Lots of training and experience over the years, (2 years technical school) but also had to teach myself a lot. Never got to work in a high-end shop. Had a hole-in the wall shop for a while, then worked for a stereo store, then did bio-med for 7 years, then joined with 2 other guys in my present shop. Working alone in those early days was difficult but a learning experience.
Picked up one of these recently. Initially it was popping the primary input fuse. Brought it up slowly on the Variac testing setup that I assembled. So I started a recap process since every cap I tested out of spec by a decent amount. Anywho during the post cap swap test phase the resistors at the power supply end of the 80v leg specifically the R205, R206, and R207 area right after the diodes D205 and D206. I pulled the output boards fearing that they were causing the issue. However with them pulled R205 and R206 continued to get ready to release the magic smoke hot even without the boards installed. Not sure you are still watching this thread anymore but I figured I'd bounce it off a fellow Wichitian and tech. Excellent video with nice technicals!
Update! I worked through that section of the power circuit and found that the original Resitors were just failing. Replaced the 2X 100Ω resistors and all is well again.
I haven't had any luck finding new 39,000uF caps that fit. There are 56,000uF caps that fit, such as the Mallory cgs563u050x3l. They run about 70.00 or each so plus freight from Digikey.
Hi Mark! Wonderful & interesting videos! I don't know if you answer questions or not, but here goes: I have two MC2100 amps. They have never had anything done to them in the 35 years I have owned them. They are operating perfectly. If these were your amps are there any caps that you would immediately replace for safety sake? Or because, if they haven't blown yet it is just a matter of time. I am happy to pay for your advice.
On the amplifier driver boards I would replace the electrolytic caps, and resolder any suspicious connections, there are a couple solder points at resistors and maybe at the transistors on that board which cause the amp to blow up and cause the damage like the board in the video. The caps on those boards can cause bad frequency response & phase shift. I do Paypal, but I've never asked or received for answering a simple question... sometimes I'm able to walk people through a complete repair.
@TheElectricnoob This amp has what they call Autoformers. Their purpose was impedance matching so you did not lose power driving a higher ohm speaker and losing output power. The other reason was if the amp shorts out it will protect the speaker. This amp has taps for 16 Ohms 8 Ohms and 4 Ohms and puts out about 135 watts channel and can be ran in monoblock mode 240~250 watts 1 channel. Thats just silly idea wanting to remove the Autoformers. The amp runs on ebay at $500 to $1000 or more.
Thanks for the channel... Am interested in doing a capacitor replacement for my original mcintosh 7270. Have seen some ads for replacement kit on ebay $195. Wondering if that's a good idea?
It's definitely old enough just from the standpoint of future reliability. I would say the work should be done by someone well qualified; I've seen some bad results from do-it-yourself-ers. As to the quality of the kits out there, I'm skeptical, maybe try to get some recommendations from some of the techs on Facebook groups like Vintage audio Repair and Restoration.
The buzzing is my solder station. Naw, the output transformers are great. Just a different way or doing it, that's all. They protect the speakers and at the same time step up the output voltage to the speakers. The frequency and phase response is excellent. Sounds better than most direct coupled amps, and no relay needed. If you did get rid of the transformers, you'd be limited to 40 or so watts per channel with the power transformer used in these... about plus and minus 37 volts.
@ mdzacharias i must confess this amplifier looks bizarre but t the sound quality is fabulous, in this circuit the rated output impedance is 2 ohms and they used a matching impedance transformer for this job all the mcintosh solid state power amplifier employs this topology
I used to get it from B&D Enterprises 800-458-6053. I've also see them on eBay. Chemtronics 10-50L . Best I've ever used. Actually works, unlike some brands.
Hi Mark and all who may know. Please clarify something for me as I am a complete newbie to this hobby. I have a Mc2100 as well and looking at the C309 and C310 (input board) which is a 10uf 25v electrolytic, the service manual parts list does not indicate NP but looking at the drawing of the circuit board it isn't polar defined. I'm confused of this because doing research the input board is the same part number as the MC2105 but the 2105 explicitly indicates "NP" in the parts list. So my question... Is the MC2100 C309 and C310 Polar or Non Polar? The cap I pulled out is polar type but I question because I found C303 and C304 had wrong value caps. Thanks in advance. -Mary
The voltage shown is rather low so it probably would not matter, but I would probably lean towards using a non-polar capacitor, but if I'm replacing original caps and they originals were polarized like I say I wouldn't worry too much about it. One thing to remember is that a non-polar cap automatically has twice the esr as an otherwise identical polarized one, so if you use a NP cap do at least use the best quality you can find.
