Crate GX130C Pop then hum

[FLDeathMetal]

Just got a Crate GX130C. Previous owner says he hadn't played it in years and the last time he did it didn't work. He plugs in his guitar and it works miraculously. I take it home, fiddle around with it for like 10 mins or so, then I hear a loud pop then a hum; no guitar sound at all. The volume knob doesn't increase the volume of the hum. This event can be replicated any time I turn the amp on. I wait a few hours, turn it on and play it for a few minutes and it pops and cuts out, but the lights and power stay on. I do not have another cab to test it with. Seems like an issue with overheating? I cleaned the internals of all dust and debris and all the solder joints looked fine. The only thing that looks off is the output transformer is either rusty or has some red dirt caked on it. Any tips would be greatly appreciated.

[Helmholtz]

Schematic?

[Enzo]

If it were overheating, you could feel the chassis getting hot. Also, the speaker is working, you hear the hum.

When it cuts out, ball up your fist and whack the top of the amp. Does that wake it up? Does the amp react in any way?

[Helmholtz]

What output transformer?

[FLDeathMetal]

Schematic?

pulled from the internet

[FLDeathMetal]

If it were overheating, you could feel the chassis getting hot. Also, the speaker is working, you hear the hum.

When it cuts out, ball up your fist and whack the top of the amp. Does that wake it up? Does the amp react in any way?

tried this a number of times to no success, whacked the top and sides just to see if anything happened. Still only has a hum

[g1]

Can you see the speaker? If it is pushed forward or back (and stays there) when the hum happens, turn off the amp immediately. That will be caused by DC on the output which will burn the speaker out pretty quick.

[The Dude]

^^^^^^ Yes, that. I'd first determine if the output is DC or AC.

[FLDeathMetal]

Well if this changes anything I plugged the amp into a different cab and had no issues, at least none within an hour straight of playing. Zero issues at all compared to the cab it came with. Still looking at a DC issue or could it be a cab specific issue?

[dbraun]

"output transformer is either rusty or has some red dirt caked on it."
This is what I found with my Crate ...generally a lot of oxidation on the enclosure. Any place where there are heat sinks bolted to the enclosure or ground connections bolted to the enclosure it is worth cleaning those bright/wire brush/light sanding and seeing if that helps.

[DrGonz78]

Yup it’s all about that output transformer.

[The Dude]

You mean the one that doesn't exist in this solid state amp?