MC-2105 Differential Transistors options?

santacruztv

santacruztv

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Hi, I'm wondering what you guys suggest for the original 132-031 transistors Q101-104)? I've found 2n4250 or 2sa1016 listed in threads as replacements.

Does anyone have a reliable source?

I'm wondering about using a KSA992 and understand that pin-out is different . I could bend the pins correctly.

I could try calling McIntosh as well, but I wanted to see if something I have in stock would work.

Thanks!
 
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Hello santacruztv

I will not suggest you anything but just follow the MCINTOSH LABS recommandations
132-031 can replaced by 132-236 commercial type 2SA970BL
Do not try something else

PATRICE working on MCINTOSH units since 45 years
Happy new year to all
 
Be careful!!! If you use the 2SA970xx transistor, please recall that the collector is the center leg, not the base as such with the 132031 and 132096 devices.
 
I have used 2N5401/2N5551 and 2N5210/2N5087 to replace most small signal transistors in vintage McIntosh units without issues.

BC556 and BC546 should also work well but have a reversed pinout compared to the original McIntosh transistors.

2SA970bl should have more gain and a little less noise when compared to all the transistors I mentioned so if you want absolutely maximum performance use the Toshibas.
 
Thanks very much everyone!

Does anyone have a good source for the 2sa970BL's?

I'm also considering replacing all the remaining small signal transistors on the input board and amp boards while I'm in there if anyone has thoughts about the best substitutes?

Q1-4 on input board (132-054),


Q107, 108 on amp board (132-021),
Q109, 110 (132-032).

I can also reach out to McIntosh on Monday to see what they have.

Happy New Year and thanks again!
Greg
 
clinic-audio said:
Hello santacruztv

I will not suggest you anything but just follow the MCINTOSH LABS recommandations
132-031 can replaced by 132-236 commercial type 2SA970BL
Do not try something else

PATRICE working on MCINTOSH units since 45 years
Happy new year to all
Click to expand...


KSA992F has very similar specs to 2SA970BL. I’m interested to know what specifically would cause you to reject it for this application?
 
For what it is worth, I looked at some recent purchase orders for the past few years and could not find any 2SA970's ordered for repair use. What I did order where Fairchild BC550C and BC560C devices from Great Britian that I would screen before use. Make yourself a spreadsheet on Excel with all the devices mentioned in the important categories. You will find it useful and use it more than once. It helps me decide my choices when it comes to select a device. You can obtain these BC550 and BC560 I mentioned as well as the BC546 and BC556 devices Tala Mink mentioned.

Most important, have fun doing it and learn. WE will not steer you wrong in making a final selection and explain why. DIG IN!!!
 
I used 2n5210 for Q1-Q4 and 2n5401 for Q5&Q6 in the last MC2505 I worked on (the 2505 and 2105 share the same input board) though all of the transistors recommended in this thread should make adequate replacements.

Also a big tip is Keystone 1238 works well to replace the sockets that Mcintosh used all over their units, they have a slightly larger diameter so they need a little squeeze to fit, but if you want an original look without reusing sockets they are the best option I have found.

T20250801_222929.jpg20250801_194844.jpg20250801_193458.jpg

2n5401 and 2n5551 will work to replace Q7-Q10 but may have slightly less power dissipation than the originals, this shouldn't be an issue unless you are constantly clipping your amp.

You should be able to keep the originals in as I have only ever seen VI limiter transistors fail when the power transistors short or the amp is extremely overdriven.
 
The material is silicon
:)
Noise specs can be confusing and misleading because of the test method used. Not all follow the same test having the same source impedance which affects the current noise contribution to the total noise. Some specs have noise contour graphs which give more info and ways to compare.
 
Thanks for the replies everyone! McIntosh had substitute parts for all the part numbers I was looking for. $1.00 ea.

I'll post part numbers and results when I get the 2105 back on the bench.
 
A point of contention (for me) here: McIntosh Parts has researched and stocks transistors for a 60-year-old amplifier, sells them for $1.00/ea., likely is at best breaking even on this effort.

Personally I will continue to pay McIntosh for parts, unless the price difference makes a SIGNIFICANT difference in the affordability of the project, in hopes that this goodwill will continue on their part.

It could end any day and it’s good to have the part numbers I agree, but as @santacruztv did I hope that most (if not all) of us will consider buying parts from McIntosh or Audio Classics (or another McIntosh dealer) before going 3rd-party like Mouser, Digikey, etc.

The biggest exception is shipping unfortunately, I get hit pretty hard on shipping from McIntosh if I’m buying $5.00 in parts (not much better at Mouser though).
 
SaturationPt said:
A point of contention (for me) here: McIntosh Parts has researched and stocks transistors for a 60-year-old amplifier, sells them for $1.00/ea., likely is at best breaking even on this effort.

Personally I will continue to pay McIntosh for parts, unless the price difference makes a SIGNIFICANT difference in the affordability of the project, in hopes that this goodwill will continue on their part.

It could end any day and it’s good to have the part numbers I agree, but as @santacruztv did I hope that most (if not all) of us will consider buying parts from McIntosh or Audio Classics (or another McIntosh dealer) before going 3rd-party like Mouser, Digikey, etc.

The biggest exception is shipping unfortunately, I get hit pretty hard on shipping from McIntosh if I’m buying $5.00 in parts (not much better at Mouser though).
Click to expand...

I agree with this completely. Unfortunately on my last two attempts I was not able to reach anyone at McIntosh parts.

I’m interested to know which transitors McIntosh sent to @santacruztv
 
They lost heat for a few days this winter and closed unexpectedly while it was out, and then it took a while to get caught up. I know, I was waiting for parts during that time!
 
McIntosh Order:

Q1 - Q4 input board orig: 132-054, sent 132-254 (2SC2362)
Q101 - Q104 amp board: orig 132-031, sent 132-255 (2SA1016)
Q107 - Q108 amp board: orig 132-021, sent 132-317 (MPSA06)
Q109 - Q110 amp board: orig 132-032, sent 132-304 (MPSA56)

$1.00 ea. Shipping $10.00
 
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