Soviet East German Radio

[Murphyv310]

You holding the book Mike?

[pwdrive]

Here is a discovery I made tonight I decided to share. It came from something in ARRL where reactance in resonant circuits compared to loads on the circuit is discussed. It states if power dissipated across the load on the resonant circuit (such as a transmitter) is about 10 times as great as the power lost in the inductor and capacitor, then power lost in reactance will be greater overall. So I did the following:
VAC in = 230
XL and XC at resonance = 250 R
Load on circuit (transmitter) = 3000 R
So, 230/250 reactance = current 0.92 amp. To get voltamps I get 211 dissipated power.
Then the load of 3000 watts (real power) I get current = 0.07 amp and watts = 17.6
So the power in the resonant circuit is now BIG.
Here is what gave me a kick: Divide the load wattage into the Voltamp power which is 211/17 and lo and behold 12. And ARRL in their sums gives 12 as the circuit Q.
I think my maths here is correct but, if not, apologies in advance.
Although pointless I admit, I like doing this kind of numbers game.

Don't forget that reactance doesn't dissipate power.

Also don't forget that in a parallel resonant circuit connected to an AC voltage source the voltage across the inductor and the capacitor will be the same as the source voltage, however that's not the case with a series resonant circuit, in that situation it's sometimes easy to forget that although the reactance's cancel out the individual reactance's are real and the voltages developed across them are only limited by the current flowing through R, in some situations those voltages can be very nasty.

Lawrence.

[Terry]

As a starting point I assume any primary and secondary should normally be opposite in phase. 

Why on earth should you assume that?

You can connect the windings whichever way round you want - there is no rule that says otherwise.

[Nowhere-Man]

Bets on if NM is ever going to get his radio repaired.

Mike

I think I will. I mean already I could maybe cut out the FM and put the HT to R12. Overall, though, I just figured it's wise to get the schematic under control. It's a design that's just about doable (unlike transistorised circuits at this time). Also I did finally find a supplier for my germanium transistors outside of Ebay. I wanted some spares just in case any broke when pulled from sockets. Now spring is here I have my GRP boat to finish too. Pity solar panels still seem to be costly.

[Nowhere-Man]

Just been contacted by the tech company in Russia. I can get my components from there including germanium transistors. Also the odd valve. I joined a Russian site too that specialises in USSR TV and radio. A guy there told me the Astrad is pretty rare over there and differs in range from the VEF.

[Murphyv310]

Bets on if NM is ever going to get his radio repaired.  

Mike

I think I will. I mean already I could maybe cut out the FM and put the HT to R12. Overall, though, I just figured it's wise to get the schematic under control. It's a design that's just about doable (unlike transistorised circuits at this time). Also I did finally find a supplier for my germanium transistors outside of Ebay. I wanted some spares just in case any broke when pulled from sockets. Now spring is here I have my GRP boat to finish too. Pity solar panels still seem to be costly.

Hi.
No bodges NM so no cutting out bits, think of every set you have as a customers so removing bits to make one bit work and the other not is a no no. Now let me say this. If the switch unit is duff, I'll let you off, simply as this part if not repairable is as rare as hens teeth but a faulty component or broken track/connection is in my view a straightforward repair, don't forget a lot of us saw many one off sets that came in for repair from those in the forces or those that picked up "this lovely looking set while on holiday". We had no diagrams and just the pin connections of the valves to go by, very few were not repaired.
Like I have said before on other forums if you were in a busy workshop the gaffer would have been wielding the big stick by now.

[Crackle]

Bets on if NM is ever going to get his radio repaired.  

Mike

I think I will

Thats what I want to hear, now please take some decent photos, no smaller than 2400 x 1800 and in good daylight, of the switches from various angles and the circuit board where they are soldered and post them here.
This thread is now on its 17th page, the radio faults are long forgotten, I think we need a recap of where you are in the repair and what has been discovered (relevant to the actual faults on this radio) so far.

Why not let us advise you, and if you follow the advice conscientiously, without wandering off on a tangent, and put the books down we should get somewhere, if it is repairable at all we will get it finished.
At the same time you WILL gain experience as you go from the likes of Lawrence and the few others who are still here to help you.
There is no need to fog your mind with all these distracting facts from books which frankly have probably nothing to do with the radio you are working on, but sound like they are from an Amateur (ham) type radio.

Come on lets go and metaphorically kick some radio ass.
Sorry NM if this sounds a bit harsh.

Mike

[Nowhere-Man]

I hope you all have a sense of humour. Pretty much all my friends are female and one of them thinks it's some sort of "numbers OCD" as she puts it. I had to chuckle when I read this, though, as I'd been working out some random 0.6 modulation index to compare Narrowband FM to AM. Let me say though, crazy as it may be, it somehow focuses the mind away from the problems of routine life (such as bills, stresses and other factors). Tonight I think I pretty much got the basic concept of how an FM modulated carrier can be rectified using phase to convert to amplitudes and AF.
On the practical side those knobs operate the two IF's I have. That's where my thead got kind of wacky when I was figuring out the FM 30 Mhz IF circuit (Lawrence was very helpful there).
I feel sure button one is where the trouble lies. On Grundigs you can unscrew the mech but these are tab soldered. However my plan is to insert a micro-camera or sthe imilar contrivance (the Russian engineers say they used syringes as well). The PCB board is not the best and does show wear. You can see this by shining a light. The amount of dirt I shifted from the upper board and around the switch mec was awesome. I do need to change "that capacitor". And one or two wax caps if I can get to them. As to performance it is now much better.

[Murphyv310]

Ok, enough is enough. Send the set to me, I'll fix it and do a YouTube video of the work. I'll do it free omg with the return postage. So are you ok with that?

[Nowhere-Man]

For learning new things it's been good. At the very beginning here is what I didn't know:
(1) PCB soldering and component removal.
(2) Particulars of Telefunken valves.
(3) No experience of transistors (except a brief intro some years ago).
(4) Far more understanding of oscillators and IF's.
(5) A so far emerging grasp of FM PM modulation.
(6) Improved schematic reading.
In other words any progress is always better than no change. The ideal is to mix the theory with practical. I guess that's why we had those demanding practical classes in Biology back in 1990.