|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
47.197.10.172
In Reply to: RE: 6N1P posted by Brad225 on February 15, 2023 at 06:08:41
It looks like the problem has an answer.
Yesterday Phil did a diagram of the entire bias circuit with values large enough to make notes on it.
This morning he started unsoldering some parts to test values and found 5 resistors on the "non zeroing" side of the amp that were nothing like the schematic or the resistors on the other side of the amp. Their values or markings were not there on any of them. Phil mentioned other parts that they had removed any identifying marks in the past, probably for proprietary design reasons.
He texted today me and said the believes he found the problem being, the 5 resistors.
An hour later he called to tell me that he had received an email from Greg at ARC. Greg said that he found an engineer that had been there long enough that he remembered an issue they encountered with the bias circuitry.
Apparently during production they ran out of the parts that were originally designed to be used and changed the 5 resistors in different places (with no markings) and never put it on the original schematics. So, the only people that ever knew were the engineers and the person installing the parts.
The weeks Phil has been trying to figure this out is a design change with no public record. Pardon my language but, that is F-ed up. I guess, the only good news is that they owned up to the unrecorded change and gave us the correct information.
They do have the original correct parts and will sell them to us so Phil is ordering them today.
As one of my pair of amps has both configurations I asked Phil to find out what year my amp was assembled. It would seem, it was possibly the first one, hence, the different design on each side of the same amp.
I am so thankful for Phil. I don't think I could find anyone else that would have the patience and curiosity to make this happen. To say nothing of the labor bill if I didn't trade my furniture making skills for his EE skills.
Hopefully my next post will be confirmation of the problem being corrected.
Follow Ups:
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.
Back home and ready to be enjoyed again.
So, here I am a few months later and 300 hours into breaking in all of the new parts.
I'm stunned at the difference/improvement in the sound of what are virtually new amps. The clarity is not something that I would have thought could improve this much. The size of the sound stage has moved wider and deeper than the previous version.
Small details in the music such as string vibration and the sound of a plucked string are clearly present. Not that it exists on all music but it is much more noticeable than previously showed when it does. Low-end is much more pronounced that I had experienced. I could ramble on but I will leave it with my opening comment that the sound is stunning.
I did also choose to eliminate the 8m interconnects by moving 1/2 of the front end equipment to the front of the room. This allowed me to run 8m fiber optic from the previous location to the front. This helped shorting the new DIY interconnects to 2m. Being able to purchase 2- 8m fiber cables for $18 was not all bad either.
This was also an improvement in the overall sound.
It did mean I had to DIY an 8m #10 power cable to run through the conduit to the front of the room so I could keep the existing power conditioning feeding the new location.
I'm glad everything is working out for you Brad . Both ARC REF 610 T's and REF 40 Anniversary are keepers .
Thanks, monodial,
I am thrilled. Everything is working properly and sounds the way it does. Neither of those pieces is going anywhere soon.
Brad
Thanks, monodial,
I am thrilled. Everything is working properly and sounds the way it does. Neither of those pieces is going anywhere soon.
Brad
Wow ! Congratulations , happy listening !
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: