SOLVED Busted TS9 - Troubleshooting

EGRENIER

Well-known member
Dear experts,

I got my hand on a busted TS9, and offered a friend to troubleshoot the issue. Long story short, he inserted a 12v reverse polarity adaptor, saw or smelled the smoke and voila.

Remotely, we had identified that the reverse polarity/voltage regulator diode had broken in half, D8 in the following diagram.

C1B45765-CAFE-4A34-B992-286DF0052A23.jpeg
My friend replace it with a 1N5819, I know that it’s not the same as a W30C, and will not act as voltage regulator, but that should not impact the circuit.

A few picture of what I’m working with followed my my actions.

F4BBF5DF-591B-47AD-B120-C5D2B2BDB6DB.jpeg
1BDB302F-FEEC-4600-8681-3B47A99673EE.jpeg
C6FCD570-0727-44AD-9F7F-DA3D79DA5E68.jpeg
0AA9DC72-3525-4343-923D-BC1A14DBEC30.jpeg

Through visual inspection I noticed that the 100u (C17) cap was blown and for good measure also replaced the 47u (C16) cap.
E1EB2DB9-3BDA-4446-BDCA-74D847C78E26.jpeg

I also notices some white residue between a cap and a resistor:

E51FB7A5-0041-4E07-A0FD-CCC62789C07D.jpeg

So I replaced the cap, but not the resistor…


Current state:
- works in bypass
- Switch works, I see a very faint red in the LED, reading a voltage of only 1.78V. I tested the LED at 9V and it shine bright.
- IC readings with the switch on:
1: 0.8v
2: 0.77v
3: 3.34v
4: 0v
5: 1.03v
6: 0.93v
7: 0.92v
8: 9.06v

- When engaged, the pedal only produce white noise that seem affected by the Level and Drive pots.

So now I can’t see anything suspicious visually to replace and not knowing the board, find it hard to audio probe.

Any suggestions ?
 
What voltage do you get on the 47uf cap? I would expect pins 3 and 5 of the op amp to be 4.5v. If you can audio probe the emitters of the BJTs (2SC1815?) that might be useful to see if signal is getting to the buffer before the op amp. 1658003128927.png
 
As mentioned above, Vref is definitely messed up. Can you measure the junction of R33 and R32 (it's the same as the voltage at C16)? It should be (1/2)Vc.

The faint LED is not that surprising. The network is a bit more complicated since it's a part of the JFET switching with a huge CLR (36k) and a series Zener diode. Also, can you confirm the polarity of the newly installed 1n5817?
 
What voltage do you get on the 47uf cap? I would expect pins 3 and 5 of the op amp to be 4.5v. If you can audio probe the emitters of the BJTs (2SC1815?) that might be useful to see if signal is getting to the buffer before the op amp. View attachment 29161
Ok, so voltage at the 47u is 3.37V, so not at the expected 4.5V.

as for the 1815, well there are 4, so not sure which one we need here. I checked them all at C and E.

Based on this picture:

2CDBCCF1-004B-4174-9EAF-F6F68B30781B.jpeg
A and B read identical - E: 2.9V and C:9.06V

C reads E: 1.2V C: 0.65V
D reads E: 0.24V C: 6.03V
E reads: E: 1.2V C: 0.73V
Can you measure the junction of R33 and R32 (it's the same as the voltage at C16)?

I’m not sure wheee they are located…
 
As mentioned above, Vref is definitely messed up. Can you measure the junction of R33 and R32 (it's the same as the voltage at C16)? It should be (1/2)Vc.

The faint LED is not that surprising. The network is a bit more complicated since it's a part of the JFET switching with a huge CLR (36k) and a series Zener diode. Also, can you confirm the polarity of the newly installed 1n5817?
The 1n5817 looks correct to me

F5637D01-A56A-4148-9B5F-E8BADD33A150.jpeg
 
Something is amiss with the voltage divider. You should read 4.5V there. There may be an issue with something connected to the Vref net since those resistors look fine. Are you working from a schematic?
The only one I found is this.

1658007215220.png

I agree with you that the voltage divider is not providing the expected 4.5V. But I don’t understand how I could lose 2V in this part Of the circuit. The only difference is that the Zener D8 was replaced by a schottky… Could this be it ? I’d be surprised.
 
That wouldn’t be a bad idea and could easily rule a lot of things out.
So there was only one other radial polarized cap I could spot A 10uf. The other 2 radial are non-polarized, 1uf, never seen that before… Swapped the 10u, no change.

Now the schematic shows polarized cap at C5 and C6, but on the board they only look like ceramic.
 
There are a couple of tantalum caps on the board. If they are C5 and C6 then they are polarised - tantalum caps are definitely polarised.
 
If you have 2 identical resistors to make up a voltage divider, and the divider is not giving you half voltage then there is a lot more current drawn from one half of the divider than the other. I would be guessing a blown component that is not fully shorted to a power rail
 
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So getting back at this… found a bit more info helping to understand what’s wrong.

74ECEB23-5D79-4B0F-9933-F502C0EFB990.jpeg

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C105 and C106 are the last 2 polarized components I haven’t replaced before considering transistors and the IC. They are both tantalum .22uf. I was wondering if I can swap that with non polarized film box… I don’t have tantalum of that value on hand.

As for the voltage divider, I have no clue how to identify where the drain could come from. Maybe @fig, @Chuck D. Bones or @PedalPCB could help me on this ?
 
If C105 is suspect, maybe that could provide the drain to the divider before IC1-5. Just a guess really. I have tantalum in that value I’d be happy to send you, but you have a much better chance solving this with PJS and the others you mentioned.
 
If C105 is suspect, maybe that could provide the drain to the divider before IC1-5. Just a guess really. I have tantalum in that value I’d be happy to send you, but you have a much better chance solving this with PJS and the others you mentioned.
I’m looking at that one first, but I don’t see why a non-polarized cap couldn’t be used. Any thoughts ?
 
That would depend on the usage in that situation. If if is being used to filter DC current, then I think polarized is chosen. If it is a frequency filtering situation, then a non-polarized cap is used.
 
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