Hello from Cuba

[Miguel Lopez]

Turret contacts can be cleaned very easily with a rubber eraser. The ones that kids use in the school.

[Nowhere-Man]

I recall you mentioning that before. The update is I have repaired the aerial windings and cleaned the waveband contacts. I retested the radio. No stations received. The aerial coils I repaired did test OK for continuity. However, I detected my waveband contact points are still way too dirty as moving the dial creates stronger audio output. Wow, now I know why my German set is playing up because you ideally need access to the contact points.
I don't think my Astrad has worked in many years. Hopefully I am making progress and will just do my best to get it working. I have Servisol now so should I spray a little on the potentiometer?
When the contacts are bettter cleaned I will try again.

[Miguel Lopez]

Some advices:

I don't think my Astrad has worked in many years.

Which means that probably there would be some transistor with broken legs. Had you checked that all transistors have their legs intact?

Check all coils in the PCB for continuity. I had had to repair some sets with open coils.

Forget audio at this stage. Connect the scope at the output of the demodulator and see if there is audio signal there. Once you get signal at that point, the rest is easy.

[Nowhere-Man]

Something I noticed of importance. I tested continuity in ohms from the main battery negative wire to the potentiometer. The connection is fine. Yet connecting 9 volts negative at that point and the positive connection has no response. That suggests there is some problem with the pot. Also I want to ask does the pot also act as a switch as well as variable resistor becausee it does not switch on and off. It only rotates.
Basically my main power lines are not functional.
Your other points I will follow through so thanks for the advice. I haven't yet checked all the transistor legs and will do this with great care.

[Miguel Lopez]

does the pot also act as a switch as well as variable resistor

Yes, it does. Completely to the left, it disconects the power supply from the circuit.

It only rotates.

You've got a problem there.

[Nowhere-Man]

Just confirmed it before checking your post. I pulled out a 1959 transistor radio ((Bush) and powered negative direct at battery negative and at the pot. It powered up no problem. So, my first task is to restore the pot or fit a new one. To be expected I suppose since these radios are pretty old.
By the way that Bush radio is far simpler - a very large set with large wires and point soldering.

[Nowhere-Man]

Mil disculpas! Switch does click although the negative contact on it doesn't do anything. That is, connecting + to battery and - to the - pot terminal has no effect. Possibly the pot is very dirty so maybe try my Servisol (if safe to use).
I am going to rest now for today.

[Nowhere-Man]

Just in case anyone is confused, this Astrad didn't power up directly from the battery compartment. You will know the negative battery lug normally has a wire that traces to the volume/switch pot. The wire connects fine from pot lug to battery - lug but the 9 volts between it and battery + does nothing. Whereas on a working radio it powers up as normal. I fixed the aerial windings and cleaned up the waveband contacts and need to test all the coils and transistor legs. The pot is probably just very dirty.

[Crackle]

I do not think it is a good idea to assume the workings of one radio are the same as another make, especially one made in a different country.

When fault finding on a radio, I always start by getting the audio working first, then work my way forwards,  in stages, to the RF section.
Mike

[Nowhere-Man]

I tend to like to work with more than one radio at the same time to avoid getting bored or bogged down. One thing that already helped is being able to see first hand how dirty waveband contacts can get. On my East German model I don't have access to manually remove the grub with erasor but the Russian design here is far better. I got loads of grime off. The use of a rotating drum quite a good idea too - not sure if this is a purely Russian design.
I have known grime totally break a circuit such as fuse holders in AC supply to transformer.
The Servisol I now have seems to split opinion on use for volume pots with some claiming it caused damage or can leave residues. Mine says non harmful to plastics. I wonder if it's sold in Cuba?