Proper mute circuit operation must be verified operationally.
Connect a 1V 1kHz sine to the amplifier input.
Verify the signal is present at the positive lead of C419 with a scope.
Verify the signal is present at the positive lead of C401 with a scope.
If the signal is present at these two points, the muting circuit is functioning normally.
Connect a 1V 1kHz sine to the amplifier input.
Verify the signal is present at the positive lead of C419 with a scope.
Verify the signal is present at the positive lead of C401 with a scope.
If the signal is present at these two points, the muting circuit is functioning normally.
Hey everyone…it seems this thread has been dormant quite a while, but I’m even more desperate than Saran was when starting out. I recently purchased a MC2500 that was missing both preamp boards, the power supply board, the cap/interconnect boards, and the meter board. Some are available on eBay at or beyond top retail prices, so I’m looking for suggestions on alternative replacements. I have an objection to buying from someone parting these units out for profit instead of repairing them and putting them back in service. Long story short, I need a full (or partial) set of unpopulated boards to build up or someone’s cast offs needing a lot of work. I have the ability to create the boards, but prefer to not to reinvent the wheel here. Anyone with parts or any kind of assistance would be greatly appreciated!
Hi 928,
The most important step has already been taken by you. YOU HAVE ONE OF THE BEST AMPLIFIER EVER MADE. Now, nobody is re inventing the wheel here. The factory is simply not manufacturing these boards in a long time. Any other decent repair facility, won't touch the amps anymore without any replacement boards. Then you turn to online used boards which are as you say, overly expensive, maybe a scam and most importantly, could already be faulty boards or working boards that are in very so so conditions. Your best alternative, go make new boards yourself. You will know the board's quality because you are making it yourself and you can use decent parts. You will have a new board at a decent price, that you would never have to worry about again for a long time. If you need any help, please do not hesitate to ask. I will tell you what I know.
The most important step has already been taken by you. YOU HAVE ONE OF THE BEST AMPLIFIER EVER MADE. Now, nobody is re inventing the wheel here. The factory is simply not manufacturing these boards in a long time. Any other decent repair facility, won't touch the amps anymore without any replacement boards. Then you turn to online used boards which are as you say, overly expensive, maybe a scam and most importantly, could already be faulty boards or working boards that are in very so so conditions. Your best alternative, go make new boards yourself. You will know the board's quality because you are making it yourself and you can use decent parts. You will have a new board at a decent price, that you would never have to worry about again for a long time. If you need any help, please do not hesitate to ask. I will tell you what I know.
Now, this post is anything but dormant. My sincere apologies for not updating. The problems with my new boards where never diagnosed. The engineer who made the boards and the McIntosh technician tried but could never get the amplifier to work. The boards gave all the correct readings but there simply was no sound. When one of the older working boards where switched in, immediately the poor amplifier sang. They have given up and the McIntosh technician is returning back my amplifier in as is condition, sadly without it being repaired as they are unable to. I now probably have to spend a fortune sending it to Audio Classics, hoping that they will repair it. I will keep updating all of you as it goes. My sincere gratitude to everyone who helped me along the way.
Thanks for the reply…and please note that I meant no disrespect about the reinvention comment. I was just hopeful in that someone might have already developed new boards that could be purchased and used, or have a set of discarded ones gathering dust. I am happy to begin the board-making process. If I am successful, I will likely build up a few extra to help recoup some of the associated costs. I have photos of the boards (front and back), so it should be easy enough when accompanied by the schematics. I will be doing this in my very limited amount of spare time, but I will check back in from time to time with updates. Thanks for the info everyone has been passing along, and the words of encouragement.
I think you were poorly served by an inexperienced "McIntosh technician".
A problem like this is just not that hard to resolve.
None taken, 928. Yes. Usually when having boards done, you have to order minimum quantity. Get extra done for future use. Please get back if you need help. Good luck with the building.
Good day Rayma,
I couldn't agree more but in the entire India, as far as I know, there is only two McIntosh dealers. They only opened shop after 2017. Before that, there were none. Me and my MC never stood a chance ever since the beginning. I have now shifted to Europe and am working here. My amp is still at the McIntosh in India. I'll have to have it sent to Audio Classics. I don't know if there is anyone like them in Europe. We'll see. I'll definitely get the poor amp to sing one day.
I couldn't agree more but in the entire India, as far as I know, there is only two McIntosh dealers. They only opened shop after 2017. Before that, there were none. Me and my MC never stood a chance ever since the beginning. I have now shifted to Europe and am working here. My amp is still at the McIntosh in India. I'll have to have it sent to Audio Classics. I don't know if there is anyone like them in Europe. We'll see. I'll definitely get the poor amp to sing one day.
You should inform the McIntosh home office in the USA about your problems.
McIntosh used to have good service people, as they should.
McIntosh used to have good service people, as they should.
