BradJudy
500+ Head-Fier
- Joined
- Jun 26, 2003
- Posts
- 848
- Likes
- 10
My PPA has been in storage for a while and I pulled it out to use. The epsilon 12 in it was oscillating on the relay, switching it on and off. I remembered this being an adjustment issue, so I popped it open and started working the trimpot. Unfortunately, the only stable state I can get it into is a permanently open relay. I went back through the setup doc and walked through the steps again, checking my voltages. When I get it adjusted so that U1 pin 6 and the amp output ground voltage is about zero, it starts to oscillate again. I can tweak VR1 until the relay is properly closed, but then after I power it off and back on, the relay stays open again.
Any ideas?
For reference, this is on a PPA v1 with Glassman buffers (checked DC offset on outputs and they are good) and a STEPS power supply at 24VDC. The pin 4/7 voltage measurement is 21.6VDC for both U1 and U2. The U1 6/7 measurement is 10.8VDC. One note is that U1 was not seated properly when I opened it to start tweaking, so I seated it. I don't know if another part could have been damaged by the fact that U1 wasn't seated properly at first.
Any ideas?
For reference, this is on a PPA v1 with Glassman buffers (checked DC offset on outputs and they are good) and a STEPS power supply at 24VDC. The pin 4/7 voltage measurement is 21.6VDC for both U1 and U2. The U1 6/7 measurement is 10.8VDC. One note is that U1 was not seated properly when I opened it to start tweaking, so I seated it. I don't know if another part could have been damaged by the fact that U1 wasn't seated properly at first.