Fairly new to servicing macs. I want to refresh the thermal grease on the output transistors. I am used to using micas with white thermal grease. The MC2100 appears to have some sort of thicker black pad with a sticky clear grease. What is the usual procedure here? Throw out the pads and use micas and white thermal grease or re-use the thicker pads that are on it with thermal grease?
MC2100 Service/Maintenance of output transistors
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If you're a Tech, you should be starting by looking at the schematic. Not trying to bust your chops but if you've already removed transistors without first consulting the schematic and doing the appropriate troubleshooting, ...
The MC2100 family runs a hot heatsink, some of the output transistors are isolated from the heatsink and some are not and it's important to get that arrangement correct. Don't mix up the pads.
Normal heatsink compound is what is used on these.
The MC2100 family runs a hot heatsink, some of the output transistors are isolated from the heatsink and some are not and it's important to get that arrangement correct. Don't mix up the pads.
Normal heatsink compound is what is used on these.
The amp functions despite almost all its capacitors being out of spec. I dont think its ever been serviced. While I wait for the new caps, it seemed like a good idea to grease the output transistors. I took off 1, it wasnt what I expected, so I put it back on. I expected to see either a mica or white grease. When I saw neither, I came here for advice. I typically use Wakefield Type 120 Thermal Compound.
The MC210x is known for meltdowns, if it has never been serviced you should download the correct service manual (by schematic) and the Service Bulletin and service it correctly. It is well past-due for the SB and many of us recommend it, as did McIntosh decades ago. Chances are the bias resistors are also drifted by now and the TO-3 output transistors are no longer matched among other things, a good analysis of its current performance is the best start.
Any quality non-conductive thermal compound should work on these TO-3 transistors.
Any quality non-conductive thermal compound should work on these TO-3 transistors.
I have the service bulletin. Thanks for the help.l!
I think that I read that McIntosh still sells the SB parts in a kit. That flying-saucer heatsink is the most expensive part, even if you buy it directly from the manufacturer.
When I went through my 2105 several years ago I also bought the ceramic resistors from McIntosh, the output transistors I bought from Mouser (or Digikey?) and bought extras so that I could ensure close matches, replacing the entire set wasn’t that expensive. The big one is the two power-supply filter capacitors, I can’t remember but IIRC they were $$ back then / hopefully still available.
When I went through my 2105 several years ago I also bought the ceramic resistors from McIntosh, the output transistors I bought from Mouser (or Digikey?) and bought extras so that I could ensure close matches, replacing the entire set wasn’t that expensive. The big one is the two power-supply filter capacitors, I can’t remember but IIRC they were $$ back then / hopefully still available.
My driver boards have those weird plastic disc heat sinks. Does that mean the SB was done at some point or does the SB call for different heatsinks?
The flying-saucer looking ones, two per PC board? They’re Avid or some manufacturer, aluminum.
Yes, if that’s what the board has then most likely the SB was completed and your 2100 might have been serviced in the past, and maybe not even that long ago. Check date codes on your electrolytic caps and also compare the SB to the replacement parts’ values to see if it was done (again most likely yes if the flying-saucers), whether all electrolytic caps were updated, and when. The ceramic resistors also have date codes as might the TO-3s.
Yes, if that’s what the board has then most likely the SB was completed and your 2100 might have been serviced in the past, and maybe not even that long ago. Check date codes on your electrolytic caps and also compare the SB to the replacement parts’ values to see if it was done (again most likely yes if the flying-saucers), whether all electrolytic caps were updated, and when. The ceramic resistors also have date codes as might the TO-3s.