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Mcintosh MC2300 Rebuild

damacman said:
Yes. This change occurred in early 2Y s/n units. I used to add the circuit to all my 1Y amps. My MC2300 fans cycle a bit under normal use as both amps are rack mounted. I've never been able to kick on the fans on the 2500s or 2600s though!
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I suppose it was inevitable they'd do this. BTW I never actually had an MC-2300 on the bench myself (nor actually seen many in the wild) but '2500's and a few '2600's came through.

I wonder if it'd make sense (more for curiosity) to use 2 different temperature switches giving each fan its' own threshold of operation. I can see you'd lose flow through the 'late' fan in reverse. Or make a PWM motor controller work off a voltage ramp.

I was going to ask what diameter, and realized I have 2 downstairs to look at. OK, holes are 4 inches apart, fan is likely 4 1/2 or 5 inches across. What voltage?

Wait, I'll never know I have a bad fan....The good ones don't run either.
 
CruzBay said:
I suppose it was inevitable they'd do this. BTW I never actually had an MC-2300 on the bench myself (nor actually seen many in the wild) but '2500's and a few '2600's came through.

I wonder if it'd make sense (more for curiosity) to use 2 different temperature switches giving each fan its' own threshold of operation. I can see you'd lose flow through the 'late' fan in reverse. Or make a PWM motor controller work off a voltage ramp.

I was going to ask what diameter, and realized I have 2 downstairs to look at. OK, holes are 4 inches apart, fan is likely 4 1/2 or 5 inches across. What voltage?
Click to expand...

The 2300 fans are run off the 120v AC input.

My second 2300 is a 1Y. It has the stock PA motor fans, which a previous owner had installed resistors to slow the fan speed to a crawl. After I restored the amp, it seems sufficient for cooling. It moves enough air to keep the tops of the heatsinks around 120f after some long and spirited listening sessions. This makes the stock PA motor fans virtually silent.

The BEST electronic and machine co. fans that I used to replace the PA motor fans in my 2Y were more quiet than the stock config, but I added thermo switches, and also slowed down the fans down, but when operating are still slightly noticable in quiet passages. The thermo switches also have a loud click when they go off and on. I wish I could find a silent option for that.
 
Here is what I see under the lid. I have next to no electronics experience but I'm a good mechanic and can "re and re" just about anything. If you guys and gals see something obvious please point it out. Thanks.
 

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OldMcintosh said:
Here is what I see under the lid. I have next to no electronics experience but I'm a good mechanic and can "re and re" just about anything. If you guys and gals see something obvious please point it out. Thanks.
Click to expand...

Only thing I see is a slightly rotated power transformer, was this amplifier used with a band, or in the field, at one time? (Might've been dropped)

(BTW, these things got dropped all the time, only thing that got hurt was what it landed on)
 
OldMcintosh said:
Here is what I see under the lid. I have next to no electronics experience but I'm a good mechanic and can "re and re" just about anything. If you guys and gals see something obvious please point it out. Thanks.
Click to expand...

Looks like yours got the driver board updates. That's nice, but imho it could benefit by replacing the old e-caps. Is there any clinic stickers on this amp? Just curious.
 
Last time on a bench was July 2018 by a dealer on Canuck Audio Mart. They went over everything and brought it up to spec (according to them). They are still a dealer in good standing. They decided to leave the fans as they were and I didn't ask before getting it. They suggested the ultra quiet fan route because of the shipping costs.
 
In the 5th photo, you're holding back a heat shrunk splice. That's likely the culprit. Here is a schematic of the fan circuit from the service manual. It's quite simple. S304, 5, 6, and 7 are the switches mounted to the heat sinks. Compare this to what you see in the amplifier.
 

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Thanks for the info. I have a friend about an hour from here who knows how to read that. I'll see if he's willing to help out.
 
If I could find a picture of an unmolested one, I could probably replicate it with you schematic but I've search several times and came close but nothing detailed enough.
 
I took out one fan and found the sniped wires on the thermal switches. Where the "surgery" occurred is in red. Two spots on the right, one on the left. I also included where the wires are now. I can't read schematics and can't get anyone out here for awhile (Covid-19). Can anyone tell from here which wire goes back to which terminal?
 

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Will see if I need to open a new thread but I now got a MC2300 which has one channel not working. I am yet to open it up but is there anything to watch once I open. I dont think there are any fuses (wish I was lucky.lol). Also once fixed I plan to recap them so any BOM listing available? Thanks
 
Hi, y'all!

I just got a 2300 myself and the fans haven't kicked on yet.

I'm only finding the 1Y service manual, mine is a 2Y.

It looks like the circuit was redone on the fans, they have a .047 200vdc cap in parallel across the thermal sensors?, one of which looks like it's in parallel with a diode.

I'm not as advanced as many of you guys are. I was about to recap it, but I couldn't find a matching schematic.

I was also curious if I should change the diode and if so what type is it?

Thanks!
 

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