Replacing Germaniums with Silicons on my old Soviet radios

[Miguel Lopez]

Hi all

I've been experimenting with replacing the Germanium trasistors of some of my old Soviet radios with Silicon transistors. Reason: Germaniums are scarse and I have a lot of Silicons which I can use if they would be suitable. I have succeeded on replacing the Germaniums in the audio section, and the last IF amplifier, but when I move to the RF section, that's another baseball game. Althought they work when I adjust the biasing by changing resistors, the audio signal deteriorates.

Would be that the tuning circuit moves outside the tuning peak?

Any idea on how to improve this?

Thanks in advance.

[Murphyv310]

Hi Miguel.
Hope you are well and the recent terrible storms have not caused any great problems for you.

I have found that using Silicon transistors in a set designed for Germanium doesn't always works successfully. IF stages can work but as you have found biassing needs to be altered, also you will need to re-align the cores and trimmers as different construction of the transistors alter the internal capacitance.
This is one reason that the mixer or RF stage can be out. Best idea is to try a full re-alignment after fitting the Silicon replacements and see if it improves matters.
I tend to stick with germanium types if at all possible, often using the Russian GT332 transistors.

[boater sam]

Replacing Mixer/Oscillators is the tricky one I find. Its very hard to get the operating point of the oscillator correct.
As an idea, can you copy a known working silicon front end layout and component values onto a germanium set using the same coils?

[Miguel Lopez]

Well, hurricanes didn't much damage where I live, some tree branches fell down and nothing else. Other parts of the country were devastated by those beasts. Anyway, we were without electricity and water supply for three days.

I will try soon with one of my VEF radios to see if I can improve the audio signal by moving the IF cores. Then I will move to the RF section. Today I can say that I understand much more about radios than what I knew a couple of years ago, so this is an opportunity to improve my knowledge about this so, I will keep putting my fingers on the little animal.

What can go wrong? The radio will stop working.....well that would be a challenging situation to go ahead. This is a hobby after all.

One of my dreams it's to re-bias a VEF-206 to NPN polarity. Maybe I will do it some day.....

[Murphyv310]

Great attitude Miguel. Yes its a hobby, enjoyable and fun but should never take over your life.
Good luck with your modifications.

[bigtom]

HI
    Just to say that I have one of  V F 206  Russian radios . I came into my possession in bits although there were no missing parts. It works really well. I use  six rechargable batteries to work it.I could never find  a proper  replacement  for the Dial lamps.They  only draw  60ma  current at 2.5 volts.Is there anybody out there  who might know  a source   for them  or something similar.
    
Thanks
        Bigtom

[bigtom]

HI
    Just to say that I have one of  V F 206  Russian radios . I came into my possession in bits although there were no missing parts. It works really well. I use  six rechargable batteries to work it.I could never find  a proper  replacement  for the Dial lamps.They  only draw  60ma  current at 2.5 volts.Is there anybody out there  who might know  a source   for them  or something similar.
    
Thanks
        Bigtom

[Ed_Dinning]

Hi Big Tom, try using LEDs, they should work nicely at that voltage and be a good bit brighter.


Ed