Have tried contacting them many times previously, Rayma. Nobody answers or returns calls. I understand that they cannot keep manufacturing parts and keep stocks but at least provide support for certain highly owned amplifier models and most importantly return customer calls or hire someone to do it? These days it's becoming like mobile phones, I guess. One after the other being bought and disposed. I'll try calling again today. 😔
Hi Rayma,
The attached screenshot is the email that was just sent to me by the head service person, John Messemer at McIntosh USA an hour ago as a reply to my email about how, after being made to purchase all the expensive spares from McIntosh, the local service centre still failed to repair my amplifier and is just returning it back. To be honest with all of you, I feel extremely cheated. I don't know if I am correct to be feeling this way but I still do.
The attached screenshot is the email that was just sent to me by the head service person, John Messemer at McIntosh USA an hour ago as a reply to my email about how, after being made to purchase all the expensive spares from McIntosh, the local service centre still failed to repair my amplifier and is just returning it back. To be honest with all of you, I feel extremely cheated. I don't know if I am correct to be feeling this way but I still do.
Attachments
The characterization of cheated may be too strong, but certainly the local McIntosh authorized repair facility
has failed you.
has failed you.
Yes. After a bill of an equivalent of almost 1600 USD and a still broken amplifier, anybody would still feel cheated, Rayma. This is just a transistor amplifier made in the 80s. If an authorised service facility is incapable of completing their job that they have even billed me for, someone has to take responsibility for it. The company that authorised this facility is McIntosh isn't it? So, who has to take charge and be responsible for this? Instead, all I get from these people are a ' I am sorry, our bad ' email. Is that the kind of response and attitude, one would expect from a company such as McIntosh? I am not complaining here. This is just an answer to your reply last Tuesday about contacting the company. You were right in advising me to but there is something to learn from this for everyone reading this post and anyone who considers purchasing anymore of this company's products. 928, please pm me should you need any help with your amplifier. This post is now closed.
@SaranMc85
I wanted to offer encouragement on your restoration effort. If I understand correctly, your amp is still in India.
If you're able to pursue repair yourself, I think there's still a good chance of restoring operation. You may have patience and persistence that a service shop can't devote, plus lot's of support on this forum.
I still have the schematics you provided, but if you sent voltage measurements (post 17), I'm unable to find them. I recall there was some probing of the mute circuit that didn't seem fruitful. I would suggest checking voltage across R11; it will confirm activity of the coupler LED and related activity at the gate of Q8. I drill deeply here to encourage. 😉
Regards.
I wanted to offer encouragement on your restoration effort. If I understand correctly, your amp is still in India.
If you're able to pursue repair yourself, I think there's still a good chance of restoring operation. You may have patience and persistence that a service shop can't devote, plus lot's of support on this forum.
I still have the schematics you provided, but if you sent voltage measurements (post 17), I'm unable to find them. I recall there was some probing of the mute circuit that didn't seem fruitful. I would suggest checking voltage across R11; it will confirm activity of the coupler LED and related activity at the gate of Q8. I drill deeply here to encourage. 😉
Regards.
Good morning BSST,
It's very kind of you to offer support. I haven't given up. How can I? That amp was a gift from my father, no. The McIntosh technician however has. So has the fella who built the boards for me. I'll have to bring it to Europe where I live now and give it to a properly qualified technician here. Not McIntosh. A person who worked on MC amps before. I have completely given up on McIntosh and will never purchase anymore of their products. We'll see. Getting the amp here is going to be One Big 60 Kilo Hail Mary. I'll keep updating on this forum. I know well that there will be others like me out there. I will continue to update for everyone's knowledge and benefit. It's going to be a while before it gets here but when it does, I'll immediately start uploading information here for your references. I'll never give up. Not just for my dad but also because of all of you. You never gave up on me and my Mc either. Wish that you all ran McIntosh. If that happened, I wouldn't be in this situation today. Thank you and please take care.
It's very kind of you to offer support. I haven't given up. How can I? That amp was a gift from my father, no. The McIntosh technician however has. So has the fella who built the boards for me. I'll have to bring it to Europe where I live now and give it to a properly qualified technician here. Not McIntosh. A person who worked on MC amps before. I have completely given up on McIntosh and will never purchase anymore of their products. We'll see. Getting the amp here is going to be One Big 60 Kilo Hail Mary. I'll keep updating on this forum. I know well that there will be others like me out there. I will continue to update for everyone's knowledge and benefit. It's going to be a while before it gets here but when it does, I'll immediately start uploading information here for your references. I'll never give up. Not just for my dad but also because of all of you. You never gave up on me and my Mc either. Wish that you all ran McIntosh. If that happened, I wouldn't be in this situation today. Thank you and please take care.
I've encountered a similar situation where I was on the verge of giving up on repairing my non-functional driver board MC2255. The problem initially arose from a burnt resistor and a small transistor. After replacing them, the amp worked fine until I moved it. Unfortunately, it wouldn't turn on, and I later discovered that two big capacitors were damaged. Upon replacing the capacitors, the amp worked for a while but eventually stopped again.
I was quite frustrated as I couldn't find any visible damage on the driver board. Finally, I realized that I had adjusted the bias too high. Once I reduced the bias, my amp started working without any issues. In your case, I believe it's still repairable, so don't lose hope.
I was quite frustrated as I couldn't find any visible damage on the driver board. Finally, I realized that I had adjusted the bias too high. Once I reduced the bias, my amp started working without any issues. In your case, I believe it's still repairable, so don't lose hope.