Aargh!! Toasted a great old stompbox with reverse polarity

[JimR]

Why do power supplies for network routers have the same plug but 12 V + on the center pin?? 

(Or - why am I that stupid for not checking the voltage and polarity)... 

I just bought a great sounding Ibanez Super Tube STL from the mid 80's. It has (had!) that 'exactly right' Tube Screamer SRV sound.

Now it's completely dead and I'm not sure where to look. Does any of you know which parts burn when it recieves reverse polarity?

thanks

JimR
Denmark

[composition4]

Probably a 1n400x diode in there (smallish black cylinder, silver band) for polarity protection - would start with that

Jonathan

[frokost]

http://www.diystompboxes.com/smfforum/index.php?topic=55003.0

[JimR]

thank you both, off course there was an R.G. document about it... 

JimR

[petemoore]

Now it's completely dead and I'm not sure where to look. Does any of you know which parts burn when it recieves reverse polarity?
  Only the polarized ones, hopefully the diode did it's job, RP has been known to get around the protection diode.

[petemoore]

(Or - why am I that stupid for not checking the voltage and polarity)...
  Not really, everything else is dummy proof.
  Someone recently commented that PS misuse is the #1 cause for pedal returns where he works.
  Why do power supplies for network routers have the same plug but 12 V + on the center pin?? 
  Because it was left to become that way by] 'us'.
  It just kind of came to pass somehow that the issue was never properly adressed [imo, it could have been].
   It's about the 1 other wire left that you have to check, it can be very hard to read the transformer text, very easy to get wrong.
   Another one to not try is plugging the amplifier output to the input, of the amplifier [same amp or even another amp]. Less common but still happens.
  Other than that, power and other cables and connectors of all other types seem to have been assigned configurations to tasks, one won't fit in the other, they can't cause a miswire with normal use. 

[slideman82]

I'm sick of that "japanese polarity" system!!!!!! WTF!!!!!!! Negative in the plug's center? c'mon!!!!!!! What about using metallic chassis mounting jacks? You have to reverse polarity, or isolate it, but it's not quite simple! Why Boss, Ibanez and the others didn't use that?

Oh, now I see, while I was answering this... battery desconection works with the ring, I think.

[JimR]

Probably a 1n400x diode in there (smallish black cylinder, silver band) for polarity protection - would start with that

Jonathan

Hmm, I checked the diode and it was alright (took it out and it was about 0,6 volts), changed it anyway.

I changed the Electrolytic caps too but it still doesn't work.

Now I'm about to get these components if I can find them. Anyone know what they are?

TR1-TR4: C2458
www.radmer.dk/web/k118.jpg

Q1 and Q2: K118
www.radmer.dk/web/c2458.jpg

And if all fails, the JRC chips
www.radmer.dk/web/stl.jpg

thanks

JimR

[slacker]

Reversing the power supply won't kill transistors, so they should be fine. The op amps might have died but only if the reverse polarity protection diode didn't do its job.

If you've got a meter try running it off a battery and measure the voltages before and after the polarity protection diode and on the pins of the op amps and post them. The might point to what's gone wrong.

[JimR]

Haleluja, found the last error and now it's working great SRV Mojo again 

The power plug had torn a fine crack in the copper layer on the PCB, leaving the external power unconnected while the battery connection was working.

It took me a while with a multimeter and a lot of head scratching.

Thanks again for all the help.

best regards

JimR