- Joined
- Nov 13, 2024
- Messages
- 5
I have a question and maybe someone might be able to provide some insight. I purchased and built 2 PL14-20 Rev E kits a couple years ago. I finally have had time since retiring to work on my Phase Linears.
I am currently working on my 400 Series II which I replaced bad outputs and emitter resistors. The amp is "quasi-complimentary". I installed the PL14-20 Rev E board, and everything seems to work nice (have not listened yet). I can get over 60v output with a signal generated into the input both channels. I tried to set the bias as per instruction so that I could actually listen to it. I get around 10mV (bias between the test point and output terminal) on the right channel and less on the left channel. The potentiometer(s) on the PL14-20 Rev E do not change those values at all.
This is what I have done so far concerning the bias. I have replaced both bias transistors with new. The current bias transistors have an HFE of 263 (left channel) and 255 (right channel). I have tried the other PL14-20 Rev E board I built with the exact same results. With the amp being "quasi-complimentary", I have installed the 10 Ohm, 1/4w resistors in place of D4 (L and R). I have verified a number of times that the bias transistors are wired correctly.
Again, if anyone has any ideas, I would appreciate it.
I am sure it is something I am overlooking. I will be looking at the PL14-20 Rev E schematic and doing further trouble shooting.
Thanks!
Jerry
I am currently working on my 400 Series II which I replaced bad outputs and emitter resistors. The amp is "quasi-complimentary". I installed the PL14-20 Rev E board, and everything seems to work nice (have not listened yet). I can get over 60v output with a signal generated into the input both channels. I tried to set the bias as per instruction so that I could actually listen to it. I get around 10mV (bias between the test point and output terminal) on the right channel and less on the left channel. The potentiometer(s) on the PL14-20 Rev E do not change those values at all.
This is what I have done so far concerning the bias. I have replaced both bias transistors with new. The current bias transistors have an HFE of 263 (left channel) and 255 (right channel). I have tried the other PL14-20 Rev E board I built with the exact same results. With the amp being "quasi-complimentary", I have installed the 10 Ohm, 1/4w resistors in place of D4 (L and R). I have verified a number of times that the bias transistors are wired correctly.
Again, if anyone has any ideas, I would appreciate it.
I am sure it is something I am overlooking. I will be looking at the PL14-20 Rev E schematic and doing further trouble shooting.
Thanks!
Jerry