UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Reply
 
Thread Tools
Old 16th Jan 2020, 3:08 pm   #1
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default My next project - the first French transistor radio

I have a particular interest in portable radios, especially first generation transistor sets. I have recently acquired from France a Solistor Transistor 8 whiich was the first French transistor radio, their equivalent to the British PAM 710. Solistor was part of the CSF group and the radio uses early CSF junction transistors which look a bit like the well known Ediswan top hat type. The transistors have an interesting numbering system - just a letter depending on function - A to F. Like the 710 it was released in 1956, also like the 710 it has a low IF but in this case very low - 130KHz which might lead to some image problems. It was reviewed in Toute La Radio (All Radio) Dec 1956 edition (anyone got a copy?). The set was manufactured in its original form for about a year and was then superceded by a revised version which was housed in the same case. The revised version can be identified by the rotary wavechange switch, mine is one of the original type. After some searching on Google France I found a website a bit like Electrotanya which had a copy of the service manual (in French of course) which I have spent a few days translating.

As received it was in quite good shape (see photos), the rexine covered wooden case had no woodworm problems, the battery compartment has some minor battery leakage damage and the volume control knob is not original but the PCB looks free of tampering. The volume control pot has been changed (which may explain the non original knob as the Solistor knobs fit over a shaft with a key). The only other obvious mod was a badly soldered wire visible in the battery box picture, this effectively bypasses the first 4.5V flat type battery. I can only assume someone was trying to run it from 9V, it would have been unlikely to work as the first (bypassed) battery provides a bias voltage for the transistors (unlike the later model which uses normal biassing with resistor chains). I have removed the wire. There was a small area of damage to the speaker cone (the paper has become brittle with age) which I repaired using model aircraft tissue and diluted PVA. The repaired speaker was tested on another set and works fine.

The components on the PCB are of French origin and I have no idea of anything that might be suspect, the electrolytics visually look OK, I think it is going to be a case of powering it up and taking it from there. I'll report back in due course of how I get on. If anyone out there has one of these early French sets I would love to hear from them of any potential problems, I could also supply them with a copy of the translated manual.
Attached Thumbnails
Click image for larger version

Name:	SolistorT8-s.jpg
Views:	224
Size:	131.1 KB
ID:	197213   Click image for larger version

Name:	My-Solistor1-s.jpg
Views:	230
Size:	169.2 KB
ID:	197214   Click image for larger version

Name:	My-Solistor4-s.jpg
Views:	191
Size:	144.9 KB
ID:	197215   Click image for larger version

Name:	Toute La Radio-s.jpg
Views:	185
Size:	138.4 KB
ID:	197216  
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 16th Jan 2020, 4:04 pm   #2
poppydog
Heptode
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 594
Default Re: My next project - the first French transistor radio

I have got a French Sonolor Electra 7 on the bench at present, however I'm green with envy with what you have there.

poppydog
poppydog is offline   Reply With Quote
Old 18th Jan 2020, 12:28 am   #3
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

I've spent a bit of time playing with the Solistor. On powering up the current was a rather alarming 200mA but his subsided down to 12mA after a few seconds, I think this was electrolytics reforming - it hasn't happened again. I had an earpiece connected in place of the speaker and there was a typical germanium hiss which altered with the volume control, so far so good but no sign of any stations on MW or LW . I set the tuning dial to 300m (1MHz) and using my Tecsun PL660 looked for any sign of a LO signal, encouragingly I found a signal at 1.130MHz (IF is 130KHz). I repeated the exercise on LW and that was OK as well. Going back to the AF side of things I injected a 1KHz sine wave into the volume control wiper and was greeted with a healthy tone in the earpiece. So we have a working LO and audio stage but no sign of stations. I think the next stage will be to inject an IF signal at 130KHz and see what happens. I need to sort out something to provide 130KHz, the little Nombrex I was using won't go that low. I've got a decent signal generator right at the back of the cupboard with test equipment in it, I'll have to dig it out and see if that will go that low.
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 18th Jan 2020, 7:15 pm   #4
smiler411
Triode
 
smiler411's Avatar
 
Join Date: Apr 2008
Location: Rhondda Cynon Taff, Wales, UK.
Posts: 36
Default Re: My next project - the first French transistor radio

probably worth checking the detector diode
smiler411 is offline   Reply With Quote
Old 19th Jan 2020, 1:48 pm   #5
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

I've dug out the decent signal generator which is a Dymar 1525 and covers 100KHz to 184MHz so should be good for testing the RF and IF stages. I haven't used the Dymar for ages and for an all solid state device it is big and heavy. I've fired it up and given it a soak test and all seems to be working well and indeed it functions down to 100KHz. This is a nice signal generator with lots of capability, eg AM or FM mod, adjustable mod frequency and depth or external mod, fixed level output independent of attenuators for connecting a frequency counter (a particularly useful feature) and lots more. Next stage will be to inject a modulated 130KHz signal into the start of the IF stages and see if anything comes out the other end
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 19th Jan 2020, 3:00 pm   #6
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 8,705
Default Re: My next project - the first French transistor radio

Quote:
probably worth checking the detector diode
My Rexine covered Perdio has a repair, the diode has bee replaced (in the 60's I guess). Obviously a repiar as the wires have been cut and a new one soldered to them.

