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Last news I have restored this RTX with MRF477 instead of 2sc1945 (pin to pin similar)..just to try. The bias has been adjusted correctly..50ma on 2sc2166, 80ma on MRF477, Now the max power out is 3watt and there is no selfdistruction for Tr.driver and Tr.final, so i have changed the couple capacito...

During the bias current setting on 50w dummy load ..i've used USB with DEAD KEY. After that, i re-insert again the pcb, change to AM and push PTT without modulation.. ..And you know the rest of story. :cry: No one have some idea about this ?! :cry: What can i do !? :? AleX ps: Thanks again for your ...

It sounds like there is a short from the collector to the chassis of the 2166. Make sure there is no connection between the two, do a continuity test from the tab of the driver to the chassis just to eliminate that possibility. Already Checked ...it's isolated :cry: It sound strange...cause for the...

Driver...Dead again for the 2nd time.

Some Details:

After change driver 2sc2166 ..

driver bias 10ma 0.7volt Base/Emitter
final bias 35ma 0.7volt Base/Emitter

Next advice, please ?!

Regards
AleX

Before to start, just one consideration.. If a put a "Digital tester" to check Base and Emitter for 0.7 volts, i suppose that this measure will be alterd by the internal resistance of my D.T . :doh: May you give me, please, some good advice to read this "load" between Base and Em...

Ok..Thank you for your support.

I will let you know as soon as possible,
depend by my free time after work .

Tell me just one think:

It's correct to use bias 50ma (or less as 30ma) for the final transistor as 2sc1969,
and 15ma for the driver as 2sc2166 !?..what do you think.

Regards
AleX

Yes..My friend, i have already checked the pinout connection for the 2sc1969 and it's correct, also for the thermal diode seems ok. :? Today, in my mind is born a new question : Why have you don't checked the capacitors between driver and final stage !? :?: And, what about the bias current for the 2...

Hallooo.. I've a new problem... :mrgreen: A friend of mine have gave me a Pr.Jcks to fix (1st version 2sc2166 + mrf477 or 2sc1969). I have find the TR503 - 2sc2166- broken, so i have tried to replace this transistor: 0: disconnect PCB - 834 1: replace 2sc2166, check the 2sc1969 seems ok . 2: check t...

Please...describe your solution here to solve your problem.

Thanks
AleX

Hallo .. Is there a solution to replace the "thermal diode" as MV1Y, used in the majors RTX as Galaxy Saturn, Pr.Jackson (...and so on) !? Someone have told me to use 2 parallel 1n4148, but other says to me that Mv1y it's not a simple diode but something similar to zener diode . I'm waitin...

Ok...good.

What about the bias current change between MRF477 and 2sc1969 !?

Thanks again.

AleX

Hallo and goodevening from Italy... I have another President Jackson 1st version.. I have seen that this RTX are using the 2sc1969 instead of MRF477. Who knows the steps to go back at the original MRF477 !? I know that 2sc1969 has different pin respect to MRF477 .. I'm wating for your reply :wink: R...

Hallo at all.. I have a RTX president jackson 1st version.. someone can tell me the correct range value for the bias current on 2sc2166 and MRF477 ??? :? When i have change the curren on 2SC2166 from 12ma to 40ma, the transistor is dead. :doh: I have the service manual and it says : MRF477 trimmer V...

Radio Make and Model: intek497 (dragon ss-497) PCB Number: n.c PLL Number: n.c Symptoms: When the RTX is in RX state, i see the signal at +4db and more on s-meter only if i receive a strong signal. But for the less +4db signal, i see 0db on s-meter..leaving open clockwise RF-Gain . What is working: ...