MC2150 cosmetic quirks and questions

[cnolanh]

Last year I bought an MC2150 from AudioClassics and it's a terrific amp. This particular one is in good condition but arrived with two small weirdnesses, which I was reminded of recently when I moved the amp:

1. On the rear chassis, the white serial number area is blank. I highly doubt that this amp has needed/gotten a replacment chassis as all the parts look normal for their age. Has anyone else seen an MC2150 — or other Mc amp from that vintage — with a missing serial number? Is there anywhere else on/in the amp I can find its serial number? McIntosh made fewer than 400 of these so I'd love to know where mine was in the production.

2. The Normal lights work properly but unlike all other MC2150 photos I've seen, these lights glow white instead of green. There are tiny hints of green at the edges of the lights, so my hunch is that the green tint has faded somehow. If the amp had once been installed in a place with direct sunlight on it, could that have turned the plastic pieces from green to clearish? Any suggestions for getting them back to the right color?

Thanks for any wisdom about these small things, folks.

 

[jlovda]

Maybe you got an engineering prototype?

 

[VintageMac]

Those also have serial numbers - starting with an E.

The serial numbers were rubber-stamped on and it is pretty easy to eradicate them, especially if someone waxed the chrome.

Larry

 

[cnolanh]

Those also have serial numbers - starting with an E.

The serial numbers were rubber-stamped on and it is pretty easy to eradicate them, especially if someone waxed the chrome.

Larry

Then possibly a previous owner got overeager about cleaning. Arg. And there’s no other (internal?) place where the number is repeated?

 

[skippy_ps]

It's supposed to have green gels taped to the back of the glass and a defuse'r to concentrate the light in the correct place. You'll just have to take the front panel off and see what the deal is. Don't attempt to peel the tape off the back of the glass as you'll almost for sure damage the paint.

Also, make sure you have the correct lamps in place.

 

[jlovda]

It's supposed to have green gels taped to the back of the glass and a defuse'r to concentrate the light in the correct place. You'll just have to take the front panel off and see what the deal is. Don't attempt to peel the tape off the back of the glass as you'll almost for sure damage the paint.

Also, make sure you have the correct lamps in place.

Can you provide a picture of the other end of the front panel? The glare masks the section you are interested in.

 

[clinic-audio]

Hello cnolanh

1) is it a MC2150 or MC2155 ? MC2150 has aluminium panel not glass
2) And there’s no other (internal?) place where the number is repeated ? yes , there is two places where you can see a "stamped number" on the side of the chassis (easy to see) and the other place is under the power transformer .
This is true for every MCINTOSH produced during these years .
The number is a "codification" of the real serial number . Finding this number will not help you because the file with all these "secrets" has not been saved at factory and getting an answer is impossible today .
Here is what it look like :



Your original serial number should be like this : DA12XX and 1984 dated
We did not import a lot here in France during these years

 

[cnolanh]

Thanks, all. This is the MC2150 in question. On these metal face amps, does the green color come from a diffuser behind the face, or is the plastic piece itself colored green?

 

[jlovda]

I will take a guess and say the 2120 series is close to the 2150 series regarding the metal front panel. Here are pictures of the front of the chassis and the back of the front metal plate for my 2200.

The red lamps have two red filters; one taped to the chassis and one to the back of the front plate. I'm guessing Mac wanted the red color to be deep. The green lamps have one filter on the back of the plate. I am guessing that the green filter was placed on the plate because the green lamps are on all the time and there is an air space between the chassis and plate. If the white cup for the green lamps are closed (as the case for the red) it might get too hot and damage the plastic.

BTW, my 2200 sits like this all the time without the front plate because the plate is terribly dented.

John

 

[cnolanh]

John, that's so helpful! So probably I just need a new green filter on the back of the front panel. Next time I've got the amp out of its case I'll take off the front and check that out.

 

[cnolanh]

2) And there’s no other (internal?) place where the number is repeated ? yes , there is two places where you can see a "stamped number" on the side of the chassis (easy to see) and the other place is under the power transformer .
This is true for every MCINTOSH produced during these years .
The number is a "codification" of the real serial number . Finding this number will not help you because the file with all these "secrets" has not been saved at factory and getting an answer is impossible today .

