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Author Topic: Peavy Rage 158 no sound after 1-5 mins (SOLVED)  (Read 6297 times)

substatica

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Re: Peavy Rage 158 no sound after 1-5 mins (SOLVED)
« Reply #45 on: August 09, 2019, 02:34:34 PM »
Pin3 of TDA2040 is connected to chassis via AGND1.  Now if we insulate the tab of the TDA2040, and run an extra wire from pin3 to chassis, the chip will overheat and shut down.   ???

As far as I can tell AGND1 should not ground to chassis. AGND is the chassis ground. It could have been a combination of the missing thermal compound (which I cleaned off when I disassembled) which dropped the resistance between AGND and AGND1 and a cold joint destabilizing the circuit in another way.

Enzo

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Re: Peavy Rage 158 no sound after 1-5 mins (SOLVED)
« Reply #46 on: August 09, 2019, 06:01:51 PM »
All the grounds are grounds, they are just not all wired in common.  This is to prevent instability or ground loops.  The power supply might have a separate ground from the preamp, but the input jack connects both together and to chassis.  That sort of thing.  SOme complex amps like 5150 can have five or six ground circuits.  They all join, usually at a panel jack.  R63 links them here.