Looking for Cross-reference for Motorola M9639 transistor?

Thread Starter

Johnnyb60

Joined Sep 6, 2013
36
Having trouble finding a replacement transistor for a 14VDC power supply. The numbers are 185, M9639, MEX, 8532 and a photo below.



Would appreciate it if someone could point me in the right direction.
 

Hypatia's Protege

Joined Mar 1, 2015
3,228
That's a Motorola in-house 'ID' --- While, ostensibly, there is no exact generic equivalent, please consider the following...

The closest generic cross = 2N3772
Note: Although many sources cite the 2N3773 as an acceptable cross, unless you are well versed with your application's parameters, I strongly advise against it - inasmuch as the 2n3773's Ic (Max) figure ~ 1/2 that of the M9639! --- You may rest assured that the 2N3772 will 'fit the bill' in nearly all cases... :)

FWIW A reasonable after-market sub = NTE181

In general the device's 'on-label' App is high power audio amplification.. (Common off-label applications include Royer power oscillators, linear EMF regulators, high current switching, etc...)

Best regards
HP
 
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Hypatia's Protege

Joined Mar 1, 2015
3,228
Thanks, well I guess I'll keep looking.
At risk of sounding the shill, I'm bound to say you could just order an NTE-181:)

In case my post (above) was unclear please note

2n3772 ~ NTE181 = Good MATCH

2n3773 (notice the '3' in the rightmost digit of the 'ID') = Dubious, unrecommended substitute

Best regards
HP
 
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ian field

Joined Oct 27, 2012
6,536
That's a Motorola in-house 'ID' --- While, ostensibly, there is no exact generic equivalent, please consider the following...

The closest generic cross = 2N3772
Note: Although many sources cite the 2N3773 as an acceptable cross, unless you are well versed with your application's parameters, I strongly advise against it - inasmuch as the 2n3773's Ic (Max) figure ~ 1/2 that of the M9639! --- You may rest assured that the 2N3772 will 'fit the bill' in nearly all cases...
A firm I worked for that made high power ultrasonic generators used a house coded transistor that was equivalent to the 3772.

A quick google finds that the 3771 is the highest current in that family - the 3773 is only a tiny bit better than a 3055 but a fair bit better for breakdown voltage.

[/QUOTE]
 

AnalogKid

Joined Aug 1, 2013
10,987
It might be that the original part is way overkill for the application, but was what was in the manufacturer's inventory.

Another approach is to tell us the requirements of the power supply and reverse-engineer the device selection. For example, a 14 VDC output linear power supply probably has less than 30 Vpeak into the pass transistor. If you take the rated output of the supply times 1.5 or 2.0, that should be a safe estimate of the current rating needed. The last thing is the gain, and I seriously doubt that it needs to be much above 20 at max current because the 2N3055 influenced generations of designers. BTW, is this the only pass device or are there more than one in parallel?

ak
 

Hypatia's Protege

Joined Mar 1, 2015
3,228
A further caveat:

Please! Please!! Please!!! beware of counterfeits!!! Buy only from reputable distributors (e.g. Mouser, Digikey, Newark and their ilk) *PLEASE* don't even think about Ebay! My "tuition", in this regard, was $20K+ :rolleyes:

Best regards
HP
 
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Thread Starter

Johnnyb60

Joined Sep 6, 2013
36
It might be that the original part is way overkill for the application, but was what was in the manufacturer's inventory.

Another approach is to tell us the requirements of the power supply and reverse-engineer the device selection. For example, a 14 VDC output linear power supply probably has less than 30 Vpeak into the pass transistor. If you take the rated output of the supply times 1.5 or 2.0, that should be a safe estimate of the current rating needed. The last thing is the gain, and I seriously doubt that it needs to be much above 20 at max current because the 2N3055 influenced generations of designers. BTW, is this the only pass device or are there more than one in parallel?

ak
There are two I posted a thread earlier about my 14v power supply was putting out 24VDC and determined that I had a bad pass transistor. I've been searching for a week and can't find one. I even started to wonder if maybe I had the wrong numbers, because there was nothing available.

This is the original thread http://forum.allaboutcircuits.com/threads/14-vdc-power-supply-putting-out-24-vdc.108329/
 

Thread Starter

Johnnyb60

Joined Sep 6, 2013
36
A further caveat:

Please! Please!! Please!!! beware of counterfeits!!! Buy only from reputable distributors (e.g. Mouser, Digikey, Newark and their ilk) *PLEASE* don't even think about Ebay! My "tuition", in this regard, was $20K+ :rolleyes:

Best regards
HP
LOL well eBay was my next move and unless i find something it might be my only hope.
 

Thread Starter

Johnnyb60

Joined Sep 6, 2013
36
Again, as stated in post #5 (q.v), you may buy the NTE-181 Directly from New Tone Electronics:
http://www.ntepartsdirect.com

Piece price = $9.77 (USD) / No minimum order --- You can't beat that!:)

Best regards
HP
Thank you I missed that some how. I was just getting overwhelmed over all the information and how it all fit together. Anyway I just placed my order ntepartsdirect.com, thanks again.
 

Thread Starter

Johnnyb60

Joined Sep 6, 2013
36
NTE can be handy, but they average 3x the original part price.
I only use in a dire emergency.
Max.
Well I just didn't know of anybody else that had it although I wasn't looking for a NTE-181 at the time. Oh well it cost me $30 for two with shipping. Anyway I'm just glad its ordered. :)
 

ian field

Joined Oct 27, 2012
6,536
NTE can be handy, but they average 3x the original part price.
I only use in a dire emergency.
Max.
Bit like Maplin in the UK - similar price ratio.

They do components, kits and manufactured items - but I have to be even more desperate to also travel all the way to the next nearest town.

Ordering from somewhere like Farnell is not only a lot cheaper - but Maplin *ALLWAYS* screw up postal orders. On one occasion I bought 10 each from a range of E24 resistors, one of the values was out of stock so they agreed to take the payment and forward those items from the warehouse - typically, they sent the wrong value - when I returned the pack of 10 resistors with a letter explaining it, they sent bacl only one resistor - still the same wrong value.

The same happened, only much worse with a large order of turned pin DIL sockets, it took well over a month of exchanged e-mails to finally get the right quantity of the right parts - that was the last time I ever used Maplin.
 
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