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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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4th Oct 2011, 1:24 pm | #1 |
Dekatron
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Characteristics of this transistor, please?
I have a handful of bipolar transistors in a T0-3 package, marked 1693. That's all I have on them.
Can anyone provide characteristics, please? I have a feeling they're old LOP transistors, but that could be a red herring. Any info much appreciated, Cheers,
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4th Oct 2011, 1:43 pm | #2 |
Octode
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Re: Characteristics of this transistor, please?
My instinct is telling me (for some reason!) suspect that they should have a 2s prefix, maybe 2sa or 2sd.... Try a google search for 2sa1693 ?
Cheers, Steve.
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4th Oct 2011, 2:14 pm | #3 |
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Re: Characteristics of this transistor, please?
Or try 2N1693, though my Towers says this is a PNP TO102 medium power transistor. It doesn't list a 2SA, 2SB or 2SC1693.
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4th Oct 2011, 2:42 pm | #4 |
Dekatron
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Re: Characteristics of this transistor, please?
Thanks, gents. The other markings it has are 'BRC' stamped bang in the centre, 'EV' bottom left and 'ID' bottom right.
Paul, I will try your 2N.... theory. That's a high current, medium voltage VHF, PNP transistor. If I test it and it behaves like one, that'll do me.
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4th Oct 2011, 3:13 pm | #5 |
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Re: Characteristics of this transistor, please?
Sounds like a Thorn (BRC) special line output transistor. The 2000 chassis uses a D1693 in the EHT generator. Probably made by Texas Instruments. I think the earliest 2000 chassis used a very odd looking TI transistor for line scan and EHT in a square package.
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4th Oct 2011, 3:35 pm | #6 |
Nonode
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Re: Characteristics of this transistor, please?
Hi,
As Jeffrey said, these will be Thorn re-numbered devices, Thorn used their own 'house codes'
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4th Oct 2011, 3:45 pm | #7 | |
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Re: Characteristics of this transistor, please?
Quote:
Do you know what voltage it can stand-off, Jeffrey?
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4th Oct 2011, 4:41 pm | #8 |
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Re: Characteristics of this transistor, please?
Several hundred volts for certain. Maybe over 1000V, possibly something like a BU105. Because of the charge storage mechanisms in these early high voltage transistors switching them off is critical in their intended application. Too slow and you overdisspate them, this is normal. Too fast and there is another overdisspation mechanism that will cause them to fail. From memory this is caused by charge storage in the collector. Said charge has to be removed at the right speed to make it reliable. Usually achieved by a small inductor in the base lead.
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4th Oct 2011, 5:39 pm | #9 |
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Re: Characteristics of this transistor, please?
Yes - switching off high-voltage bipolar transistors is quite an art. Rather than suddenly stopping and slamming base current into reverse, to suck out stored charge until all junctions start blocking, you have to reduce base current at a quick but controlled rate. A suitable inductor does just this. And a suitable snubber or resonant capacitor collector-emitter is necessary to stop the collector voltage from rising massively until the turn-off has been accomplished.
So if your transistors are indeed as ppppenguin suggests, read up about it before trying to use them as high-voltage fast switches! |
4th Oct 2011, 5:51 pm | #10 |
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Re: Characteristics of this transistor, please?
TI did an article on the subject back in 1975 which I think has been posted somewhere on UKVRR. I know I have mentioned the subject before in UKVRR as I encountered the problem in my final year university project in 1978. The TI reference is:
Norris B (ed) Semiconductor Circuit Design Vol IV Texas Instruments Ltd 1975 |
4th Oct 2011, 5:55 pm | #11 | |
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Re: Characteristics of this transistor, please?
Quote:
Otherwise... I could always turn the poor things into humble HV diodes. No... no, that doesn't seem quite right.
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4th Oct 2011, 5:57 pm | #12 |
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Re: Characteristics of this transistor, please?
Jeffrey, v. helpful reference there. Thanks, I'll look into that.
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Al |
4th Oct 2011, 6:42 pm | #13 |
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Re: Characteristics of this transistor, please?
Expect a few casualties during development
If you are lucky enough to have access to a current probe and a scope that can multiply 2 inputs together (some DSOs can do this) then you can directly monitor the dissipation in the transistor. I had a current probe available back in 1978 but not the multiply function unless I plotted and mutliplied the traces by hand. |
4th Oct 2011, 7:13 pm | #14 |
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Re: Characteristics of this transistor, please?
Perhaps if you have genuine BRC2000 line outputs your best bet would be to trade them with people who have these sets who might be in need of them, and get more modern transistors for experimental purposes? The widespread use of SMPSUs has led to the availability of bomb-proof HV transistors at keen prices.
Lucien |
4th Oct 2011, 7:21 pm | #15 |
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Re: Characteristics of this transistor, please?
AFAIK, any ordinary LOP transsistor such as BU105 or BU208 will work in the BRC2000 LOP and EHT boards.
The LOP transistors in the BRC2000 were marked R2008. Possibly a higher rated part than the D1693 used on the EHT generator. |
4th Oct 2011, 8:00 pm | #16 | |
Dekatron
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Re: Characteristics of this transistor, please?
Quote:
But yes, if anyone is short of a bipolar LOP transistor, please give me a shout and I'll happily supply one.
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