Peavey PV500 Bridge mode

[tdlunsfo]

I have this amp on the bench and the complaint is static out of one channel. The first thing that I noticed is the customer had it in bridge mode. After placing in stereo, hooking up audio generator, watt meter and scope I get a good clean sine wave out of both channels. Where I am getting confused is in bridge mode. When I place it in bridge mode per the user manual I cannot see any change in the wattage between the two modes. Setup is the red lead from channel A and the negative lead from channel B to the watt meter and 4 ohm dummy load. Unit in bridge and input on channel A set at 80W output. When I deselect bridge mode there is no change in wattage. It seems to me the wattage should drop (half?) but I may not be thinking clearly on this one. Thoughts?

[Helmholtz]

Did you consider that you must not connect any of the floating outputs in bridged mode to scope gound? Otherwise you are shorting one of the channels. Rather scope ground should be connected to amp ground and each output be scoped separately.

[Jazz P Bass]

" complaint is static out of one channel".
So the amp arrived with Bridge mode switch engaged.
How can "one channel" be staticky when the two amplifiers are bridged?

I would verify with the owner how the amp was being used.

Note: In Bridged Mode the two RED binding posts are used for the output.
The Black posts are not used.

[tdlunsfo]

Yep my mistake, sorry I don't do a lot of power amps and only have minor experience with them. It should be both reds and also my mistake on the scope grounds. I had the scope across the dummy load. Also, I do suspect he had this connected wrong betting he had it in bridge and outputs connected in stereo. I just wanted to be sure both modes worked before handing it back to him without doing anything to it. Semi off topic question, how do you handle these types of situations where you are given something that works just fine? Bench fee or let it slide? I guess I could clean the inputs and outputs just so they feel like they got something.

[Leo_Gnardo]

how do you handle these types of situations where you are given something that works just fine? Bench fee or let it slide? I guess I could clean the inputs and outputs just so they feel like they got something.

They ate up your time, which you could have spent fixing someone else's actual problem. Charge bench fee. It's also nice to instruct the equipment owner in how to use his amp properly (which he could have learned by reading his owner's manual, but didn't.)

I'll admit, I'm guilty of NOT charging lots of folks for fixing things that ain't broke. That game's over. My time is worth something.

[tdlunsfo]

Good idea on the instructions. I may print out that page of the user manual and attach it to the ticket. Probably will charge half the bench fee this time as I obviously wasn't perfect in my assessment the first time around.

[Leo_Gnardo]

Good idea on the instructions. I may print out that page of the user manual and attach it to the ticket. Probably will charge half the bench fee this time as I obviously wasn't perfect in my assessment the first time around.

Fair 'nuff. You also might have cleaned up the bridge switch by moving it. I've had that happen.