SOLVED Magnetron unity gain issue

[Coop]

Fighting a strange issue with my latest build.

I am getting some odd noise and switch popping at unity gain.
I have been playing with the trim pot for a solid 30 minutes. I have found 2 points that sound great, no extra noise or switch popping. One is above and the other is below unity....So too loud or too quiet. I can't get it just right without loud switch popping or it sounding like a droid from SW depending on where the level knob is set.

The above and below unity points work great.

Any thoughts on where to start?

 

[BuddytheReow]

Pictures would be good for starters

 

[Coop]

I just find it odd that I can get it sounding and working perfectly with no popping at 2 points. Too loud or too quiet. Absolutely love it so far so I really hope I can get it sorted...Ignore the burning on the io board...I reused that one and had a hell of a time desoldering. I still need to clean this one up

 

[HamishR]

I'd take a look at the trim pot. Why is there a little blob of silver coming out from under it?

 

[Coop]

I will take a look but the lead/pad is right at the edge so that is what you are seeing there. I can try replacing it. Looks fine from the other side. I just went through all resistor values and everything looks good there.

 

[Coop]

C6 was wrong and replaced but did not fix my issue. Delay works great. I just get the popping and a bit of noise in the middle of the trim pot. Both ends (Quiet and loud) seem fine. Will dig around for a replacement

 

[Coop]

Replaced the opa2134 I purchased from Tayda with a 4558 and it works like a dream. No issues at all....Nothing like wasting a few hours expecting you made a mistake...

 

[MichaelW]

Replaced the opa2134 I purchased from Tayda with a 4558 and it works like a dream. No issues at all....Nothing like wasting a few hours expecting you made a mistake...

Man, I was about to order some OPA2134's from Tayda because they're the only ones that have them in stock. (That in and of itself is probably a little suspicious.) They've been out of stock everywhere else including from TI directly. I've been subbing NE5532's in my builds that have called for OPA2134's. So far so good.....

 

[szukalski]

I got some OPA2134s from ebay along with some ICL7660SCPAZ and RC4559D. The 7660s were not great (high pitched squeal in some pedals), but the OPA2134s and 4559Ds were good. YMMV.

 

[Diynot]

A borked $7 chip, that ain’t cool. I have one on it’s way from Tayda. I guess fingers crossed.

 

[Coop]

Man, I was about to order some OPA2134's from Tayda because they're the only ones that have them in stock. (That in and of itself is probably a little suspicious.) They've been out of stock everywhere else including from TI directly. I've been subbing NE5532's in my builds that have called for OPA2134's. So far so good.....

I probably would have went with the NE5532 if I had some on hand. I have a pile of 4558s and it did the trick.. It is socketed so I can easily swap it out.

A borked $7 chip, that ain’t cool. I have one on it’s way from Tayda. I guess fingers crossed.

I hope it works out. I could have just had bad luck on this one.

 

[fig]

Man, I was about to order some OPA2134's from Tayda because they're the only ones that have them in stock. (That in and of itself is probably a little suspicious.) They've been out of stock everywhere else including from TI directly. I've been subbing NE5532's in my builds that have called for OPA2134's. So far so good.....

Deja Vu

fyi: The SMT version is also purty scarce.

 

[BuddytheReow]

A borked $7 chip, that ain’t cool. I have one on it’s way from Tayda. I guess fingers crossed.

Let me know how your Tayda ones go. I have a handful in my inventory from them I haven’t used yet

 

[Diynot]

Let me know how your Tayda ones go. I have a handful in my inventory from them I haven’t used yet

Thanks BTR.