McIntosh A129 Monoblock

well looks like youve got quite a job ahead of ya on this thing. All i can say is good luck, fixing old MCintosh stuff isint my forte lol but maybe you will have better luck fixing yours. I cant speak for the resistors which look pretty shot, that thing definetly went up in a puff of smoke. but i believe the part on the far side of the board which has the cutout in the cover, facing down on the monitor. yes that part is a selenium recitfier, which is toxic. I know you can replace these with a diode and resistor device because thats what we did on my MC240 when i was repairing it.

this site has some info on the MC240 and points out parts and stuff. might be intersting to look at anyway. MC240
 
That is the strangest looking MC40 that I have ever seen, you are in for a real job figguring out the circuit, a MC40 has all its parts mounted on the terminal board like a 240 does.
 
My guess....

I've spent the last few minutes reading all the posts on this amp-of-mystery. Here's my guess for what it may have been used for:

Most likely: It was made for Square D to drive a shake table/vibrating platform of some sort. The only argument I can see for this application is that the amps were usually higher in wattage than this one appears to be able to produce.

Second most likely: It provided a solid 60 Hz or other frequency (like 400Hz for aircraft) signal for testing breakers and other power control devices.

- This may account for the hole cutout on the bottom of the chassis, which may have been used for a way to control the power input in some way.

BTW, just the amount of contributed expertise to dig out detailed information on this amp (can we call it that?), is just amazing.

Thanks for drawing us all into one of the more rare Mc devices I've ever seen.

Cheers,

David
 
I have a MC2500 that was used in the Oil Exploration industry. It had an additional back panel on it with some Mil type connectors one of which was labelled "Tow Fish". That is only strange amp that I have seen. I did dig up some additional info about it but since I have a tendency to yack too much,I will shut up now unless someone wants all the gory details. :)>)
 
NOW it gets interesting!

I decided after dead end to dead end, to call Square D.

Ended up speaking to a really nice guy over there who's been with the company quite a long time. Apparently Square D at one time produced a system called the Square D Elan, which was a residential in-home full control system for music reproduction with speakers placed throughout the home and a single control panel to control the speakers. In 1995, that part of the business was sold and is now http://www.elanhomesystems.com/ . According to the gentleman I spoke with, he had no recollection of McIntosh ever having contracted with them, that their systems were amplified mostly with Jensen components. He was kind enough to give me a phone number to contact Elan directly.

Next phone call.....

Ended up in touch with another really nice fella, Mr. Ross, over at Elan. He'd never heard of McIntosh being used in one of their systems either, so he went and spoke to the VP of their engineering department. He couldn't recall McIntosh gear being a part of their systems either, so he kindly offered to look into it for me if I would send him some pics.

The most ironic thing, is that when Mr. Ross put me on hold, what was playing on hold but Boddhastiva!

Karma I tell ya! Karma! :D
 
Re: NOW it gets interesting!

Originally posted by Kamakiri


.....
The most ironic thing, is that when Mr. Ross put me on hold, what was playing on hold but Boddhastiva!

Karma I tell ya! Karma! :D

And would a Boddhastiva be animal, vegetable or mineral and be larger or smaller than a breadbox? :dunno:
 
Originally posted by Wardsweb
OH Pleeeaaaaasssssssee :saywhat:

Steely Dan - BABY - Steely Dan

Sorry 'bout that. My eyesight has gotten so bad I can no longer read the tiny writing on CD cases so I don't worry about the names of any songs at all. I just know 'em to listen to if I like 'em. ;) My identification resolution goes about as macro as the name of the album these daze.
 
Kamakiri,

What you have is an MC75 that has a custom output transformer that appears to only have one tap of some unknown impedance.
Rather than use an RCA input they are using some of the speaker terminals for the input. This was common on industial units and the MI200 is like this. This is also your tip off that the 2,4,and 8 ohm impedances are not available.
The inside looks like a MC75 that had a plumber work on it! The outputs should have the wire wound inductors and 2, 220ohm sand block resistors run between them. McIntosh would not use the 5 watt resistors running between the small tube sockets. On the end of the board by the output tubes there should be 2, 12 uf electrolytics for the bias but they seem to be MIA. Yikes.
If you pick up an MC75 schematic you should be able to compare.
The hole in the bottom screen looks to be for access to the fuse which by the looks of the inside blew often.

Ron-C
 
Ron-C, look at the length of the terminal board, does it look short to you ? I think I had better get a MC75 and take some pictures of the bottom and post them.
 
The terminal board is the right length for the MC75 but the stereo units like the 240 and 275 are much longer. Those five watt resistors should be mounted on the board behind the 12bh7. The amp if very far from original inside.

Ron-C
 
Part number for the one transformer is 043-343, the other is the one I had redone, and I put the tag in a special place....now I just have to find it :confused:
 
Email from Elan:

Tim

What a very interesting device! The pictures also helped me determine that this is definitely not an ELAN or SquareD/ELAN product. I’m a little baffled why McIntosh was unable to help you as it clearly has their logo on it. I’m trying to imagine what the Square D number relates to, but this unit definitely predates the existence of ELAN as an individual entity or as a subsidy of Square D. I had hoped that we could shed more light on this, but this unit is not related to us in any way... Good luck w/ your project!

Brent Ross

ELAN Technical Writer/Support
 
K,

If you call McIntosh with the part numbers to those transformers, they might be able to tell you something about the equpment they went into. Call it reverse engineering. (">)

r
 
That may be the next step. I'm beginning to think, however, that this piece of gear was created for Area 51 :tongue:
 
Originally posted by Kamakiri
That may be the next step. I'm beginning to think, however, that this piece of gear was created for Area 51 :tongue:

Maybe it was brought here from"away":zoom: :yikes:

Alan
 
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