• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

MC2155 Left channel problem fixed. New problem is worse than than the old one.

Ricktptman

Ricktptman

High Fidelity Enthusiast
Subscriber
I found the intermittent contact on my (new to me) MC2155. It was on one of the harnesses at the front of the amp. I tightened up the contact for that pin (on the harness) and it's 100% percent functional in both channels. Now....the bad news. There was a flickering LED in the rightward most housing (from the bottom) so I pulled it out and started to replace it. I had to go through about four LED's before I found one that was consistently "good". I move to insert the housing (the one with vertical holes) back into chassis and it must have (I had to take my bifocals off) brushed against something hot. There was a very small wisp of momentary smoke. Everything's peachy keen and all the Green LED's work just fine. I decide to peak around at the front of the amp before replacing the bottom cover and there's no meter lighting. The meters aren't deflecting. #$!$%.
I could use a little help. TIA.....
 
Register to hide this ad
There is a fine strand wire inside a clear plastic tube that acts as a fusible link for the 12volt and 5 volt supply. It is in one leg of the 5.6volt AC secondary of the transformer....it is buried but access is from the bottom and links two sides of a tag/solder lug.

The schematic says 30AWG I use a single strand of copper......
 
It looks like the green fascia lamps are out/dim now as well. But the meters are "trying' to work when I switch the meter function switch back and forth between positions. The meter lamps come back up momentarily as well. So this is a SINGLE strand of 30awg? How do I access it? It's not near that lamp I replaced, correct? I'll screw up my guts and give it a try if I can get you guys to walk me through it. I just got the thing put back together and flipped back upright. Next time I'll set it up on a table so I can get these old, nearsighted eyes closer to it. I'm going to take a few minutes to indulge in some good old fashioned self-recrimination before I go back in though...... ; - )
 
Okay, I thought from the post it may have been inside the transformer. (Which made me wonder about how it faired with all that tar.) It'd be nice if the warning sticker showed you where the thing that apparently either had been replaced before (no plastic tube) or vaporized completely (except for a few nubs of single strand wire on one lug) was located. But I figured it out. It's back at 100% now. For the first time since I bought it actually. I turn it on. It works. Immediately. Every time. This is the Mac experience I'd always imagined. "Thas' what I'M talkin' about....." New glass is here and new meters are on the way. I'm saving those for a rainy day. There are only two drawbacks to the glass and meters I have now. A slightly faded decibel scale and a few light paint issues on the glass. I had to remove the blue filters to clean the glass when I got it and doing that caused a fleck-fest. The charms of static electricity in Winter (where I live) encourage me to wait until Spring to take a run at replacing the meters. There's nothing wrong with the meters themselves......I don't waste a lot. Of course I'm running out of room with parts and backups for my collection....seems like a good time to call it a day for new acquisitions......at least for a while.....
 
I used 28 gauge solid strand. Is that close enough? I also left the insulation on it. THANK YOU, Mackie 1975 and c_dk for your help. You got me out of a tight spot and your experience made all the difference. I sincerely appreciate it. This is what makes AK the best audio group I've ever been on. And I've been (and I'm still on MOST of 'em) in a lot of them.
 
Last edited:
UPS destroyed one of the meters in shipment. I thought they were brittle from the post-installation heat crazing from the lamps. Turns out they're that brittle from the factory. When the time comes, I'd sure appreciate some advice from from whomever the meter reconstruction gurus are.
 
I thought they were brittle from the post-installation heat crazing from the lamps. Yes , this is the reason why . Overheat in MC2155 meter housing is cooled by holes on the top of the dust cover . This is a real problem with the MC2125 which is not cooled like the MC2155 is .

Turns out they're that brittle from the factory. No , when they were new they don't have any problem and the light box is strong . Heat is the drastic factor .

Please send a picture of your meter to see if it is refixable or not .
 
Ricktptman said:
UPS destroyed one of the meters in shipment. I thought they were brittle from the post-installation heat crazing from the lamps. Turns out they're that brittle from the factory. When the time comes, I'd sure appreciate some advice from from whomever the meter reconstruction gurus are.
Click to expand...

Can you post some picture?
 