I do like the early transistor sets too, well made mechanically, good sound, proper sized components and cheap to run.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is online now   Reply With Quote
Old 19th Jan 2020, 3:46 pm   #7
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

Some aspects of the circuit are a bit strange, there isn't a detector diode - it appears to use the first transistor following the final IF stage as a rectifier/amplifier. I've got a lot going on for the next few days so I will take a closer look when I've got more time.
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 19th Jan 2020, 4:28 pm   #8
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,599
Default Re: My next project - the first French transistor radio

Detector/amplifier.

Explanation here:

http://electriciantraining.tpub.com/...tector-161.htm

Lawrence.
ms660 is online now   Reply With Quote
Old 19th Jan 2020, 5:32 pm   #9
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

Thanks for the link, the example circuit is very close to the one used in the Solistor.
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 21st Jan 2020, 8:06 pm   #10
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

I've carried out a few tests on the IF stage (cct attached). Starting at the last IF stage and working towards the first I injected a low level 130KHz AM modulated signal at various points. I got to Q4 base where a healthy tone was heard from the speaker but injecting at Q3 base there was nothing, even when increasing the signal level. I then did some tests with a multimeter in diode test mode (observing polarity of meter), at Q4 I observed b-e 0.18V, b-c 0.18V and c-e no reading much as expected. Now looking at Q3 I got b-e 0.2V, b-c 0.2V, c-e 0.9V. I was immediately suspicious of Q3 but on removal the transistor readings were normal (c-e no reading ) and in my chinese transistor testing I got the results attached which look normal for a PNP germanium device. With the transistor now removed I did a diode test on Q3 position and got no reading so the transistor is involved in the strange result. I subsituted an OC45 for Q3 with identical results. The circuit arrangement of Q3 and Q4 (which gives the expected results) is basically the same unless I am missing something so what is the mystery path? Any suggestions welcome as at the moment I am mystified.
Attached Thumbnails
Click image for larger version

Name:	CCT.jpg
Views:	48
Size:	63.7 KB
ID:	197547   Click image for larger version

Name:	Q3-test.jpg
Views:	32
Size:	50.8 KB
ID:	197548  
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old 21st Jan 2020, 8:31 pm   #11
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 8,599
Default Re: My next project - the first French transistor radio

What are the voltage readings for Q3 and Q4 between b-e and e-c using your meter set to measure voltage.

Lawrence.
ms660 is online now   Reply With Quote
Old 21st Jan 2020, 9:14 pm   #12
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

Q3 b-e = +1.56V and c-e = -6.27V
Q4 b-e = -38mV* and c-e = -7.9V
* slowly creeping more negative
Note: meter negative probe on emitter
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old Yesterday, 9:35 pm   #13
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,329
Default Re: My next project - the first French transistor radio

Q3 has a very high leakage current? Can you test the emitter voltages as it will tell us the current.

Do you have any other PNP germanium transistors? Silicon might work in that circuit too.
PJL is offline   Reply With Quote
Old Yesterday, 11:37 pm   #14
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 4,313
Default Re: My next project - the first French transistor radio

Surely there id no bias to the base.
Check the coil and 20K resistor in the base of that transistor.
Refugee is online now   Reply With Quote
Old Today, 12:32 am   #15
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,329
Default Re: My next project - the first French transistor radio

Quote:
Originally Posted by Refugee View Post
Surely there id no bias to the base.
Check the coil and 20K resistor in the base of that transistor.
I think we may both be wrong. The AGC voltage provides the bias to both Q3 and Q4 but Q3 has a potential divider making it's emitter less -ve than Q4 and that explains why Vbe Q4 looks better. My next guess would be the 2uF AGC capacitor is leaking but quite a few other faults could cause the AGC line to be less -ve (I hate PNP and their upside down power rails).
PJL is offline   Reply With Quote
Old Today, 11:58 am   #16
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

I haven't been able to spend much time on the radio for a couple of days but as noted above I had tried swapping Q3 with an OC45 with exactly the same results. One more test I did was to remove Q3 and connect a germanium diode first from b-e then from b-c to try and find the mystery path causing the strange result. The result was that performing the diode test again from c-e resulted in no reading in both cases showing that it is a transistor effect not a single junction effect. I will report back after carrying out some more tests.
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old Today, 12:19 pm   #17
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,329
Default Re: My next project - the first French transistor radio

Measure the AGC (AVC) voltage, it is almost certainly not -ve enough. Leakage in the 2uF would cause this so I would replace it. If this is not the problem then measure the voltage on Q5 collector. We can't see the entire circuit for the AVC line so there may be other circuit elements that could cause it to be not -ve enough.
PJL is offline   Reply With Quote
Old Today, 1:07 pm   #18
Vintage_RC
Pentode
 
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 140
Default Re: My next project - the first French transistor radio

There was one other test I had carried out which I forget to mention and which may move the investigation in a different direction. While Q3 was removed I injected a low level modulated 130KHz signal into each terminal of the IF transformer MF2 and the sound level from the speaker was monitored. The result was a healthy response at pin 6 but a very weak sound in the speaker when the signal was injected into pins 2 or 3. On reflection the O/P impedance of the sig gen is 50 ohms so there would have been a big mismatch which may have severely dampened the IF transformer.
__________________
Alan G6PUB, BVWS
Vintage_RC is online now   Reply With Quote
Old Today, 3:01 pm   #19
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,329
Default Re: My next project - the first French transistor radio

Do the voltage measurements first. +1.56V on Vbe indicates Q3 is completely cut-off. When all the transistor DC voltages indicate they are conducting properly you can move on to looking at other problems.
PJL is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 7:21 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.