MF200 bias adjustment info
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- Beginner
- Posts: 2
- Joined: Sun Oct 31, 2021 7:07 pm
MF200 bias adjustment info
Hello,
I am in the process of restoring my MF200. Does anyone have a copy of the service manual and schematic diagram?
I would also appreciate if any of you can provide me a detailed walk thru procedure to adjust the bias.
Thank You in advance.
I am in the process of restoring my MF200. Does anyone have a copy of the service manual and schematic diagram?
I would also appreciate if any of you can provide me a detailed walk thru procedure to adjust the bias.
Thank You in advance.
Re: MF200 bias adjustment info
First, welcome to CJO. Great to have you with us.
All our available schematics can be found in the troubleshooting section of the forum. If it's not listed, we don't have it.
All our available schematics can be found in the troubleshooting section of the forum. If it's not listed, we don't have it.
-admin
Home Theater in Member Gallery
Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
Home Theater in Member Gallery
Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
- AnotherJohnson
- Ultimate
- Posts: 5219
- Joined: Sun Apr 26, 2020 12:29 pm
- Location: Tennessee
Re: MF200 bias adjustment info
FWIW, there really aren’t any service manuals for CJ gear. CJ prefers that you return their gear to them for repairs so that they can control the quality and protect their sonic reputation. They won’t sell you parts, so getting it restored will be a challenge. But you can probably get it working.
Transistors may get biased, but it is not commonly considered an amateur activity. Sometimes there’s a pot. Sometimes not. You will need a bench quality volt meter or scope.
An MF200 is a good project amp. If you ruin it, you haven’t lost a gem. Just sayin’.
It sounds like a fun project. I would look forward to hearing about your progress.
There are a couple of guys who sometimes post here who are doing restorations from that era. They report excellent results, and you may achieve this too.
Best of luck!
Transistors may get biased, but it is not commonly considered an amateur activity. Sometimes there’s a pot. Sometimes not. You will need a bench quality volt meter or scope.
An MF200 is a good project amp. If you ruin it, you haven’t lost a gem. Just sayin’.
It sounds like a fun project. I would look forward to hearing about your progress.
There are a couple of guys who sometimes post here who are doing restorations from that era. They report excellent results, and you may achieve this too.
Best of luck!
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
-
- Beginner
- Posts: 2
- Joined: Sun Oct 31, 2021 7:07 pm
Re: MF200 bias adjustment info
I do have a scope, variac, ampere meter, dbt, dmm’s, signal generator but no distortion meter yet.
I’ve done a few BK mosfets, Moscode and Counterpoint hybrids before, MOSFET are very tricky to calibrate. I would assume it would be similar procedures for doing the MF-200 since it’s also a mosfet amp. It best to get a copy of the SM. Idk if there any CJ dealers close to me here in Toronto Canada. I have an electrical engineering background so I am bit adept with electronics.
I’ve done a few BK mosfets, Moscode and Counterpoint hybrids before, MOSFET are very tricky to calibrate. I would assume it would be similar procedures for doing the MF-200 since it’s also a mosfet amp. It best to get a copy of the SM. Idk if there any CJ dealers close to me here in Toronto Canada. I have an electrical engineering background so I am bit adept with electronics.
- AnotherJohnson
- Ultimate
- Posts: 5219
- Joined: Sun Apr 26, 2020 12:29 pm
- Location: Tennessee
Re: MF200 bias adjustment info
Maybe one of the guys who does restorations will help you out.
Maybe the Canadian importer would help.
CJ is not Technics or Sony or Yamaha. They do not offer service manuals. The protection of their IP is a major focus on this era of counterfeiting and Asian knockoffs.
Best of luck.
Maybe the Canadian importer would help.
CJ is not Technics or Sony or Yamaha. They do not offer service manuals. The protection of their IP is a major focus on this era of counterfeiting and Asian knockoffs.
Best of luck.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
- AnotherJohnson
- Ultimate
- Posts: 5219
- Joined: Sun Apr 26, 2020 12:29 pm
- Location: Tennessee
Re: MF200 bias adjustment info
https://www.conradjohnsonowners.com/vie ... php?t=2285
This thread is related to one of the restorers.
Bob Backert is another guy who has a following. Bill Thielman is another. I may have spelling wrong.
This thread is related to one of the restorers.
Bob Backert is another guy who has a following. Bill Thielman is another. I may have spelling wrong.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
- Joe Appierto
- Pro Master
- Posts: 650
- Joined: Fri Aug 24, 2012 5:04 pm
- Location: NJ
Re: MF200 bias adjustment info
It's Bill Thalmann at Music Technology. He's the one who converted my PV10AL to a PV10A when he added the phonostage. I believe he was CJ's chief designer/#3 guy for about 20 years or so and left CJ around 2000.
https://www.musictechnology.com/about-us.html
https://www.musictechnology.com/about-us.html
Oppo BDP-105D and PSA DS DAC
Conrad Johnson CA200
MartinLogan EML
In-Akustik Exzellenz Cat 6 Ethernet and HDMI, Q-Audio IC and speaker cables, and Acrolink 6N P4030 power cords; PSA Duet PLC and Juice Bar, Oyaide R1 wall outlets
Conrad Johnson CA200
MartinLogan EML
In-Akustik Exzellenz Cat 6 Ethernet and HDMI, Q-Audio IC and speaker cables, and Acrolink 6N P4030 power cords; PSA Duet PLC and Juice Bar, Oyaide R1 wall outlets
- AnotherJohnson
- Ultimate
- Posts: 5219
- Joined: Sun Apr 26, 2020 12:29 pm
- Location: Tennessee
Re: MF200 bias adjustment info
Thanks Joe. I knew I had it spelled wrong.Joe Appierto wrote: ↑Sun Jul 24, 2022 12:03 am It's Bill Thalmann at Music Technology. He's the one who converted my PV10AL to a PV10A when he added the phonostage. I believe he was CJ's chief designer/#3 guy for about 20 years or so and left CJ around 2000.
https://www.musictechnology.com/about-us.html
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.