Bias on MC 2205
- Thread starter aedaza
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- mc 2205 mc2205 ribbon
McIntosh will usually email you a Service manual .pdf if you email them with your serial# included in the correspondence. Watch out though, it is quite common to have some changes that are not documented during production. Always check to see the actual part you are replacing and compare it with the schematics and parts list. If you find original parts in your unit that differ from the documentation then I would replace with a match to the physical part.
Try sending the email to:
BScott@mcintoshlabs.com
Try sending the email to:
BScott@mcintoshlabs.com
What happened to that amp? It must have been really corroded.
aedaza
Active Member
Yes it is ... 40 years stored in a house in front of the beach here in Colombia. Look how it arrived. If this amp sings again, it will be a testament of McIntosh quality.
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aedaza
Active Member
All right guys! Partial recap in the power output and power supply + the flex cable change and I have a powerful and balanced output!
Have not done serious listening but happy to report success!
Power supply board before
Power supply board after
Power output board before
Power output board after
Have not recapped the meters board. I'm having one slight issue and it is that the green "normal" lights in the faceplate are not lighting up.
Thank you guys for all your help
Best,
Alejandro
Have not done serious listening but happy to report success!
Power supply board before
Power supply board after
Power output board before
Power output board after
Have not recapped the meters board. I'm having one slight issue and it is that the green "normal" lights in the faceplate are not lighting up.
Thank you guys for all your help
Best,
Alejandro
"I'm having one slight issue and it is that the green "normal" lights in the faceplate are not lighting up."
That's a problem caused by 1. the power supply board, 2. the ribbon cable, or 3. a burn't out lamp.
Wow, that poor amp. Excellent job bringing it back to life!
Do yourself a favor and re-solder every one of those Molex posts on the amp boards. I've had a few intermittent ones and if you lose either one of the 15V supplies to that board, you're in for replacing about a dozen transistors and 6 .15 ohm power resistors.... ask me how I know this.
Do yourself a favor and re-solder every one of those Molex posts on the amp boards. I've had a few intermittent ones and if you lose either one of the 15V supplies to that board, you're in for replacing about a dozen transistors and 6 .15 ohm power resistors.... ask me how I know this.
aedaza
Active Member
Yes!! Will save some as all my Macs need new Faceplates.. 2205, c29 and c32
Did you measure the bulbs with an ohm meter to see if they were open? Is the socket for the ribbon cable clean for all contacts? The fact that both are out reduces the probability the lamp switching transistors on the power supply board are bad. The red lamps are normally on only 0.01% percent of the time. The green lamps are virtually permanently on and wear out faster.
Speak for yourself
The 2205 at my GFs, driving Soundlab electrostats spends a goodly portion of its time in powerguard. She likes it loud!
damacman
Resident Psycho
She certainly has style! Those speakers can obviously soak up some power. May be time to find her a 2500!Speak for yourself
The 2205 at my GFs, driving Soundlab electrostats spends a goodly portion of its time in powerguard. She likes it loud!
aedaza
Active Member
Hi guys!
Trying to tackle the power guard lights in the front (green and red) as they are not turning on.
Measured pins from 1 to 10 in the lamp pc board (according to service manual positions).
1-> 0.8 mv
2-> 1.6 mv
3-> 38 mv
4-> 29 mv
5-> 1mv
6-> 5.1 ac
7-> 2.3 v
8 -> 5.1 ac
9-> 0.4 mv
10 -> 0.4 mv
Hope my assistant ( my dad LOL) notted them OK
Thank you all
Alejandro
Trying to tackle the power guard lights in the front (green and red) as they are not turning on.
Measured pins from 1 to 10 in the lamp pc board (according to service manual positions).
1-> 0.8 mv
2-> 1.6 mv
3-> 38 mv
4-> 29 mv
5-> 1mv
6-> 5.1 ac
7-> 2.3 v
8 -> 5.1 ac
9-> 0.4 mv
10 -> 0.4 mv
Hope my assistant ( my dad LOL) notted them OK
The bulbs show a small resistance. Meassured 3 in the 200k ohms scale. Cleaned too the ribbon cable socket with electronic cleaner. I remember there are some diodes in the power supply that are part of the lights. Could they be the problem? I ordered replacement 1n4004 for D302 and D303 and have them in hand.
Thank you all
Alejandro