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Old 6th Aug 2020, 1:52 pm   #21
paulsherwin
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Default Re: Vega Selena 215 Poor FM

The 210/212 were Ge PNP throughout I think. The 215 was supposedly a major redesign around silicon, but there were strange things going on in the Soviet Union in the 1980s, so who knows?

Maybe the Minsk factory was allowed to use foreign parts by 1987 as part of perestroika. I don't know of any Ge transistors that look like the one in your pic - the typical Soviet ones certainly don't.
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Old 6th Aug 2020, 2:49 pm   #22
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Default Re: Vega Selena 215 Poor FM

To su GT---- PNP
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Old 7th Aug 2020, 7:05 pm   #23
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Default Re: Vega Selena 215 Poor FM

Further investigation shows that C1 (15pF?, ceramic) in the VHF tuner head is O/C.

It is marked:

12
M750

I will check all the ceramics in this circuit.
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Old 7th Aug 2020, 10:26 pm   #24
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Default Re: Vega Selena 215 Poor FM

Did you measure the cap?
Just that the paint off one leg might not mean that the cap is faulty!

Your measurement of the transistors as PNP devices certainly raises a red flag!
Paul is correct that the Russians probably never used such looking transistors.
Also there is no chance that in a radio they would have a mixed Ge PNP transistor tuner module and Si transistors in the rest (supply voltage polarity would not simply work).
Do replace those transistors with Si VHF transistors, for replacement guidance look for circuit diagrams of newer radios that use Si devices in the FM stages.
Present day "Chinese replacements" are the transistors marked 9018, those are 2SC9018 VHF transistors and suitable for FM tuners. eBay has lots of those cheaply.

Regards, Peter
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Old 7th Aug 2020, 11:11 pm   #25
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Default Re: Vega Selena 215 Poor FM

The capacitor is not recognised by my component tester. It is also reads open with my DMM.

I'm a bit confused. I was not trying to suggest that the transistors in the VHF front end of my 215 were Ge. They are definitely Si PNP.

Good point about the polarities. If the circuit was designed for PNP transistors I would be measuring negative voltages. The voltages I have measured are all positive.

Could the wrong transistors have been installed from the factory? I was the first one to open this set so it hasn't been touched since it left the factory.

I have some VHF transistors I could try.
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Old 7th Aug 2020, 11:17 pm   #26
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Default Re: Vega Selena 215 Poor FM

If the wrong transistors had been installed then the radio is unlikely to have worked at all, though the SU was in a pretty chaotic state in the mid 80s and nothing is impossible. Soviet engineers were highly capable, though they worked under difficult constraints and were often badly managed..
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Old 7th Aug 2020, 11:24 pm   #27
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Default Re: Vega Selena 215 Poor FM

"The capacitor is not recognised by my component tester. It is also reads open with my DMM."

Some of the Chinese component testers have difficulties measuring low pf values. Trick is to measure the exact capacitance of, say, a 100pf or 150pf cap, make a note of it, and then measure value of that and your "15pf" cap connected in parallel. Then subtract the exact measured value of the 100/150pf cap from that total. That gives you the value of the "15pf" capacitor.

Does my description make sense?

Mike

Last edited by Boulevardier; 7th Aug 2020 at 11:46 pm.
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Old 8th Aug 2020, 12:09 am   #28
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Default Re: Vega Selena 215 Poor FM

I guess it was unfortunate for me to mention Ge in the same sentence as PNP transistors in that tuner.
The bottom line is if that tester identified that transistor as a Si PNP then it probably is, and a "genuine" B215 FM tuner does not use such transistors in them!

In this thread you can find links in my posting to the detailed operation, strength and weaknesses of these testers, and if it can measure accurately low value capacitors:
https://www.vintage-radio.net/forum/...nsistor+tester

The B215 uses Si NPN transistors in the FM tuner.
I would put in known good Si NPN VHF transistors there and would go from there.
The B210-B211-B212 radios used the same looking FM tuners, though they used Ge PNP transistors in them.
It is highly unlikely that such a tuner would work in a B215 radio.
One easy way to distinguish the B210-B211-B212 FM tuners that they only use two transistors in them, they do not have a separate oscillator circuit (the third transistor in the B215 tuner).

