SS Guitar Amp Transformer Fault?

[mojofelix]

I am engaged in my first noobee venture of attempting to repair a guitar amp.

The amp was operating fine but stopped during a live gig and no longer powers on.

Tracing it down with multimeter leads to conclusion there there is no output from the transformer, so I am planning to find and install a new replacement transformer in this solid state amp.

My question is simply this: Is faulty transformer a fairly common not-too-unsual fault? Or would this be considered a rare thing to find wrong?

Best, Felix

[glebert]

Everything will fail eventually. That being said, did you verify that the transformer was getting full AC voltage on its primarly leads? If you have disconnected the transformer have you checked for continuity on the primary and secondary sides?

I don't think I've seen a PT failure on a SS amp that wasn't caused by shorted output transistors. Before you get too far into the repair you might want to check those out.

[loudthud]

Some transformers have internal fuses or thermal cutouts. Most of these are not considered replaceable. A resistance check of the primary will usually reveal failure.

[galaxiex]

I am engaged in my first noobee venture of attempting to repair a guitar amp.

The amp was operating fine but stopped during a live gig and no longer powers on.

Tracing it down with multimeter leads to conclusion there there is no output from the transformer, so I am planning to find and install a new replacement transformer in this solid state amp.

My question is simply this: Is faulty transformer a fairly common not-too-unsual fault? Or would this be considered a rare thing to find wrong?

Best, Felix

What brand/model amp?
Did you check the fuse or circuit breaker?

[mojofelix]

I checked the continuity of the fuse and it is fine. It is an old "Centaur Acoustic PA" which is both it's brand and it's model. Despite it's "PA" name, it is an acoustic guitar amp with 12" speaker, a tweeter, reverb, two channels, one XLR and three 1/4" inputs.

[g1]

Can you outline how you determined transformer problem with your meter? You found 120V AC on primary and no AC volts on secondary? (or other line voltage on primary if not in North America)

My question is simply this: Is faulty transformer a fairly common not-too-unsual fault? Or would this be considered a rare thing to find wrong?

transformers are usually top suspect on-line, yet one of lesser common items to actually fail.

[galaxiex]

The O/P still hasn't said if he checked the fuse, or not.

I ass-u-me he did.... but it would be nice to have confirmation...

[52 Bill]

We've been selling those in the store for 10-15 years now. I see maybe one or two in for repair every year. Never seen a dead power transformer, and rarely anything more than dirty loop jacks or bad reverb tanks.

I'd suggest checking fuse and power switch and all primary wires before even looking at the transformer. Could just be a bad AC plug.

[Tom Phillips]

The suggestions are starting to repeat.
Assuming that you are safety aware and comfortable working on live circuits, I suggest that you cut to the chase and make an AC voltage reading right at the power transformer primary leads. If the correct AC line voltage is present, then that rules out problems with the line cord, fuse, ON/OFF switch and all the associated wiring. If the voltage is OK then proceed next as Loudthud suggested in post #3.

[loudthud]

mojofelix, was this you that posted on the SSGuitar forum ? https://www.ssguitar.com/index.php?topic=2720.0

Did you follow up and contact the manufacturer ?

[g1]

That thread is from 10 years ago.
The company is still around though, and they have a number for tech. support on their website. ( 1 760 964-2670 )

[loudthud]

Sorry, my flux-capacitor has too much ESR.

[mojofelix]

Thanks to all of you for your helpful posts! The post from Tom Phillips led me down the righteous path. Turns out it's the power on/off switch that is faulty. I bypassed it and now the amp just plain works. Pugging it our out of the wall is the new on/off.

[Helmholtz]

A while ago the power switch of my Fender Super Champ stopped working (open in both position of the toggle)
A little Deoxit sprayed into the toggle hole cured the problem.
(Just one of many success stories using Deoxit D5).

[Simon baldwin]

Some transformers have internal fuses or thermal cutouts. Most of these are not considered replaceable. A resistance check of the primary will usually reveal failure.

I repaired an Orange Crush bass 50 a few weeks back that wouldn't turn on... thermal fuse had gone in the transformer. I was able to get to it and replace with a good one... now working nicely. (2nd attempt though as i think i got the first one too hot with the iron )

Glad you got yours sorted though!