Just a shamless plug to Don for his much appreciated time and effort to make my vintage Phase Linear amps sing again. His speaker protection boards were a very welcome addition, no more thumps. 700 Series 2 for the DQ 10’s, 400 Series 2 for the DQ 1W’s. Early 400 with the custom led meter lights as a back up. Just a 40 year old system that still sounds pretty incredible again.
Many thanks to watts abundant !
- Thread starter jljim
- Start date
I installed the relay board in Jim's 400II. He got it home and the relay wouldn't engage. He brought it back and I tested every part in the channel. All were good. That left only the opamp as a culprit.
Direct couple amps like this do not allow for signal tracing to troubleshoot. Pulled the opamp, installed a socket and new chip. All was good. As far as I can remember that's the first opamp I've seen fail on PL36 board. BTW, R 101 (7.5K/2W) on the PL36 board has a tendency to fail and cause high DC offset that the relay board detects. I replaced R 101 on both channels as a preventive measure.
Direct couple amps like this do not allow for signal tracing to troubleshoot. Pulled the opamp, installed a socket and new chip. All was good. As far as I can remember that's the first opamp I've seen fail on PL36 board. BTW, R 101 (7.5K/2W) on the PL36 board has a tendency to fail and cause high DC offset that the relay board detects. I replaced R 101 on both channels as a preventive measure.
No, LF351, Not sure the difference. The TO5 can be used, you would have to bend the pins to fit the socket. The failed opamp's output went right to the rail. The board was in pristine condition. Most of this vintage are scorched pretty bad.
On Jim's 2 fin 400, I plugged in the AGC fuse type LEDs. That amp was also in excellent condition. Sheet metal looked new. Had to build a voltage doubler circuit off the low voltage secondary to get enough voltage to adequately light the LEDs.
On Jim's 2 fin 400, I plugged in the AGC fuse type LEDs. That amp was also in excellent condition. Sheet metal looked new. Had to build a voltage doubler circuit off the low voltage secondary to get enough voltage to adequately light the LEDs.
Last edited:
