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GEC 2114 Junior FineLine

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crustytv
(@crustytv)
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There's a chap over on UKVRRR desperate to find service data for the above set.

 

He said he's searched and found nothing, however a 'google' search of "GEC 2114 Junior Fineline" would have brought up as the very first link, a Vrat thread which contained a link to the free data here.

If any Vrat member here is also a member of UKVRRR, they might like to help and point him to the fact the data is available via our free-to-view B&W TV data section as shown below.

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Posted : 24/02/2019 11:13 am
Lloyd
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Just posted a link to your thread about the repair, on his thread 🙂

Regards,

Lloyd

 
Posted : 24/02/2019 11:50 am
GreasedMonkey
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Many thanks Lloyd and Crustytv.

I have made a little progress now I have a circuit diagram. I now have a functioning tuner and nice clear audio, but still no video. More work later this evening.

 
Posted : 24/02/2019 3:12 pm
crustytv
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Hi GM,

Welcome to Vrat. ? 

I'm glad you're making progress and pleased you found the LLJ article with circuit diagram of use.  It certainly makes life a lot easier with, than without. 

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Posted : 24/02/2019 3:29 pm
GreasedMonkey
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Ok, so a little background for anyone who is interested.

 

I was looking for an old CRT TV to play with as I wanted to find a new hobby, something that takes up less room than my current vintage car obsession. Also something quiet that I can do after the small people are fed, washed and sent to bed of an evening, rather than just sitting in front of the telly stuffing biscuits into my face hole. (my trousers appear smaller every day).

I am an electronic engineer by trade, but this is in the automotive industry. Many years ago I had a part time job at a telly shop while at college. Fixing up old ex-rental TVs to be sold off, though mainly this would involve cleaning them and if the picture was a bit soft 'adjusting' the heater drive on the tube. I have basic tools at my disposal at home, A couple of oscilloscopes, function generators, meters etc. I figured an old TV would make a nice resto project and I have everything I need (other than the set itself). Also nice to stop something going to landfill where possible. Nobody mends anything any more and that is a shame. As Fred Dibnah once said "nobody makes or fixes anything anymore, we have become a nation of conmen selling insurance to one another".

The set was kindly donated by a forum member over on Vintage-radio forum.

I collected the set and put it on the kitchen table, where it stood for a while as I was busy with family type stuff. Eventually I plugged it in and stood well back, there was no 'pop', no funny smells and none of the magic smoke came out. I could hear a line whistle which instantly took me back to the 80s. A dim, blank raster appeared on the screen, but no snowy picture or sound other than a very slight hum from the loudspeaker, but it was signs of life so I was happy.

Knowing the wifes return was somewhat imminent I moved it to a less prominent table and removed the back. Turning it on I was greeted with the familiar line whistle, though it somehow sounded more sort of laboured than before, like It was working too hard. Looking at the screen I was faced with one horizontal right white line. Total vertical collapse! At this point I had no data but could at least identify the scan coils and components directly driving them. Starting with the scan coils and working backwards I found L202 to be open circuit, I managed to open it up and repair it only loosing half a turn from the winding. Bingo Full raster was restored.

On to the tuner, it had a power supply and nothing obvious amiss, but I was now struggling without any data. Then I got a link to this forum and a very helpful circuit diagram. 2 open circuit resistors later and the tuner appeared to be functioning, but without sound of video I could not know for sure. Referring back to the circuit diagram I found there was no 13.6V supply to the Audio PCB. This was due to some of the track lifting from the PCB, after this was repaired I had a bit of a hiss and loud crackles when the dirty volume pot was turned.

After a trip to the attic to retrieve my old VCR and a copy of Apollo 13 (first cassette out of the box) I plugged it in, hit play and set about merrily twisting my chosen channel button, eventually I heard some nice clear audio, thus proving the operation of the audio bits, and tuner bits.

So, Audio working, tuner working and a CRT capable of creating a nice bright full screen raster, how hard can it be from now on, just video to go.

Later in the evening with small people dealt with I decided, with a sense of confidence (either from my earlier successes or from the cider that came with Sunday lunch, not sure which) to go back to the video stages. So I sat myself down and powered up the scope to be greeted with nothing more than a small green light and a blank screen. B&^%%R! Off to search the darkest regions of the workshop for the small single channel handheld scope that I KNOW I have somewhere. Eventually found it and started looking at the video stages. Working my way backwards from the CRT end, for no reason other than I know no better, I found only steady state DC levels, nothing that looked like a video signal of any sort, getting back as far is the input to the vision detector array I was still finding only DC levels, until I poked the junction of R117 and R118 with my scope probe and was rewarded with a brief, but quite sharp looking image, the image was not stable and was scrolling vertically, but still it was an image and identifiable as my VCR menu. prodding the PCB anywhere in the area of R117 produced this fleeting vision of happiness. So with power removed I set about searching for a possible dry joint I had missed. I could find nothing so decided to re-solder that area of the PCB.

Much sadness was to abound however, upon reinstating power, there was no video, just a blank raster and no amount of prodding would restore the picture this time. At this point it was time to go to bed, so I packed up for the night. I will go back to it this evening if I get some time, but I am now working on the theory that a component has gone short circuit and my initial prodding was not making a connection somewhere, but breaking one. Maybe a filter or decoupling capacitor somewhere is short.

If anyone more experienced in such matters has any better Ideas, I would love to hear them.

Thanks for reading, if indeed you still are.

 

 

GEC picture
 
Posted : 25/02/2019 12:54 pm
Red_to_Black, crustytv, Red_to_Black and 3 people reacted
crustytv
(@crustytv)
Posts: 11995
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Topic starter
 

Hi GM,

I'm sure folk here are following along, just that many will be at work, so please keep up the reports on your TV repair and I'm sure many will comment this evening.

Personally I think you're on the right track (excuse the pun) and looking in the right area. As LLJ points out in his article, when faced with apparent lack if signal, the final IF stage is the place to start due to large signal swings and thus prone to failure.  Good that you have the article as it gives the expected voltages on TR101/02/03, so a quick run over with the meter in the current state to see where they are at, might also give us all a clue.

Look forward to your next update and keep up the good work. ? 

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Posted : 25/02/2019 3:05 pm
GreasedMonkey
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Would a fault in the IF stages not affect audio also? I have nice clear audio from the set regardless of what is going on with the video.

Hopefully I will be able to find a little more this evening. I had to knock it on the head last night as it was gone midnight and I had to be in work for 07:30 today.

 
Posted : 25/02/2019 3:41 pm
crustytv
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Ooops forgot you said there was audio (now where's the slap-head emoji when you need it). ? 

Did you have a poke about around TR107 yesterday? Stock fault seems to be this going o/c giving your symptoms (screen illuminated with good sound) with its collector way up at 100V and no emitter volts, worth a quick check I'd say. If its low then it suggests looking back at TR106.

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Posted : 25/02/2019 3:50 pm
Nuvistor
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Sound take off is from the collector of TR103, R117/118 are the base bias components for TR103. Its possible an open circuit base emitter could allow enough signal through for the 6 MHz sound to be detected by D104 and amplified/processed by the TBA120.

 

A simple voltage check on TR103 for an open circuit base emmiter would be quick and easy test. The BF197 were known for this failure mode in other sets. The base/emmiter should have a PD of around 0.6v. Also check the collector volts in case of an O/C IF transformer.

If that is OK and your scope shows no video on the output of the detector D103 then that diode and circuit requires checking.

 

The video output transistor has Chris mentions was a common failure so worth checking but unless your scope is faulty I would have expected it display some video waveform.

 

Frank

 
Posted : 25/02/2019 7:06 pm
GreasedMonkey
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A little more progress, but I will be honest, I don't know why just yet. I need to go back to the diagram to work out what was going on.

I was quite tired last night so I decided that rather than do thinking I would spend a little bit of time going over the audio PCB as there are various crackles and pops whenever this is touched. So I removed it, cleaned the plug and socket, resoldered a few suspect looking joints and replaced 2 capacitors and a resistor.

At this point I planned to put the audio board back in, power up the set to confirm the crackles and pops had gone and go to bed. But upon powering the set I was greeted not only by clear audio the no longer popped and crackled when the board was touched, but also by a feint image, it was waving about and scrolling like a good un, but it was an image. At this point I was back to suspecting a bad connection somewhere, but despite all my efforts poking, prodding, shaking, even a good thump. I could not make the picture go away again.

Filled with renewed enthusiasm I squirted a little contact cleaner in the contrast pot and gave it a wiggle. I did a bit of fiddling and managed to obtain a watchable picture, not perfect by any stretch, but I will make the final adjustments with the Freeview test card when all is said and done.

There are still issues, there are rather annoying flyback lines visible and it seems incredibly fussy on the Vert and Horiz hold adjustments.

But hey, Progress is progress even if I don't know why or how. 

Any advice on flyback will be much appreciated.

Flyback
flyback2
 
Posted : 26/02/2019 9:50 am
crustytv
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Don't you just hate it when things seemingly fix themselves, you can bet the set is teasing you and it will only be temporary. Did you try a shunt cap across C301? With your TR107 collector volts being reported as "low", it certainly feels like an intermittent fault in C301 that has perhaps healed temporarily. Worth checking C218 & R139 as well.

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Posted : 26/02/2019 10:06 am
Jayceebee
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As you will have noticed this set has double sided print, these sets were produced long before plated through holes became the norm for connection between the two copper layers. This was one of GEC's trademarks and used the component legs to join the layers which meant there was a possibility of a dry joint on either side which could produce very intermittent and some real head scratching faults. For me this method was never a good idea and many manufacturers who used it had problems, Akura digital chassis anyone?

