Low impedance led means shorted outputs in most cases. PPI never released schematics openly, and the new company likely does not even have any of the old documents. A400 ??? do you mean A402.2 or A404.2 ???
Ohm out your outputs I kind of bet you will find some at 1 ohm or less
Oh also check the 10 ohm 2 watt resistors behind the RCAs they tend to go open with shorted outputs. They are your ground loop current limits, and they almost always burn open with blown channels, just a maybe but I would check them...
It is an a404 sorry. it has audio even with no speakers connected and plays 2 ohms normal, clean signal. but the yellow led stays on at all times. it has to do with the led driving circuit. the transistor that drives the led is fine but didn't test further I need schematic. output circuitry is fine no shorted fets or anything like that.
Hummm. I'm still think something is drawing too much current somewhere. What was the nature of your reason for working on it in the first place? Just the low Impedance led issue ?
How much current in amperes does it draw off your bench supply at 12 volts DC with nothing else hooked up, just power and turn on lead ??? Should be just at ~1.0 amperes, maybe just a tad less < I'm A B comparing with one on my bench right now.
What are your output transistors rail voltages as measured with your black probe to the center tap of the power toroid? I get +&- 23.50 VDC on this amp outputs, Whats your voltage like ?
Could you post a picture of yours inside?
You also mention 2 ohms what does the amp do at 4 ohms ? same ?
How much current in amperes does it draw off your bench supply at 12 volts DC with nothing else hooked up, just power and turn on lead ??? Should be just at ~1.0 amperes, maybe just a tad less < I'm A B comparing with one on my bench right now.
What are your output transistors rail voltages as measured with your black probe to the center tap of the power toroid? I get +&- 23.50 VDC on this amp outputs, Whats your voltage like ?
Could you post a picture of yours inside?
You also mention 2 ohms what does the amp do at 4 ohms ? same ?
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