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Old 11th Nov 2022, 1:20 pm   #1
G7LAS_Rob
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Default Vega Selena 215 - FM oscillator/mixer

Hi all... my first time here. Excellent forum!

The FM oscillator/mixer metal can on my Vega 215 outputs nothing on pins 5 & 6 . I understand the capacitors don't age well, go out of tolerance and, because the design is very value critical, it stops oscillating.

So, I've decided it's caution to the wind time and I've taken it all apart with a view to replace ALL the caps here whilst it's in pieces.

I have a schematic for the 216 (which I think is almost the same as the 215 and probably the same on FM) and there are values for the caps on the diagram, but also a table with DIFFERENT values! I've attached the snippet. For example, should I replace C1 with a 15pF as shown in the schematic, or with a 12pf as shown in the table?

I wonder if any one has an idea on this one? I'd be really grateful for any input.

Cheers, Rob
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Old 11th Nov 2022, 1:46 pm   #2
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Default Re: Vega Selena 215 - FM oscillator/mixer

It would appear there are different values for each set as the snip of the data I have posted shows, different values for 216 vs 215/217. If it was me I would be replacing with the same value I removed from the unit as as presumably it worked with those values in.
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Old 11th Nov 2022, 6:52 pm   #3
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Default Re: Vega Selena 215 - FM oscillator/mixer

Hello Rob,

Welcome to the forum.

While you have the tuner module apart, check for any metal whiskers growing across the insulators on the variable capacitor. I worked on a B210 version of the Selena last year which was dead on FM. I was surprised by the fur coat of whiskers that was growing across the ceramic insulators. Once the whiskers were removed, the tuner worked perfectly again.

Paula
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Old 11th Nov 2022, 7:10 pm   #4
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Default Re: Vega Selena 215 - FM oscillator/mixer

Hi Rob

Normally, small value caps like this are pretty reliable. I guess the manufacturing quality in the USSR may have been a bit suspect.

In the first place I would be inclined to replace like for like on value and try to keep the leadout wires of similar length. I guess the originals were ceramic, so NP0 (low temperature coefficient) leaded types would be suitable. I don't know if the miniature Philips ceramic plate type are still available, but they always used to be a reliable choice.

If it were me, I think I would change say 2 capacitors at a time and then test before going any further. I appreciate that it's a nuisance replacing the screening can.

I may be barking up the wrong tree, but if there was a "home market" version of these sets covering the 66 to 73 MHz FM band it would have been fitted with alternative capacitor values.
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Old 11th Nov 2022, 7:21 pm   #5
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Default Re: Vega Selena 215 - FM oscillator/mixer

There was indeed an OIRT version of this radio. I suspect it was originally an OIRT design that was tweaked for export.

Service data for the 21x series should be treated as a rough indication rather than a detailed specification. Some really major changes were made during production runs, including Ge->Si and PNP->NPN.
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Old 11th Nov 2022, 8:34 pm   #6
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Default Re: Vega Selena 215 - FM oscillator/mixer

Quote:
Originally Posted by paulsherwin View Post

Service data for the 21x series should be treated as a rough indication rather than a detailed specification. Some really major changes were made during production runs, including Ge->Si and PNP->NPN.
Agreed Paul. I had a right old time when using the available schematics for the 215. I began to suspect that they only ever issued schematics for one or two variants of the 21 series, and that you were pretty well on your own when it came to working with a particular example of the radio.

Also, be very careful when working with the fastenings between the circuit board and the plastic case. The very elderly plastic they used for the shell is terrible - I found that the threaded mouldings in the case carrying those long steel mounting pillars for the circuit board crumbled into bits when you tried to reassemble the thing by rescrewing those steel pillars - and the whole structure of the radio depends on them being held properly to the case. It was a complete nightmare to reconstruct those mouldings!

Mike

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Old 11th Nov 2022, 10:34 pm   #7
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Default Re: Vega Selena 215 - FM oscillator/mixer

They are strange radios, a bizarre combination of overdesign and shoddy materials. I guess that was how consumer electronics worked in the Soviet days.

The plastics have certainly aged badly. The knobs are famous for disintegrating.
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Old 12th Nov 2022, 2:01 am   #8
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Default Re: Vega Selena 215 - FM oscillator/mixer

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They are strange radios, a bizarre combination of overdesign and shoddy materials. I guess that was how consumer electronics worked in the Soviet days.

