McIntosh C28 Transistor Replacements and Substitutes

[MisterFishey]

Having scoured Google and AK for this information, I figured I would post it so it could be of use to others. This data was compiled from original parts in my unit, AK searches, official McIntosh part substitutions, and Echowars recommendations. The McIntosh part numbers are valid for all units, though the set of transistors as a whole are from the C28 preamp.

McIntosh Part Number, original transistor number, then valid replacements:

132-028 - 2N3738 - TIP50
132-065 - 2N4231 - TIP41B and TIP41C
132-090 - MPSA14 - MPSA14
132-092 - BC238 - BC549
132-093 - BC239 - BC549
132-095 - BC414C - 2SC2240BL and KSC1845(F or E) *
132-096 - BC416C - 2SA970BL and KSA992(F or E) *
132-105 - BC239C - BC549C

* The pin assignments/bias for these transistors are different from the originals, as shown here:

 

[MisterFishey]

Transistor Data by McIntosh Part Number:

Transistor Data by C28 Schematic Part Number

 

[c_dk]

According to my 1990 McIntosh semi data/sub paper the 092,093,095,105 all are replaced with the 132-235 or 2240BL. It seems that Toshiba has discontinued this device even though some high HFE (BL graded) are said to be available. It also seems that the Fairchild 1845 high HFE (E,F) are also being phased out.

Why not a tab sub for the 028 instead of the NTE?

 

[MisterFishey]

According to my 1990 McIntosh semi data/sub paper the 092,093,095,105 all are replaced with the 132-235 or 2240BL. It seems that Toshiba has discontinued this device even though some high HFE (BL graded) are said to be available. It also seems that the Fairchild 1845 high HFE (E,F) are also being phased out.

Why not a tab sub for the 028 instead of the NTE?

Thanks for that information! I didn't see the 2240BL listed as a replacement for the 092, 093, or 105 anywhere online, I determined the substitutes for those based on the data sheets. The BC549 and BC549C are low-noise transistors like the 2240BL, I have them in my C28 now and they are working great. Same pin assignments/bias, too. Seeing as the 2240BL has been discontinued (I snagged a few from BDent, the last remaining reputable supplier, it seems), it looks like the KSC1845(E, F) are the best subs available, but I don't think they are being phased out, at least not entirely. Mouser has the bulk KSC1845F listed as End of Life, but the ammo pack KSC1845F appears to still be in production.

Hmm, I don't know why I didn't list a tab sub for the 028. I should be able to find one. :scratch2: I'll update the OP tonight to reflect this change in information.

 

[dewickt]

2N3738 and 2N4231 are available, I personally avoid NTE general replacement parts as they are so generic.

 

[CountD]

Yes, I have heard about dubious quality control issues with NTE...

 

[c_dk]

For most all of the last 15 years I was not allowed by management to have an active bench so I am still catching up in some cases. To my memory as we replaced a malfunctioning transistor with a new replacement we would see a substantial S/N improvement and would often swap new parts into the functioning channel to bring it also to a higher performance level. To be fair this was most often in the phono stages of C-28 and older units. Is this still the case?

As the TO-66 trans are replaced with tab trans as power regulators does it not seem to make more sense to replace the whole mulicap supply with a modern 79XX regulator based supply?

 

[MisterFishey]

2N3738 and 2N4231 are available, I personally avoid NTE general replacement parts as they are so generic.

Yes, I have heard about dubious quality control issues with NTE...

Heard loud and clear! I've heard about quality control issues too, they don't seem to be as reputable as ON Semi or Fairchild.

For most all of the last 15 years I was not allowed by management to have an active bench so I am still catching up in some cases. To my memory as we replaced a malfunctioning transistor with a new replacement we would see a substantial S/N improvement and would often swap new parts into the functioning channel to bring it also to a higher performance level. To be fair this was most often in the phono stages of C-28 and older units. Is this still the case?

As the TO-66 trans are replaced with tab trans as power regulators does it not seem to make more sense to replace the whole mulicap supply with a modern 79XX regulator based supply?

From my own personal experience, swapping out the old transistors with the substitutes I listed in the OP made a huge difference. I didn't expect a difference in sound (though I did expect a better S/N improvement), but the improvement was extremely obvious. It would be hard to deny the huge progress in transistor technology from the time the C28 was released to now or even to the 80's and 90's, when the 2240BL was listed as a substitute part. I would be interested to see how my re-transistored C28 would compare to a stock C28 in an A/B test, or the next-generation C29 and C32.

