A Friends DIY For Me

Both amps are back working with 200 new parts in each one.
The upgrade to KT120 tubes should not take long at all.

Front screen lit and tubes happily glowing.

I had planed on replacing both front screens as they were getting hard to see in places. Phil said they were covered with dirt, finger prints and gunk. Who would have thought they only needed to be cleaned.
 

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Great Stuff , interesting to hear the SQ difference on your ESL’s when you do make the switch to KT 120’s ..


Regards
 
Upgrade parts are in and we installed the new tubes. One amp is fine and bias is great. The other won't bias correctly on one bank of tubes. One of the variable resistor is not allowing adjustment to the correct specs. Phil thinks the V18 bias control tube is bad.

Waiting for a response from Greg at ARC before putting a new tube in the socket.

They are so close to being finished and coming home. I can't wait to have music again.
 
brad225 said:
Upgrade parts are in and we installed the new tubes. One amp is fine and bias is great. The other won't bias correctly on one bank of tubes. One of the variable resistor is not allowing adjustment to the correct specs. Phil thinks the V18 bias control tube is bad.

Waiting for a response from Greg at ARC before putting a new tube in the socket.

They are so close to being finished and coming home. I can't wait to have music again.
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Woo Hoo!!!!
 
It didn't take me long at all. Then again I didn't do the technical work.

I moved them to Phil's home the second week of November. He was working on other things for a while and started taking measurements on existing parts on the 17th.

Then waiting for parts and more parts and then more parts.

Should have parts for one of the two bias circuits in one amp by mid week and both amps should be complete. One amp is finished and passed every test on ARC's checkout procedure.
 
What is loud, that you can't hear, is the sound of Phil and I tapping our respective feet. ARC didn't ship the parts order until a week after they were ordered.
They are scheduled to arrive on Tuesday the 10th.

I am so ready to have them finished and me back in my listening room. Tap-tap-tap. :)
 
Wow! What an undertaking! Looking forward to hearing your amps/setup as well as Phil's latest speaker project sometime down the road.
 
brad225 said:
They are scheduled to arrive on Tuesday the 8th.
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Holly Molly Brad, not until August ??? That's the first month I could find where the 8th fell on a Tuesday ! :lol:

I am so ready to have them finished and me back in my listening room. Tap-tap-tap. :)
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patience my young Jedi warrior !
 
THEIR ALIVE.

Last delay was replacing the adjacent parts for the "adjustable offset resistor" in the left amp this time. This controls the bias voltage to the tube controlling the bias of half the KT120's.

It is hard to tell the difference A to B as the amps are still at Phil's. Considering all new tubes and hundreds of new parts they sounded amazing. Unlike his rebuilt McIntosh amp has sounded.

I won't be able to bring them home until next weekend it looks like. Strong nephews have work commitments.

They put out about less than 1/2 the heat with the KT120 upgrade.

More to come.
 

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brad225 said:
their alive.

Last delay was replacing the adjacent parts for the "adjustable offset resistor" in the left amp this time. This controls the bias voltage to the tube controlling the bias of half the kt120's.

It is hard to tell the difference a to b as the amps are still at phil's. Considering all new tubes and hundreds of new parts they sounded amazing. Unlike his rebuilt mcintosh amp has sounded.

I won't be able to bring them home until next weekend it looks like. Strong nephews have work commitments.

They put out about less than 1/2 the heat with the kt120 upgrade.

More to come.
Click to expand...



wooo hoooo!!!
 
brad225 said:
THEIR ALIVE.

Last delay was replacing the adjacent parts for the "adjustable offset resistor" in the left amp this time. This controls the bias voltage to the tube controlling the bias of half the KT120's.

It is hard to tell the difference A to B as the amps are still at Phil's. Considering all new tubes and hundreds of new parts they sounded amazing. Unlike his rebuilt McIntosh amp has sounded.

I won't be able to bring them home until next weekend it looks like. Strong nephews have work commitments.

They put out about less than 1/2 the heat with the KT120 upgrade.

More to come.
Click to expand...

Brad , could you give more details regarding your McIntosh comments..


Regards
 
His Mac was purchased new in 1972 I don't remember the model. He has rebuilt it numerous of times and by his admission the limitations are the age and designs of the amp.

In comparison the ARC that is 33 years newer with mostly new parts has a much larger and way more defined image and staging. The upper mids and highs are so much more apparent and precise in ARC.

The Mac in and of itself didn't sound bad. It is just in comparison the 610t's sound so much better in his system.
He is currently watching the internet for a Ref 150SE to replace the Mac.
 
Last edited:
I went to Phil's on Wednesday to so the final disassembly of tube removal and put sides and top back on in order for moving them home on Thursday.
We needed to put the final pair of 6n1p tubes in each amp that control the biasing. We had been using a mix of tubes, as some from each set I purchased had issues.

Those tubes need to be adjusted to 0 volts on the + and - side by way of a zero Offset Variable Resistor.
When tubes, that a few days before would 0 out now would not, Phil decided it was something else other than the tubes.

He looked at the schematic and determined it was the field effect transistor "FET" in the path of the circuit to the variable resistor. We shut the amp down and after finding the value that should be attributed to the FET he tested it and it was the issue. He tested all of the resistors again the that part of the bias circuit and they all tested to within .001 of each other at the proper rating.

He ordered 4 new FETs from ARC that afternoon and they will arrive on Saturday. I will be there on Sunday for the install and final (I HOPE) check the 0 voltage is working properly again. We are replacing it in both amps even though the other amp has not had issues with the "0" adjustment.

They, will be ready to come home after that.

I asked him to tell me honestly the other day. Has there been many times you are sorry you agreed to do the rebuild. Without hesitation, he said, nope I find the whole process so satisfying. I thanked him again, for probably the 100th time.
 
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