I ordered 20 SFT322 transistors at 67cents a piece from a seller online. I hope they are good and I know that I can use the MPSA92 transistor too. I am gonna try out these germanium one's and cross my fingers. This thread is really far from over but I have finally had a great success now. Just got to wait for some parts now to get the whole thing finished.

[52 Bill]

So I got it!!

Congrats on the progress. Great price on the transistors too. Keep us informed as to your progress.

For me, on any Germanium based device, if there are no obvious things like burned bits I always suspect the transistor before I start looking at caps and resistors.

[DrGonz78]

So the transistors came in yesterday and I got to finishing the repairs on this old organ. I have to say that I was more than pleased with the GT1322 Germanium Transistors that I bought from an Ebay user in Sofia, Bulgaria. 20 of them for about $13. The outcome is that I tested only one to be leaky and only 2 to be somewhat a high HFE reading out of the 20 transistors. So, I replaced all the bad transistors in the A# tone card and it works perfectly now. Then I went on to trouble shoot the B sound card and quickly with the scope saw the collector for Q3 was not working. I changed it out with new one and presto I have a fully functional B card now. Then the C card was acting a bit funny too as I had lost my lowest note. So I could not accurately detect with the scope or voltage checks what was wrong completely. However, I could deduce that Q6 or Q7 must not be functioning correctly. I could get the lowest C to activate if I played the next highest C note then pressed the lowest C key. After thinking about that for a minute I just replaced Q6 and Q7 and it got the C card working again. So now I have a fully functioning organ and it sounds fantastic!! Thanks for all the input Bill and Jazz!! I will probably recap on this thread any important information later on, but for now I am just really happy to have this thing working again! thanks.

[Steve Conner]

Glad to hear you got it working.

A basic transistor tester, like the one built into some multimeters, can't tell the difference between leakage and hfe. It can read a very high value of hfe when the transistor is actually just leaky as hell.

[pelon9932]

HEY THERE, PLEASE BE AWARE!

When a note in a Vox Jaguar plays high, please note that not always will be a transistor from the divider section. My problem was the same, all G keys sound high. I bought some from Sofia Bulgaria, 20 transistors GT1 322. I have changed it one by one, and the problem continues. So i decided to change the diode from G card and it solved problem.

So please consider it, if you have the same problem. I will upload a youtube video with the complete fix of my Vox Jaguar.

Thank you!

[DrGonz78]

Great advice! Yeah in my case I had fault checked the diodes right off the bat, so I knew that they were not the problem. Would make sense that if the diode failed that it would effect the way the voltage divider circuit worked. Still interesting how symptoms can be the same and have totally different faults. Glad you made a youtube video as those will help many a people with future repairs.