BATC Forum

Having torn my hair (sorry, fur) out, replaced the TX RF Preamp 3 times and finally having to conclude that the ones for sale on Ebay must be El Cheapo Chinese rubbish... they won't even withstand 7V Collector-Emitter (should be 35V max).

Does anyone have or know where to buy proper Mitsubishi 2SC1971 Transistors please?

Or maybe even the ASI 2SC1971 equivalents..

Many thanks, Gra.

Or maybe just ANY equivalent transistor which would replace it?

Can't you just use an RD06HVF1 and modify the circuit accordingly?

Thanks for the reply.

I'd rather replace like for like, but if it comes to that then I'll need some pointers what needs modifying where, it's a device I never heard of..

I've been made to feel like I'm already going beyond the call of (Ham) duty by replacing this. When I first asked around, the first reply I received was why not just buy an xxx? And I also received links to said rigs on Ebay..

Hi Wolfie,

See your inbox (PM) for a link to a genuine one.

Steve

I think mostly you just need to change the bias arrangements for a MOSFET rather than Bipolar. Output matching should be the same or close enough. Input matching may need some damping to allow for the higher gain so include a 100 ohm with a DC blocking capacitor. It will need about 2-3V bias, e.g from 5V adjusted with a POT.

Mike

Hi Graham

Have a look here: https://www.littlediode.com/components/2SC1971.html

They're bl**dy expensive but the guy does not sell fakes.

BTW, EY is off as it is very close to going full repeat mode.

73

Clive G3GJA

Thanks Clive.. I though EY must be off air. I went out of the house last weekend to get away from the atmosphere and just chucked the Ae on the car but.. no EY found. Hope it's not too serious.

I'll have a new QTH shortly but guess what? More Trees to the East and a close brush with a cooling tower.. I'll have to see how it pans out. I stand a better chance with the Barnsley gang though.


Meantime, I've paid for some more Transistors... but while I am waiting I put in any old NPN power transistor and wound the Input voltage up with no detrimental effects.. I could read 16mV on the base.

When I had put the last chinese one in, I linked the base and emitter and it still died when the Collector reached around 6V. Just about confirming my suspicion that they are made of rarified earth or something.

Not sure about rarefied earth though Graham; I think 'Guano' would be more appropriate!

There's a full report on EY issues here: viewtopic.php?t=6870&p=24281#p24281

Sorry to hear about the move to a less helpful location. You might find the cooling tower helpful though; I know Bob G7AVU makes use of some reflections of industrial buildings to good effect.

Cheers

Clive