I picked up a Phase Linear 400 Series II in unknown state of condition. I have some experience with electronics repair but not much experience with amplifiers in particular. I took it apart and found one of the main filter caps open. I have ordered replacements for both of these caps and also all of the other electrolytics in the amp. So far I have not found any other problems in the amp.
I noticed that this is the older PL400 Series II, without the complimentary output transistor banks. Everything is NPN. I also noticed that the left channel uses 2x RCA 66546 driver and 6x NEC 2SD555 output, and the right channel uses 2x RCA 66546 driver and 6x Motorola MJ15011. Everything tests good, no shorts or opens. But I am thinking more long-term about replacing so that both channels are the same.
After googling a lot, I could find no clear answer as to what modern transistors work the best. I saw plenty of people that don't like the 2SD555. It seems that people tend to like to use MJ15024 for the drivers and MJ21194 or MJ21196 for the outputs. I am a little bit confused about this though. When I look at the datasheets for these parts, they all seem pretty much identical. Why wouldn't I want to use the same transistor for all 16 of them, drivers, outputs, everything? For example, a quote from d3imlay about the PL400:
What problems or disadvantage might I face if I used all MJ15024 for example? Since the driver and output transistors would be the same, wouldn't this make oscillation unlikely?
Also, another question more out of curiosity. Would there be any advantage to rewire this for complimentary outputs? I remember one person somewhere saying that they had rewired for complimentary, but they did not explain the reason why or mention any improvements from doing it.
I noticed that this is the older PL400 Series II, without the complimentary output transistor banks. Everything is NPN. I also noticed that the left channel uses 2x RCA 66546 driver and 6x NEC 2SD555 output, and the right channel uses 2x RCA 66546 driver and 6x Motorola MJ15011. Everything tests good, no shorts or opens. But I am thinking more long-term about replacing so that both channels are the same.
After googling a lot, I could find no clear answer as to what modern transistors work the best. I saw plenty of people that don't like the 2SD555. It seems that people tend to like to use MJ15024 for the drivers and MJ21194 or MJ21196 for the outputs. I am a little bit confused about this though. When I look at the datasheets for these parts, they all seem pretty much identical. Why wouldn't I want to use the same transistor for all 16 of them, drivers, outputs, everything? For example, a quote from d3imlay about the PL400:
When I do a repair for someone I replace all outputs and drivers with 21196's as a matter of convenience and long term reliability.
What problems or disadvantage might I face if I used all MJ15024 for example? Since the driver and output transistors would be the same, wouldn't this make oscillation unlikely?
Also, another question more out of curiosity. Would there be any advantage to rewire this for complimentary outputs? I remember one person somewhere saying that they had rewired for complimentary, but they did not explain the reason why or mention any improvements from doing it.