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MC2100 repairs

Not sure what you mean when you state that you can't get the "heatsinks from the older transistors."

Yes, use a light bulb "variac." Pull the driver boards then add one at a time.

Light bulb comes on bright and stays bright, you have a short.

Murray
 
skippy_ps said:
Not sure what you mean when you state that you can't get the "heatsinks from the older transistors."

Murray
Click to expand...

When I removed the 2 driver transistors from the driver board, the little heat sinks where still attached. They would not separate, is this normal, is there a different heat sink to use with the new one.

skippy_ps said:
Yes, use a light bulb "variac." Pull the driver boards then add one at a time.

Light bulb comes on bright and stays bright, you have a short.
Click to expand...

This will pin point exactly which card is bad, is there a certain watt light bulb to use. I have one and will dig it out, just need to get a light bulb.

Thanks
 
duder1982 said:
When I removed the 2 driver transistors from the driver board, the little heat sinks where still attached. They would not separate, is this normal, is there a different heat sink to use with the new one.

Thanks
Click to expand...
The original RCA drivers had heat sinks that were permanently attached. The replacement transistors (TO-5 case) require separately attached heat sinks that I believe came with replacements from Mcintosh. They looked like an ~1-1/2" disk with a pressfit underneath. Look at Mouser if you need to get them separately.
 
Ok, thought you meant the output transistors.

Use a 40 or 60 watt lamp. That's what I would suggest. Incandescent. :)

Murray
 
jlovda said:
The original RCA drivers had heat sinks that were permanently attached. The replacement transistors (TO-5 case) require separately attached heat sinks that I believe came with replacements from Mcintosh. They looked like an ~1-1/2" disk with a pressfit underneath. Look at Mouser if you need to get them separately.
Click to expand...

I thought they were to-39, maybe that's the same, maybe I have the wrong ones.
 
I believe the MC2300 schematic details all the mods needed to use the last updated kit for driver update.

The kit from Mac consisted of drivers, heatsinks, new bias diode, resistor and instructions to remove ceramic caps and add a jumper. IF I REMEMBER CORRECTLY. it was 30 years ago when we expected to do ALL mc2300s. MC2105s were optional.

The AKdatabase might have the MC2300 schematic.

i checked the database....the schematics are incomplete, they do list all updates supplied to warranty service shops.
 
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Driver board updates are to replace 132-153 + 132-154 with 2N5322 and 2N5320 and add jumper. Change 22 ohm bias resistors to 18 ohm. Remove c13 & c14 and replace c9, c15, c10 & c16. Cap values escape me. Notes are at work.
 
Somebody posted the update in another thread, but sounds like everyone has it covered as well.

Sent from my HTCONE using Tapatalk
 
Well the bulb was brighter on one channel then the other. So I plugged the board in with the dimmer test and the fuse didn't pop. Which makes since, since that was the channel with the bad output. So I will order some of those heat sinks for the new transistors. Complete the update on that board and see what happens.

Sent from my HTCONE using Tapatalk
 
jeffs79 said:
The replacement heat sinks are Thermalloy 2227B.
I get them from Electronic Surplus:

http://www.electronicsurplus.com/It...eatsink_ For TO-5_ TO-39 components_ - 2227B/
Click to expand...


I will look at ordering a set of those, I have seen some other styles out there, is there a chance something else might work. I would like to stop by a local shop and see if they have anything laying around.

These look to be the same, though I need to double check the sizes.

http://www.ebay.com/itm/Heatsink-fo...594?pt=LH_DefaultDomain_0&hash=item46224b4b82
 
I finally got around to ordering those heat sinks, now for the 680 pf caps for the update, anybody have a preference. All so it says place the bias diode under the transistor, I all ready have a diode there, which is the one that I have in the picture that needs replaced anyway. Last whats all this mumbo jumbo about running a piece of wire between the 2 circuit board lands.
 
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The soldered mounting pins for the original heatsink completed the audio circuit, the jumper wire is soldered from hole to hole on the back side.
 
Mac always sent a new diode with their kit. I have seen it mounted in contact with the transistor many ways. The way DOB showed me at a amp clinic I hosted set the diode in the crook or corner of the top hat heatsink. Insulate the leads, solder in place just proud of the transistor top, apply heatsink grease, and then press the top hat down putting the diode in intimate contact with the transistor.
 
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