[Russtafarian]

It seems the UCD-400 stereo amp I built about 5 years ago has started making a putt-putt-putt noise in one channel.  Both channels still work, but one is working a little too much with its extra-curricular flatulance sound effects.  I'm guessing this is the "motorboating" effect that I've read about and am now actually hearing.

The amp uses a simple linear PS (toriodial transformer, dual 25A bridge rectifiers and around 25,000uF of capacitance per rail) to power both UCD modules.

I'm wondering why one UCD module is doing this and the other isn't.  Has something given out in the PS portion of the UCD module?  Might it be time to recap the linear power supply?  Any other ideas? 

Thanks.

Russ

[jaywills]

If you can switch the power supply feeds between the channels, you might be able to identify the problem as between the UcD modules or the supply itself if the putt-putt sound follows the change.  Good luck.

[Russtafarian]

Thanks jaywills, I will give that a try to see if I can isolate the problem to either the PS or one of the UCD modules. 

As a general question for anyone who may know, if it is an issue with a UCD module, are there any obvious parts or connections I can check on the module to fix this? 

I can probably swap in a new PS e-lytic on the module if that will solve the problem.  Anything beyond that, I'll send it back to Hypex and have them fix it.

Thanks.

Russ