MC2205 Left Meter Problem

[mozcho]

My MC2205 lately has an issue with the left side needle: it totally stops moving in the dB modes, and only moves a little in the watts mode, while the right side is working normally. The sound is not affected though. Is there any easy fix for this? I hope not to bring it out of the house for fear of breaking my back.

 

[damacman]

Sounds as if the Meter Range switch needs to be thoroughly cleaned. Work it aggressively in an effort to restore operation and report back. This affects both of my MC2300s at present so it's a very common problem.

 

[clinic-audio]

Hello mozcho

where are you ?

 

[mozcho]

Hello mozcho

where are you ?

Hi, I am in Malaysia.

 

[mozcho]

Sounds as if the Meter Range switch needs to be thoroughly cleaned. Work it aggressively in an effort to restore operation and report back. This affects both of my MC2300s at present so it's a very common problem.

I'm not from the electrical/electronics background and I have no experience in this kind of work, though I'm fairly confident with repairing the innards of computers. I will need to find some tutorial or video clips on opening the 2205.

 

[c_dk]

Have you purchased or downloaded a correct service manual for your amp?

First thing that should be done is to determine if the meter itself is the problem or the circuit that drives it is acting up.

The simplist way to do this is to swap the wires from each meter to the circuit board containing the driving circuits.

Disassembling a meter for repair is not for the faint of heart or non steady hands.

 

[mozcho]

Have you purchased or downloaded a correct service manual for your amp?

First thing that should be done is to determine if the meter itself is the problem or the circuit that drives it is acting up.

The simplist way to do this is to swap the wires from each meter to the circuit board containing the driving circuits.

Disassembling a meter for repair is not for the faint of heart or non steady hands.

I got one from here:

https://www.vintageshifi.com/repert...e.php?pdf=McIntosh-MC-2205-Service-Manual.pdf

Is this sufficient?

 

[damacman]

I'm not from the electrical/electronics background and I have no experience in this kind of work, though I'm fairly confident with repairing the innards of computers. I will need to find some tutorial or video clips on opening the 2205.

1 - Grab Meter Range Knob
2 - Turn it both directions aggressively in an effort to dislodge junk from carbon tracks

No skills required

 

[c_dk]

There are at least three, maybe 4 schematics for the MC2205.......depends on you serial number if what you posted is correct.

However the latter schematics do reference the early units and changes made in the service notes.

So the first schematic issued will not have the changes implemented years later.

The last schematic that comes to mind covered the last production run of which the serial numbers started with CHxxxx if I remember correctly.

 

[IvoCRO]

There could be few reasons for meter not working. First, a dirty switch, then electronics which drives meter, and then meter itself.

For dirty switch you can try to work it aggressively, but you can also try it to move (rotate) it very slowly and gently and pinpoint position where you might catch meter to work fine. If this method fails, you can spray switch with contact cleaner and contact lubrication spray, but be careful which sprays you use. Do not use WD 40 or similar!

You can switch meter wires as c_dk suggested to be sure that meter works, but if meter is still not moving, problem is inside meter.

Whatever you do, take your time and do nut rush.

 

[mozcho]

1 - Grab Meter Range Knob
2 - Turn it both directions aggressively in an effort to dislodge junk from carbon tracks

No skills required

I did that, but it's still the same. Might have to try c_dk's method.

 

[c_dk]

I think the majority of meter issues happen because of a bad connection inside the meter as documented in a Gregory post from many years ago.

The meters are driven by a dedicted amplifer circuit not the more typical feed off the main amp drive so it has been found to cause a issue as any amp cicuit can.

Lastly member captouch has Mc2255 with a meter issue that he has been told has a broken meter movement itself.

I am still trying to find my box of meter movements to see if I can assist him.....moving out of my rented shop space has left parts boxes everywhere.

So by switching the wires to the meter it would at least help narrow down where the problem is.

Shipping a meter to someone for repair would certainly be less dear than shipping the whole amp.
Lastly

 

[Gregory]

I had the same LEFT meter problem in the 2205, it would power up and the LEFT meter would be Inop. Sometimes running the volume up would `shock´ in into moving.

You can test it by temporarily swapping the RED wires on the LAMP PCB.



The fix was to open up the meter and resurface the brass terminals with a jeweler's file.





The circuits driving the meters are sketched below.. kinda' long and elaborate. Four spring-pins and wires at the METER PCB would have been better IMHO.



You must be very careful inside those meters, removing one nut at a time, so the movement doesn't fall out.


-Greg

 

[mozcho]

An update: I did nothing, and having bought some newer toys, the 2205 have been left idle for almost 6 months. I just powered it up and used it—guess what? The left meter springs back to life! Any explanation?

 

[twiiii]

A friend of mine had the same issue and it was a loose PC board. He removed and cleaned the contacts and it works like new. His main problem has been with the C-28 the input selector switch, the mode selector and tape monitor switches being intermittent.