Is my lm308 bad? Rat problems

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Is my lm308 bad? Rat problems

Sensei Tim
So I'm building a rat and I'm gettingnjo sound from it at all.

I probed the audio signal and it's all good where it enters pin 3 on the input, but I get no signal on pin 6

Voltages
1 8.46v
2 0.62
3 1.207
4 0
5 0
6 0.486
7 8.97
8 0.2 but this seems to be moving all over the place  (due to the capacitor connecting pins 1 and 8?)

Is my lm308 shot?

I've run a scraper between all the solder joints and I can't find a short. Reflowed all the joints. Checked continuity on the socket pins...


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Re: Is my lm308 bad? Rat problems

Emil
Your voltages for pin 2, 3, 6 and 8 are all too low. The others look fine. Post a picture of your board, there might be some other faults I suspect.
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Re: Is my lm308 bad? Rat problems

Sensei Tim




based on this pcb/layout



the project is a generic layout to make all of the rat variants. R12 and R14 are not in the original rat
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Re: Is my lm308 bad? Rat problems

Sensei Tim
i rebuilt this last night using the vero layout here and same results - no audio passing.

I really think this is the IC that's fried.
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Re: Is my lm308 bad? Rat problems

Emil
Alright. Try putting another opamp in your builds to make sure (I think TL071 or similar should work with compensation cap removed?). I could'nt find any obvious mistakes on your board either.
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Re: Is my lm308 bad? Rat problems

Sensei Tim
Turns out everything was fine on the board, but the Distortion pot was bad!

Now have a functioning rat :)
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