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Old 19th Nov 2018, 5:15 am   #21
Argus25
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Default Re: Counterfeit transistors: a cautionary lesson

The issue of HOT's failing makes a very important point about the whole industry that has cropped around semiconductor fakes and relabeled parts. Probably more than 90% of the time, the people selling fakes get away with it, because the part is placed in a low stress circuit. Nobody knows it is an inferior part, probably with a shortened life, because most of the time everything seems ok. But put an inferior part in a television's line output stage (especially a large screen type) where the peak collector voltages are only just inside a genuine transistor's rating, and it will fail in milliseconds to hours. The counterfeiters should stay away from HOT's, and they would get away with it a lot more.
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Old 19th Nov 2018, 6:53 am   #22
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Default Re: Counterfeit transistors: a cautionary lesson

I must have 2 or 3 thousand total of IC diodes and transistors owned 30+ years that should be genuine. All unused. I probably only used half a dozen transistors, and a few diodes in the last 5 years.
If I tried selling, they wouldn't make a lot I imagine. I even used to have 2 or 3 RCA 2N3055 from 1968! I can't imagine they would go the way of ECC83 though.
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Old 19th Nov 2018, 12:02 pm   #23
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Default Re: Counterfeit transistors: a cautionary lesson

You’d be surprised. The early 2n3055’s work better than the new ones in some power supply arrangements. Tek 7000 linear supply comes to mind. You have to stick a capacitor across base-collector to slow the new ones down.
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Old 19th Nov 2018, 12:45 pm   #24
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Default Re: Counterfeit transistors: a cautionary lesson

Old 2N3055 are needed for fixing Quad 303 power amplifiers, so there's an audio connection ready to push the prices up.

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Old 19th Nov 2018, 2:10 pm   #25
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Default Re: Counterfeit transistors: a cautionary lesson

I have been a 2N3055 enthusiast from the early 1960's when I first saw one as an awestruck boy. Then I used them many times with a happy outcome in each case. They definitely are the "me love you long time transistor".

A while back I picked up 10 of the type shown in the attached photo, RCA and the 2N3055H variant made for an early 1980's mil contract I would think. Super quality. Pic attached.

Yet I saw on another forum the 2N3055 being rubbished and it was said that many superior modern transistors had out spec'd them and that the TO-3 case was obsolete too.

However, the TO-3 case is thermally superior to any epoxy cased modern power transistor. I would think that the person criticizing them didn't have the emotional attachments or the familiarity I have with them and forgot that they are outstanding transistors and "revolutionary" compared to the germanium types they replaced. If if you select the right application for them that is.

They shouldn't even be compared with a modern device with a higher transition frequency. But it was the fact that it is on the lower side that makes the 2N3055 dead easy to work with and easy to tame in power supply and audio applications.

But if you attempt to use them in a Royer oscillator, to replace a germanium type, they do require the C-B 0.1uF to tame them or HF instability results, proving that they do have quite a bit of high frequency pep in their step, compared to their germanium predecessors.
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Old 19th Nov 2018, 2:51 pm   #26
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Default Re: Counterfeit transistors: a cautionary lesson

Completely agree on all points. They feel good to hold as well. Now I sound like a weirdo
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Old 19th Nov 2018, 3:32 pm   #27
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Default Re: Counterfeit transistors: a cautionary lesson

@ Argus 25
"They shouldn't even be compared with a modern device with a higher transition frequency. But it was the fact that it is on the lower side that makes the 2N3055 dead easy to work with and easy to tame in power supply and audio applications."

But sellers' specs are muddled for the 2N3055. Here's an example where Solid State give the ft as 800kc/s. However, the tagged date sheet gives 2.5Mc/s. I've noticed this variation (error?) with other manufacturers/reputable sources -

https://www.newark.com/solid-state/2...-me-pd-mi-alte

Any thoughts on this? Are they just citing opposite ends of a range?

Mike

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Old 19th Nov 2018, 3:50 pm   #28
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Default Re: Counterfeit transistors: a cautionary lesson

It is probably the minimum ft, specmanship rears its head and so 2.5MHz, still within spec..
 
Old 19th Nov 2018, 5:03 pm   #29
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Default Re: Counterfeit transistors: a cautionary lesson

Quote:
Originally Posted by Argus25 View Post
I have been a 2N3055 enthusiast from the early 1960's when I first saw one as an awestruck boy. Then I used them many times with a happy outcome in each case. They definitely are the "me love you long time transistor".
Here's just a few thousand (7,200 of them driven by 360 more!) 2N3055's in a 13kA pulsed power supply at CERN in 1970 https://cds.cern.ch/record/274991?ln=en

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Old 19th Nov 2018, 5:20 pm   #30
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Default Re: Counterfeit transistors: a cautionary lesson

"It is probably the minimum ft, specmanship rears its head and so 2.5MHz, still within spec.."

Still massively weird not to give the 2.5MHz figure in the official datasheet though - which surely should be the minimum ft ...

Here's another one the same from Farnell -
https://uk.farnell.com/multicomp/2n3...o-3/dp/1165889

Last edited by Boulevardier; 19th Nov 2018 at 5:32 pm.
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Old 19th Nov 2018, 8:14 pm   #31
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Default Re: Counterfeit transistors: a cautionary lesson

Are you talking about the 2N3055E or 2N3055H?
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Old 19th Nov 2018, 8:19 pm   #32
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Default Re: Counterfeit transistors: a cautionary lesson

I've never encountered 2N3055E. No, I'm just talking about plain old 2N3055, though I don't think any of the variants differ in ft. I think 2N3055H only differs in SOA.

