Hello everyone.
I recieved this Punch 500S in for repair, board number PC-3082-C.
The amp was pulsing from 0vdc to 60vdc on the power supply. Now at first thought its like someone turned the bias pots up as a gain as I see alot.
One of the channels had pulsing DC on it. I thought someone had cranked the bias pot and blew some outputs. I removed the outputs from that channel and re-powered amp with same result.
I thought maybe a bad bias pot, so I removed the pot and re-powered amp with same result.
I had this problem with a 200ix Perry helped me with and it was some bad smd resistors and smd bjt's but am unsure if this could be it or it is something else. I dont like replacing uneeded parts as it is time consuming and costly to me.
I was wondering if someone could point me in the right direction, any help would be greatly appreciated...........Thanks again.
I recieved this Punch 500S in for repair, board number PC-3082-C.
The amp was pulsing from 0vdc to 60vdc on the power supply. Now at first thought its like someone turned the bias pots up as a gain as I see alot.
One of the channels had pulsing DC on it. I thought someone had cranked the bias pot and blew some outputs. I removed the outputs from that channel and re-powered amp with same result.
I thought maybe a bad bias pot, so I removed the pot and re-powered amp with same result.
I had this problem with a 200ix Perry helped me with and it was some bad smd resistors and smd bjt's but am unsure if this could be it or it is something else. I dont like replacing uneeded parts as it is time consuming and costly to me.
I was wondering if someone could point me in the right direction, any help would be greatly appreciated...........Thanks again.
Im sorry should have been more clear.
The DC on the speaker bridging terminal was with the outputs installed, and it went up and down with the pulsing of the amp on the power supply amp meter.
I did not check for DC on the emitter esistors with the output fets installed but with them uninstalled it is 0.000vdc on all of them.
There are no solder bridges.
The amp is pulsing just like it would if the bias pot was fully cranked clockwise.
The opposite channel did not have DC pulsing on the bridging terminal.
I am afraid to leave it on to long pulsing dont want to blow the power supply.
Do you still have excessive current draw without the outputs in the circuit?
You need to insert a current limiting resistor in the B+ line. If you have big dummy loads, you can use those. 1.5-2 ohms is a good value. It protects the transistors (if they're clamped down) and allows enough current to find many faults.
You need to insert a current limiting resistor in the B+ line. If you have big dummy loads, you can use those. 1.5-2 ohms is a good value. It protects the transistors (if they're clamped down) and allows enough current to find many faults.
The draw isnt continuous. It pulses up and down from 0 amps to 60 amps really fast up and down up and down.
The output fets are out of the circuit.
I will have to go to radio shack and get some current limiting resistors, I dont have any.
Just dont know what is causing the pulsing, its also jumping the voltage meter up and down on my power supply as well.
The output fets are out of the circuit.
I will have to go to radio shack and get some current limiting resistors, I dont have any.
Just dont know what is causing the pulsing, its also jumping the voltage meter up and down on my power supply as well.
Hey Perry finally got back to this amp I have been swamped with repairs.
Opened the bag from radio shack and I didnt get what I thought I did.
I ended up purchasing 3 8 ohm 20 watt resistors. Which I think is 2.66 ohms but not sure.
Anyway wired them in parallel and powered up the amp. The amp powers up fine no issues with the resistors in line with the B+.
The resistors are letting about 4 volts through to the amp but it still powers up.
Checking the rectifiers red probe on middle leg of CR1 and black probe on middle leg of CR2 I get -25.15 vdc of rail voltage.
Where do I go from here?
I get both positive and negative 12.75 vdc on the rectifiers.
I get 0.000vdc on all the source resistors with the pots turned full CCW.
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