SOLVED Busted TS9 - Troubleshooting

[EGRENIER]

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.


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.






Through visual inspection I noticed that the 100u (C17) cap was blown and for good measure also replaced the 47u (C16) cap.


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



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 ?

 

[EGRENIER]

I think that in your situation before I replaced anything more I would trace through with an audio probe just to see what happens to the signal. That should hopefully give you some idea which component is busted.

Yeah, I'm not too enthused by the idea of randomly swapping parts... I can audio probe it, will get to it when I have a chance. I'll share my findings when done.

thanks for your help...

 

[music6000]

Yeah, I'm not too enthused by the idea of randomly swapping parts... I can audio probe it, will get to it when I have a chance. I'll share my findings when done.

thanks for your help...

Can you Test for Continuity between 1 & 2, 2 & 3, 3 & 4, It looks Iffy ????

 

[Robert]

Measure the resistance of the opamp Pin 3 to ground and Pin 5 to ground.

Next measure the DC voltage on each of those pins as well.


If you're comfortable with desoldering components you could lift one end of R105 then measure VREF again.

Reconnect and do the same thing with R109. If VREF comes up to 4.5V in either case you might have to suspect that the opamp is damaged.

 

[fig]

Yeah, I'm not too enthused by the idea of randomly swapping parts... I can audio probe it, will get to it when I have a chance. I'll share my findings when done.

thanks for your help...

I think that’s wise. You’ll have it working in no time.

 

[EGRENIER]

Can you Test for Continuity between 1 & 2, 2 & 3, 3 & 4, It looks Iffy ????

Got continuity on all points.

Measure the resistance of the opamp Pin 3 to ground and Pin 5 to ground.

Pin 3: 17.8 K
Pin 5: 36.08 K

Next measure the DC voltage on each of those pins as well.

pin3: 3.36v
pin5: 0.993v

Will now work on measuring VREF with R105 and R109 removed... more to come.

 

[EGRENIER]

If you're comfortable with desoldering components you could lift one end of R105 then measure VREF again.

Reconnect and do the same thing with R109. If VREF comes up to 4.5V in either case you might have to suspect that the opamp is damaged.

OK progres... with R105 removed, VREF remained at 3.36, however with R109 removed, VREF went up to 4.5V ...

I tested R109 and it read a near perfect 10K (9.96)...
Now what that means ? OPamp busted ?

Edit: Now that's going to be a b1tch to replace... I do have JRC4558 tho.. any good trick to remove a soldered IC ? I normally socket mine...

I'm thinking to sacrifice it and chop the leg off and slowly remove one leg at the time but that's if I can reach in with the cutter

 

[music6000]

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.

View attachment 29152
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.

View attachment 29154
View attachment 29155
View attachment 29156
View attachment 29157

Through visual inspection I noticed that the 100u (C17) cap was blown and for good measure also replaced the 47u (C16) cap.
View attachment 29158

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

View attachment 29160

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 ?

You should be getting around 4.5v on all IC pins except pin 4. - 0v & pin 8. - 9.06v , so something is definitely amiss!

 

[EGRENIER]

You should be getting around 4.5v on all IC pins except pin 4. - 0v & pin 8. - 9.06v , so something is definitely amiss!

Yeah, figure that... VREF should read 4.5V off the power divider, but I was getting a reading of 3.36 at R132 and R133... so something is sucking up power on the VREF rail..

Seem with the latest test @PedalPCB suggested that the JRC4558 is busted... just waiting confirmation that the fact that lifting R109 getting me 4.5V back on R132 and R133 is a sign that the OpAmp is the guilty component...

 

[music6000]

Yeah, figure that... VREF should read 4.5V off the power divider, but I was getting a reading of 3.36 at R132 and R133... so something is sucking up power on the VREF rail..

Seem with the latest test @PedalPCB suggested that the JRC4558 is busted... just waiting confirmation that the fact that lifting R109 getting me 4.5V back on R132 and R133 is a sign that the OpAmp is the guilty component...

I think you have the less desirable Toshiba 75558 chip!

 

[EGRENIER]

I think you have the less desirable Toshiba 7555 chip!

Yep, just checked and it is a A75558P, but that should be a direct replacement for a JRC4558 right ?

Repairs may actually make it sound better Mojo tone !

