20-02-2017, 05:05 PM
It may be more polite to just open a thread on this, rather than possibly hijack the Cuba "Hello" thread. I don't know if anyone will be interested in it and I wouldn't expect too much. The main thing for me is to simply learn as I go along. Those who have more experience with these more modern receivers may feel I make mistakes as I go on (which is natural) and polite suggestions are welcome.
Today, I decided it made sense to do something with the ferrite core and windings. I had soldered it before but now I realise I ought to have done a bit more than that as it's tended to loosen and unwind. Not good. So, the really dodgy bits I rewound more neatly. The use of language at this point I leave to the imagination but my eyesight is awful so it led to some frustration. I then tried sealing with some wax. I've never done this before. Most of the radios I worked on to date never had ferrite rods but just used a large wire. Anyway, I simply lit a candle, melted some wax and sealed the windings. It now looks a fair bit neater although I am not too happy with the circuit as a whole since the delicate threads show some wear. After I finished I tested with the meter and that read O.K. It was the best I could do really.
I only just noticed the other day the barrel waveband selector has lots of simple access hatches to the oscillator windings. Simply undo the screw and you can remove the panel and check with a meter. I have that job later.
I located one red square capacitor Miguel recommended to remove as they are unreliable.
The P and MP Type transistors have all been checked around the legs very carefully. I did notice the RF transistors may really whistle like a dentist's drill when you touch the case.
My goal is to do the best I can with the knowledge I have so far. As always, I tend to use a repair job also as a schematic study of the circuit which is why it all goes pretty slowly. In the course of the last 3 weeks I've learned about bias, PN junctions, AF17 transistors and whatever else I chance upon. And yes, I did read Mark's very helpful transistor articles.
Today, I decided it made sense to do something with the ferrite core and windings. I had soldered it before but now I realise I ought to have done a bit more than that as it's tended to loosen and unwind. Not good. So, the really dodgy bits I rewound more neatly. The use of language at this point I leave to the imagination but my eyesight is awful so it led to some frustration. I then tried sealing with some wax. I've never done this before. Most of the radios I worked on to date never had ferrite rods but just used a large wire. Anyway, I simply lit a candle, melted some wax and sealed the windings. It now looks a fair bit neater although I am not too happy with the circuit as a whole since the delicate threads show some wear. After I finished I tested with the meter and that read O.K. It was the best I could do really.
I only just noticed the other day the barrel waveband selector has lots of simple access hatches to the oscillator windings. Simply undo the screw and you can remove the panel and check with a meter. I have that job later.
I located one red square capacitor Miguel recommended to remove as they are unreliable.
The P and MP Type transistors have all been checked around the legs very carefully. I did notice the RF transistors may really whistle like a dentist's drill when you touch the case.
My goal is to do the best I can with the knowledge I have so far. As always, I tend to use a repair job also as a schematic study of the circuit which is why it all goes pretty slowly. In the course of the last 3 weeks I've learned about bias, PN junctions, AF17 transistors and whatever else I chance upon. And yes, I did read Mark's very helpful transistor articles.
