My Transistors, original or copy?

[wg_ski]

Originally Posted by basreflex

fake MJ15023 and 22's are all over . I bought these from ondaradio.es , barcelona, stay away from them, it's all junk

That looks more like a "good copy" than an outright fake. The die looks very close (and it may be 15023 die or similar), they are using a heat spreader, and they have the two bond wires on the emitter (which the real PNPs do). Counterfieters usually don't go to that much trouble. I would label it "fake" if the can said "M" or "ON" on it, but there are third parties making MJ15023's. And some of them (Harris, RCA, etc) were good. The only way to know is to test one. The fakes I recieved had the white goo, no heat spreader, and a 2955-size die. And from the poor screen-printing job, quite obvious before popping the covers.

[unclejed613]

also if anybody is interested, Fairchild Semiconductor makes a licensed 2SA1943 and 2SC5200. those will have a fairchild logo on them and beta codes are O and R. so if you see these devices with a slanted F on them, they're not as likely to be fakes as the toshibas. if you want to be more positive, order them with the fairchild numbers FJL4215 (for the 2SA1943) and FJL4315 (for the 2SC5200)

[PB2]

Originally Posted by pdul

WOW!
Counterfeit american transistors, sold by an american retailer to an american
buyer
How the heck can the chinese counterfeiters break into that chain?

It is always good to check if a dealer is franchised for a particular product:
Power Management ICs, Power Semiconductors, Signal Path ICs, Lighting and Display, Logic, Optoelectronics, Fairchild Semiconductor - Global Leader in Power Optimization

Scroll to the bottom:
ON Semiconductor: Find Local Sales Support

[PB2]

I've got an old Soundcraftsman amp with a repaired channel that has Toshiba 2SD424 and 2SB554 outputs. The other channel has the remarked Toshiba transistors with Soundcraftsman markings. A Soundcraftsman #5 tested shorted and I cut it open to find what looks like white/clear silicone covering the die. It's been a long time since I last cut open some TO3's but I've never seen this type of coating. Is it normal or more common with fakes?

[unclejed613]

motorola used to use a very thin layer of clear silicone on their TO-3 dice to prevent oxidation of the surface layer and bond welds, but it was very thin less than 0.050" or so. i don't know if ON or other manufacturers use the same process or not.

[PB2]

This was so thick that I could not see the die through it. I peeled back the silicone and the die is large, estimating by eye, about 6mm square so I think it is real. I believe that these are early 1980s production.

[unclejed613]

different manufacturers have different processes. some transistors and flat packs have a silicone goop in them that never hardens, kind of like the weatherproofing goop in some types of harsh weather rated coax cable and telephone cable. it is also stable at high temperatures, so it stays in place, but touch it, and it's like a thick glue that never sets and sticks to everything. it's like Acme Wile E Coyote glue.

[anatech]

Hi Pete,
That transistor is probably real. These amps were built using the proper parts distribution channels way back then. Of course, it would be nice if the audio industry didn't deem it necessary to use "in-house numbers" on their parts.

I do recall seeing white silicone sealant inside a few TO-3 cans I opened now and again. There is no way I could remember what was found inside each types. TO-3 transistors are supposed to be hermetically sealed as I recall.

-Chris

[grappay]

Call you email the name of the shop where you purchased 2sc2500 in bangalore, since iam planning to start Symasym 5 project latest version
My mail id is : grapheal@gmail.com

[Praudio]

10, MOTOROLA PNP MJ15025 HI POWER AUDIO TRANSISTOR 250V - eBay (item 390226921008 end time Aug-22-10 21:14:58 PDT)

Get some 15024/25 made in mexico(from digi-key ,avnet and mouser,and nothing look like that.