ВЭФ 12 (Astrad VEF 12 Project) - including a transistor tutorial

[Refugee]

You are almost there.
4.7 is the voltage across the resistor. That gets you very close to the answer.
Well done.

[Mark Hennessy]

What's the collector voltage? I am going on 4K7 as 4700. As it's the load resistor for the collector I'd say multiply 4700 by 0.001 to give 4.7. However, with a valve anode you would just use the current tables to drop whatever voltage difference exists between HT and listed anode voltage.

With time, you'll see that it's so much easier to use milliamps and k-ohms with transistor circuits. I'd much rather say "1 times 4.7" than "0.001 times 4,700". You might not believe me now, but try to keep an open mind there...

Anyway, as Ref says, 4.7V across the 4k7 resistor. Good...

So is that the final answer?

[ppppenguin]

Hint: The calculation here is done exactly the same way as for a valve. If a valve was passing 1mA anode current and had a anode load resistor of 4k7 you would have 4.7V across that resistor.

[pwdrive]

However, with a valve anode you would just use the current tables to drop whatever voltage difference exists between HT and listed anode voltage.

What are current tables?

Lawrence.

[Nowhere-Man]

In order to see if maybe I can source these old Soviet PNP transistors, I attempted to join the Russian Radio Cat today. It's a Russian forum of radio engineers and hobbyists. I have no idea if I'll be accepted because I'm not sure if many foreigners join. Plus, sadly the political climate has never been worse but we won't get into that. It may be some of the members can help me locate sources for the Soviet P and MP transistors, although it's not likely. Already from what I gather, germanium transistors aren't in large supply normally in Russia. My impression is they do still make decent valves but silicon has long since taken over the engineering field.
The funny thing about the Russian radio sites is you get a fair few female engineers. I mean, years ago my girlfriend over there was a leading inventor and another friend was a satellite engineer.

[Nowhere-Man]

I was asked about HT and anode voltage. If HT supply is 200 volts and a valve anode must be 120 volts you need to drop 80 volts (if the original resistor has no marking). If you know the HT current of the valve from the schematic tables, divide this current into the 80 volts you need to drop. This will give you the resistance. So a valve with 5 milliamps 16000 R. I often forget these sums as rarely would I find a missing resistor.

[Mark Hennessy]

OK - this all sounds very encouraging. It sounds like you're not going to fall into the usual trap that I see

So, what's the collector voltage?

[Murphyv310]

Ah Ha. So NWM ve have found you out............... A Russian spy in our midst. So Comrade you vill know that there are many Soviet Germanium transistors on E-bay from the Russia and the Ukraine.
This trader will source what you want even if he has no stock. http://www.ebay.co.uk/usr/uralspirit?_tr...2749.l2754

[Refugee]

Oh the voltage.
We have now got a worked out example of how to work out the voltage.
The valve circuit had the anode voltage and the HT voltage and the voltage across the resistor was quickly worked out and the resistor value calculated with little if any bother.
With the transistor we have got 9V as HT and the voltage across the resistor and its value. With those figures it should be easy to work out the voltage between the collector and ground.

[Miguel Lopez]

It may be some of the members can help me locate sources for the Soviet P and MP transistors, although it's not likely.

There are plenty of those transistors still in existence. A friend of mine sent some of them from Spain. He bought them in Bulgaria, via ebay. Anyway, they are not estrictly needed as they can be replaced by other types. The P type (RF) can be replaced by 1T308, and the MP type (audio) can be replaced by any silicon one. Currently one of my VEF-206 is fitted with 1T308 in all RF positions and any other MP (MP15, MP16, MP25, MP26) on the audio section.