Mark, Thanks for the reply. If then it does not matter polar or non-polar would film type cap benefit from the C309 and C310 locations? I noticed on the schematics that it's directly in the primary signal path? Otherwise I do have panasonic FC cap (10uf 25v) also have Elna (M) 10uf 100v (non-polar) but now that you mentioned the non polar has 2x the esr value normally then I'm on the fence at this point.
Hi very nice video. I'm planning on buying a mc2100 on eBay my question is how do I check for proper function with a signal generator and an oscilloscope. Thank you
+discoking62 This can get pretty involved, but: 1. Resistive loads of appropriate value (like 8 ohms) connected between the COMMON (negative) and matching taps on barrier strip ( 8ohms, in this example). 2. Scope leads: positive probe to positive of load, scope ground to chassis or speaker COMMON (chassis probably safer - less likely to accidentally short to the speaker positive connection.) 3. Audio or function generator via appropriate adaptor to amplifier input. 4. Start with generator output to zero and/or amp input level at min. 5. Turn amp ON, carefully bring up levels on generator and amp to see display on scope. Maybe start off the scope at 0.5 volts/division. Adjust higher for larger signal. I will usually bring the amp input to maximum providedthe generator output is still pretty low. At 2 volts/division, 4 divisions will be near 1 watt with eight ohm loads.
Great video Mark,, lots of good tips. I have a 2105 with output problems on my bench now. No smoked parts I can see, but someone has replaced the output transistors with all sorts of mongrel devices (ELM130, 32-070, QP-8). I want to get back to stock parts before I go any further. The problem is I don't know how to translate McItosh's part numbers with industry standard parts. The service manual calls Q119 to Q126 output transistors for serial numbers below 20M01 as 132-517 I'm guessing that's the MJ15003G you referenced. But Q115 to Q118 is specified as 132-518. It is also a NPN, but is it the same replacement? Thanks in advance, Steven.
+constitutionfst I've had very good luck using the MJ15003G for all outputs including Q115 to Q118. That is the recommended replacement so far as I know. The driver boards do contain transistors that are hard to source.
+Mark Zacharias Thank you Mark. I saw the two caps you recommended replacing because they are known trouble makers, any other suspect caps I should replace while I'm in there? Also, Only one transistor has an insulator under it. (the driver) Shouldn't there be an insulator under each one? Would it hurt to put one under each? (as I forgot which one I took the insulator off of. :-o ) Lastly, the front panel is cracked, is this the factory only replacement source? ($150 I am told) Again, thank you for all your help. Steven
The other transistors are connected through the heat sink. No insulator necessary. The heat sink is isolated from chassis. It's pretty easy to replace all the small electrolytics in one of these. It's a good idea because they can cause problems that might not be obvious like frequency response problems and phase shift.
+Mark Zacharias Got all the parts in. One channel is still out. I traced the problem to Q107 & Q109, on the pre driver board (043899) they are not shorted, but measure half the resistance of the working board. Mcintosh part numbers 132-021 & 132-032 don't help. The (Motorola) devices themselves read 090 & 100 plus a date code which also doesn't lead anywhere in the NTE substitution book. How do I find out what these devices are?
As I recall, the capacitors are not glued at all - only the component leads are soldered, holding the caps in place. Forgive me if I'm wrong - haven't watched this in quite a while.
hi mark Many thanks for the reply back .Isn't this glue tube??,,, watch the video in 9.03 time There are glues that cause problems of capacitance change over time Therefore, this issue is important to me have no intention to disturb or bother you, answer only if you have the interest and time to do it , anyway thanks for your reply best regards amnon
hi mark thank u very much for your replay I also do repairs and replacement capacitors Mostly vintage stereo amplifier .And I love this job thank u very much for your help I appreciate your kindness your sincerely amnon
Pull the output autoformers? You are obviously ignorant about things like autoformers in audio gear. Take them out and you are transforming that Mac into an old Sony, Kenwood, or Sansui amp. The resale value will also plummet to 1-2 pennies on the dollar.
@imoogi59 I am interested in selling. The barrier strip is still damaged so you need to be really careful with that. Otherwise nearly pristine. My daytime phone number is 316-686-8324. My name is Mark. My eBay seller ID is Markz. (include the period) and you can see my seller rating.
Lots of training and experience over the years, (2 years technical school) but also had to teach myself a lot. Never got to work in a high-end shop. Had a hole-in the wall shop for a while, then worked for a stereo store, then did bio-med for 7 years, then joined with 2 other guys in my present shop. Working alone in those early days was difficult but a learning experience.