Strange indeed - "Tuning Indicator", what tuning indicator?
Must have been a bad Friday afternoon in Minsk!
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Old 12th Nov 2022, 11:43 am   #9
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Default Re: Vega Selena 215 - FM oscillator/mixer

Most models did have a tuning/battery meter there. Maybe the Minsk factory couldn't get supplies for a while, so just used a front panel without the aperture punched out.
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Old 12th Nov 2022, 11:51 am   #10
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Default Re: Vega Selena 215 - FM oscillator/mixer

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Originally Posted by paulsherwin View Post
Most models did have a tuning/battery meter there. Maybe the Minsk factory couldn't get supplies for a while, so just used a front panel without the aperture punched out.

If so, they must have gone to the trouble of modifying the punch, so you'd think they'd have had the common decency to have left off the label as well!
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Old 12th Nov 2022, 12:24 pm   #11
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Default Re: Vega Selena 215 - FM oscillator/mixer

See the Radiomuseum pics: https://www.radiomuseum.org/r/vega_vega_215_selena.html

Versions with and without the meter are shown there.
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Old 12th Nov 2022, 12:32 pm   #12
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Default Re: Vega Selena 215 - FM oscillator/mixer

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Originally Posted by paulsherwin View Post
See the Radiomuseum pics: https://www.radiomuseum.org/r/vega_vega_215_selena.html

Versions with and without the meter are shown there.

Thanks Paul, that's interesting and I hadn't noticed it before. Very odd though that even the indicatorless model shown on RM still has the label saying "Tuning Indicator". I don't understand why they'd do that...


Mike
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Old 12th Nov 2022, 12:34 pm   #13
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Default Re: Vega Selena 215 - FM oscillator/mixer

Presumably they didn't want to reconfigure the printing machinery. As I said, strange radios...

My 215 has the meter, and it must be said it isn't a lot of use.
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Old 30th Mar 2023, 6:44 pm   #14
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Default Re: Vega Selena 215 - FM oscillator/mixer

Quote:
Originally Posted by paulsherwin View Post
Most models did have a tuning/battery meter there. Maybe the Minsk factory couldn't get supplies for a while, so just used a front panel without the aperture punched out.
After the collapse of the USSR, production remained, and components had to be not only obtained, but bought, and often already in another country. Indicators - hand-assembled and very expensive. The factory had to make what it could get.
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Old 31st Mar 2023, 8:09 am   #15
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Default Re: Vega Selena 215 - FM oscillator/mixer

Hi Rob,

I too have worked one a couple of these sets. Personally I would try substituting the oscillator transistor before starting to replace caps. The small value caps are actually pretty reliable, but I have had that transistor fail. Tests fine with a multimeter, but goes low gain.

Also, have you checked the voltage going to the FM can? On another one of these I had, the voltage was low causing the FM oscillator to stop. That was the wavechange switch needing attention.

Cheers.
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Old 31st Mar 2023, 12:27 pm   #16
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Default Re: Vega Selena 215 - FM oscillator/mixer

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Originally Posted by agardiner View Post
Hi Rob,

I too have worked one a couple of these sets. Personally I would try substituting the oscillator transistor before starting to replace caps. The small value caps are actually pretty reliable, but I have had that transistor fail. Tests fine with a multimeter, but goes low gain.

Also, have you checked the voltage going to the FM can? On another one of these I had, the voltage was low causing the FM oscillator to stop. That was the wavechange switch needing attention.

Cheers.
Interesting .... I've yet to attack the FM front end in mine. What would you recommend as an oscillator replacement?
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Old 31st Mar 2023, 2:40 pm   #17
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Default Re: Vega Selena 215 - FM oscillator/mixer

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Interesting .... I've yet to attack the FM front end in mine. What would you recommend as an oscillator replacement?
Well.... my choice will be controversial! On the set I had where the transistor had failed, I replaced it with an AF115, which I treated for tin whiskers before fitting. Worked a charm. Others however would not want to use this series of transistors!

Interesting though, I note from the OP that the part of schematic re-produced shows an NPN front end, yet my manual and certainly the sets I have encountered use PNP.
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Old 1st Apr 2023, 12:07 pm   #18
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Default Re: Vega Selena 215 - FM oscillator/mixer

They are indeed interesting and challenging sets .... more so given the various seemingly undisclosed chassis variants! All that said - the circuit design is very good and the AM performance is quite exceptional ..... and they sound almost as good as [say] a Hacker 'Hunter'!

(Your choice of oscillator is indeed controversial i.e. certainly from a reliability perspective!)
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Old 1st Apr 2023, 1:14 pm   #19
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Default Re: Vega Selena 215 - FM oscillator/mixer

Use an AF125. Direct equivalent and no tin whiskers!
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