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ARC PH7

Hello everyone. 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
dweller's avatar
dweller
3,827 posts
 
If R/L channels are mirror image, swap the tubes to see if it's a tube problem (problem shows up in left channel?).
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barnettk OP
410 posts
 
@dweller I have deduced with further testing that the problem is temp related. If I remove the cover and allow more ventilation the problem does not occur. Once the cover is put back on 15 mins later its back so I am thinking a resistor that is sensitive to heat or maybe a cap. Should  be an easy fix as the problem is easily reproduced. I found a guy here in Atlanta that specializes in tube gear and I am going to drop it off today. I will report back on what the problem turns out to be.. thanks for all the replies. 
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yogiboy's avatar
yogiboy
5,820 posts
 
@barnettk
Instead of using the mute when silencing the output,you should just switch to another source on your preamp. That’s what I do !
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