Audio Research PH7

@wlutke Good to know on reseting the tube hours. I figured there had to be a way to do it since tubes can be replaced. I agree that the PH7 is an outstanding pre. Great sound staging and very quiet even though I have not had the power supply upgrade. I have a call into ARC to see if that upgrade is still available. After more testing this appears to definitely be a temp problem and most likely with a bad resistor or maybe a cap. If I remove the cover to allow more ventilation the problem does not occur. Once I put the cover back on 15 mins later after heat collects in the cabinent the problem is back. Sonically there is no problem. it sounds fantastic, but don't want this to lead to a larger problem down the road. I found a guy here in the Atlanta area that specializes in tube gear and I am going to drop it off today. If I send it to ARC Im sure that i can count on being without it for 4-8 weeks. I will post back to let you know what the problem turned out to be. Thanks for all that replied. 

  Hi guys well we found the problem with the PH7. The mute relay was bad. The tech found the problem in about an hour including the time it took to fail. Right under $200 to fix the problem. Hopefully we have had our glitch for this mission.
Thanks for all the help. Back to the music.

I have been using a PH7 since 2009, having had a PH5 before that.  Mine developed an issue with either a cold solder joint or a weekend solder joint and so on occasion I get a loud hum when first turned on. I know where I have to push on the board to get rid of it. I sent mine in for the upgrade. I thought would've been repaired BUT it went to the upgrade w/o going through the proper procedure for repair. Hence my issue wasn't cured. But the upgrade is worth it. The (3) 6H30's were all aging faster than they should have and all at different rates. After the upgrade you're left with 1-6H30 and a 6L6G/5881 plus the 4-6922. I have rolled many a tube to get the sound I need. I really like the PH7 and wouldn't go with an all 6H30 ver. like the newer units. I have switched to the EH 6H30 gold pin versions and they are much better, warmer with a more even top to bottom sound. The 6L6G/5881 also rolls well. 
I also found that the unit sounded better with the top off, so I have mine velcro'd on and pop it off for serious listening sessions.  I wouldn't trade the RC cart. loading for anything.  Every once and a while it won't turn on either by RC or front panel. So I have to unplug-plug-in the cord from the back and all is fine.  ARC didn't seem concerned about it and told me what I was doing was what they recommend. I'm not sure why it does this and ARC never said why either. 

@gerardff 

i agree that ARC should have found the problem with the unit when In for the upgrade based on the checklist that they say the do whenever the unit comes in for service. However I can see them missing it if it was not exhibiting the symptoms at the time. I would think if it's not a weak solder joint but rather a weak resistor or other component sometimes those things are hard to see with a visual inspection.they say the check for cold/weak joints.  I am however happy you found a work around that you are ok with. 

In regards to the power supply tube upgrade I did finally get a call back from ARC a few days after the unit had been taken to the local tech and the upgrade is still available for $300 and I do plan to send it in, but I am going to enjoy it for a few weeks first. I was told it would be a 3-4 week turn around and with round trip shipping add another 2 weeks  plus another $100 lol. 

I hear you on rolling the output tubes and i have have made a note of the ones your using and I have planned to do just that at some point. The unit sounds so darn good As it is and it is hard to imagine it sounding any better but that is the beauty of the hobby right. 

Regarding it soundibg better with the the top off I wondered about that and may operate it in that way as well. It kinda makes sense when you think about it and I'm sure that is the reason why most of their newer gear has the tubes exposed on the cabinet design. 

Thanks for the info. Good stuff.