NOTES:
- This cap list is only for electrolytic capacitors and does not include the two main 38,000uF filters. I have another post that covers the main filter caps:
https://audiokarma.org/forums/index...pacitor-replacement-diy.962462/#post-14856137
- I wanted to replace electrolytic caps with like in kind. The same uF value and type (polar or bipolar) as found in my amp. So this list shows what I actually found in my amp.
- I wanted to keep my amp as Mcintosh designed it as much as possible. I did bump up the cap voltage rating by one place when convenient because of what I had on hand.
- Based on the service manual, there are different schematics (and thus different circuit boards) used in the 7270 amp. These differences are are based on serial numbers. My serial number is AE3242. I have not studied the differences so I can NOT say if this cap list will exactly work for your amp.
- This cap listing shows what I actually found in my amp, not what the schematics show.
- This listing indicates where you need a polarized cap ("polar") or a cap with no polarity ("bipolar").
- You don't need the exact lead spacing I list. Mcintosh bent the cap leads as needed to fit.
- Of the 5 boards, all but the "Input Level" board can be easily unplugged and removed for the work.
* Power Supply and Power Guard PCB 046557:
- 3 x 100uF 50v 5mm (lead spacing) polar
- 1 x 10uF 50v 2.5mm polar
* Meter Drive PCB 046532:
- 1 x 100uF 25v 5mm polar
- 2 x 47uF 25v 3.5mm polar
- 2 x 10uF 50v 2.5mm polar
- 2 x 6.8uF 35v 2.5mm polar
The above two boards are behind the front power meters under the metal cowl cover.
* Amplifier Driver PCB 046534:
- 1 x 100uF 25v 5mm polar
- 1 x 47uF 80V 5mm polar
- 4 x 47uF 25v 3.5mm polar
- 1 x 10uF 25v 2.5mm bipolar
- 1 x 2.2uF 50v 2.5mm polar
- 1 x .47uF 2.5mm polar
There are two of these amplifier driver boards, one for each channel, so you need the double caps listed. Accessible with bottom cover removed.
* Input Level PCB 046552:
- 2 x 10uF 25v 2.5mm bipolar
Do NOT go up on voltage rating, you may not have room for a physically larger cap.
Located at the RCA input jacks and accessible with the bottom cover removed.
The input level board, with the two bi-polar cap's on it, is a bit of work to free up for cap replacement.
Work will be done with the unit upside down and the bottom cover removed.
You will have to remove 4 screws that hold the big output transistor heat sink in place, allowing the heat sink to be slid/dropped out of the way. Then remove the two screws that hold the sensitivity switch to the chassis rear. I desoldered the two input RCA jack center pin leads from the input board, allowing manipulation of the input board for capacitor replacement. It was easier than it looked.
******EDIT: several of the removed capacitors have high ESR. I'm not talking about the bipolar caps either. Six polar cap's were anywhere from 1.96 ohms to 3.80 ohms using a Peak Atlas ESR70 tester.
Again, I decided to replace only the electrolytic caps. I resisted any temptation to replace polar caps with bipolar in the signal path. I resisted the temptation to go from electrolytic to film caps. I love the sound of this amp and didn't want alter it.
Consider replacing the illumination lamps while in there.
You need 3 x 7382 lamps and 4 x GE259 lamps, unless going LED.
The plastic lamp housing for the 4 meter bulbs is VERY fragile and breaks like a potato chip!!!
Good luck and please let me know if you found my post useful.
Jef
- This cap list is only for electrolytic capacitors and does not include the two main 38,000uF filters. I have another post that covers the main filter caps:
https://audiokarma.org/forums/index...pacitor-replacement-diy.962462/#post-14856137
- I wanted to replace electrolytic caps with like in kind. The same uF value and type (polar or bipolar) as found in my amp. So this list shows what I actually found in my amp.
- I wanted to keep my amp as Mcintosh designed it as much as possible. I did bump up the cap voltage rating by one place when convenient because of what I had on hand.
- Based on the service manual, there are different schematics (and thus different circuit boards) used in the 7270 amp. These differences are are based on serial numbers. My serial number is AE3242. I have not studied the differences so I can NOT say if this cap list will exactly work for your amp.
- This cap listing shows what I actually found in my amp, not what the schematics show.
- This listing indicates where you need a polarized cap ("polar") or a cap with no polarity ("bipolar").
- You don't need the exact lead spacing I list. Mcintosh bent the cap leads as needed to fit.
- Of the 5 boards, all but the "Input Level" board can be easily unplugged and removed for the work.
* Power Supply and Power Guard PCB 046557:
- 3 x 100uF 50v 5mm (lead spacing) polar
- 1 x 10uF 50v 2.5mm polar
* Meter Drive PCB 046532:
- 1 x 100uF 25v 5mm polar
- 2 x 47uF 25v 3.5mm polar
- 2 x 10uF 50v 2.5mm polar
- 2 x 6.8uF 35v 2.5mm polar
The above two boards are behind the front power meters under the metal cowl cover.
* Amplifier Driver PCB 046534:
- 1 x 100uF 25v 5mm polar
- 1 x 47uF 80V 5mm polar
- 4 x 47uF 25v 3.5mm polar
- 1 x 10uF 25v 2.5mm bipolar
- 1 x 2.2uF 50v 2.5mm polar
- 1 x .47uF 2.5mm polar
There are two of these amplifier driver boards, one for each channel, so you need the double caps listed. Accessible with bottom cover removed.
* Input Level PCB 046552:
- 2 x 10uF 25v 2.5mm bipolar
Do NOT go up on voltage rating, you may not have room for a physically larger cap.
Located at the RCA input jacks and accessible with the bottom cover removed.
The input level board, with the two bi-polar cap's on it, is a bit of work to free up for cap replacement.
Work will be done with the unit upside down and the bottom cover removed.
You will have to remove 4 screws that hold the big output transistor heat sink in place, allowing the heat sink to be slid/dropped out of the way. Then remove the two screws that hold the sensitivity switch to the chassis rear. I desoldered the two input RCA jack center pin leads from the input board, allowing manipulation of the input board for capacitor replacement. It was easier than it looked.
******EDIT: several of the removed capacitors have high ESR. I'm not talking about the bipolar caps either. Six polar cap's were anywhere from 1.96 ohms to 3.80 ohms using a Peak Atlas ESR70 tester.
Again, I decided to replace only the electrolytic caps. I resisted any temptation to replace polar caps with bipolar in the signal path. I resisted the temptation to go from electrolytic to film caps. I love the sound of this amp and didn't want alter it.
Consider replacing the illumination lamps while in there.
You need 3 x 7382 lamps and 4 x GE259 lamps, unless going LED.
The plastic lamp housing for the 4 meter bulbs is VERY fragile and breaks like a potato chip!!!
Good luck and please let me know if you found my post useful.
Jef
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