Amp fail

[Axelerator]

Hi Guys, I just wanted to hookup my girlfriends AudioAnalouge Amp (Puccini if anybody knows this) to the speakers and there is a high frequency feedback-style tone together with the normal sound. As the tone is on both speakers and is going up /lower with the normal sound i assume the issue is somewhere at the PSU.
maybe in the voltage regulator area ? anybody has some experience and suggestions where i should look in the beginning ?

thank you alot !
axel

 

[MagnetoSound]

Yes, regulators can oscillate if not well decoupled at both input and output. If you have a 'scope those are the areas to probe, a capacitance meter is useful here too, or just try replacing any electrolytics around the regs to see if it helps. It is probably only one of them that is doing it but best to recap both rails to prevent future failure.