I'm reviving this older Hifonics 6 channel here. It currently goes into protection due to high DC offset on the output channels. I can force the TL594 to produce output (by shoring pin 3 to ground) and get the amp fired up through current limiting.
I'm getting DC on all six outputs. The odd thing though, is that the DC on each and every channel is different. The readings range anywhere from 1.8v up to over 5v for each channel. These readings are with current limiting on B+ so the DC would be much higher without the current limiter of course. The outputs are good. I'm reading high voltage on the base of each output transistor. There isn't a bias pot in this amp.
I've read that the differential and driver transistors (2sc2389, 2sa1038, 2sc2061 & 2sa935) in these amps have a tendency to leak over time, but is this really the case for ALL 6 channels in this amp, or am I missing something here? In a way, I'm hoping I am as all of these parts are obsolete now.
Here's a schematic I drew up for reference. I believe I got it down right:
I'm getting DC on all six outputs. The odd thing though, is that the DC on each and every channel is different. The readings range anywhere from 1.8v up to over 5v for each channel. These readings are with current limiting on B+ so the DC would be much higher without the current limiter of course. The outputs are good. I'm reading high voltage on the base of each output transistor. There isn't a bias pot in this amp.
I've read that the differential and driver transistors (2sc2389, 2sa1038, 2sc2061 & 2sa935) in these amps have a tendency to leak over time, but is this really the case for ALL 6 channels in this amp, or am I missing something here? In a way, I'm hoping I am as all of these parts are obsolete now.
Here's a schematic I drew up for reference. I believe I got it down right:
What is the DC voltage across the drain and source of the muting transistors? It should be VERY near 0.000v.
Thanks Perry.
I found that the ribbon cables coming from the pre-amp board were pretty toasty. Most of the contacts had broken solder joints.
I found that the ribbon cables coming from the pre-amp board were pretty toasty. Most of the contacts had broken solder joints.
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