McIntosh 2125 in the house, and I need advice.

dobyman

dobyman

Turntable Addict
OK the 2125 is in the house, so I will have questions and I hope everyone here will be willing to help me. First question, ( and I have to be honest, some of these will sound stupid because I am still a newbie) but here goes. I have bad caps on the power board and I am wondering if that ribbon just unplugs at the board so I can completely remove it? And I want to do the LEDs in the meters, and have heard horror stories about how brittle the meter housings are. Should I just break one of the tabs off to release the lamp holders, or do I try and bend them back?
Thanks in advance for any help, and I promise I will have plenty more! :thumbsup:
 
Thanks John James, but I actually read that post about 5 times, and I even asked this question at the end of it, but damacman said I should start a new thread because my question would get lost since its already 8 pages into the thread. That's why I started this one.
Moewillis posted great pics, but he never showed the board without the ribbon, that's why I asked if it is removable. And someone had already broken off his tabs on the meters, and I wanted to know if this was the best option when changing the meter lamps.
I also sent a PM to moewillis to ask where he got those 2200mfd16v caps in axial. All I can find are radial caps.
Like I said, I'm a newbie to a lot of these things, but I want to learn, and I need help.
 
The meter housings are so brittle they will break if you look at them wrong.....Back in the day DOB would plunge them with a hot soldering iron to give them some venting from the lamp heat.

I have used a micro file, solder tip and model car type razor saw to remove the tabs holding the light boards......razor saw was best. Then used masking tape to resecure.

If you want to remove the ribbon it must be unsoldered.....since I always replace the old green PG lamps I remove the nuts that secure that board, slide the board back to slip the lamps out of the white rubber holder which will give you a little more room to work on the PS board.

Both Mouser and Digikey have always had the Vishey axial caps. Parts express has had blue and soft white LEDs 5 for $5.00, I have used the white ones, found the blue to look to goofy in a Marantz and have not yet made the time to try them in my MC2155.

The faded blotchy look to the meters is caused by a discoloration in the center almost clear 3rd color filter within the meter light box. Why the blue ones closest to the lamps do not discolor I do not know......go figure.

All the Molex pin angular solder connections must be reflowed.....lots of thermal mass when first soldered and decades of time past has caused too many of them to crack.

These amps are now approaching 40 years of age so I always replace all the old electrolytics on all the boards but surprisingly under heavy bench test stress the main filter caps still hang in there......I am really surprised they seem to most often test good........
 
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Thanks c_dk! I found the caps on Jameco so they are on their way. I have a few hundred xacto blades here so I think I have a saw blade. If not, I was thinking of heating a regular xacto blade and slicing off the tab by the lamp holder. I emailed dwojo to check on the blue LEDs, so I will check PE if he doesn't have them . 62caddy says if you use the blue LEDs, the gel condition shouldn't matter, so I am trying that first.
Any ideas on a sticky meter? The right one hangs up about half way. It goes farther, but doesn't want to go back to zero.
 
Pull the meter drive circuit card recap it, clean the card edge contacts with a pencil eraser and the sockets with D5 and see if that solves your meter issue.
 
Thanks c_dk. Ill try cleaning the contacts first, and I heard if you play with the zero adjustment screw that might help too. I cant do anything until I get the PSB caps and get them changed. Don't want to run it with the leaking caps. Is D5 the same as Deoxit?
 
Update! I got the caps from Jameco and the lamps from dwojo, but after moving and flipping the PS board to replace the caps, the ribbon was so dried out and brittle, it pretty much deteriorated enough that now the meters do not move at all. I have plenty of sound, great lights, but no meters, or Normal/Limit lamps. I did some checking with a VOM and sure enough, open lines on a few of the ribbon wires. So my next move is to replace the ribbon with a new one or just use some 22-24 ga wire and replace all of the wires from the PS board to the lamp board that also feeds the meters. The never ending McJob. The front plastic bezel around the meters was loose so I decided to leave it off. Gives it a much cleaner look.
More to come when I get some time to work on it.
 
I too have a delaminated ribbon cable on my unit. I tried to find a suitable replacement to no avail. I simply wrapped the cable in tape to keep it together and have been contemplating replacing it with point-to-point wiring with a connector in the middle to make future removal easy. I will be watching what you end up doing.
 
I tried to tape mine but it didn’t help. The connector in the middle sounds great. Where would I find one??
 
Just take a hard drive computer cable, mark the polarity and then strip off the needed number of conductors.....isn't it 9?

Solder each lead, making sure of the polarity, to the connections on the two boards and move on. It is just for the lights....

The molex pin connectors cracking on the driver boards will cause you to have sleepless nights looking for intermittents if you do not address them now that they are 40 years old.
 
I already addressed the molex connector cracking on my unit by removing it and soldering the ribbon cable directly to the board. I have not yet gotten around to recapping the unit but will address the ribbon cable at that time. Using a computer cable is an option I am contemplating. Thanks for the suggestion.
 
Thanks for all the suggestions. I think the point to point wiring is the best option for me. I do like the connector idea though. Ill be back!
 
I am speaking of all the molex pins located on the driver boards.....those do carry a audio signal and will cause channel dropout and various serious issues way beyond light bulbs.
 
UPDATE! I had the solder on the 2 PC boards reflowed, and I did the 10 P2P wires, and did the LED's in the meters, and changed the 2 caps! The Mac is back! I just thought I would show some pics now that its done. Thanks for all of the help and ideas! I did decide to leave the plastic bezel off of the face. Is there any way to get that acid spot off of the chassis from the bad cap leaking?
mc1.jpg
mc3.jpg mc15.jpg
 

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