Picked up one of these recently. Initially it was popping the primary input fuse. Brought it up slowly on the Variac testing setup that I assembled. So I started a recap process since every cap I tested out of spec by a decent amount. Anywho during the post cap swap test phase the resistors at the power supply end of the 80v leg specifically the R205, R206, and R207 area right after the diodes D205 and D206. I pulled the output boards fearing that they were causing the issue. However with them pulled R205 and R206 continued to get ready to release the magic smoke hot even without the boards installed. Not sure you are still watching this thread anymore but I figured I'd bounce it off a fellow Wichitian and tech. Excellent video with nice technicals!
Update! I worked through that section of the power circuit and found that the original Resitors were just failing. Replaced the 2X 100Ω resistors and all is well again.
Merci pour la vidéo !
Quel beau matériel !!!
Georges
I haven't had any luck finding new 39,000uF caps that fit. There are 56,000uF caps that fit, such as the Mallory cgs563u050x3l. They run about 70.00 or each so plus freight from Digikey.
Got my replacement caps for the mc-2300 from Mouser. $28 each!
Hi Mark! Wonderful & interesting videos! I don't know if you answer questions or not, but here goes: I have two MC2100 amps. They have never had anything done to them in the 35 years I have owned them. They are operating perfectly. If these were your amps are there any caps that you would immediately replace for safety sake? Or because, if they haven't blown yet it is just a matter of time. I am happy to pay for your advice.
On the amplifier driver boards I would replace the electrolytic caps, and resolder any suspicious connections, there are a couple solder points at resistors and maybe at the transistors on that board which cause the amp to blow up and cause the damage like the board in the video. The caps on those boards can cause bad frequency response & phase shift. I do Paypal, but I've never asked or received for answering a simple question... sometimes I'm able to walk people through a complete repair.
@TheElectricnoob This amp has what they call Autoformers. Their purpose was impedance matching so you did not lose power driving a higher ohm speaker and losing output power. The other reason was if the amp shorts out it will protect the speaker. This amp has taps for 16 Ohms 8 Ohms and 4 Ohms and puts out about 135 watts channel and can be ran in monoblock mode 240~250 watts 1 channel. Thats just silly idea wanting to remove the Autoformers. The amp runs on ebay at $500 to $1000 or more.
I agree 100%. You'd have less power as well. In the Mac design, there is a voltage step-up from the autoformers.
Thanks for the channel...
Am interested in doing a capacitor replacement for my original mcintosh 7270.
Have seen some ads for replacement kit on ebay $195.
Wondering if that's a good idea?
It's definitely old enough just from the standpoint of future reliability. I would say the work should be done by someone well qualified; I've seen some bad results from do-it-yourself-ers. As to the quality of the kits out there, I'm skeptical, maybe try to get some recommendations from some of the techs on Facebook groups like Vintage audio Repair and Restoration.
@mdzacharias are the new output power transistos the MJ15003?
The buzzing is my solder station. Naw, the output transformers are great. Just a different way or doing it, that's all. They protect the speakers and at the same time step up the output voltage to the speakers. The frequency and phase response is excellent. Sounds better than most direct coupled amps, and no relay needed. If you did get rid of the transformers, you'd be limited to 40 or so watts per channel with the power transformer used in these... about plus and minus 37 volts.
hi,
im looking for two capacitors (big blue)' one of them blown..
where can i find it?
how much it should cost?
thanks
@guimbadriver Yes, that is what I use, and what McIntosh recommends.
@ mdzacharias i must confess this amplifier looks bizarre but t the sound quality is fabulous, in this circuit the rated output impedance is 2 ohms and they used a matching impedance transformer for this job all the mcintosh solid state power amplifier employs this topology
Hi Mark, I see you are using a large roll of Solder Wick. Where can I get a large roll like that?
I used to get it from B&D Enterprises 800-458-6053. I've also see them on eBay. Chemtronics 10-50L . Best I've ever used. Actually works, unlike some brands.
Thanks Mark.
Hi Mark and all who may know. Please clarify something for me as I am a complete newbie to this hobby. I have a Mc2100 as well and looking at the C309 and C310 (input board) which is a 10uf 25v electrolytic, the service manual parts list does not indicate NP but looking at the drawing of the circuit board it isn't polar defined. I'm confused of this because doing research the input board is the same part number as the MC2105 but the 2105 explicitly indicates "NP" in the parts list. So my question... Is the MC2100 C309 and C310 Polar or Non Polar? The cap I pulled out is polar type but I question because I found C303 and C304 had wrong value caps. Thanks in advance.
-Mary
The voltage shown is rather low so it probably would not matter, but I would probably lean towards using a non-polar capacitor, but if I'm replacing original caps and they originals were polarized like I say I wouldn't worry too much about it. One thing to remember is that a non-polar cap automatically has twice the esr as an otherwise identical polarized one, so if you use a NP cap do at least use the best quality you can find.
