Peavey Headliner 1000 problem

[JB Lonewolf]

Hi. I've just repaired the preamp on a Headliner 1000 that was down, replaced two 4565's U4 and U5 which were leaking/ getting hot. Amp now works but here's the problem: when hitting the mute switch or turning it off without turning the master and gain down it bangs hard, and I mean hard. It killed my bench speaker. With the master off it's fine. I'm not really sure how the mute circuit works (or if that's the problem) but I've replaced mosfets Q8-13 and it hasn't made any difference. I've tried getting through to Peavey and I don't what's up these days, they haven't got back to me. I realize these things are complicated but any suggestions would be greatly appreciated. Thank you in advance. JB

[The Dude]

My first suggestion would be to upload a schematic or schematic link so we know what those circuit board designation numbers mean.

[JB Lonewolf]

Thanks for the response. There are three schems, the one marked patch is for the back panel jacks but
I'll put it up anyway. I've only dealt with the pre board, I'm hoping it's nothing in the power section. Thanks again, JB

[Jon Snell]

The High and Low side driver chip should mute (pin5 goes high) to stop drive to the power Mos Fets.
There is a PIC chip that is programmed to detect power down, amongst other functions and performs the mute/power off function.
It would help to know which chips you changed. I may have a better clue as to the issues with that knowledge.
I think the High/Low side driver is an IRS type but cannot cross reference the Peavey part number with the manufacturers part number so the type number would also help.

My understanding is that Peavey just sell replacement panels as they no longer repair to component level.

[Jon Snell]

D7 & D8 are to protect the gate/inputs of the opamps from exceeding the rail voltages and thus minimising any damage from static pops and clicks.
Various double diodes are fitted withing the pre amp section as well.
Good to hear you have it working now.