Been trying like anything to build a MC2500 driver board as the original ones in my amplifier were burnt due to bad repairs a long time ago. I built a new set of boards but they just don't seem to work. I did this out of desperation as new boards aren't available with McIntosh anymore. If someone has experienced working with the McIntosh MC2500, please help take a look at the circuit diagram and see what mistake I have done on it. The lights and meters are turning on but there's no sound. Please help.
Hi Patrick,
Thank you for your response. The voltage is showing -21v but still no audio. We do not know if there is a problem within the circuit diagram that I have attached in my first post or the transistors parts list itself are wrong. I've attached my transistors list. I bought all of these parts from Mouser Thanks again.
Thank you for your response. The voltage is showing -21v but still no audio. We do not know if there is a problem within the circuit diagram that I have attached in my first post or the transistors parts list itself are wrong. I've attached my transistors list. I bought all of these parts from Mouser Thanks again.
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These are the pictures that the engineer sent me. Nothing much clear in it, I guess. I've also attached my original damaged driver board picture. In my first post, I've attached the exact circuit diagram of the pcb that I made. Please let me know if there is anything else that I can add here. All the voltages around the board check out perfectly except there is no sound at all.
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The original driver board condition is not that bad. Since it was single sided PCB, fix it is not hard.
Please also show the other side of the original driver board.
Please also show the other side of the original driver board.
You have new boards and you can debug them first.
For an old circuit board, this condition is not so bad, cause we are easily trace the tracks on a single sided PCB. We are just checking the failed components and replace them.
For an old circuit board, this condition is not so bad, cause we are easily trace the tracks on a single sided PCB. We are just checking the failed components and replace them.
The McIntosh service technician has the board and he told me that the board cannot be used anymore. He said that the tracks on the board are damaged. It's why I ended up having to make these new boards. We checked our diagram with our online schematics copy but we couldn't find any problems. Patrick, is it possible if you could please kindly check my diagram, the one that I attached on my first post against your copies of schematics? You might be able to notice any anomalies between them. Thank you.
I will try but checking the diagram may not be found out the problem, if the problem is caused by PCB layout or bad component, therefore you must try your best and carefully check each component one by one, checking their value, polarity NPN/PNP, good function or not and is it connected to their nearby component correctly according the circuit diagram. Use your multimeter and your time to do that.
Good luck!
Good luck!
Sure. I'll check every component again individually. Thank you very much for helping me with this Patrick. Please let me know if you find anything on my diagram that you suspect.
I’d like to compare schematics in the first two posts. Patrick, is there a more compete schematic?
Thanks.
Thanks.
I'd checked and compared your diagram with the online copy, there is no difference. Please double check the optocoupler polarity in your PCB, or there is other circuit caused the problem.
If you have no measuring instrument on hand, you can make a simple interface for an audio input like CD, connecting the circuit direct to the power amp input on your board to check if your board is working ( Remember turning down the volume first before turn on the power amp) .
If you have no measuring instrument on hand, you can make a simple interface for an audio input like CD, connecting the circuit direct to the power amp input on your board to check if your board is working ( Remember turning down the volume first before turn on the power amp) .
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No sound in both channels likely means either a bad power supply, or wrong operation
of the muting circuit, since those are common to both channels.
If the power supply measures ok, then it must be the muting circuit.
Use a scope to check the signal both before and after the muting circuit.
of the muting circuit, since those are common to both channels.
If the power supply measures ok, then it must be the muting circuit.
Use a scope to check the signal both before and after the muting circuit.
I haven’t seen many voltage measurements. As a sanity check, would you report DC Volts on Main Feedback and bases of Q9 and Q10? And DCV across R5 and R11?
Thanks!
Thanks!
Before I reply to the above messages, I need to pass on a separate message to those personally messaging me to hand over the diagram to them for copying purpose, please understand that the schematics are available widely online.
A) You don't have to get it from me.
B) This is a FORTY YEAR OLD circuit which I am reviving due to a sentimental attachment but logically it's not even worth ONE bit due to the obsolete parts and extravagant costs which you will incur.
C) Building individual boards and selling is also dumb again due to the obsolete parts. If you change the parts to something else, the sound changes. Please consider what you are doing.
Otherwise, my humble gratitude to everyone else here who has contributed their time and patience.
Good day Patrick and Rayma,
Thank you for your time and much appreciated help. The optocoupler has to be checked after this. Might be the reason. I'll only know on Friday as the McIntosh service technician is on leave till then. I'm trying to present every possibility to him so that we can somehow resolve this. We have only one original driver board that is damaged but still working. That is how apart from the relevant measurements, we are able to verify that the rest of the amplifier is in good condition. I also attached my parts list. If you find any problems with the transistors list, please kindly let me know. We checked and found no issues. These driver boards have been made over the last five months and our minds are totally clouded up with fault finding. Your help in this is truly indispensable.
A) You don't have to get it from me.
B) This is a FORTY YEAR OLD circuit which I am reviving due to a sentimental attachment but logically it's not even worth ONE bit due to the obsolete parts and extravagant costs which you will incur.
C) Building individual boards and selling is also dumb again due to the obsolete parts. If you change the parts to something else, the sound changes. Please consider what you are doing.
Otherwise, my humble gratitude to everyone else here who has contributed their time and patience.
Good day Patrick and Rayma,
Thank you for your time and much appreciated help. The optocoupler has to be checked after this. Might be the reason. I'll only know on Friday as the McIntosh service technician is on leave till then. I'm trying to present every possibility to him so that we can somehow resolve this. We have only one original driver board that is damaged but still working. That is how apart from the relevant measurements, we are able to verify that the rest of the amplifier is in good condition. I also attached my parts list. If you find any problems with the transistors list, please kindly let me know. We checked and found no issues. These driver boards have been made over the last five months and our minds are totally clouded up with fault finding. Your help in this is truly indispensable.
Sure, BSST. Thank you for looking into this. I will get the measurements this week in send it to you.
The mute circuit is more than the optocoupler. For example, it also includes the -22VDC voltage supply,
the two coupling capacitors, and the FET.