That's good info. I'll make note of that stamped number if I can find it, though I see your point that I won't be able to translate that into a proper serial number.

 

[jlovda]

John, that's so helpful! So probably I just need a new green filter on the back of the front panel. Next time I've got the amp out of its case I'll take off the front and check that out.

That would be a good time to put new light blocking foam strips around the filters. My foam was shot and scraped away.

Notice also that there are white filters to diffuse and soften the light from the lamps.

 

[skippy_ps]

Can you provide a picture of the other end of the front panel? The glare masks the section you are interested in.

That's just a pic that I found on the 'net.

Murray

 

[cnolanh]

A while ago I did pull the faceplate on the MC2150 and I found that, as expected, the green filters had faded to near-white in the spots right over the faceplate holes. Maybe it sat in sunlight or near a bright light for much of its previous life? I was able to shift the filters a little to get green light once again showing through the faceplate.

I also recently sent the amp back to Audio Classics for repair after one channel began overheating. They replaced a driver transistor, bias transistor, and light-dependent resistor. They also replaced lamps, cleaned the pots and switches, and bench tested the amp. Upon return, it sings more beautifully than ever — it sounds more transparent and effortless to me than it did before, though of course that might be my confirmation bias after paying for the repair/updates.

It's a wonderful amp. Here it is sitting pretty in the rack, with a Nakamichi RX-505 above it.
[EDIT: I must have bumped that Left Gain while dusting for the second photo. It's back to full now! ]

 

[62caddy]

At 390 units produced, MC2150 is one of the rarest McIntosh power amplifiers.

http://www.mcintoshcompendium.com/Compendium Docs/Power Amplifiers/PDFs/MC2150.pdf

 

[twiiii]

I installed 4 or 5 in smaller discos for the HF speakers, normally Klipsch Las Scalas, and used 2250's to drive the MWM. woofer used as subs. Sounded great and with two La Scalas on each channel 90 watts or so was a perfect match. In one disco system we used the 2155 to drive the monitor speakers while 18 2255's drove the fill and dance floor speakers and 4 2600 drove the sub woofers. I liked 2155's and 2150's. They were smooth and easy to listen, too. Power Guard protected the speakers and my ears. I tried them at home but preferred the 7200, because of its much higher damping factor because it didn't have autoformers. It really showed up the PSA2 and DC-300 A's I was using at the time.

 

[Gregory]

It's supposed to have green gels taped to the back of the glass and a defuse'r to concentrate the light in the correct place. You'll just have to take the front panel off and see what the deal is. Don't attempt to peel the tape off the back of the glass as you'll almost for sure damage the paint.

Wow, they stuck polyfoam tape on the back of the glass!!?


-Greg

 

[Gregory]

Thanks, all. This is the MC2150 in question. On these metal face amps, does the green color come from a diffuser behind the face, or is the plastic piece itself colored green?
View attachment 1128149

That's a nice amp, been keeping an eye out for one of those. Did you buy it from Audio Classics? Yes, now I see the Eval sheet. The one they had was some kind of factory proto or Eng model. Are the covers missing from the back of heat sinks? That's what AC sent me photos of, a 2150 with missing back covers.

Please post a photo of the back side.


-Greg

 

[Gregory]

This is the amp that AC sent me photos of in Oct of 2012.






Should look like this:




-Greg

 

[Gregory]

A while ago I did pull the faceplate on the MC2150 and I found that, as expected, the green filters had faded to near-white in the spots right over the faceplate holes. Maybe it sat in sunlight or near a bright light for much of its previous life? I was able to shift the filters a little to get green light once again showing through the faceplate.

I also recently sent the amp back to Audio Classics for repair after one channel began overheating. They replaced a driver transistor, bias transistor, and light-dependent resistor. They also replaced lamps, cleaned the pots and switches, and bench tested the amp. Upon return, it sings more beautifully than ever — it sounds more transparent and effortless to me than it did before, though of course that might be my confirmation bias after paying for the repair/updates.View attachment 1833246

There's no date on the Eval sheet?


-Greg