Regarding the power supply, I don't know anything about regulator-based supplies, but I don't see any reason why it couldn't be done.

 

[MisterFishey]

Updated on 1/7/12 to include TIP50 as a replacement for the 2N3738, and TIP41C as a replacement for 2N4231. The TIP41C is just a higher voltage rated transistor than the TIP41B, so it would actually be a superior replacement.

 

[USMC Spike]

Thanks for posting this information Mister Fishey.
I will be using your data, where applicable, for my
own C24 update.

Cheers,

Spike

 

[jlovda]

Heard loud and clear! I've heard about quality control issues too, they don't seem to be as reputable as ON Semi or Fairchild.

Remember, NTE does not make any semiconductors. They just supply blister-pack (or bagged) parts from other suppliers to service the electronic parts distributor trade. Some parts could very well be ON or Fairchild.

 

[waldo041]

132-092 - BC238

Mcintosh sent me these for a replacements 132-254 = 2SC2362

 

[clinic-audio]

Hello MisterFishey

I just wanted to let you know (and to all the other AK members ) that KSC1845 (Fairchild ) is simply a 2SC1845 (NEC) !

Both have same HFE classification :yes:

Complement KSA992 is also a 2SA992 !!

I will take a look on your tables and let you know if I see something wrong

Have a nice week end !

Clinic Audio 35 years working on MCINTOSH :thmbsp:

 

[c_dk]

132-092 - BC238

Mcintosh sent me these for a replacements 132-254 = 2SC2362

They must have bought a bunch while they were readily available.

The originals were part of the mass substitutions done by the 2240/970s in the late 80s.

I know some of these are still around but are they the real deal?

The 1845/992 are still readily available from most suppliers.

I am right now trying to determine if the mc7270 on my bench has counterfit 132-188/89 outputs in it.

 

[clinic-audio]

Hello C DK !

I am right now trying to determine if the mc7270 on my bench has counterfit 132-188/89 outputs in it.

What do you mean by counterfit ? don't they have 132-188 and 132-189 original MCINTOSH factory "stamp" on them ?

132-188 are MJ15003 x3
132-189 are MJ15004 x3
132-203 is sorted MJ4248 x 1
132-204 is sorted MJ4238 x 1

But I am sure that you already have these informations ! :thmbsp:

 

[c_dk]

Yes, know the subs. To my knowledge Mac has always used either RCA or Motorola TO-3 style outputs until they went to tabs. There are some marked 132-188/189s from a different supplier in this amp.

 

[Kenny1964]

According to my 1990 McIntosh semi data/sub paper the 092,093,095,105 all are replaced with the 132-235 or 2240BL. It seems that Toshiba has discontinued this device even though some high HFE (BL graded) are said to be available. It also seems that the Fairchild 1845 high HFE (E,F) are also being phased out.

Why not a tab sub for the 028 instead of the NTE?

According to my 1990 McIntosh semi data/sub paper the 092,093,095,105 all are replaced with the 132-235 or 2240BL. It seems that Toshiba has discontinued this device even though some high HFE (BL graded) are said to be available. It also seems that the Fairchild 1845 high HFE (E,F) are also being phased out.

Why not a tab sub for the 028 instead of the NTE?

Is there any way I could get a copy of your 1990 MacIntosh semi/sub data ? Some one you know I could get it from ? I am working on a Mc252 and need to cross reference the transistors. Thank, You Kenny1964

 

[c_dk]

The parts used in the MC252 are not in a 1985 data sheet......most all those parts have been obsolete for years now.

This does remind me of a dinner conversation I had with DOB after a amp clinic.

He was explaining to me about " bell curve pricing" for the relationship McIntosh had with it's parts suppliers.

I was familar in a sense with this pricing concept in the purchase of steel alloys but did not think to apply it to the purchase of tubes and semiconductors......and speaker drivers come to think about it.

As a part of buying at the top of the bell curve Mac's suppliers were contracted to print Mac's own part numbers on the highly selected parts. Mac Q/C would then further cull the parts or if the parts needed were purchased in bulk would be graded and identified by Testors paint highlights on the device.

The paper scrap with the color codes he gave me are long gone unfortunately.

The impetus for this work interfering with a pleasant dinner was the Toshiba BL grade devices that were so consistently in tight spec that they did not need such grading. Those two devices replaced over 3 dozen older parts.

Alas I do not believe the current Toshiba numbered BL grade are nearly as consistent as the 20 year old devices, at least the last batch I bought from BDent weren't.

I do believe the latest through hole devices Mac has been using are Sanyo sourced and are so marked with their commercial numbers.