Transmission1

rocketry23 wrote: ↑06 Jan 2020, 19:21 It is hard to find even a 2SC1969 in Hungary.... Maybe if you can link me a trusted seller on ebay?

2SC1969 here

https://www.ebay.co.uk/itm/272488057198

An MRF477 might be a bit harder . There's a couple of originals on Ebay , but they're £40+ , which is too expensive . If I were you I'd just repair the driver and final stage and stick in a Eleflow CB-20 .

Sammy

cb4ever104 wrote: ↑06 Jan 2020, 20:06
2SC1969 here

https://www.ebay.co.uk/itm/272488057198

An MRF477 might be a bit harder . There's a couple of originals on Ebay , but they're £40+ , which is too expensive . If I were you I'd just repair the driver and final stage and stick in a Eleflow CB-20 .

Sammy

Thanks for link but they do not ship to my country..

They ship to Europe, and Hungary is in Europe. Send them an email and ask them.

Sammy

I'll give it a try! Thanks!

Or

https://rover.ebay.com/rover/0/0/0?mpre ... 2804571096

in Hungary it is easier to find a Soviet transistor kt 920 V

please read the service manual for the device.... what transistors are in presidents ....2sc1969 or 2sc2166 ARE not SUITABLE !! by gain and mode....when installing KT920V mechanical alteration! when you install the other transistors...- designers put 2sc1969 (2sc2166) in parallel - not just like that

If you want use mrf455 or similar just mount transistor on back and connect it with wires. Put 1n4148 as bias diode.
Set bias with PR and job done.
Chris

ch25 wrote: ↑07 Jan 2020, 15:24 If you want use mrf455 or similar just mount transistor on back and connect it with wires. Put 1n4148 as bias diode.
Set bias with PR and job done.
Chris

Ok I wired in my SD1487. I had to replace VR9 because it was faulty.
It is interesting, there is 7mA bias current even the radio is switched off!
I set 150mA bias on TX.

There is 10W AM/FM output, but i cannot set SSB power above 20W. I even tried to adjust the related coils L43 42 41 33 30 as written in manual.


Thank you all for your help!

rocketry23 wrote: ↑13 Jan 2020, 21:00It is interesting, there is 7mA bias current even the radio is switched off!

So there is something really weird with your radio

ch25 wrote: ↑13 Jan 2020, 21:58 So there is something really weird with your radio

Haha, yeah its a weird radio
Or maybe I'm doing something wrong.

But at least I learnd lot of things thanks to you!

Is the base on your SD1487 connected to the chassis ?

cb4ever104 wrote: ↑14 Jan 2020, 15:12 Is the base on your SD1487 connected to the chassis ?

No it is not connected to chassis.

rocketry23 wrote: ↑15 Jan 2020, 07:38

cb4ever104 wrote: ↑14 Jan 2020, 15:12 Is the base on your SD1487 connected to the chassis ?

No it is not connected to chassis.

OK . It was difficult to see in the photo .

I did a Mosfet conversion at two President Jackson with very good results. Easyly 8-10 watts AM/FM and over 20w SSB PEP clean audio with two Fqp13n10 for driver and final. You will need to swap some more parts, but they are cheap. But it's not a job for starters.