counterfeit mj15003's (pics)

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
These MJ15003's were purchased from MCM electronics several months ago. When I got them, there were two types, different letterings on them as well. I did not know about there being conterfeit transistors out there so I thought nothing of it. But with people mentioning the fact that there are some out there, I thought that I might post a pic of some of the ones that I have. I saw the a picture posted of how to tell the fakes, some of mine look a little like that with the horizontal printing vs the vertical. Take a look at the pics and let me know. FYI, most of the transistor in my batch had weak printing on them, both kinds, some were hard to read, but all were spelled correctly.
I have MJ15003 from run 9721 here. Twelve to be exact. None have the indentation, and every single one has the text aligned like the one on the right in your top.jpg

None of the TO3s (not many but yet hundreds) I have seen in my life have had the indentation. And all my Motorola 15003/4 have proven themselves true with torturous testing and toying, my water cooking experiments included.

Or can six fake 15003/4 dissipate 300W for minutes without failing in a 60 deg. C heatsink? Or put out a 15A peak lasting 15 seconds, having 26V average over them, heatsink being the same?

All MJ15003/4 in the heatsink I am holding now in my lap have the text better visible than in your picture. Of the production run code, the last letter is always the thickest. And the lower end of the J in the type marking doesn't point up in any. My MJ15004 are quite old, the run is 9150.

Rod Elliot has much to say in and my summary goes...

The marking should stand acetone. If it dissolves, you are sure to have found a fake. If it doesn't, they might be real. No MJ15003/4 (or any Motorola/ON) has been made to an aluminium case since 1982.

I don't know if the text should always be in line with the case's baseplate. All of my MJ15003/4 have it tilted a bit. My guess is that the pictured are fakes. If mine are fakes too, then this is really wicked and I'm desperate.

-Kimmo Sundqvist
Geoff ... point taken....

I warned against the dangers of dismantling a transistor because it was little trouble to simply retype it .... and it aint hurting anyone... as for the image, i have changed it to a link.

I feel that the above posts i made have added worthwhile content to this thread ... granted it could have been found elsewhere on the forums but this has ensured that this information is not overlooked....

I also dont mind spending heaps of time in this forum helping other people when i can and i feel that i should be free to do so as it is my time.

Having said that, I am all for anything that would take some of the load off the 10 or so major contributors to this board (you included)....
well, if I scratch at the lettering on the cases with my finger nail, it will come off. Also, when I mount these transistors to a heat sink, they do not lay perfectly flat.

I cracked one of these bad boys open to take a look.

Here are the pics.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

I seperated the leads further in the second pic so that you can see clearly that there are two seperate leads. That fact combined with the white epoxy tells me that these are indeed fakes.

Before I call MCM Electronics, I want others to verify this for me please.
I just called MCM Electronics and they were very unhelpful. They told me that they sell two models of the mj15003 transistors, a generic version and a motorola version. They said I must have ordered a generic version. I told them that the cases have the motorola logo right on them and they got all quiet. I'll call them back tomorrow to see if I can get any further with them. The guy I talked to evidently had no idea that there was such a thing as a counterfeit transistor. I'm not too happy about MCM electronics right now.

I'm mad because I bought 24 of these to replace blown output stages on some of my amps I built and fried.

I checked the two type of that I had by cracking them open, and they are the same. All of them are counterfeit. I doubt I will get any sympathy from MCM since I bought these almost a year ago.
ON Semiconductor is the spin-off of Motorola that makes power
semiconductors under the ON name, and that's what I'd be
looking for now.

I've been picking up most of my power transistors through
Future-Active Electronics local store in Bellevue, WA, so I'm
pretty sure everything I've got is genuine, and not second-
sourced or downright fake--which I suspect these are.
The silicon chip looks a bit small for a 200 watt transistor too.
I'd write MCM's president and send him copies of your

I haven't blown any MJ15003/4s in a long time, though I
sometimes removed the tops of power transistors at work
for post-mortem analysis. It might be worth sacrificing a few
to have as reference; I've got about ten MJ15002s that I'm
not planning to use (anyone want to buy some?).

Sometimes places like MCM pick up various lots of transistors
from some manufacturers inventory rather than directly from
the original factory source. It's best to buy from an authorized
dealer and to specify ON Semiconductor to be sure of getting
new parts of recent manufacturer.

I'd be willing to bet the MJ21193/4 are not popular or well-known
enough to be counterfeited or even second-sourced. NTE lists
replacements with specs that match them, but they also want
$10 apiece for them. I'm not that desperate to take a chance.
There is only one way to deal with MCM: obtain a RMA number, ask to speak to a manager, be a real bitch and get it out of your system.
Nothing else really works. In a couple of weeks some chick from the "customer care department" is going to call you up and give you 20% discount coupon. Feel free to either use it or tell her to shove it up hers.

edited: most importantly, get your money back!
There is no use to get a discount if all you can buy from them is shite.
Oh i'm gonna be a real bitch to them if they don't resolve my issue that they caused. If they give me a discount coupon I would be a lot happier with them. This was an expensive mistake for me to buy them from MCM. I've never had trouble with them in the past. Let's hope that they make good on this.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.