Hi ya guys
I have a peavey studio pro 112 amp. It has recently started giving out a very loud popping sound when it's turned off.....its just like it's on full volume ,it's so loud..
What I've tested
No instruments connected
All controls set to zero
Different speaker
The noise is still there, does anyone have any ideas, as my local music shop have told me all amps do this ?
IT NEVER DID BEFORE !
Amy help appreciated
I have a peavey studio pro 112 amp. It has recently started giving out a very loud popping sound when it's turned off.....its just like it's on full volume ,it's so loud..
What I've tested
No instruments connected
All controls set to zero
Different speaker
The noise is still there, does anyone have any ideas, as my local music shop have told me all amps do this ?
IT NEVER DID BEFORE !
Amy help appreciated
I downloaded what eserviceinfo.com said was the studio pro 112 schematic. What the pdf says is studio pro tt2
There are a couple of jfets, j12 and j14, J174 that have the gate go to "mute"
I can't find "mute' on the print, but presumably it is a switch on the control panel.
Do you have the control in "mute" when you turn it off?
Next would be checking that the gates of Q12 & 14 actually change voltage when the mute switch is engaged. Perhaps the contact has oxidized. Maybe the connector from the switch has oxidized, especially pcb edge connectors (rare) or punch block KKR connectors (common in 90's Peaveys)
Many peavey PA amps have a resistor capacitor arrangement to mute things with a J174 while turning on or off. Those capacitors, when electrolytic, get old and lose ESR. I don't see that here. As this schematic is annotated 1999, this amp is probably old enough to have lots of dried up electrolytic capacitors. Also some oxidized switches, and especially punch block connectors. I had a ground lose contact through the punch block connector in my PV-1.3k PA amp. Requires removing & replacing the wire to scrape the oxide off.
I wouldn't replace the J174. They are under low stress in these positions and don't usually fail. Also generally not stocked by distributors, only from Peavey. Also comes in two different pinouts, the National Semi pinout and the European pinout. So don't mess with them. Mine was blown when the output transistors on the PV-1.3k shorted and let 180 v rampage through the boards, taking out 140 parts.
Expect this to get moved to instruments and amps forum when the moderator notices this thread under solid state forum.
There are a couple of jfets, j12 and j14, J174 that have the gate go to "mute"
I can't find "mute' on the print, but presumably it is a switch on the control panel.
Do you have the control in "mute" when you turn it off?
Next would be checking that the gates of Q12 & 14 actually change voltage when the mute switch is engaged. Perhaps the contact has oxidized. Maybe the connector from the switch has oxidized, especially pcb edge connectors (rare) or punch block KKR connectors (common in 90's Peaveys)
Many peavey PA amps have a resistor capacitor arrangement to mute things with a J174 while turning on or off. Those capacitors, when electrolytic, get old and lose ESR. I don't see that here. As this schematic is annotated 1999, this amp is probably old enough to have lots of dried up electrolytic capacitors. Also some oxidized switches, and especially punch block connectors. I had a ground lose contact through the punch block connector in my PV-1.3k PA amp. Requires removing & replacing the wire to scrape the oxide off.
I wouldn't replace the J174. They are under low stress in these positions and don't usually fail. Also generally not stocked by distributors, only from Peavey. Also comes in two different pinouts, the National Semi pinout and the European pinout. So don't mess with them. Mine was blown when the output transistors on the PV-1.3k shorted and let 180 v rampage through the boards, taking out 140 parts.
Expect this to get moved to instruments and amps forum when the moderator notices this thread under solid state forum.
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Many thanks for your info...I have an ESR meter so I'll test the caps
So grateful for you help and time
So grateful for you help and time
Instead of turning it off with the power switch pull the plug instead, still pop? If it does the power switch is causing the problem.
Craig
Craig