Mark, Thanks for the reply. If then it does not matter polar or non-polar would film type cap benefit from the C309 and C310 locations? I noticed on the schematics that it's directly in the primary signal path? Otherwise I do have panasonic FC cap (10uf 25v) also have Elna (M) 10uf 100v (non-polar) but now that you mentioned the non polar has 2x the esr value normally then I'm on the fence at this point.
If there is room, by all means try the film caps.
Hi very nice video. I'm planning on buying a mc2100 on eBay my question is how do I check for proper function with a signal generator and an oscilloscope. Thank you
+discoking62 This can get pretty involved, but:
1. Resistive loads of appropriate value (like 8 ohms) connected between the COMMON (negative) and matching taps on barrier strip ( 8ohms, in this example).
2. Scope leads: positive probe to positive of load, scope ground to chassis or speaker COMMON (chassis probably safer - less likely to accidentally short to the speaker positive connection.)
3. Audio or function generator via appropriate adaptor to amplifier input.
4. Start with generator output to zero and/or amp input level at min.
5. Turn amp ON, carefully bring up levels on generator and amp to see display on scope. Maybe start off the scope at 0.5 volts/division. Adjust higher for larger signal. I will usually bring the amp input to maximum providedthe generator output is still pretty low. At 2 volts/division, 4 divisions will be near 1 watt with eight ohm loads.
+Mark Zacharias Thank you very much
Great video Mark,, lots of good tips.
I have a 2105 with output problems on my bench now. No smoked parts I can see, but someone has replaced the output transistors with all sorts of mongrel devices (ELM130, 32-070, QP-8). I want to get back to stock parts before I go any further. The problem is I don't know how to translate McItosh's part numbers with industry standard parts.
The service manual calls Q119 to Q126 output transistors for serial numbers below 20M01 as 132-517 I'm guessing that's the MJ15003G you referenced. But Q115 to Q118 is specified as 132-518. It is also a NPN, but is it the same replacement? Thanks in advance, Steven.
+constitutionfst I've had very good luck using the MJ15003G for all outputs including Q115 to Q118. That is the recommended replacement so far as I know. The driver boards do contain transistors that are hard to source.
+Mark Zacharias Thank you Mark.
I saw the two caps you recommended replacing because they are known trouble makers, any other suspect caps I should replace while I'm in there?
Also, Only one transistor has an insulator under it. (the driver) Shouldn't there be an insulator under each one? Would it hurt to put one under each? (as I forgot which one I took the insulator off of. :-o )
Lastly, the front panel is cracked, is this the factory only replacement source? ($150 I am told)
Again, thank you for all your help. Steven
The other transistors are connected through the heat sink. No insulator necessary. The heat sink is isolated from chassis. It's pretty easy to replace all the small electrolytics in one of these. It's a good idea because they can cause problems that might not be obvious like frequency response problems and phase shift.
+Mark Zacharias Got all the parts in. One channel is still out. I traced the problem to Q107 & Q109, on the pre driver board (043899) they are not shorted, but measure half the resistance of the working board. Mcintosh part numbers 132-021 & 132-032 don't help. The (Motorola) devices themselves read 090 & 100 plus a date code which also doesn't lead anywhere in the NTE substitution book. How do I find out what these devices are?
Probably have to order them from McIntosh. I've seen them supply NTE subs for the TO-66 package transistors but they seem to work ok.
??? Great video Mark, What kind of glue do you use to glue the capacitors
As I recall, the capacitors are not glued at all - only the component leads are soldered, holding the caps in place. Forgive me if I'm wrong - haven't watched this in quite a while.
hi mark
Many thanks for the reply back
.Isn't this glue tube??,,, watch the video in 9.03 time
There are glues that cause problems of capacitance change over time
Therefore, this issue is important to me
have no intention to disturb or bother you, answer only if you have the interest and time to do it , anyway thanks for your reply
best regards
amnon
OK, yes - that was a silicon sealant.
People also use something called RTV and "silastic" for this.
hi mark
thank u very much for your replay
I also do repairs and replacement capacitors
Mostly vintage stereo amplifier
.And I love this job
thank u very much for your help
I appreciate your kindness
your sincerely
amnon
great video! thanks
Only one. I think it was a 4B...
Sure - link all you like!
Pull the output autoformers? You are obviously ignorant about things like autoformers in audio gear. Take them out and you are transforming that Mac into an old Sony, Kenwood, or Sansui amp. The resale value will also plummet to 1-2 pennies on the dollar.
mark_zacharias
and the domain sbcglobal,
daught net.
@imoogi59 I am interested in selling. The barrier strip is still damaged so you need to be really careful with that. Otherwise nearly pristine. My daytime phone number is 316-686-8324. My name is Mark. My eBay seller ID is Markz. (include the period) and you can see my seller rating.