Fender stage 160 blowing fuses

[Resorb]

Hi I am a hobbiest at electronics, I know enough to troubleshoot most minor problems but I have ran into a problem I can't seem to track down. I need help so anyone familiar with guitar amp repairs I would really appreciate some help. So here is a link to my amp

https://www.google.com/url?sa=t&sou...AQFjAC&usg=AFQjCNGQ6cCxuT1XLGULEnus3axV8HowUA

I received this amp with a large hum found the high voltage side filter caps were loose I resoldered and it played beautifully for about an hour then pop. I have replaced the transitors 10-13 and also the darlington transitors 15-19 15 and 14 were shorted so I replaced them all, also the filter caps on the high end........ The transistor shows the right voltage when I tested it. Here's what's happening. If I plug it directly into the wall it blows the 4amp fuse, I built a poor man's voltage limiter with a light bulb, when I run it through that the 300 Watt light lights up but I am able to play guitar through the amp with a loud 60hz hum. If I unplug the two red wires for the circuit (hi voltage end) the amp does not hum or pop fuse. Any help anyone could be I'd really appreciate it! Thanksfor your time

 

[tunedwolf]

Check diode bridge D54-57 and filter Capacitors C86-87 and work your way around the supply rails, same for the low voltage regulated supplies beginning with diode bridge D48-51, C82-8. All supplies should be clean and pretty much ripple free. A quick google will find you the schematic to follow. I doubt your trouble is in the low voltage regulated supplies, but check them anyway just in case it's a bridge failure, popping the 4A fuse takes a bit of effort, so I suspect your trouble lies within the main amp stages. Also watch out what transistors you fit, I have been caught out in the past with non matched second sourced devices causing imbalance and high frequency oscillation in the output stages of these types of amp. It leads to fast heat up, distortion and if not caught quickly, it's goodbye output stages, drivers and just about anything active along with their emitter resistors. Good luck

 

[Resorb]

I ordered new diodes for both bridges, the diodes on the larger side were measuring odd.... They would show voltage then cut off, pulsed I guess?

 

[cowboybob]

... So here is a link to my amp

https://www.google.com/url?sa=t&sou...AQFjAC&usg=AFQjCNGQ6cCxuT1XLGULEnus3axV8HowUA ...

Getting this error:
"The previous page is sending you to an invalid url.

If you do not want to visit that page, you can return to the previous page."

when accessing that URL.

 

[KeepItSimpleStupid]

yea there is a "..." in the middle of it. You need to do a "copy link location"

 

[cowboybob]

KISS, may be (no doubt for sure ) showing my ignorance here, but "copy link location" (right mouse click option) and then do what?

 

[KeepItSimpleStupid]

the OP has to use "copy link location" and "paste", not you.

 

[cowboybob]

Thanks, KISS. Thought so, but you know how it is; sometimes I lose track of what I DO know... .

tunedwolf responded is such a way that I thought he had access to the schematic, which I assumed (that word again) meant he successfully used the link.

 

[KeepItSimpleStupid]

CBB:

I did my magic and here the working link: https://www.google.com/url?sa=t&sou...AQFjAC&usg=AFQjCNGQ6cCxuT1XLGULEnus3axV8HowUA

 

[tunedwolf]

CBB, as it happened I already had the schematic in my library, so I just had a quick peek at it before responding, but I also googled it at the time to make sure it was still available on the net. I didn't use the link as posted, as it was obviously malformed