The input board was removed due to wires kept breaking. And the pre-drivers are still off the board. All have checked good so far.
There should be no voltage on the emitter resistors (leg 3 of the outputs). Something is passing the negative rail to the emitter resistors or to the emitter legs of the low-side outputs.
If you touch a dummy load across the speaker wires for that channel, does the amp draw more current?
Or does the voltage on the emitter resistors drop to 0v with no increase in current?
Be careful. It could draw enough current to blow the outputs if they're in the circuit.
If it does draw more current, repeatedly tap the load across the speaker terminals to see what gets hot.
If you touch a dummy load across the speaker wires for that channel, does the amp draw more current?
Or does the voltage on the emitter resistors drop to 0v with no increase in current?
Be careful. It could draw enough current to blow the outputs if they're in the circuit.
If it does draw more current, repeatedly tap the load across the speaker terminals to see what gets hot.
Okay here is what i have found...
When i do the dummy load across the speaker terminals it draws high current. The other channel got hot... not the channel that i am working on. And only the NPN's on that channel. I removed the outputs from that channel and repeated. Even the driver would pass current but only about 2.5amps on the power supply. So I removed that as well. Now no over current.
Uploading a pic to show current state of the board.
No pre-drivers installed No drivers on channel 3 installed, No outputs or driver on the NPN side of channel 4.
When i do the dummy load across the speaker terminals it draws high current. The other channel got hot... not the channel that i am working on. And only the NPN's on that channel. I removed the outputs from that channel and repeated. Even the driver would pass current but only about 2.5amps on the power supply. So I removed that as well. Now no over current.
Uploading a pic to show current state of the board.
No pre-drivers installed No drivers on channel 3 installed, No outputs or driver on the NPN side of channel 4.
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Too answer your question Perry, i replaced only the four outputs that were getting hot in the first place. No difference was made so i put the originals back. Once i found the faulty one i just changed all on the rear channels. I like to keep these as original as possible.
jkrokenberger, It is my personal now. A customer sold it to me as was broken. For a great deal. The only thing i will be changing is the molex plugs are coming of and terminal binding posts will be going on a new end plate. Those have been the only draw back to PPI amps. I love the simplicity of these amps. just gain control only. I will also be switching the filter caps for the rails to a higher farad to give some good headroom. But thats the end of my mods on these.
Amp is fixed and for now going on the shelf waiting the new end plate.
jkrokenberger, It is my personal now. A customer sold it to me as was broken. For a great deal. The only thing i will be changing is the molex plugs are coming of and terminal binding posts will be going on a new end plate. Those have been the only draw back to PPI amps. I love the simplicity of these amps. just gain control only. I will also be switching the filter caps for the rails to a higher farad to give some good headroom. But thats the end of my mods on these.
Amp is fixed and for now going on the shelf waiting the new end plate.
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