Searching for original MC2155 manual

[clinic-audio]

Hello Ricktptman

You did not offend me , I just tried to "explain" you why you did not found anything on it on the web.
Maybe one nice AK member may send you a nice copy of original if the factory don't have it anymore.

I really am concerned about the meter lamp boards. I'm told it functions flawlessly. It's not going to be a daily driver. But I will run it enough to help its longevity.
You have nothing to fear with your lamp meter . Everything has been made during production of this model . You will never get any trouble like we got with MC2125 who was keeping the heat inside the "meter housing" and produce overheat on pcb and meter box (ebenoid very fragile once exposed to heat) . Your MC2155 has a vented dust cover and heat can come out of the unit ! the MC2125 was completely closed

 

[clinic-audio]

There is one or 2 caps with reverse polarity on the schematic (errors). Go with the board layout as reference.

Yes ! 2 capacitors are drawed on wrong polarity and the PCB drawing

please find here the corrected version of the both "countdown pcb " (part 045727 and 045914) . All the + are in the same side for C703/705/709/710 .

These boards are used in MC2150/2155 and MC2250/2255

 

[clinic-audio]

What happen to you meter scale if you don't use original lamp ?

This :

 

[c_dk]

Gosh Patrice, never saw one get that hot before......is it one of yours? I might have a extra MC2155 meter scale around.....

Who has the time to copy the four sides of 2 sheets made up of 6- 8.5 X11 inch panels?

 

[MACKIE1975]

If you want to work on the meter lamp then detach the whole assembly so less likely you are going to destroy the white box.


The lamp is right behind the the brown PCB.

 

[MACKIE1975]

 

[clinic-audio]

Gosh Patrice, never saw one get that hot before......is it one of yours? I might have a extra MC2155 meter scale around.....

Who has the time to copy the four sides of 2 sheets made up of 6- 8.5 X11 inch panels?

Yes ! very impressive , no ?

It is not one of mine , it was from a customer ...I have replaced this defect scale of course ! keep yours it can be helpfull on of these days !

Who has the time to copy the four sides of 2 sheets made up of 6- 8.5 X11 inch panels? I don't have the time , and I don't wish to spend money using specific copy machine because of the size of these documents !!

 

[Ricktptman]

View attachment 1083358

Is that a new replacement or a sample of one that was only fired up on Sundays and driven to .015 watt by a little old lady? ; - )
That looks CLEAN to me......

 

[c_dk]

Patrice

I ended up with three of the last four small meters that Mac parts had to replace the light boxes of a MC2125. Still have one light box squirreled away for the day I can find someone to scan it to create a 3d printer file.

So I have saved a few meter movements as well as some MC2255 pulls just in case as I am sure you have also.

 

[MACKIE1975]

Is that a new replacement or a sample of one that was only fired up on Sundays and driven to .015 watt by a little old lady? ; - )
That looks CLEAN to me......

All original, just happened to restore the unit from front to back

 

[Ricktptman]

Then there's hope. I keep seeing these crispy critters showing up on the 'bay as replacement parts. It caused me concern. I know I'll have to replace whatever lamp is leftward most on the FP. But the rest of it looks pretty nice. I didn't get as good a price as I did on the 2205 I nearly wound up with, but this one appears to be closer to "plug and play" than that one did. I was going to have to go down the whole "replace the faceplate" road with the 2205. I think this one will fit my application better.

 

[Ricktptman]

I have the unit and replaced the lamps. It sounds and looks fine (the Faceplate and meter windows were a bear to clean though) with the exception of channel balance. If I goose the gain of the C28 I can usually cajole the 2155's Left channel into behaving like it's supposed to with respect to the right channel. But if I cut it on cold, I've gotten varying results ranging (I changed cables just to rule that out) from lower than the right to (now) higher than the right channel. I've De-oxited the rear slide switches, input RCA's and I've tightened up all the screws (to maximize grounding throughout the chassis). But still this stubborn thing persists. I hate to blast the inputs on the thing every time I cut on after having left it for a day or two. Any suggestions? TIA.....

 

[c_dk]

If you are referring to the meters not reading correctly but the volume from the speakers is correct see Gregory's old post on MC2205 meters. Detailed, with pictures of the meter movement disassembly and the burnishing of the internal contacts that complete the circuit.

 

[jlovda]

This is not much different than the music videos on YouTube. The artists hate it because you are using their music without getting paid (either directly or through ASCAP/BMI). Especially if you use a website to download and strip the audio from the video. But there is some legal precedent that says you can use the music for "research, etc." It seems the only thing you have to do is state you do not own the rights to the music or lyrics when you upload it. A few owners of copyrights have forced YouTube to remove some songs. If you can buy an original service manual from Mcintosh Parts, even for a 50 year old model, it would seem we are all infringing copyrights using Internet downloads unless Mcintosh has put them in the public domain.

 

[Ricktptman]

I'm not sure about the DL issue. I don't worry about it because that stuff belongs in the unenforceable Laws Hall of Fame. I've fixed the varying sound (meters and output) problem and traded it for something (much) worse.
I left the amp on the floor of my living room (with the cover off) in order to trace the signal. The problem was one of those input harnesses at the front of the amp. There was a loose connection on the leftward most pin. I pushed the conductor in the harness inward and voila, issue fixed. While in it, I noticed the rightward most LED flickering. These cheap green LED's have a really high failure rate. So I decided (I hate going in these things anyway) to replace the one flickering lamp with the vertical holes on the rightward most side of the amp. I had to lean over pretty far in a chair (I have sensitivity issues in my left hand and arm, from a cervical neck injury. I had to have a plate inserted in my neck to treat it) and momentarily brushed the lamp housing against something really close to it. The only reason I know it happened (I had to take my glasses off, damned Bifocals) was a very small puff of smoke. The amp continues to run and I didn't think anything was wrong.....until I peaked around at the front of the amp and the Blue meter lights (and the meters) are no longer working correctly. The meters aren't working at all. The Watts/Decibels lighting is out. (But the green LEDS now work 100%. Yay.) But now there's sporadic meter deflection and dim blue (flickering) meter backlighting. I really hate being old. So, having fixed the "hard" issue does anybody have a clue about how to diagnose this meter/meter lamp issue? I don't curse often, and stuff like this doesn't happen to me often, but I just didn't feel like lugging that boat anchor to my workshop table. Also, the test sequence isn't working. Some digits appear in no particular order and there's no "countdown". But, remember, the amp is going 100%. Lil' help, please. I hope it's not what I think it is......I guess this needs a new thread. TIA.....Update: Solved. Thanks c_dk and Mackie1975.