McIntosh 2100 driver boards

daveyh

daveyh

Super Member
I have acquired a McIntosh MC2100 and I would to find out where to get some upgraded driver boards. I can rebuild the ones I have but would prefer some new ones since the ones I have are burnt in several places. I have seen them online and I have searched Google and can't a link on where or who makes them. Does anyone know????
 
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McIntosh totally redesigned them several years back. They're not inexpensive but they work very well. I bought a pair for one of my MC2300s.
 
damacman said:
McIntosh totally redesigned them several years back. They're not inexpensive but they work very well. I bought a pair for one of my MC2300s.
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Wow! According to the site they are $250 for each card @ audio classics if I am reading it right. No picture. If this is the case, I will just rebuild the ones I have.
 
ManhattanUp said:
Mc will build them to order for $150 each. Just contact them directly.
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Thanks. I just ordered some parts and they are suppose to be in today.

I do have a question. On the schematics for the driver board it says C11 and C12 are 63v 150uf caps. But on the board the blue caps are 63v 330uf. I went by the schematic and ordered 63v 150uf caps not knowing they were different. I guess I should have looked? Can I mount the 63v 150uf in place of the ones that are in there now and what difference would it make if any.
 
There are probably 4 different schematics for the MC2105......you need to always see what they might have changed between builds. Buy some 330s.

Does any one know what changes they made with the new build boards? The predriver transistors have always been an issue, I believe there were 3 versions back in the day.
 
Chris - if my MC2300s weren't rack mounted, I'd just take a picture of one of the boards and post it up here. The new boards look nothing like the originals. Maybe AC can send you a pic and specifics.
 
daveyh said:
Wow! According to the site they are $250 for each card @ audio classics if I am reading it right. No picture. If this is the case, I will just rebuild the ones I have.
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How many boards total in the 2100? I'm looking at three in a pic but dunno if that's all.

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Mc2100 & Mc2105 Have 2 driver cards, Mcintosh has update kits for the cards, I installed them in both my 2100 & 2105. It came with new predrivers and a few other updates. It did not come with caps I installed 330uf. Make sure you check the 22 ohm resistors. If they read high your amp will heat up.
 
No PG in the original MC 2100 or 2105.

Must have been a lot of MC2300 cards burned to get them to start making new replacements. I also never liked productions diode placement between the transistor legs.
 
Thnx, thot there was from some of the posts.
Do they overhaul the predriver boards as well, for how much?

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Good question if they have updates for the pre board ??? I only replace the caps and out of tolerance resistors on mine . Hmm
 
I'm trying to decide if I really want to get involved with one of these, the economics vs the result is something to consider for something that may end up being a shelf ornament. The cost of Mac rebuilding one driver board gets a decent working Adcom 100 WPC amp used, this thing would have to offer something sonically remarkable if the sonic result is the goal.
I love the esthetic of the chrome chassis Mac amps, but have been using an Adcom 545-II in my 'big' system for a few weeks and have nothing but praise for what it does. Very underappreciated imo. Otoh, until I experience a properly working example of the early gen Mac, I'll never know.
Thnx to the Mac folks for responding to my postings.

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The pre-driver boards can be repaired simply enough and the amp can be made to meet specs with the originals. You really don't have to buy new boards. I believe Mc issued several tech bulletins over the years in regards to these boards.

It'd be interesting to know just how many MC2100s, MC2105s, and MC2300s are still in service.
 
Update

I was able to rebuilt the driver boards with new transistors, capacitors and some new resistors. I also added a jumper to the driver board where I pulled the old square heat sink off and I used some TO-5 heat sinks in their place. Although the driver boards had burnt carbon where some of the old resistors had fried, I was still able to use them after cleaning. I also changed all the 0.33 and 0.56 resisters on the heat sinks plus I installed new output transistors.

Someone had tried to fix one of the boards at one time and used several resistors with 2% tolerance and my DBT would not go dim and was as bright as could be. After hours of pounding my head trying to find the short I changed them to 10% and the lamp went dim. I then was able to plug it into direct current and both channels now function correctly and it sounds fine. I ran it awhile and used my thermal laser reader and it reads around 80 degrees on all four heat sinks. I also checked the speaker terminals for excessive current.

I will play it again tomorrow and hopefully all is well.
 
Great news. The service manual specifies how much current the amp should draw at idle. As long as you're under that you should be fine. Based on the temps you reported I bet you're well under.
 
There are a couple of places were a solder bridge is easy to have happen. Did you use the Central Semi replacements for the pre drivers? Which resistors did you swap for a wider tolerance one? R119 and 120 should be a 22 ohm not 18.

Look carefully at the waveform on your scope for high frequency oscillation or ringing. If you look carefully at the schematic you can see that the first output, both Darlington and compound half, is really a driver transistor. The higher gain of the MJ15003/4, compared to the original, can cause the circuit to oscillate in some amps.
 
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