14-02-2017, 04:57 PM
(14-02-2017, 02:11 PM)Miguel Lopez Wrote: That set looks in very good condition. Are those transistors mounted on sockets? If that is the case, did you removed them from the sockets to check the legs? Did you test the transistors with the meter to check that they are OK? Sorry, just elementary questions.
Really nice set. I'm now the happy owner of a couple of VEF-204 that a neighbourg gave me. He was going to dump them, and them he thougth on me. The sets look well by the outside, but I have not given them a look in the inside. I want to finish other projects now, before tune my self on radios for a while again.
I am currently doing some work on the USSR transistors. Since all of my experience to date has been with valves, I feel I need to do a crash course in Soviet transistors. Last night I found the P type and MP classification and read up on them a bit.
http://www.wylie.org.uk/technology/semic...oviets.htm
Another development is I now have a very good schematic for this radio.
I started by testing the emitter/collector voltages. This was strange because I was getting around 5 or so volts. Whereas with OC transistors on another radio I was getting around 7. Also strange is my scale lamps take 5 volts but are not lighting, even though I removed the bulbs and tested they work fine.
I don't know if there is any logic to testing emitter/collector voltage but I was curious and not sure if it tells me much.
I did check the legs and yes they are mounted in sockets. I didn't test for breaks in the sockets so I will do this as you suggest. I did notice the radio bursts into high pitched whistles if I disturb the transistors or tap them. They also go wild if I put the meter probe on.
I don't have a scope but I do know the RF stage is at fault and that (possibly) some circuit voltage may be cut off. Maybe people would suggest a good scope for me or even alternatives?
Why is there string bits emerging from the turret inside? I assume it is just string as no wire seems to be visible after scraping the end.
Not sure if I should start a thread on this radio apart although progress is likely to be slow as I learn more about transistorised circuits.
