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Audio Research PH7

Hello everyone. Going to post this in this forum as well as the amp/preamp forum. Just want to run this buy you guys to see what comes out of it. I recently purchased gently used Audio Research PH7 phono preamp. The Preamp had 3 hours on the tubes according to the display. I have had it for a week now and till now it has worked flawlessly. Typically I will mute the preamp to change records, etc. Today I muted changed a record and when I unmated the right channel did not play. turned the unit off and waited for about 10 mins and powered it back up, and the right channel came back. muted/unmuted right channel goes out. According to the seller the PH7 lay dormat for a few years prior to selling it. I am wondering if it could be one of the tubes could simply be failing, but it seems more like a curcuit problem than a tube problem. Any thoughts or experience with this particular issue with the ARC PH7?
barnettk
tablejockey
3,808 posts
 
My personal experience with a weird/intermittent tubed equipment 
problems-
its rarely/never the tubes. It is however, easy enough to pop in a known good tube if you have spares or just switching like tubes.

A dead channel in my tubed phono, had tech support stumped.Eventually found  a cap wasn't seated correctly on the board.Apparently wasn't easy to see the problem.



barnettk OP
410 posts
 
Thanks Tablejockey. I agree about the tubes. I figured I would at least try and reseat them just to see what if any impact it would have. Further investigation I have determined that it has something to do with Temp as well. When I let the tubes cool and reseated them the unit performed as expected until it got to full operating temperature. Once hot the problem returned. It plays fine until I either mute it or put it in mono.Other than that it sounds great. As long as I don't mute it lol.  The PH7 originally was made with 3 power supply tubes which ARC came out with a upgrade to the unit to convert it to 1 power supply tube. This unit does not have that upgrade and I was considering sending it in anyway to have that done. I thought I would take my time doing that since I just got it and enjoy it for a month or two but I think I am going to just send it in with this new development. The buttons on the front panel connect to a small circuit board in the front of the unit that is not part of the main board so maybe its just simply replacing that board. 
randy-11
1,913 posts
 
does it have any electrolytic caps in it?

age?
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