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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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20th Nov 2018, 8:02 pm | #41 |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,657
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Re: Counterfeit transistors: a cautionary lesson
Yes, and since the likes of Onsemi, Multicomp and Newark are still advertising new 2N3055Hs - long after hometaxial version manufacturing ended, the H must mean something other than Hometaxial. They really should have used a new number or a suffix if they were suddenly upping ft by three times. It would also have made life a whole lot easier for Quad 303 rebuilders!
Mike |
21st Nov 2018, 10:06 am | #42 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Counterfeit transistors: a cautionary lesson
H is 60V Vce instead of 40V on standard 2N3055.
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21st Nov 2018, 11:21 am | #43 |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,657
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Re: Counterfeit transistors: a cautionary lesson
I think both 2N3055 and 2N3055H are 60V VCEO. There is apparently a 2N3055HV version that has 100V VCEO - though I've never come across one.
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21st Nov 2018, 1:42 pm | #44 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Counterfeit transistors: a cautionary lesson
Might be down to manufacturers' individual specifications. JEDEC numbering went to hell pretty quickly
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21st Nov 2018, 7:37 pm | #45 |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
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Re: Counterfeit transistors: a cautionary lesson
On the topic of the TO-3 case and TO-3 transistors, like the 2N3055, there is something wonderful about them that you cannot do as well with modern transistor packages. Like all good ideas, it starts in the imagination. This idea is not new, I picked it up mainly from studying automotive electronics of yesteryear:
If you have the requirement for a low to medium power transistor, which the design might dictate needs a transistor the physical size of a TO-5 or a TO-220 with a heatsink...you have two parts, the heatsink and the transistor. But instead if you imagine that the TO-3 device is a lower power rated transistor die, attached to a larger metal heatsink, when you simply use the TO-3 with no additional heatsink as the TO-3 body is big enough on its own. I have attached a couple of photos where I did this in the past, it is much more elegant than a smaller transistor with a heatsink and more physically robust. |
11th Dec 2018, 4:58 am | #46 |
Banned
Join Date: Feb 2018
Location: Horncastle, Lincolnshire, UK.
Posts: 203
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Re: Counterfeit transistors: a cautionary lesson
I had the same issue with some 3055's I bought to rebuild a PSU,as soon as I drew over 150 mA from then them 5 out of 10 went short C to E. At 3 quid for 10 it's the old tale of you get what you pay for!
M3VUV. |
11th Dec 2018, 10:03 am | #47 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,273
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Re: Counterfeit transistors: a cautionary lesson
At around the turn of the century I took in a philips matchline TV for repair, one of the last 4:3 jobbies with luxurious mahogany cladding and matching VCR cabinet with black glass doors, can't remember the chassis but maybe FL2..something? 28in FST. Anyway, the LOP transistor was gone along with about 20 SMT components. I ordered a pack of 5 transistors and replaced the blown fleas according to the service manual procedure, and it worked. Left it on soak then sent it back. It came back a few days later, the same fault. Replaced the transistor and fleas, sent it back, heard nothing more.
Months later I saw the guy and asked him about the tv. 'oh it failed again, I took it to the tv shop down the road and it's been fine ever since'. Awkward pause, then I asked, 'Did they say what they found?'. 'Yes,' he said, 'just a transistor or something, cost me a tenner'. I do wonder if my packet of transistors were fakes, as I'd subsequently had definite fakes off the same supplier a time afterwards (supplier was well known but no longer trading AFAIK). Like others have said, if a part is obsolete but miraculously offered by a chinese company for peanuts, I opt for fitting a current equivalent from a reputable trade supplier instead which I know at least will meet its specs.
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Kevin |
11th Dec 2018, 11:46 am | #48 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,087
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Re: Counterfeit transistors: a cautionary lesson
Unfortunately even authorised, bona-fide suppliers do occasionally supply fakes!
The situation goes like this. A customer establishes an account with them, trades for a while, then places a large order. Sometime later, they contact the distributor to say that the parts they bought onder Purchase Order XYZ123 and supplied with Certificate of Conformance ABC456 are no longer needed, would they accept them back for credit (maybe with restocking fee etc). But what they actually do is sell back a load of fakes. So the poor distributor ends up with counterfeit parts, which in good faith they supply to someone else. Meanwhile, the dodgy customer still has his good devices, which he sells at market value on eBay or wherever - to delighted customers who are completely satisfied! |