Can anyone Identify this mod chip installed in a JCM2000?

[FleshOnGear]

My understanding of the board conductivity issue is that heat causes the board to become conductive over time, and once it happens it stays conductive regardless of current temperature. Maybe it gets worse while it’s hot?

All I really know is that the stable bias kit works. I installed one in my buddy’s TSL100 and it went from red plating to normal operation and has stayed that way.

 

[daddysouldonut]

My understanding of the board conductivity issue is that heat causes the board to become conductive over time, and once it happens it stays conductive regardless of current temperature. Maybe it gets worse while it’s hot?

All I really know is that the stable bias kit works. I installed one in my buddy’s TSL100 and it went from red plating to normal operation and has stayed that way.

I was curious about this myself, whether or not the conductivity is permanent once present, or if it only happens WHEN it's hot. Make of my tests what you will.

 

[daddysouldonut]

Alright this is the last I'll be posting about this barring some explosion or fire.
Using matched pairs on each side, I was not able to get their bias readings any closer than 10mv apart. So I went to my earlier idea of mixing the pairs, and run that way, their readings are identical or very close to one another. Seem to land around 67 with cooling. Without it, I've got them going to the mid 80s but it kind of settles there for good so I think I can put the heat issue out of my mind.

And it's probably the best sounding amp I've owned. Punchy as hell, and I'm a slap happy single coil guy so I'm really pleased. Cranking the crunch channel (1) and using it like a master volume amp is pretty great. Pedals into clean with the gain near maxed is also sounding great. Thanks to everyone for the suggestions and comments!

 

[daddysouldonut]

UPDATE for those who care:
Recently I took it over to a place where I could push the volume to it's limits and I've discovered a couple issues once it's really opened up, painful loud. Basically the low end turns to mush. Farty distortion sounds, Poor sustain, one specific note causes oscillation (looks like I'll be putting C46 back in!) basically a very glitchy low end. Lower the volume and everything is fine.

Now... We're talking volumes I probably won't get to that often. But I want it correct, ya know? Switched speaker cabs, wasn't that. I once experienced something similar and the speaker was a little loose in the cab.

I'm leaning toward a loose connection somewhere or filter caps. Maybe more toward loose connection because I can create a noise through the speaker when smacking the amp. I reached out to a local who claims to have serviced JCM2000s, but after all my thorough explanations of testing the bias and just looking for the caps to be tested/replaced, he eventually just recommended the same stable bias mod or replacement board as everyone else. Great. Ya know I don't even know where I would source replacement caps, the board may be the only option to get them! And labor above the $200 anyway 😅

Really hoping I find a loose connection I missed somewhere or that C46 has way more mojo than is credited.