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Repairing a Turbo Rat
Posted: Sun Dec 14, 2014 4:58 pm
by Obulus
I got a broken Turbo Rat for free ages ago and had it sitting with a friend all that time. Visited said friend last week and finally got the pedal back. I figured out it is a 1990 Turbo Rat with an LM308 chip so I guess that's a good thing. It had a broken input jack that I already replaced but the pedal is still way quiet (even when bypassed, my signal is a lot quieter). I saw somebody messed with it and added a resistor, anyone know what the mod was trying to achieve? Will removing it get the loudness back? Or did I mess something up replacing the input jack?
Obligatory gut shots:

Re: Repairing a Turbo Rat
Posted: Wed Dec 17, 2014 5:48 pm
by Bret608
Hmm, unless my eyes are playing tricks on me, it looks like they've got that resistor going across the emitter and collector pins of that transistor that's in the bottom left corner of the board (when you're looking at it from the top. Can you let me know the part number on that transistor (if visible), as well as what color the stripes are on that tacked-on resistor? My 41-year-old eyes think I'm seeing 2.2 meg ohms. I could take a look at the schem and see what's going on there.
Re: Repairing a Turbo Rat
Posted: Mon Dec 22, 2014 7:22 pm
by Obulus
Sorry for the late response, wasn't anywhere near the pedal these last couple of days!
Transistor is a 2n5458 and it is a 2.2meg pot indeed. Thanks for having a look!
Re: Repairing a Turbo Rat
Posted: Fri Jan 02, 2015 6:17 pm
by Bret608
Really sorry it took me so long to respond again! I've been out of town for the holidays.
The 2n5458 and 2.2 meg resistor are both on the known schematic for the Turbo Rat. Even though it looks tacked-on, I bet that resistor on the bottom of the board was installed at the factory. I think the problem may be with your jack replacement. It looks like you used bare wire for the ground connection between the in and out jacks. That may be bumping against something and robbing some of the signal. Sorry I don't have more knowledge to offer in this case!

Let me know how it works out.
Re: Repairing a Turbo Rat
Posted: Fri Jan 02, 2015 8:52 pm
by Obulus
Thanks! The bare wire was there when I got it, but it makes sense that it could be the problem. I'll hopefully have some time to look into it tomorrow and report back!
Re: Repairing a Turbo Rat
Posted: Sat Jan 03, 2015 6:40 pm
by Obulus
I messed around with the grounding wire and made sure nothing was touching where it shouldn't, now it works! This means I'm retarded though, since the solution was that simple
