Fender amp problems

[Vincent Volta]

Hi all,
Lately Ive been having trouble with a Fender amp. Its a Princeton 65 with reverb, solid state. Its a cheap Mexican model, 1x12 combo and the 65 I guess means the RMS power - no specs handy.
When you drive the amp hard enough to be heard over a drum kit, the signal goes completely off and all you hear is a loud 50hz hum... a tough hit brings the signal back but not for long since another loud chord will spoil it again.
This has been happening for a year or so now, intermitently, it just got worse lately. My bassist is into electronics too and he suggested that the power supply filter caps might be the culprits- I peeped inside myself one day and noticed these are relatively small, 2200uf instead of 4700 or so.
I did notice that everything else looked fine and dead on, and the pwr amp is driven by two transistors in a wide plastic case. Had no time to check these devices or even write the numbers!
As for now I will change the filters- in a few hours when I finish work- but I wanted to share this here to see if someone has any clues. We are pretty much left on our own when we cover the subject of amp servicing here but I know for sure some of you know better than me! Thanx a lot for your patience and help.
P.D. Why are Fender solid state amps so crappy? Havent found a decently working one in ten years or more....

[cd]

Post your problem here, not in Stompbox forum, you'll get a better response:

www.ampage.org

[Paul Marossy]

It almost sounds like the transistors are going into cutoff mode or something...

[Ripper]

If a strong hit brings it back for a bit, you probably have a ground problem.   I just finished fixing a deluxe 90 with a similar problem.  It was a couple of solder joints that had gone cold and developed a "crack".  The humming is usually a good sign for a ground to.  Try resoldering any connection that looks cold and see if that fixes it.

[ninoman123]

How did this get back to the top of the board? Says the last post was in March and now its at the top...weird...

Edit: Just checked out the date on my post....says Feb!! Thats weird....

Double edit: Woah all the dates are off...never noticed it before!!!!! Ahhhh Im freaking out!

[JimRayden]

Lol, yea I've been mixing up the posting dates and the member joining dates too.


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Jimbo