Not to be argumentative, but I received new meters from Mac (thanks, Gail....you tried) and one disintegrated in the box. It's not JUST the heat, it's the plastic that the meters are made from.
The big problem (I'm pretty good with Cyanoarcylate) is the meter needle. It got bent at nearly a 90 degree angle. Down near the base, it's not flexible like it is out at the tip. These aren't used meters, they're NOS.
So, no.....you're factually incorrect. It's the plastic they're made from. I'm okay with trying to reconstruct the light box with Cyanoacrylate or epoxy. What I need is some "been there done that" advice with the meter needle itself.
One meter made it fine. I have it secured in bubble wrap and put in a very safe place. I'm new to Mac, but not new to working on gear. Any help's appreciated. I didn't want to throw shade at Mac, which is why I was non-specific.
I can't speak highly enough for Gail. They didn't charge me and the parts (especially-the Fascia) are invaluable to me. My meters are relatively "fine" except for some minor fading on the face's decibel scale.
I have glass and was going to do a final "tweak" of the appearance and go ahead and change out the meters. But now I think I'll just let sleeping dogs lie until I can find a way to reinforce both of the (yes, they're absolutely as brittle as what's in the amp. Maybe more so) NOS meters. But any and all advice is appreciated.....I read one post that talked about 3-D printing new light boxes. That'd be great, and I'd buy a set, but it still doesn't solve the needle problem on the one meter that got shook to pieces in shipment....TIA.....
 
Last edited:
I can't get photos taken with my Nikon to upload. I'll have to use a phone. You've got the details that matter. The rest of it can be reconstructed with only a few splinters missing. But the meter electromagnet housing came loose from the back of the meter (from the back face) from its being slung out of the bubble wrap. That's how the needle got 86'd. Again, I can't go to UPS for the damage, because I didn't pay anything for the meters. It was a kindness that I wasn't sure I was supposed to share, but for all of Mac's hyperinflated MSRP's, they take excellent care of their clientele. This amp was made when I was still in College. (I remember lusting after it when I'd visit SSI on Independence Blvd in Charlotte, back when I was on the road playing Trumpet and R&B acts would play in town and hire horn players.) Mac's not forced to do anything for me. But they tried. That means a lot in this day and time.....to me...anyway....
 
Yes, they both did. No blue filters, but the front of the meter face (the enclosed part) was. The meter proper. My filters are fine. The one just shattered by being slung around. It came out of its Bubble wrap and the back end of the meter "fell away" from the Fascia (which is solid and fine, btw) and that's how the meter needle issue came about. It was like that when I opened it. One was fine, the other (which had some glue on it, which was interesting) was NOT....
 
Again, I'm not that worried about trying to glue the light box back together. It's the NEEDLE issue I'm seeking help with....
 
There's not much to see. The part that covers the mechanism itself (not the meter face) had came loose from the meter face part. The Face/Fascia is fine. The meter "motor" is fine. There are some shards and small pieces and two BIG ones. And a broken meter needle, fairly close to the base. It broke when I tried to straighten it. The end is more flexible but the thicker end at the base is (apparently) pretty brittle. I can glue the rest back together. The needle is what I'm frankly more concerned with repairing. Some kind of splint would be the only thing I can think of and I don't know how to keep THAT from showing....
 
Your picture file is most likely to large to download....i often just use paint to decrease the file size.

I do have a few meter movements from a MC2125 I did before I got sick 2 1/2 years ago and move ago, around here....if you are patient i should be able to find them.
 
Hello Chris

I think that MC2125 movement has not the same ohmic value as MC2155 movement
MC2125 = 2,62K
MC2155 = 2,14K
 
Patrice,

I honestly do not remember which movements I ended up using when I installed the mc2155 light boxes in the mc 2125. I do know they calibrated correctly and I think they had the same OEM part number on them.

That was over 2 1/2 years and the infamous you got 3 days Doctor speech ago.....

I do know I had my photographer neighbor help me with the teal meter color as the owner insisted on LEDs.....the original Mac filter papers were way off when using LEDs.

I will have to pull out some parts boxes and see what I have left over.....should be 2 MC2255 meters and 3 MC2125/2155 meter movements somewhere.

I thought Gail told me I got 3 of the last 4 MC2155 meters, I too had a damaged light box that I was able to repair and save until I can find someone local with a 3D scanner to create a 3D printer file.
 
Thank you so much, c_dk, Clinic-audio and Mackie1975. C-dk, PM me about Doctors and health issues. I have several. I loved my career (teaching and playing Music) but I was forced to tap out after decades of no Health Insurance (not veering towards politics, but it is what it is) and then getting hit with a Hematological disorder at some point.
I will absolutely be patient, but please do look. They probably unearthed two extras, or maybe decided to just give these away to a motivated newbie, even if they didn't meet their stringent replacement parts standards. I don't know how big the facility at 2 Chambers St is, but I'll bet it's big enough to lose track of a couple of meters. I've wanted a Mac system all my life. I finally have one. I took it slow and started with an MR78, then a C28 (I think I got lucky with that one, it needed a little tweaking but seems to work fine) and now the MC2155. This has been a sort of bucket list thing for me. I'd love to drop the coin for new Mac, but this is the way I've collected the rest of my audio, so, it's a little late to change now. Thanks again to all for your responses. I'm still very interested in suggestions. When my subscription comes around again, I'll have to up the contribution.....Thanks....
 
You must log in or register to reply here.
Back
Top Bottom