Metropoulos Forum

So for a while now, everytime I would hit a note, or a chord, it would start crackling and popping, and wouldn't stop after I had stopped playing, this had happened once before, but it was just a weak solder joint that had come loose, so I had fixed it. This crackling noise only occured when the amp was on higher then two.

Then it came back again, checked that solder joint, it was intact.

So today, I decided to really investigate it. I warmed up the amp, plugged it in, same results. Then I put pressure on the top of the chassis near the inputs with my hand, and the crackling noise started up.

Almost any motion of the chassis resulted in the loud, crackling noise.

I took out the main board, and the wire that goes from the diodes on the rectifier board, to the 150k resistor on the main board, was barely soldered in. I'm not sure if that could have been it or not. I imagine it wasn't, because that wire has never been touched since I finished the amp.

With the Ceriatone chassis, and using BrianH's boards, the rectifier board hangs a bit over the power tube sockets. I took it out, and I noticed that on the 1k5 resistors, on the inner two tube sockets, the covering of the resistors had somehow come off in spots. Revealing some metal.

I've checked all solder joints, they are all solid, and don't have anything they could be coming into contact with. I don't have access to a camera right now, but I'll see what I can do.

I believe that the rectifier board chaffed off some of the covering. Could this cause that crackling noise?

The sound you describe is a 'dry joint' somewhere in the preamp section. When cold the joint is ok but when it expands the quality of metal-metal contact is poor and the crackles ensue.

Depending on how you have soldered the board (are the wires fed into the underneath of the turrets or did you use the feed through the board holes and round the posts like the '69 on amps(best method for relative beginners )?

I make my under board connections with an iron with a slight scoop in the end to heat the bottom of the turret and feed solder in from below, to be sure to get a solid joint, on the green grid wires I loop these through the board like the originals.

Could also be a dodgy joint on the input jacks or a preamp socket. The area with the grid resistors is not necessarily good but is unlikely to be this particular issue, you should replace them and maybe cover with shrink wrap if they are going to rub on the board.

Best way to find out other than careful inspection for unfilled joints or matt coloured solder which should be bright and shiny is to run the amp for a while with it upside down until fully warm and use an insulated 'chopstick) to methodically go through the amp wriggling each wire and connection until you track it down.

Of course this has never ever happened to me before which is not why I know how to trouble shoot it

Alright, got my resistors from Valvestorm, I'll redo all the connections on the inputs and the preamp as well. My build deserves some cleaning up anyways.

And once its all patched together, a friend of mine is bringing some NOS 12ax7s over to experiment with.

And yea, I went under the board on most of the connections.

This build was very interesting. Had to do quite a bit of improvisation.

Can't wait to start my 69 build. That thing is going to be perfect.

???

Got it all fixed up. Its working great now. When I first started playing this amp, I felt like it didn't have enough distortion, but now the amp has just the right amount.