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wsg1985Member
Thanks, but I think I’ve solved it. Looks like it was a bad ground on the input jack.
I need to properly test it when I find some time, but hopefully another vintage pedal has been saved from the scrap heap.
wsg1985MemberI’ve built myself an audio probe and I have output at the SAD1024, but when I tweek VR2 to get a output it is very distorted.
I’ve checked the output (Pin 1) of LM4558 and the distortion (almost fuzz tone) occurs here as well.
Any ideas on what the cause could be? Any other places I could probe? there is some noticeable noise at the input jack, could the Op amp just be boosting this signal during the gain stage?
Edit: I’ve just checked it at pin 7 and the distortion is there aswell, I’ve changed the LM4558 and it hasn’t made any difference.
wsg1985MemberI’ve replaced the 4558, as I was getting some bad readings on the original. Things are looking better but I’m still not getting any effect. Below are the new voltages.
LM741
1 0.2 mv
2 6.54 v
3 6.54 mv
4 0 mv
5 1.2 mv
6 8.91 v
7 17.47 v
8 0.9 mv4558
1 6.21 v
2 6.22 v
3 6.16 v
4 0 mv
5 6.161 v
6 6.22 mv
7 6.22 v
8 12.79 mvLM399
1 8.6 v
2 0-5.7 v
3 12.79 v
4 6.54 v
5 6.54 v
6 4.81 v
7 9.2 v
8 89.7 mv
9 7.47 v
10 0-5.9 v
11 431.2 mv
12 0 mv
13 13.8 mv
14 4.809 v4013BE
1 6.27 v
2 6.68 v
3 0
4 3.86 v
5 0
6 14.6 mv
7 0
8 0
9 6.42 v
10 0
11 5.25 v
12 6.42 v
13 6.38 v
14 12.79 vSAD1024 (Removed)
1 0
2 4.072 v
3 6.39 v
4 0
5 12.79 v
6 0
7 12.79 v
8 6.42 v
9 12.79 v
10 6.42 v
11 12.79 v
12 0
13 0
14 6.39 v
15 4.072 v
16 0Any assistance would be much appreciated. Starting to think the SAD1024 might be bad though.
wsg1985MemberThanks, I’ve already been using that website (and a few other forum posts). I’ve just not heard of anyone encounterung my specific issue (the distorted tone volume boost).
Ive just replaced the Lm741, so I’ll retest the voltages and see how I’m are fairing after that.
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