Lite IIb noise issue

[sandspur8088]

Greetings! This is my first post on this site. I have a lite IIB I built between 12-15 years ago. It was a Baby Will I built from a scratch build with VVR. Truthfully it was the first amp I built, and I have built a few others since that first one.

Currently it has an issue with noise ONLY when changing the volume/tone knobs on the guitar. This noise is similar to having a dirty pot on the guitar, but this doesn't occur with any other amp I own. This noise occurs with every guitar I put in front of the amp and there is no noise when turning any of the 3 knobs on the amp itself. I haven't cracked open the amp itself yet, but thought I'd ask a question about what to search for when I do open up the amp. Is there something specifically in the input section I should look for? Or would this issue lie elsewhere?

I'm about to re-house this amp into a smaller chassis. When I originally built it, I had it in a 1928 Philco radio and needed a larger chassis so I wouldn't butcher the old radio internally. With this being the case, I figured now is as good a time as any to open her up and rectify the problem. Thank you for your time and any assistance given is appreciated.

[chaliapin]

Does it happen when the vvr up full?

[Daviedawg]

Welcome.
It sounds very much like you have some probably small DC on one or more pots. Easy to check with your meter looking for DC where it should not be. If so it means a failed or failing cap(s) in the signal route.

Dd

[sandspur8088]

Does it happen when the vvr up full?

I'll check this today, thank you.

[sandspur8088]

Welcome.
It sounds very much like you have some probably small DC on one or more pots. Easy to check with your meter looking for DC where it should not be. If so it means a failed or failing cap(s) in the signal route.

Dd

Daviedawg,

Thank you - I will look into this as well.

[sandspur8088]

Does it happen when the vvr up full?

Yes, it still happens. Sorry for the delay but I had some things come up over the weekend.

[JMPGuitars]

Have you tried a different guitar? Have you verified the input wiring/grounding is correct?

[chaliapin]

Does it happen with a pedal on front of the amp? Total beginner here but I have vvr on the whole amp, not just pi and pa and was advised a small cap to block dc on the guitar input and 1M to ground at the grid after the cap.

[sandspur8088]

Have you tried a different guitar? Have you verified the input wiring/grounding is correct?

Yes, as I mentioned in my original post - it happens with every guitar I put in front of it. These same guitars do not have issues with any other amps I own using the same cables. This is not a guitar issue.
This amp worked well for quite awhile (over 10 years). This is not a new amp. I believe this amp started acting up around 2 years ago and I just put it on a shelf and used others that I own.
My guess is that a component has gone bad or out of spec and my question was if anyone had a similar experience previously that could lead me in the right direction when I cracked the amp open.

[sandspur8088]

Does it happen with a pedal on front of the amp? Total beginner here but I have vvr on the whole amp, not just pi and pa and was advised a small cap to block dc on the guitar input and 1M to ground at the grid after the cap.

That's an interesting thought and I'll check. This amp worked well for 10 years or more. Thank you for the suggestion. I'll be cracking it open this week and something may stand out.

[JMPGuitars]

lol, guess I missed that "every guitar" sentence.

Try a different input tube and see if that makes a difference. You may also want to take voltage while you have the amp open.

[sandspur8088]

lol, guess I missed that "every guitar" sentence.

Try a different input tube and see if that makes a difference. You may also want to take voltage while you have the amp open.

I appreciate your responses for certain. I have swapped both pre and power tubes with no change and have tried both inputs. I believe they are cascaded in any case. I don't think there is any way around opening the amp and testing components at this point.

[JMPGuitars]

Ah, so it's not a standard Lite IIb then? Definitely time to open it up and see what's going on. Carefully.

[sandspur8088]

Ah, so it's not a standard Lite IIb then? Definitely time to open it up and see what's going on. Carefully.

It was a Baby Will version of the LiteIIB on pcb I built between 12-15 years ago. I've built several amps since then, just haven't ever had a need to crack this one back open again. I'll take the standard precautions.

[JMPGuitars]

If it's a standard baby will, then it's parallel not cascaded. Make sure the PCB isn't leaking DC either.

[sandspur8088]

If it's a standard baby will, then it's parallel not cascaded. Make sure the PCB isn't leaking DC either.

You're probably right, I just don't remember how I wired it - it was a long time ago and there were options for both I thought. I will check the pcb as well.