eden wt405 help

[erock0138]

I have a Eden head that's been giving me problems lately. It just fizzles and has very low volume output. Anyone have any pointers of where I should start looking? I know a fair amount about electronics, just not a lot with solid state. Maybe output transformer? Anything will help, thanks.

[soundguruman]

If you have an eden speaker, check that first, it may need a new basket.

[erock0138]

It's through an ampeg 4x10. I've tested the cab with my other acoustic brand head and no issues at all.

[soundguruman]

Check to see that preamp out/ power amp in / effects loop jacks have been cleaned.
Install a patch cord between preamp out/ power amp in jack OR effects send / return jacks. This will bypass the internal jack switch, which might be causing the problem.
If the problem cuts in and out when you knock on the amp cabinet, re-solder the circuit boards.

[J M Fahey]

And ... it does not have an output transformer.

[soundguruman]

Turn the amp on and play some music through it, bang on the amp w/ your hand.
Does the problem come and go/ cut on and off? Does it make a crackle noise when you bump on it?

[mozwell]

This may help to faultfind.

Does it still have a problem if you turn the compressor off ?

If the output is low volume & severely distorted, i woudl suspect an output transistor. Is one shorted collector to emitter ?
It could also be one of the MUTE jfets D1, D3 not working properly in the power amp.

Start at the input, inject a 50mV 1Khz sine wave & trace the signal through the amp with a scope.

[soundguruman]

Yes I would think a bad FET mute circuit....is worth checking out.

[Mick Bailey]

I had an Eden amp for repair last year - low output/distortion on one channel (800w stereo amp). Turned out to be an electrolytic cap on the power amp board that had a high ESR (capacitance checked ok with a multimeter).

It came back after a short while and needed more electrolytics replacing, this time in the preamp. Worthwhile checking the caps - the amp I repaired had more than its share of bad ones. An easy check in-circuit with an ESR meter.