Late 90's Peavey Transtube Supreme repair (power transistor questions)...

[tube power]

2x MJ15024 + 2x MJ15025 Audio Power Transistor TO-3 - eBay (item 260631231083 end time Nov-03-10 03:27:40 PDT)

Yup, I took a chance on an otherwise for sure paper-weight.

I'm just tinkering and have more time than money.
Maybe I can salvage it, but as you can see, I'm not qualified, so hey...

[tube power]

Oof....watch it there. There are tons of fake (counterfiet) power transistors out there right now. I wouldn't order from "hong kong phooey" or any other unknown dealer. Get the parts from a reputable parts dealer (Digi-Key, Mouser, Allied, Newark, etc) or you will find out the hard way about whats going on.

Read this:
Counterfeit Transistors

The ones I ordered seem to have some of the signs of fakes, some signs of genuine.
Fortunately they come in sets of two, so I can dissect one or more and if they check
out I can use the others.

I looked around and found that I can get them from authorized dealers for about $10 more. So these may not turn out to be much of a bargain.

Note to self, ask questions from experts before you order...

I will say this, the sellers are excellent Ebayer's so far. Good communication, nice emails
will shipped alert etc.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=260631231083

[Steve Conner]

Yeah, I'm fairly sure those are fakes. The print looks weird, and weren't Motorola already renamed to ON Semi in 1999? The seller seems like a nice guy, but maybe he doesn't know they're fakes.

The MJ15024/5 are overkill for the job, so maybe whatever is in those cans will be OK anyway. But it would be really interesting if you could spare one to cut open.

The real devices should cost about $5-7 each from a reputable US dealer.

[Enzo]

Mouser has both MJ15024/25 in stock at $4.56 each. Discounts start at 25 pieces.

[tube power]

Yeah, I'm fairly sure those are fakes. The print looks weird, and weren't Motorola already renamed to ON Semi in 1999? The seller seems like a nice guy, but maybe he doesn't know they're fakes.

The MJ15024/5 are overkill for the job, so maybe whatever is in those cans will be OK anyway. But it would be really interesting if you could spare one to cut open.

The real devices should cost about $5-7 each from a reputable US dealer.

Find out how nice he is if they are counterfeit and I demand a refund...
Anyway, Ebay might be interested in that if it happens, or not.
I'm definately going to wreck at least one out of curiosity since I doubt I'll use any of these.

Mouser it is, lesson learned, the hard way, again.

[Steve Conner]

I'm curious too. He ships worldwide for free, so I'm going to order a set and test them in our lab.

[J M Fahey]

the sellers are excellent Ebayer's so far. Good communication, nice emails
will shipped alert etc.

Ha ha, sure they are.
Besides, they inserted so many caveats and disclaimers in the ad, that very politely they can show anybody *you* are wrong.
Just a free sample:

working PERFECTLY for ANY RADIO SATELLITE PROJECT

Ahem !! cough cough !! You *aren't* repairing a Radio Satellite, are you?
Nobody challenges your technical level.
On the contrary, we want to help, but using bad parts definitely won't help you.
.
Hi steve:

The MJ15024/5 are overkill for the job, so maybe whatever is in those cans will be OK anyway.

*Maybe*, but I have already repaired amplifiers with fake MJ15003, and been offered fake 2N3773, with the following peculiarity:
The base material is 1/8" thick, against the usual 1mm or less.
They *look* incredibly rugged, that fact was pointed to me by the salesman.
I actually bough one, to be immediately subjected to brain surgery (literally, I opened its "skull" )
Fact is, the (iron) base is so thick, because they do not use the "heat spreader" copper "coin" that's soldered inside.
The chip itself is soldered directly to the iron base, which has 1/5 the heat transmission of copper.
The thick iron base does *not* compensate for the lower conductivity.
I have it somewhere, I'll post a picture.

[tube power]

Can I use this to check these "bad" ones even though I took them out?
It says "In Circuit Tester"
(Got it from grandfather)

I see pnp / npn setting, I get that.
Low/High?
Short/Leakage/Gain?
I get the idea it has to be in the unit to use this?

[tube power]

Ha ha, sure they are.
Besides, they inserted so many caveats and disclaimers in the ad, that very politely they can show anybody *you* are wrong.
Just a free sample:

Ahem !! cough cough !! You *aren't* repairing a Radio Satellite, are you?
Nobody challenges your technical level.
On the contrary, we want to help, but using bad parts definitely won't help you.
.
Hi steve:

*Maybe*, but I have already repaired amplifiers with fake MJ15003, and been offered fake 2N3773, with the following peculiarity:
The base material is 1/8" thick, against the usual 1mm or less.
They *look* incredibly rugged, that fact was pointed to me by the salesman.
I actually bough one, to be immediately subjected to brain surgery (literally, I opened its "skull" )
Fact is, the (iron) base is so thick, because they do not use the "heat spreader" copper "coin" that's soldered inside.
The chip itself is soldered directly to the iron base, which has 1/5 the heat transmission of copper.
The thick iron base does *not* compensate for the lower conductivity.
I have it somewhere, I'll post a picture.

Thanks, I'm with you, how do you argue counterfeit via email with seller and ebay, right?

I'm going to cut the oem open and see what's in there right now...

[Steve Conner]

I've ordered mine, we'll see.

If it were me, I'd not contact Ebay or the seller. I would go straight to my local On Semi sales office and send them pictures, test data etc. If I can convince them, their word would carry more weight with Ebay than mine.

If they don't care any more because the transistors have the old Motorola brand, then it would be time to take it up with Ebay. But I like to think they would care.

I wouldn't contact the seller, don't want to give him time to think up an escape plan. (Except if he's reading this and sends me real MJ15024s printed to look like his alleged fakes. )

I'd also send the pictures and test data to Rod Elliott for his counterfeit transistor site.

I've never seen one of those "in-circuit testers" before, not sure how it works or if it's suitable. I doubt it would do any harm to the transistors, and the front panel suggests that the "short", "leakage" and "gain" modes are for use with the transistor out of circuit.

[tube power]

I'm guessing I would clip black to the case and try the yellow and red on the legs?
I think I read in a description that these are bipolar, so either way?

[tube power]

Hmm...

This is the reading I got on both transistors pretty much exactly the same for each.
Reading stays around there for "short" "leakage" and "gain"

[52 Bill]

You have the leads hooked up wrong. The case is the Collector (red wire), the emitter and collector leads are reversed.

[tube power]

You have the leads hooked up wrong. The case is the Collector (red wire), the emitter and collector leads are reversed.

Thanks.
Do the black and yellow go to either leg?

Anyway it reads a little lower with red on case, 15 on that top scale.
If I switch legs with black and yellow it drops down to 5 just on Leakage and Gain.

[J M Fahey]

Do the black and yellow go to either leg?

Nope, they are clearly marked on the measuring instrument:
E(mitter) Black
B(ase) Yellow
C(ollector) Red.
To each pin/leg you attach the corresponding alligator.