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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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7th Aug 2022, 10:03 pm | #1 |
Tetrode
Join Date: Feb 2020
Location: Exeter, Devon, UK.
Posts: 86
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2SD1976 transistor replacement ?
Hi All
Whats a modern replacement for this 2SD1976.....I've been looking at all sorts for hours and my head now hurts as all I can find is just as old no longer made transistors Its in a old computer unit and I need a swap. Thank you Last edited by river9999uk; 7th Aug 2022 at 10:09 pm. |
7th Aug 2022, 10:56 pm | #2 |
Hexode
Join Date: Feb 2007
Location: Chesterfield, Derbyshire, UK.
Posts: 483
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Re: 2SD1976 transistor replacement ?
The device is described as having an inbuilt zener diode and resistors so trying to find a modern drop in replacement is not looking straightforward.
https://datasheetspdf.com/pdf/240506...ctor/2SD1976/1 |
7th Aug 2022, 11:07 pm | #3 |
Tetrode
Join Date: Feb 2020
Location: Exeter, Devon, UK.
Posts: 86
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Re: 2SD1976 transistor replacement ?
Yeah I was looking at a 2SD1071 but I am not sure I am right......
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7th Aug 2022, 11:09 pm | #4 |
Octode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 1,003
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Re: 2SD1976 transistor replacement ?
I looked in all my books and nothing, sorry!
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8th Aug 2022, 10:42 am | #5 |
Tetrode
Join Date: Feb 2020
Location: Exeter, Devon, UK.
Posts: 86
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Re: 2SD1976 transistor replacement ?
Thanks for looking...its a tough one. Think I might get a couple of old stock 1071's and gamble as they look almost the same spec wise.
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8th Aug 2022, 2:21 pm | #6 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,725
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Re: 2SD1976 transistor replacement ?
Search on ebay.COM $9.48 inc shipping from China
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8th Aug 2022, 2:25 pm | #7 |
Tetrode
Join Date: Feb 2020
Location: Exeter, Devon, UK.
Posts: 86
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Re: 2SD1976 transistor replacement ?
OK thanks for that link. Do these transistors with Zenners test out different to a normal transistor ? Can you tell if its correct or fake?
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8th Aug 2022, 2:40 pm | #8 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
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Re: 2SD1976 transistor replacement ?
Different, but you have to work at it to see the difference. A little battery powered hand-held tester won't show it.
The zener looks like a normal diode when biased the opposite way, but then so do most MOSFETs across d-s. So nothing unusual. To find the difference you have to take d-s voltage high enough in the normal direction for the zener clamp to act. A normal MOSFET would just let Vds gohigher until damage happened. MOSFETs made the usual way have an unavoidable diode across drain-source which will turn on if the drain-source pair get reverse biased. In things like SMPS and class D transmitters, great care has to be taken to make sure this diode never gets turned on, because it's rather slow and won't turn off at the speed of the transistor itself... this leads to pops, bangs and smoke. In the case of these transistors, the implicit diode is made to have avalanche characteristics. (Zener is a misnomer, real zener effect diodes are all low voltage) David
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8th Aug 2022, 3:03 pm | #9 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,670
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Re: 2SD1976 transistor replacement ?
What voltage are they working at? I have some 2SD1276's, but they're a lower voltage, 60v as opposed to 300v
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8th Aug 2022, 3:14 pm | #10 |
Tetrode
Join Date: Feb 2020
Location: Exeter, Devon, UK.
Posts: 86
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Re: 2SD1976 transistor replacement ?
Think its quite high so might break those. Can anyone tell me if a 2SD1071 would be a good swap as to my eyes they look almost identical in the spec sheets and seem to be a few around still.
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8th Aug 2022, 7:14 pm | #11 |
Octode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 1,003
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Re: 2SD1976 transistor replacement ?
I guess if it comes to it, you will have to fit a 300v device and fit an external 300v zener.
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9th Aug 2022, 7:37 am | #12 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,670
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Re: 2SD1976 transistor replacement ?
Look the same to me, suck it and see as they say.
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9th Aug 2022, 8:36 am | #13 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,422
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Re: 2SD1976 transistor replacement ?
Hi.
Why not fit a BU2508 line transistor or similar and an external 300v avalanche diode? Mind you the original transistor has a pretty amazing spec and of course is very fast.
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9th Aug 2022, 8:57 am | #14 |
Pentode
Join Date: Jul 2007
Location: Salisbury, Wiltshire, UK.
Posts: 174
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Re: 2SD1976 transistor replacement ?
Found this on the internet, maybe an equivalent using two transistors could be used to make a darlington replacement
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9th Aug 2022, 11:27 am | #15 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
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Re: 2SD1976 transistor replacement ?
The protection diode, if you used an external one could be a suitably rated TVS type. A unidirectional one would be fine, you wouldn't need a bi-directional one.
David
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