For flyback lines this could be lack of field flyback blanking pulses which are fed to the emitter of Tr107 via C218 R139 as pointed out by Chris, or could be down to the sync being very weak and false locking as I don't see them of the picture of the VCR menu, Tr201 and C201 could be possible suspects. Any sign of hum bars? It's not unknown for a single diode of the bridge rectifier to go o/c on these types of portables which turns it into half wave.

Keep up the good work.

John.

 
Posted : 26/02/2019 11:23 am
GreasedMonkey
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Yes, the lack of through hole playing did catch me out when I repaired L202.

at work we use 16 layer boards. So I had not even considered there would be no through hole playing when I started. It is also very tricky to remove any component without lifting the track on one side or the other.

i guess first thing to try is scope the base of Tr201 and see if I can see the blanking pulses there.

 

 
Posted : 26/02/2019 12:29 pm
GreasedMonkey
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Some more progress.

Looks like someone had been here before me. R202 had been removed and D201 had been moved, it cathode was connected to C201 and the anode connect in series with a 330K resistor which was then connected to the junction of R133 and R131. after putting this back to the circuit diagram I now have a picture that is much led fussy on the vertical and horizontal hold. Still the flyback lines remain. This evening I will scope up R139 and see what I have there in the way of blanking pulses.

 
Posted : 28/02/2019 9:44 am
Lloyd
(@lloyd)
Posts: 1958
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Good to see you are making good progress with the set, sorry I can’t help much with the faults as I’ve no experience of one of these! 

Regards 

Lloyd 

 
Posted : 28/02/2019 8:25 pm
Jayceebee
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It appears these do have plated through holes, foot in mouth time again ? . Regarding the lifting print I have heard a story on more than one occasion that this wasn't a big problem until a key employee retired from the PCB manufacturer, anyone shed any light on this? When removing components it was best practice to cut the component body then remove the legs with heat applied as quick as possible

John.

 
Posted : 28/02/2019 10:33 pm
GreasedMonkey
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Some progress to report.

progress stalled somewhat recently as everything got horribly noisy all of a sudden, Nast buzz on the audio and impossible to get a lock on the picture. Scoping up the power supply showed a ripple frequency to match half wave rectification, I assume one of the diodes in the rectifier has decided not to play any more. 

None of the component suppliers I usually use had the correct part, I assume it went obsolete some time ago. I could find a suitable replacement from RS or Farnell bit that was going to have to wait until Monday as my account details are at the office.

anyway, last night it dawned upon me that the set is 12v DC as well. So armed with a small bench supply I powered it up and was happy to see all the noise had gone. 

I have now solved the fly back issue. It seems these sets are quite particular about the voltage of the fly back blanking pulse. I replaced the biasing resistors and the fly back was much reduced, only now visible at very high brightness setting. Neither resistor has failed as such but both were out of spec, I assume just down to age. Comparing the signals before and after resistor replacement, raising the blanking level from 3.8 to 4.2V had almost got rid of the fly back lines completely. Assuming most of the other resistor in the set would be similarly out of spec (other than ones I have replace already) I decided to try adding a trimmer pot in series  to try and fine tune the level. 

Raising the level a bit more (4.3V) has banished the flyback completely. 

 

 
Posted : 03/03/2019 7:41 pm
GreasedMonkey
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Also, while searching for a trimmer pot, I found a bag of MR504 3A 400V diodes. I may use these to replace the duff rectifier.

 
Posted : 03/03/2019 8:15 pm
Nuvistor
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Posted by: GreasedMonkey

Also, while searching for a trimmer pot, I found a bag of MR504 3A 400V diodes. I may use these to replace the duff rectifier.

Thats a good idea, may as well use them.

Frank

 
Posted : 03/03/2019 9:31 pm
GreasedMonkey
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4 diodes successfully installed in bridge formation and all is well again.

 

Now I have a picture and sound that I am happy with, I turn my attention to the case. During my investigations it had got to the stage where the only thing still secured in place was the tube, so this has now been removed so I can deal with an empty case. It has gone a sort of yellowy-brown colour over time. At first I thought it was nicotine stained, but I think it has been had by the sun as there is a loop of white where the cable would have been around the two hooks on the back. No amount of cleaning is bringing it back to its whiteness so I am thinking along the lines of a spray job now.

If anybody has any advise for restoring these plastic cases, I would be pleased to hear it. I did do a small abrasion test on an unseen area of the case and the yellowing is quite deep into the plastic.

@crustytv  -  I really like the look of your junior fineline set with the black facia, do you know if it was like that from the factory or has it been painted / sticky film / replacement front etc. ?

 

 
Posted : 07/03/2019 11:05 am
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