OH NO! Hum & static from my ancient Phase Linear 400

[Feanor]

After many years of stoney silence my Phase Linear 400 is sending 60 cycle hum plus some static to my speakers; also, hum is audible around the unit itself.



Why? What to do? It's already back to the technician, but I probably won't hear for a few days. BTW, I say "back" because I recently had him upgrade the input capacitors from 5900 to 22,000 uFd -- could there be a connection?

I don't think the capacitor upgrade made any significant improvement, i.e. a waste of a fair bit of money. Should I throw good money after bad or get a new amp? Unfortunately my cashflow is constrained these days: if any new amp, has anyone got suggestions under US$1000? I would consider either an intergrated or power only; (my Apt Holman preamp, 25 years old, is doing well though it has no remote control). I have Magneplanar MMGs so need an amp the can deliver 80+ watts into 4 ohms.

[poneal]

have you recently moved to a new residence or moved the system to a new location in the same residence? If so, this might be the culprit.

[Feanor]

have you recently moved to a new residence or moved the system to a new location in the same residence? If so, this might be the culprit.
Nothing at all has changed since all was well.

[CARLOS]

I am new here and mildly surprised at the amount of Phase 400's that are still around and in use. I had one that did what you are describing with yours. I took it in for a oil change, got it back and of course it performed very well until one day it went crazy..pegging one needle and with a loud hum and static in the speaker. I took it apart and discovered the tech left a small allen wrench inside. During my previous transporting it home and moving it around once here, I guess the wrench worked loose and was shorting out things. I removed it and it is working to this day. Well, I sold it several years ago, and it was parked as a paper weight for some 10 years before I sold it but the fellow who bought it claims he is still enjoying it. He likes vintage stuff. If you like vintage things also, i'd say have it repaired...maybe by someone else other than the guy who upgraded it for you. Otherwise, technology has come a llooonnnnggggg way since Bob changed to Carver and so on. May be time to move on.
Carlos

[mtrycraft]

Nothing at all has changed since all was well.

A couple of possibility but perhaps woodman will chime in. When the change was done, maybe there was a cold joint left behind? Another part of the unit developed a broken joint? Is the xformer on some isolation mounts to reduce the mechanical noise and it was messed up, left out?

[Feanor]

Actually, there was nothing wrong with the Phase -- just a severe ground loop. In fact, a NAD C270 I borrowed had the same problem!

I alleviated the problem by moving around the AC plugs and interconnects. Still a tiny bit of hum from the amp, though, but nothing through the speakers.

BTW, I bought the NAD C270 :) No more 1970's SS "etch", more air and transparency. Phase has tighter bass, at least at this stage of break-in of the NAD.