Hope this clears it up.

Regards, Peter

Last edited by orbanp1; 8th Aug 2020 at 12:19 am.
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Old 10th Aug 2020, 8:47 pm   #29
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Default Re: Vega Selena 215 Poor FM

Quote:
Originally Posted by Boulevardier View Post
"The capacitor is not recognised by my component tester. It is also reads open with my DMM."

Some of the Chinese component testers have difficulties measuring low pf values. Trick is to measure the exact capacitance of, say, a 100pf or 150pf cap, make a note of it, and then measure value of that and your "15pf" cap connected in parallel. Then subtract the exact measured value of the 100/150pf cap from that total. That gives you the value of the "15pf" capacitor.

Does my description make sense?

Mike
I've performed the above test and can conclude that C1 is not open. I took a capacitor that measured 95pF and paralleled it with C1. The capacitance measured was 107pF making the difference 12pF.

I assume that if VT1 and 3 were getting the wrong polarity voltages the transistors would be destroyed? Also, if VT2 is the same as the other transistors why would I be measuring the correct voltages on its electrodes? I'll pull it and test it.

I'll look for my BF199s.
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Old 15th Aug 2020, 12:42 pm   #30
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Default Re: Vega Selena 215 Poor FM

I've changed VT1&3 for BF199s and the radio picks up nothing. However the voltages measured have changed:

VT1 (SM spec.):

E: 1.6V (1.05V)
C: 0.3mV (3.45V)
B: 1V (1.7V)

VT3 (SM spec.):

E: 0.7V (1.3V)
C: 0V (3.8V)
B: 0.7V (1.9V)

I removed VT2 and tested it. It is an NPN transistor marked 'V1'.

I do fancy putting the original transistors back and looking at things with my 'scope. I'll hold off at the moment.

I'm not sure if it is a transistor issue at this point. Maybe some later service data will materialise?
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Old 15th Aug 2020, 12:53 pm   #31
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Default Re: Vega Selena 215 Poor FM

Double check the leadout arrangements. I think BF199s are CEB, as are a lot of VHF types. You may need to work out the original leadout from the circuit board - I suspect the original transitors will be the ECB 'Japanese standard'.

I'm still very puzzled about this though. Either the original transistors are PNP or they're not. If they are, BF199s definitely won't work. You should be able to identify and test the two junctions of the originals using the diode test function of a DMM. The measured voltage drop will also establish if they're silicon or not.

Was there any indication that the 'originals' were not in fact originals but actually later replacements? Any sign of resoldering?
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Old 15th Aug 2020, 1:25 pm   #32
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Default Re: Vega Selena 215 Poor FM

My BF119s break the spec. and are BEC. I have double checked my work and the new transistors are definitely in correctly. The originals are either EBC or CBE.

Using the diode check on my DMM I can establish that the original transistors (VT1+3) are Si and PNP.

When I had the original transistors installed I did measure 0.6V between BE. So the transistors were switched on, despite the wrong voltages.
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Old 17th Aug 2020, 1:00 pm   #33
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Default Re: Vega Selena 215 Poor FM

Quote:
Originally Posted by OldTechFan96 View Post
My BF119s break the spec.
...
I am not sure that the BF119 are the correct transistors for an FM tuner!
That was a typo, right?

If the voltages are off and the transistors checkout fine do check the resistors and the PCB traces in the circuit.

Regards, Peter

Last edited by orbanp1; 17th Aug 2020 at 1:10 pm.
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Old 17th Aug 2020, 2:01 pm   #34
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Default Re: Vega Selena 215 Poor FM

BF199 is what I mean. I will do more checking later on.
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Old 17th Aug 2020, 4:12 pm   #35
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Default Re: Vega Selena 215 Poor FM

Just remembered, I did read it somewhere (it could have been this forum) that someone was having problems with their FM tuner in one of these Russian radios, and it was shorted ceramic disk bypass capacitors, those small red square shaped ones, like those 0.01uF capacitors.
That could certainly account for the off voltages!
Also, on the schematics that I have, R12, the emitter resistor for V3 transistor reads 1.8, they probably meant 1.8 kOhm. Similarly, R9 should be 6.8 kOhm.

