Hi all,
I'm troubleshooting a power supply issue in my Roland Juno 60 synthesizer. Here's the circuit:
The +5/+10V rails are fine, but something funny is going on with the +/-15V rails. When everything was assembled in-circuit, I was getting about -15.6V on the negative rail but something like -0.7 on the positive (testing at points 9 and 10). I disconnected the board and tested: The AC inputs are hot - about 19.4Vac at points 5 and 6 from the transformer. I'm getting +/-25Vdc on the +/- outputs of D3.
I thought TR1 might be the issue so I changed it out (changed out TR2 as well but had the same result after) and still had an issue. I pulled TR1 again and tested it on a breadboard apart from the circuit and now I'm getting +/-25Vdc at points 9 and 10....
I'm beginning to think IC2 is the problem (and I have a replacement) but I don't want to pull it if I don't have to. Admittedly I'm not an expert and may be misunderstanding, but does anyone have an idea where I might be slipping up?
I'm troubleshooting a power supply issue in my Roland Juno 60 synthesizer. Here's the circuit:
The +5/+10V rails are fine, but something funny is going on with the +/-15V rails. When everything was assembled in-circuit, I was getting about -15.6V on the negative rail but something like -0.7 on the positive (testing at points 9 and 10). I disconnected the board and tested: The AC inputs are hot - about 19.4Vac at points 5 and 6 from the transformer. I'm getting +/-25Vdc on the +/- outputs of D3.
I thought TR1 might be the issue so I changed it out (changed out TR2 as well but had the same result after) and still had an issue. I pulled TR1 again and tested it on a breadboard apart from the circuit and now I'm getting +/-25Vdc at points 9 and 10....
I'm beginning to think IC2 is the problem (and I have a replacement) but I don't want to pull it if I don't have to. Admittedly I'm not an expert and may be misunderstanding, but does anyone have an idea where I might be slipping up?