Fried TS9

[Chunk3rs]

Hello all,

Being an engineering student, I've always been into building and fixing things myself, including my musical equipment.  I just never had any idea there was such a big community for DIY stuff!

Anyway, onto my predicament:

My buddy works at a pawn shop, and a guy brought in a "fried" Tube Screamer (TS9) and pawned it for almost nothing.  I'm a guitarist, and future engineer, so my buddy gives it to me in the hopes that I could make something of it.  Tried to plug it in to play with it and instantly could smell a burning smoky smell.  Unplug it and take it apart, and the damage is pretty obvious.  My issue is that I don't know what the piece is that was melted/cracked.  I pulled it off the board and have been looking at schematics for a while but just can't figure out what it is (I've been learning to read schematics as I go).  I thought the symbol underneath it on the board was the symbol for a diode, but it doesn't look like a diode to me.  I've outlined where the piece was located on the board in the picture.



My electronics knowledge is very basic (the most advanced I've done is wiring harnesses on motorcycles).  So, what is that, and what should I replace it with?  I've been reading a little bit around here while I waited for my account to be verified, but couldn't find anything that seemed similar.  I could instantly tell that this was a hobby that I'd be very interested in, so hopefully I'll take in a ton of knowledge about DIY stomp boxes, and maybe even get a few builds in myself this winter.

Thanks,
-Matt

[Meanderthal]

 That's a diode, used to protect against reverse polarity. 1N4001 most likely.

However, if what I think happened... happened, then you will also need to replace every polarized cap(electrolytics) and the opamp, probably the buffer trannys too.

[Chunk3rs]

I assume he used the wrong power supply for the pedal.  Is there an easy way to check if I need to replace anything other than that diode?

[Meanderthal]

 Yep. Replace the diode and give it a shot. You can build an audio probe and listen to every component the audio goes thru  starting with the input also, but that won't help with the FET switch, which will either still work, or... not.

Caps are hard to test beyond continuity, and in general, that opamp usually gets replaced with a 4558d as a very common mod anyway.

[Chunk3rs]

Thanks for the help!

I guess I'll start with the diode and see what happens from there.

[Meanderthal]

 Have fun with 'er!

[drewl]

If the diode did it's job, then it fried and opened  preventing the reverse polarity DC from killing any other components.
try it with a battery after replacing the diode. It should be okay.

[R.G.]

I have seen this several times.

A reverse polarity power supply often will not do that. What this is usually caused by is someone plugging in a 9VAC power supply. Some of the digital pedals use 9Vac power supplies - and lots of it - and the adapters have the same style plugs on them as the DC jack. Plug one of these into a pedal protected by a reverse-diode protector and it will first fry the diode, then go fry the rest of the semiconductors when the diode burns open.

I have designed a new generation of polarity protectors for the updated Visual Sound line that prevents this from happening, and specifically for this reason. We were getting complaints about the 1Spot power adapter frying pedals. When we investigated, in every case the person had a 9Vac power supply and had recently replugged up the pedalboard. We also tried to fry pedals with the 1Spot, and never could. But they died immediately when the 9Vac was applied.

I mention all this only to set up saying: don't get discouraged if just replacing the diode doesn't fix it instantly. Be prepared to replace the opamp and perhaps a couple of other parts. It is completely practical and possible to fix it, so whip in a new diode and let us know what happens. If it needs more help , that's available.

[Chunk3rs]

Alrighty,

Put a new diode in (had an IN4005 lying around and I assume it will have an identical effect as the IN4002 it replaced), and she works now!

Should I assume that becuase it works, and sounds like any other distortion pedal, that nothing else is damaged?  I've never used a TS9 before, so I have nothing to compare the sound to.

Thanks again,
-Matt

[Meanderthal]

 Yeah, any 1N4xxx should do fine. I wouldn't say these sound just like any other distortion pedal(ya mighta scared a few folks with that), but it should give a 'mild' distortion...  Looks like you lucked out! I was afraid of the scenario that R.G. described... but it would still have been worth the trouble.

Lots of cool mods for these if ya want to monkey with it some more. Use the search function, much to be found...

[Chunk3rs]

Well, I thought it was fixed.

Now it's making a beeping type noise (through the cab speaker) when I switch to/from distortion.  The noise only happens once per switch, and it happens exactly at the time of the switch.  It almost sounds like a dog barking, or something similar.

Guess I might end up replacing/modding this thing anyway.

-Matt

[R.G.]

Replace the polarized electrolytic caps, all of them. They're the next most likely to be dead.

[Chunk3rs]

Those are next on the list, as well as upgrading the opamp.  Hopefully I can find the time to do this soon, but finals week approaches rapidly and my free time is pretty much nonexistant. 

[Chunk3rs]

It looks like I'll have a little free time this weekend, so I'm going shopping for the parts I need.

Looking at http://www.harpamps.com/schematics/ that hyperlink, I can find 5 polarized electrolytic capacitors:  2 .22 (uf?), 1 10uf, 1 47uf, 1 100uf.  Does that coincide with the schematic?

Also I'll be getting a new opamp (4558d) if they have it available.

I'm new to schematics, so thanks for all the help.
-Matt

[petemoore]

  Opamp working is a good sign of working opamp.
  No way to get 'before' voltage bias readings now...lol.
  Probably biases fine, amps fine, and is low noise fine, ie not damaged.
  The pedal's been through a lot lately.
  Glad you've got it working again, 'RP'd' caps might start making noise or acting up sometime, of course they can also sometimes re-form with use, ~9Vac is surely a test they are not designed to pass.
 

[vanhansen]

You got it, Matt.  The .22uf caps are actual tantalum caps which are also polarized like electrolytics.  So you need two .22uf tantalum caps and the rest are your regular run of the mill electrolytics.  Since you are getting signal, the opamp is working but it doesn't hurt to have an extra on hand.  Get a socket for it too.  Makes it a lot easier to change.

[PerroGrande]

Contrary to popular opinion, Electrolytic capacitors are not the worst thing on the face of the planet... Tantalum capacitors are.

If it were my pedal, I'd replace the tantalum capacitors with electrolytic capacitors.  Your mileage may vary, but I've had *far* better performance and reliability from electrolytic capacitors than their evil tantalum cousins.  That isn't saying much for tantalum, since I'll be the first to admit that electrolytics are failure prone compared to other alternatives.  However, since you probably don't want a capacitor the size of a small asteroid in your pedal, one of the polarized options is about the only choice when you need that much capacitance. 

[R.G.]

Actually, you can get quite small film caps up to 2.2uF these days.

[Chunk3rs]

Looking directly into the pedal, where the scematic says .22uf tant, there are 1uf caps with (NP) stamped on the board (non polarized?).  They look identical to the rest of the electrolytic caps on the board.

I guess I'm going to replace them with what is identically on the board, even though I can't find a schematic that uses these in this spot.

Thanks so much for the help everyone,
-Matt

[PerroGrande]

Ya know... I saw 22 and uF and completely ignored the leading decimal point...   

Sure -- for 0.22uF a film cap would work quite nicely and wouldn't take up the amount of space I previous indicated...