Name:    Steve Kennedy
Email:   steve@pacair.com  
Subject: standby question (112RP100)
Thread:  258
Time:    Wed, 14 Nov 2001 03:57:18 UTC

That's funny, my 112RD-100 does about the same thing and I haven't yet restored it.


I am thinking that there is a bad diode (D11 on the schematic) and the hum is caused by a loss of ground reference through the transformer when you go to standby.


I am not sure as I haven't really opened this amp up yet. It seems to work fine otherwise and I have had no other ill effects from leaving it as it is (but I do not use it that much).


Anything that hums, crackles or pops should be investigated. Standby is supposed to simply remove the high voltage supply from the audio transformer center-tap winding on the primary side. Anything else (like your hum) DOES point to a problem.


That's my guess based soley on a look at the schematic. Diodes are easy enough to check, but these are high-voltage types that CAN be leaky but still test good on an ohmmeter.


The best way to try to fix this might be to replace BOTH diodes just to be safe and sure.


Steve