Regards, Peter
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Old 17th Aug 2020, 4:20 pm   #36
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Default Re: Vega Selena 215 Poor FM

Voltage readings in the Selena can be a bit of a minefield. Some parts of the circuit show voltages referenced to the positive supply (e.g. the PNP transistors in the IF amplifier), others show voltages referenced to the negative supply (e.g. the NPN transistors in the FM tuner.).

I suspect there are a few things wrong here. Firstly, the voltage on the collector is showing 0v because you are measuring with respect to the positive rail. Connect the meter to the negative rail for the reference and that problem will be sorted out.

It's also possible that you have got the base and emitter connections confused. The way to be sure about that is to remove the transistor. The trace the emitter should be connected to will measure 0v, the base position will measure around 1.7v and the collector position will measure around 4.2v.

Armed with that, you should be able to fit the replacement transistor correctly.

Paula
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Old 17th Aug 2020, 10:18 pm   #37
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Default Re: Vega Selena 215 Poor FM

Quote:
Originally Posted by frsimen View Post
Voltage readings in the Selena can be a bit of a minefield. Some parts of the circuit show voltages referenced to the positive supply (e.g. the PNP transistors in the IF amplifier), others show voltages referenced to the negative supply (e.g. the NPN transistors in the FM tuner.).

I suspect there are a few things wrong here. Firstly, the voltage on the collector is showing 0v because you are measuring with respect to the positive rail. Connect the meter to the negative rail for the reference and that problem will be sorted out.

Paula
More or less what I said in post #4.
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Old 19th Aug 2020, 12:29 pm   #38
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Default Re: Vega Selena 215 Poor FM

I've tested the red ceramic capacitors and they are OK. Non of the resistors are O/C or shorted. The three transistors test OK and are installed correctly. All of the coils are OK. The only components I have not checked are the blue tubular capacitors.

All of the voltage measurements I've taken have been with respect to ground.

I think I might button up this radio until later service data comes available unless anybody has anymore ideas?
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Old 19th Aug 2020, 1:08 pm   #39
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Default Re: Vega Selena 215 Poor FM

I know it is getting frustrating, but I would proceed to check out the reason for the off voltages as follows:

- Take out the transistors.
- When powered up, you should measure 0V at the emitter point of V1 (ground potential through R1, 1 kOhm).
- When powered down, you should measure the 1 kOhm resistance value between the emitter point and ground.
- When powered up, you should measure +4.2V (supply voltage) at the collector point of V1 through R3 and R5 (100 Ohm +560 Ohm).
- When powered down, you should measure the 660 Ohm (100 + 560) resistance between the collector point and the supply voltage point (board Pin 1).
- When powered up, you should measure about +1.7V at the point of the base of V1.
(Note all voltage measurements referenced to ground.)

Hope this all makes sense and is understandable.
I would check out the rest of the circuits at the other transistors as well.

If the circuits check out OK, and the transistors are good (and the right polarity and installed with the proper pinout), there is really no reason for the voltages to be off!

Hang in there, and double check everything, you will figure it out!

Regards, Peter

Last edited by orbanp1; 19th Aug 2020 at 1:23 pm.
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Old 19th Aug 2020, 1:24 pm   #40
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Default Re: Vega Selena 215 Poor FM

If the FM tuner transistors are PNP, my earlier comment isn't quite correct. Use the +ve 4.2V connection on the FM tuner (not the main +ve supply voltage) for your reference. That then should give you the voltages which match the circuit diagram as both Peter Orbanp1 and I have suggested.

If the transistors are PNP, the BF199 would not be suitable as it is an NPN transistor.

Some B215 circuits show PNP transistors in the tuner, others show NPN, which doesn't help.

Paula
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