Power Mod from 100V to 200V on MC2105 - diyAudio
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Old 15th April 2009, 09:28 PM   #1
Beck81 is offline Beck81  France
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Default Power Mod from 100V to 200V on MC2105

Hi all,

Everythingis in tittle, indeed.

Does somebody already try this mod ?

The mod aims at serialyzing primary windings but I would prefer having some feedback before handling it.

thanks in advance,
Beck.
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Old 16th April 2009, 12:21 AM   #2
llwhtt is offline llwhtt  United States
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Beck,

I'm assuming you mean you want to change the amp from 117VAC (120) operation to 234VAC (240) operation, correct? For 117V operation you should have Black and Black/Red tied together BEFORE the thermistor and then Black/Yellow and Black/Green tied together BEFORE the other thermistor, does that look like what you have? If it does, now disconnect the Black/Red and the Black/Yellow and tie them together. The primaries were in parallel and now they are in series. That should do it. If you are not sure of what you are doing DON'T do it.

Craig
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Old 16th April 2009, 01:42 PM   #3
Beck81 is offline Beck81  France
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Craig, you're exactly right. I am trying to do this modification to not add a power limited converter in the loop.

I agree, there are 2 steps.

I have highlighted the first one in the document attched (Red Circle). The Black/White wire have to be unsoldered.

My concern is that I cannot find the other modifictation on this side. Can you confirm me that I have to access the alimentation Bloc upside ?

Regards,
Beck.
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Old 16th April 2009, 02:52 PM   #4
llwhtt is offline llwhtt  United States
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Beck,

I think you are looking in the wrong place. To the right of the big silver can(capacitor) there are two little discs (thermistors) mounted on a terminal strip. The wires on that strip are the wires to the primary of the power transformer and the ones you need to work with. Do you see a Black, Black/Red, Black/Yellow, and Black/Green? Follow what I said in the first reply. If you are not sure DON'T do it.

Craig
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Old 16th April 2009, 02:55 PM   #5
llwhtt is offline llwhtt  United States
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Beck,

What is the serial number of your amp, the instructions I gave you were for after serial number 26M08. Yours may be different. What is the schematic in the picture?

Craig
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Old 16th April 2009, 03:56 PM   #6
Beck81 is offline Beck81  France
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the SN is scratched.

le schematics is attached.

In the meantime, I am double cheching colors on the my Amp.
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Old 16th April 2009, 11:29 PM   #7
llwhtt is offline llwhtt  United States
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Beck,

If the schematic you posted IS your amp then just flip the switch and you are done. If there is NO switch then the schematic is for a different vintage and you'll have to do what I described in the earlier posts.

Craig
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Old 17th April 2009, 12:18 PM   #8
Beck81 is offline Beck81  France
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the schematics I have posted is the recommandation from McIntosh.

I do not have the switch.

My concern, as you can see on the picture, there is neither Black/Yellow or Black/Green on the terminal switch near the Thermistor.... Could I have a model with only 1 primary and not 2 ?

also, you were talking about SN, and specially for number before and after 26M08. What is the difference ?
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Old 17th April 2009, 03:03 PM   #9
llwhtt is offline llwhtt  United States
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Beck,

The service manual I have is for amplifiers starting with 26M08, I don't know what was before that. There might even be a later manual than mine, I don't know. If you start with the power cord and follow it back you'll have to find all of the leads to the power transformer sooner or later. All of three of the transformer leads are cloth, should make it a little easier.

There is another MC2105 being worked on by Grant in a different post, maybe email him and ask him since he has one in front of him. If I had one in front of me I'd know what to do or be able to tell you where to look.

Craig
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Old 19th April 2009, 09:32 AM   #10
Beck81 is offline Beck81  France
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I have seen Grant_Mh posts about the MC2105 and having his point of view on this mod could help us.

As i am newbee, I cannot mail him to com on that post. Craig, could you do this for me since I do not want to pollute on of its posts ?
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