ok so there is more to this, the right channel has always given me fits. Today while auditioning my new Phase Linear 3000 preamp (more on that in a different thread maybe) the right channel has intermittent high frequency distortion and noise. After a bit of this, the right channel completely cuts out. Im convinced at this point that something is amiss with my right channel of my amp.
(eventually the channel came back)
Where do I begin? Let's see...
Phase Linear 3000:
There were several versions of the Phase Linear 3000 preamp. The 3000's were notorious for problems with the clear-see through top relays. Early 3000's had (13) relays. Eventually many of them had (6) or (7) of the relays replaced with the Aromat HB2E-DC24V yellow topped nitrogen gas filled sealed relays with gold contacts. A little later on all (13) relays were HB2E-DC24V's. Then Phase Linear added an additional (14th) relay in the tape loop to prevent oscillations.
The 3000's also had problems with the micro-switches... even a few megohms of resistance (caused by dirty contacts) would cause false-triggering of the CMOS IC's and in turn the relays. In which case the input selector switches would not always engage or disengage when depressing the button. In other words, more than (1) switch would be engaged as indicated by the illumination of more than 1 LED. Using an appropriate cleaner/lubricant sprayed into the switch and exercising the switch should solve this problem.
The 3000's power switches also had a high failure rate.
After all the problems noted above have been addressed you should have a good preamp.
Have you tried swapping your cables to see if the problem moves from one channel to the other?
Phase Linear 400 Amplifier:
Do you still have the original Switchcraft 3501FR RCA input jacks on your Phase Linear 400?
If so, I would suggest also checking the RCA jacks out. In order to do this; find a RCA patch cable you are willing to sacrifice.
Bend the (4) petals back so that only the center pin is exposed. (NOTE: The nominal diameter should be close to .125"). Now use the RCA jack like an inspector would use a GO-NO Go plug gage and insert it into the jack on the back of your amplifier. There should be some resistance when you plug it into the female input on the RCA jack. I have found that approximately 60% or so of all the old Phase Linear amps have at least (1) loose input jack. Unfortunately, the Phase Linear service manuals do not discuss this (nor any other manufacturer I have seen who utilizes chassis mount RCA jacks).
NOTE: This has not been a problem with PC board mount style RCA jacks.
If your jack(s) are loose.....
WARNING: Be sure to wear safety goggles.
1.) Examine the opposite end of the jack and locate the solder tab (this will be the view as taken from inside the amplifier). Note the orientation of the solder tab.
2.) On the other end of the jack locate the area directly across (180 degrees) from the solder tab.
3.) Using a small flat-bladed jeweler's screwdriver and wedge it between the formed jack and the insulating material.
4.) Reform the jack by bending it back slightly with the jeweler's screwdriver.
See attached photos.
I hope this information is of some help.
Ed