randall rg100es from1988 wont power up

[cjcarson]

if anyone can help would be realy happy to get this amp runnin again. used with a four ohm cabinet when i bought it .was told this makes it work hard as the outputs are for 8ohm. for years the signal would get weak and fade out. when i puhed the reset button on the rear it would come back. about a year ago i went to use the amp and out of nowhere it just did nothing, have never had power up since. should i try to replace the circur breaker (reset button) ? or is it more likely to be the transformer or worse . any sugg. appreciated. thx.

[Enzo]

Yes, running a 4 ohm load on an amp rated only to 8 ohms is overloading the amp.   If you keep having to reset the circuit breaker, that should be a clue the amp is not happy.  And you should stop doing that before the amp is damaged, if it is not already damaged.

It is LEAST likely to be a transformer, and there is no "worse" after a transformer on the failure list.

You may have worn out the breaker, but it isn't the breaker's fault.  YTou need to stop overloading the amp, then we need to determine if the amp has suffered some damage causing it not to power up.

[Roly]

there is no "worse" after a transformer on the failure list.

  :lmao:   :dbtu:

While the circuit breaker may be worn out it is a bit more likely that the output transistors (or some other components such as their emitter resistors) have "worn out" as a result of being driven over the edge once too often.

Rather than start replacing things randomly the tried and true method is to do some faultfinding to locate what is wrong, then fix that.  It's a lot quicker and cheaper in the long run.

The circuit is already posted here - http://www.ssguitar.com/index.php?topic=2394.0

Disconnect the speaker.

You need to determine if the circuit breaker is closing and passing power; does the pilot light come on and stay on?  Not come on at all?  Come on then go off when you take your finger off?  Come on and then go off some time later?

If so, are the main amp power supply rails are coming up, "A" = +40V, "B" = -40V?

If not you need to make up a limiting lamp.

If they are you need to determine if the output rail (speaker output) is within half a volt of ground, or not.

Post results.

[g1]

  This amp is ok to use with a 4 ohm load, specs are 120W@4ohm, 80W@8ohm
http://www2.randallamplifiers.com/images/stories/manuals/RG100ES-RG80ES-OwnersManual.pdf

So the fault was not caused by using a 4 ohm load.
Whether the fault is the breaker, or the breaker is just doing it's job is something you must determine, as Roly mentioned above.