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McIntosh MC-7270 Amplifier Find

wje

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#1
I came across a "barn find" a few days back. A McIntosh MC-7270 power amplifier from 1991. It weighs in at 82 Lbs., puts out 270 watts per channel at 8 Ohms. It was sold as a non-working unit. In 1991, it sold for $2,499 and those that are still available today, sell in the range of $3,500+. I've ordered a capacitor rebuild kit to bring it all back into the specs of new that I'll work on this winter along with new LED lights, etc. Oh, what was wrong with it? The $13.97 power cord had failed with no continuity on the hot wire. Soldered in a new power cable and the power is back on. I paid $400 for the amplifier on OfferUp and was able to pick it up locally, so no shipping. With the capacitor replacement kit, replacement LEDs, new glass panel and the cost of the amp, I'll have less than $900 invested in it when finished.


Mcintosh 1.JPG
 
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wje

wje

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She's all connected and playing beautifully. The previous owner, had one of the large Coke can (38,000 uF) capacitors replaced as the original grey one is present, along with a blue after-market capacitor. A few lights are burned out, but that's OK. The LED replacement kit should be here within the week.

I don't feel quite the urge to do the full capacitor replacement just yet. I'll save that for one of the snowy days during this upcoming winter season.

I might be able to save $200 on the replacement glass. I've read about people using an X-acto knife to trim off the loose bubbles, then apply black paint onto the glass with good results. None of the bubbling is too close to the lettering, so I might be OK in that regard.
 
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#4
She's all connected and playing beautifully. The previous owner, had one of the large Coke can (38,000 uF) capacitors replaced as the original grey one is present, along with a blue after-market capacitor. A few lights are burned out, but that's OK. The LED replacement kit should be here within the week.

I don't feel quite the urge to do the full capacitor replacement just yet. I'll save that for one of the snowy days during this upcoming winter season.

I might be able to save $200 on the replacement glass. I've read about people using an X-acto knife to trim off the loose bubbles, then apply black paint onto the glass with good results. None of the bubbling is too close to the lettering, so I might be OK in that regard.
I used to have a MC7300 which is the successor to this amp it sounded awesome. Many people say the MC7270 is even better despite being an older design. As far as the glass goes I had some pretty good results fixing the glass on some of my old Mac stuff with Testors Flat Black Enamel paint. I didn't have any bubbles on mine but there were a few minor pinholes that I was able to fill nicely with the Testors.
 
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wje

wje

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I've completed my build of a Walnut cabinet for the McIntosh MC-7270 amplifier. The amplifier is currently out of service as I'm in the process of rebuilding it with new capacitors, LED lights, etc. A good project for the upcoming cooler season. On the newer McIntosh gear, I'm not a fan of cabinets, but thought with the vintage 7270, a Walnut cabinet would be more fitting and complete the retro look for the era of this amplifier.

Walnut McIntosh MC7270 Cabinet.JPG
 
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#6
I've completed my build of a Walnut cabinet for the McIntosh MC-7270 amplifier. The amplifier is currently out of service as I'm in the process of rebuilding it with new capacitors, LED lights, etc. A good project for the upcoming cooler season. On the newer McIntosh gear, I'm not a fan of cabinets, but thought with the vintage 7270, a Walnut cabinet would be more fitting and complete the retro look for the era of this amplifier.

View attachment 89178
Cool. Do you have the original pan loc brackets? McIntosh amps from that era were actually designed to be installed in cabinets and were sold with special brackets designed to lock the units in place.
 
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wje

wje

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Cool. Do you have the original pan loc brackets? McIntosh amps from that era were actually designed to be installed in cabinets and were sold with special brackets designed to lock the units in place.
Actually, I don't. Finding the Panloc brackets for the L54 case is almost impossible. There was an aftermarket company that was making them and selling them up until a few years ago, but they stopped. However, when I finish the renovation, I'll devise a method for fully securing the amp within the cabinet utilizing the 2 posts that are available on the amp as part of the Panloc method. Then again, the amp weighs 83 Lbs., so once it's in the case, it shouldn't move. But, I'll secure it just to be sure.
 
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#8
Actually, I don't. Finding the Panloc brackets for the L54 case is almost impossible. There was an aftermarket company that was making them and selling them up until a few years ago, but they stopped. However, when I finish the renovation, I'll devise a method for fully securing the amp within the cabinet utilizing the 2 posts that are available on the amp as part of the Panloc method. Then again, the amp weighs 83 Lbs., so once it's in the case, it shouldn't move. But, I'll secure it just to be sure.
Have you checked with audioclassics or mcintoshaudio? They tend to have a lot of rare parts.
 
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wje

wje

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Have you checked with audioclassics or mcintoshaudio? They tend to have a lot of rare parts.
Yes, I have. It's OK, though, as I've had other recommendations on how to go without the Panloc system for mounting. But, when I was soldering in the new RCA inputs, my soldering iron nicked one of the power wires going to the left amplifier outputs. The missing insulation on the wire, rubbed against the heat sinks on the left channel and created a short. I now have to order the transistors to fix this issue. While a minor setback, it's probably best to get it resolved with new parts, being the original transistors are 30 years old at this point. But, about $100 in parts to put in new output transistors, resistors, etc. for both channels.
 
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#10
Yes, I have. It's OK, though, as I've had other recommendations on how to go without the Panloc system for mounting. But, when I was soldering in the new RCA inputs, my soldering iron nicked one of the power wires going to the left amplifier outputs. The missing insulation on the wire, rubbed against the heat sinks on the left channel and created a short. I now have to order the transistors to fix this issue. While a minor setback, it's probably best to get it resolved with new parts, being the original transistors are 30 years old at this point. But, about $100 in parts to put in new output transistors, resistors, etc. for both channels.
I don't think you really need the Panlocs. McIntosh still sold cabinets into the 90s and the 90s amps didn't have Panlocs they just sit loose in the cabinets. Their modern amps are also designed to be custom installed and they have a set of extra low profile feet on the bottom specifically for custom installation and the owners manuals always give recommended dimensions for custom cabinets.
 
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wje

wje

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Thread Starter #11
The McIntosh restore has been completed. Just picked it up from the shop, where calibrations were applied, DC offset, Bias adjusted yet. Slipped it into the new Walnut cabinet. The sound? I have an MC352 for comparison. The MC7270, to my ears, sounds every bit as good as the newer McIntosh amplifier.

7270 02022021.JPG
 
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