On Sat, 2007-09-15 at 13:48 +0200, Vicens Llario wrote:
> Dear Gerald
>
> Many thanks for coming back to my message. The original bias
> transistor used in the transverter is a MPSW01 capable of 1W power
> dissipation at a high collector current of 1A. There is not too much
> room on the PCB to play with the legs and that is why I am looking for
> a pin to pin exact replacement. The original transistor has the EBC
> pins left to right as you mention. While looking at the TN2219 data
> sheet I thought that it was a possible candidate.
> I contacted Jameco and the price for 9 pieces is just around $1 but
> the USPS shipping they propose is $22. Paul Clinton of Ten Tec Service
> has come back with a fair proposal, $1 per transistor plus $6 shipping
> and handling. I will decide what to do during the weekend but have not
> too many options.
>
> Best 72
>
> VicenÃ, EA3ADV
>
Since there is little critical about the part, I'd think there would be
some Siemens parts to fit available locally or in the EC without having
to ship from the USA. I remain unconvinced the 1 amp rating or the 1
watt power dissipation is all that critical. I see my 1209 does have the
MPSW01. What I found with it was that the RF drive didn't saturate the
first few control stages with detected envelope and so didn't drive the
bias as far as it should have and when I hard keyed the output of that
first transistor after the detector, I had noticeably lower distortion
in the RF output. Enough lower that people at the other end could tell
the difference. But I came up with other ways to get a signal on 6 that
were more convenient and more effective and the 1209 is being ignored.
The FT-857 does far better and is convenient. I found the NF of th 1209
receiver side was far poorer than the active device should be, mostly
due to signal loss into the transmit side and the ordinary diodes on the
receive side. I started to rework it for an external antenna relay that
should have made it a much better receiver, but that project has fallen
aside too.
Scanning through my NTE cross index backwards I see BC485 and BC487
variations matching to the NTE128P. Specifically BC485L5(CBE), BC485L18
(CBE), BC485(CBE), BC485-5(CBE), BC485-18(CBE)... similar suffixes plus
A5, A18... for the BC487.
73, Jerry, K0CQ
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