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RE: 6N1P

I am ecstatic to say the amps are home and functioning properly. I can't say I was excited at 69 years to be moving them to my second floor listening room but I guess you have to pay to play. Nothing that ibuprofen and wine couldn't fix.

I will try and make this short. The last 2 months Phil spent trying to figure out why one amps, 2 adjustable resistors would not zero out, turns out to be surprising and frustrating at the same time.

Apparently during the production of the 610t amps ARC received more orders than they ever expected for the time. They ran out of some resistors and chose to make a design change to the board and not include it on the schematic. The change was only used until more of the original parts arrived.

We found this out because one of the engineers that Greg at ARC spoke with, as Phil encountered more dead ends with the amp remembered they changed it.

ARC offered to send us the proper parts at no cost, which was great. The problem is when Phil put the new resistors in, the amps + and - voltage at the 2 zero out resistors was still too far off to adjust properly.

Phil next decided he had to eliminate the chance of a problem tube socked or something under them that was unseen. We ordered 6 sockets, as he wanted to keep both amps the same for base line readings. Under the sockets he found some ugly soldering but nothing he thought would be the problem. He did though find more ground loops under sockets 19 & 20 and he eliminated them on both amps.
He installed the new sockets and the amp that had been problem free was still just that. The amp with the issue still had that.

He decided that the new replacement parts ARC sent to fix the issue had to be the problem.

On the side of the amp that the voltage was to low he, through best guess measuring and trial and error added different value resistors in series until it was at a value that was within specs to be able to zero out.
On the side that was to high he did the same thing but in reverse and lowered it to be within spec. That side also zeroed out.

We were both ecstatic and frustrated that was a long 2 months trouble shooting the problem that was an unpublished design change.

So, the end result was they sent 2 different design 610t amps to the original owner.

From the 1 1/2 hours Phil and I listened to them yesterday evening they are going to be amazing in more than one way once broken in some.

I was stunned that even after 1 1/2 hours I could actually put my hand on 4 or 5 tubes and they were hot but you could have never gotten close to the 6550 tubes with your hand. We found that the room was much to cold to be comfortable listening to music at the same thermostat setting when the 6550 tubes were in and running.

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Follow Ups Full Thread
Follow Ups
  • RE: 6N1P - Brad225 09:40:36 03/13/23 (6)
    • RE: 6N1P - Brad225 09:42:32 03/13/23 (5)
      • RE: 6N1P - Brad225 15:35:43 07/19/23 (3)
        • RE: 6N1P - mondial 18:18:42 07/24/23 (2)
          • RE: 6N1P - Brad225 16:57:28 07/26/23 (0)
          • RE: 6N1P - Brad225 05:35:56 07/25/23 (0)
      • RE: 6N1P - mondial 02:37:12 03/15/23 (0)


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