Music Man HD 212

[Steve L]

I can only think of one more thing to look at.
I have seen many amps where people have spilled drinks on them. A lot of times the drink will get inside the amp. The alcohol evaporates, but the sugar and whatever else was in there will be left behind and cause problems for a long time.
Sometimes you can easily see the residue and sometimes you can't. Try cleaning the board, chassis and especially the tube sockets with a good solvent and see if the noise goes away.
If not, I am out of suggestions.

Steve

[lowell]

thank you guys. I will clean that stuff and then ask the owner if they want new wiring on the power tube sockets and new sockets. After that there's nothing left!

[lowell]

Does it still crackle with the power tubes removed? (sounds crazy, but humour me!)

Have you tried replacing the power tube sockets? It's looking like carbon tracking on your sockets.

Steve, no it doesn't still do it w/o power tubes. I've replaced all the sockets and wiring for the power tubes, still there. I did not say before that there is audible hum when the static is there and they both seem to go up and down in volume together, they must be of the same source. Maybe hum tips someone off on what this is? I'm bout to remove the board and clean it, am not looking forward to it though.

[lowell]

ok so I disconnected the screens on 1 pair of power tubes and the crackle/static is GONE. I'm wondering if one side of the OT is arcing. Gonna try new tubes again, just to be sure, then will cut the primary for those 2 tubes shorter, and solder in a new wire to see if the wire is the issue. I never decided to clean the board because I lifted a bunch of connections, most of them, off the board so they're floating and it didn't fix the issue.

[lowell]

The orange primary wire to those 2 tubes has some gunk on it that is also on the chassis, I pulled it up away from the chassis and problem's still there. I'm thinking the OT is the issue here. Any thoughts? I think the screen being disconnected from that side says something about this. The source is not from the board or components on the board but after that.

[lowell]

Any had an OT cause static like this?

[Mac Guy]

Music Man HD 212

FWIW...I had a similar problem for about 2 years with a Fender amp...turned out that a complete re-tube cleared it. It was, in my case, the last of the 4 power tubes I changed out. I went through the entire amp one tube at a time and finally found it.

Good luck.

MG

[lowell]

New OT still static

still there w/ sub OT... wow, I'm at a loss.

PI coupling caps are disconnected, bias supply has new components and is floating off the fiberboard as to eliminate any possible issue w/ the board, new wiring on all tube sockets including grid wires etc. Screen supply wire is still the same but I'm not seeing the static on the screen supply. It's ONLY on the grids and plates.

[lowell]

actually now i see it on screen supply. I'll replace those wires and then possibly try a sub choke.

[lowell]

wait a minute... i just found that someone had previously wired the supplies wrong. The screens were coming off the initial side of the choke, instead of after, and the preamp supply was at the wrong node too. Wow, should've caught this long ago, but as it is wrong to do, I assumed the amp was wired correctly when it came in. Anywho I rewired it and wasn't getting any static but not sure if I fixed it yet. I'm gonna let it cool down over night and try it in the morning.

[lowell]

Ok, DAMNED static still there after all this bull@#$%. Anyone know what this little xmas tree lightbulb thingy is going from the ground switch to the fuse? Does it light up when the fuse blows or something?

[lowell]

so I was sitting there trying to get this amp to act up as much as possible by cycling the power switch on and off. I realized that the static did not come back when I did this, however a bad hum DID, and it would last about 5 seconds and go away. I thought this odd so I subbed a power switch in and all seems fine. I've let the amp cool down 3 times now and powered it up w/ no problem. I ordered the correct switch in hopes that it fixes it.

[Enzo]

While you wait, try this. Drool some Deoxit into the switch and flip it back and forth a few times. Any help?

And if you plan to replace the switch, then for now, just wire it together - short across the old switch. The amp can be without an off switch. Reassemble everything and test the amp thoroughly. That way you will know you are installing your new switch into an amp that is otherwise 100%.

[lowell]

good call. I pretty much have it rigged like that now and after 3 cool downs/restarts it's great. I'll try spraying the wash in there.

[lowell]

new switch is in and static still there. I'm quite bummed at this point. Could a power transformer cause this? My thoughts are that anything could cause this, just don't wanna swap in a PT for nothing. Anyone have any ideas on scoping this issue further? I'm not too good w/ a scope when it comes to troubleshooting power supply issues.