 

[Robert]

I'm not sure if you mentioned that you had already replaced C105 and C106...

If you have replaced them you can suspect the opamp is bad.

If not....
Reinstall both resistors if either are still desoldered.

Now repeat those tests, this time with R108 and C105.

If VREF doesn't measure around 4.5V with either of those desoldered it's time to replace the opamp.

The easiest way to avoid damage to the PCB is to clip all 8 pins as close to the IC as possible, then desolder each pin from the PCB.

 

[Robert]

Instead of lifting R108 you can try measuring VREF with the Tone pot at minimum, and again at maximum.

If you see no significant difference in the measurement move on to C105.

 

[EGRENIER]

I'm not sure if you mentioned that you had already replaced C105 and C106...

If you have replaced them you can suspect the opamp is bad.

If not....
Reinstall both resistors if either are still desoldered.

Now repeat those tests, this time with R108 and C105.

If VREF doesn't measure around 4.5V with either of those desoldered it's time to replace the opamp.

The easiest way to avoid damage to the PCB is to clip all 8 pins as close to the IC as possible, then desolder each pin from the PCB.

C105 and C106 are the last 2 polarized cap I didn't replaced. I don't have tantalum of .22uf value, so I was asking if I could replace them with non-polarized... can I ?

So I'll disconnect R108 and C105 and measure VREF. If that doesn't get me to 4.5V, am I right to assum C105 is my next replacement ? Re-enforcing me wondering if it can be replaced with a box film non-polarized ?

 

[Robert]

If neither of those tests give you 4.5V you should replace the opamp.

If removing C105 gives you 4.5V VREF then replace C105.
If removing R108 gives you 4.5V VREF then replace C106. You can, of course, remove C106 instead of R108, but I thought the resistor might be easier.

 

[EGRENIER]

Instead of lifting R108 you can try measuring VREF with the Tone pot at minimum, and again at maximum.

If you see no significant difference in the measurement move on to C105.

If neither of those tests give you 4.5V you should replace the opamp.

If removing C105 gives you 4.5V VREF then replace C105.
If removing R108 gives you 4.5V VREF then replace C106. You can, of course, remove C106 instead of R108, but I thought the resistor might be easier.

Oh I didn't get it the right way... so the test is:

Remove R108 and test Vref, if I don't get 4.5V then reconnect R108 and disconnect C105 to test VREF.

For the record, I'm measuring VREF at the junction of R132 and R133, I assume this is correct.

 

[Robert]

Yep, that's correct.

 

[EGRENIER]

If neither of those tests give you 4.5V you should replace the opamp.

If removing C105 gives you 4.5V VREF then replace C105.
If removing R108 gives you 4.5V VREF then replace C106. You can, of course, remove C106 instead of R108, but I thought the resistor might be easier.

Oh well... Removed R108, no impact on VREF still reads 3.36V
Remove C105, same thing.. .so OpAmp it is...

I think I may have damage C105 a bit in the process, spread the legs to much and crack a bit of the drop... is this a concern ?

And finally a JRC4558 would work right ? Every thing I read is that the circuit is always the same on TS9 but many similar chips were used.

 

[Robert]

Yep, JRC4558 is fine.

Do you have a meter than can measure capacitance? If so, check C105.

If not, I'd try it before I called it bad and tossed it.

To answer your question earlier, you can use a non-polarized cap there, yes.

 

[music6000]

Oh well... Removed R108, no impact on VREF still reads 3.36V
Remove C105, same thing.. .so OpAmp it is...

I think I may have damage C105 a bit in the process, spread the legs to much and crack a bit of the drop... is this a concern ?

And finally a JRC4558 would work right ? Every thing I read is that the circuit is always the same on TS9 but many similar chips were used.

Cut the 75558 pins individually & remove one at a time!

Socket the OpAmp!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[EGRENIER]

Yep, JRC4558 is fine.

Do you have a meter than can measure capacitance? If so, check C105.

If not, I'd try it before I called it bad and tossed it.

To answer your question earlier, you can use a non-polarized cap there, yes.

Yes, I have a tester for the cap. Actually brand new thanks @fig for the reco

So, I’ll swap the IC next, will socket it too

We’ll keep you all posted.

Thanks @PedalPCB, @music6000, @swyse, @benny_profane and of course @PJS …