Mike
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Old 19th Nov 2018, 8:45 pm   #33
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Default Re: Counterfeit transistors: a cautionary lesson

Quote:
Originally Posted by Argus25 View Post
Yet I saw on another forum the 2N3055 being rubbished and it was said that many superior modern transistors had out spec'd them and that the TO-3 case was obsolete too.
This is the trouble with many aspects of life, not just electronics- folk get mesmerised by sales BS and specmanship, rather than saying to themselves, "OK, let's see, just what do I really need in the real world, what is bang-for-buck in the particular situation?" The sort of playground "Top Trumps" analysis that says, "Well the Lockheed SR-71 beats the Cessna 172 in every parameter- why did they even bother building the latter?"

T0-3 is only obsolete in the sense that it costs more per device than modern plastic packages- not obsolete in the sense of ruggedness, environmental sealing or heat transfer. There's a degree of "doing the job properly" about marking out and drilling a thick chunk of aluminium in that 4-diamond (yeah, need to get out more...) I don't suppose that NOS vintage RCA 2N3055s will attain the mystique and value of M-O V U52s anytime soon, but I reckon they're at least worth not chucking out too glibly.
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Old 19th Nov 2018, 11:06 pm   #34
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Default Re: Counterfeit transistors: a cautionary lesson

Quote:
Originally Posted by Boulevardier View Post
I've never encountered 2N3055E. No, I'm just talking about plain old 2N3055, though I don't think any of the variants differ in ft. I think 2N3055H only differs in SOA.

Mike
Isn't 2N3055E just a "slang" term for the livelier epitaxial versions vs the "dormant doorstop" that was the original (latterly called 2N3055H to identify it as hometaxial) type?
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Old 19th Nov 2018, 11:36 pm   #35
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Default Re: Counterfeit transistors: a cautionary lesson

Don't know what "E" could stand for - I've never even seen it. If you look at some 2N3055H data sheets it says that the "H" signifies extended SOA, so I'm pretty sure it doesn't stand for Hometaxial. Similarly, in 2N3055G, "G" stands for lead-free construction.

If only the "H" did separate out the old lower ft hometaxials! Life would be a lot simpler. As things are (afaik) the only way to tell them from epitaxials is to actually measure the ft on a test jig! I don't think they should ever have been given the same type number - the differences are too important to leave them with the same number.

Mike

Last edited by Boulevardier; 19th Nov 2018 at 11:50 pm.
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Old 19th Nov 2018, 11:48 pm   #36
Argus25
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Default Re: Counterfeit transistors: a cautionary lesson

Quote:
Originally Posted by Craig Sawyers View Post
Here's just a few thousand (7,200 of them driven by 360 more!) 2N3055's in a 13kA pulsed power supply at CERN in 1970 https://cds.cern.ch/record/274991?ln=en
Wow, they look fantastic assembled in those numbers !

Quote:
Originally Posted by Boulevardier View Post
But sellers' specs are muddled for the 2N3055. Here's an example where Solid State give the ft as 800kc/s. However, the tagged date sheet gives 2.5Mc/s. I've noticed this variation (error?) with other manufacturers/reputable sources
The only data sheet I would trust is RCA's original one from the early 1960's, applied to a genuine vintage (probably pre 1970 or 1980) 2N2055.Most likely after that the data sheets got altered to match the faster parts.
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Old 20th Nov 2018, 1:18 am   #37
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Default Re: Counterfeit transistors: a cautionary lesson

Quote:
Originally Posted by Boulevardier View Post
Don't know what "E" could stand for - I've never even seen it. If you look at some 2N3055H data sheets it says that the "H" signifies extended SOA, so I'm pretty sure it doesn't stand for Hometaxial. Similarly, in 2N3055G, "G" stands for lead-free construction.

If only the "H" did separate out the old lower ft hometaxials! Life would be a lot simpler. As things are (afaik) the only way to tell them from epitaxials is to actually measure the ft on a test jig! I don't think they should ever have been given the same type number - the differences are too important to leave them with the same number.

Mike
AFAIK the extended SOA was down to the original hometaxial construction, hence the -H suffix with the -E as a (possibly unofficial) suffix for epitaxial. As to whether later epitaxial variants were made with the extended SOA of the original type and thus got the H suffix, I've no idea.
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Old 20th Nov 2018, 2:40 am   #38
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Default Re: Counterfeit transistors: a cautionary lesson

Interesting thoughts - that could explain the "H". But I have never seen an "E", and a google search on 2N3055E comes back with zero matches.
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Old 20th Nov 2018, 5:49 pm   #39
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Default Re: Counterfeit transistors: a cautionary lesson

I used '2N3055E' as shorthand for the epitaxial version which has been mentioned in previous threads.

I don't want anyone to waste their time looking for one. I'm sorry for the confusion.
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Old 20th Nov 2018, 6:18 pm   #40
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Default Re: Counterfeit transistors: a cautionary lesson

I was told the 'H' simply signified heavy duty - it makes no sense for it to be for Hometaxial, e.g., the RCA 2N3055H in Argus25's photo above, are date stamped '8218', so wk. 18 of 1982 - which I believe (?) was several years after RCA stopped using the Hometaxial process.
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