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1971 GEC 2103: 2040 Series Chassis

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Sun Mar 13, 2016 12:38 pm

Took the decoder out and gave it a blast with compressed air to shift the 46 years of clinker. C353, 8uF which decouples the 20V supply was in a poor state, physically leaking. It was replaced.

Still no colour, so the colour killer was over-ridden by connecting a 27K rersistor on the junction of R386/385 to the +20V rail.

No colour, so the reference oscillator isn't running.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Sun Mar 13, 2016 2:23 pm

Checked the crystal by substitution, no change. Was checking round the buffer oscillator, when I noticed there was now no raster and precious little sound! HT is present on the IF, so I've removed the panel, removed the 46 years of detritus from it, and I'm now stating from the beginning!

Curse of the lockfit???

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by colourmaster » Sun Mar 13, 2016 3:00 pm

Hi
The same fault occurred on my 22" version and it was TR106 BF197 on the IF panel.
Regards.
Gary.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Rebel Rafter » Sun Mar 13, 2016 3:15 pm

Hi, folks, RR here. If you struggle with the double-sided print as I did with GEC sets watch out for the transductor suffering shorted turns as it sometimes does on the old GEC hybrids. If I remember right it was mounted on a little PCB fitted on the scancoil housing and if it does fail just try removing it from it's little PCB, you need a really good solder sucker and loads of patience. I had to replace the whole PCB with one from a scrap chassis. Also watch out for the cut-out in the line o/p, if I remember right, it's decades since I last worked on any hybrids, ISTR the cut-out fails open or is it a resistor in the PL509's cathode return that fails and blows up a capacitor that lives there somewhere. RR.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Tazman1966 » Sun Mar 13, 2016 8:37 pm

Hi Andy

It's normally the "line" section of the transductor that shorts so in order to test it, simply remove R704 (680R) which supplies the line scan current to the transductor. As it's a 19" set you might not even notice the slight distortion...

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Wed Mar 16, 2016 8:23 pm

OK, IF removed. Transistors checked, all innocent-ish although one BF196, when tested on my Peak DCA55 said it had a protection diode between collector and emitter, Tested a NOS BF197, which showed the same?? I've got loads of BF197, but not a single 196!

A couple of Sprague electronlytics on the board were in poor physical nick, so they were changed.

No change. It's almost like the tuner isn't connected. If I scope the output of the tuner, what should I see?

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Cathovisor » Wed Mar 16, 2016 8:33 pm

Doz wrote:If I scope the output of the tuner, what should I see?

Nothing until it's tuned in, whereupon you should see an envelope of the modulating signal. Use something simple like a greyscale or sawtooth from your signal generator, and trigger the scope from the video output of the pattern generator.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Wed Mar 16, 2016 8:52 pm

Then it appears my tuner has slung in the towel.

Untitled.jpg

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by colourmaster » Wed Mar 16, 2016 9:03 pm

Hi
I have a spare tuner you can have .
Pm me your address and I'll post it to you FOC .
Regards.
Gary.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Wed Mar 16, 2016 9:07 pm

405 fan wrote:Hi
I have a spare tuner you can have .
Pm me your address and I'll post it to you FOC .
Regards.
Gary.


Wow, thanks ... you have a PM. :aad

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by colourmaster » Wed Mar 16, 2016 9:12 pm

Hi
No problem I'll post it off in the next couple of days .
Regards.
Gary.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by colourmaster » Thu Mar 17, 2016 6:13 pm

Hi Andy
I've posted the tuner today so it should arrive soon .
Regards.
Gary.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Thu Mar 17, 2016 8:37 pm

405 fan wrote:Hi Andy
I've posted the tuner today so it should arrive soon .
Regards.
Gary.


Thanks Gary.

Watch this space!

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by colourmaster » Sat Mar 26, 2016 9:10 am

Hi Andy
I was wondering how are you getting on with your set .
I hope the tuner arrived ok .
Regards.
Gary.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Sat Mar 26, 2016 11:35 am

Hi Gary,

Tuner's arrived safe and sound thank you (it isn't even seized!!)

Got a couple of commercial jobs to shift out before it makes it's way back to the bench, hopefully by tomorrow...

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Fri Apr 29, 2016 5:24 pm

... tomorrow finally came .... and the tuner proves it's innocence :zx:

Back to the IF...

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Fri Apr 29, 2016 7:59 pm

Every BF194 in the IF is open circuit!

TR115,116 (Sound IF and ratio detector) and TR108 (Video emitter follower)! I've temporrarily fitted BF197's, but it's unstable but working. I'll order a bag up!

Damn those lockfits!

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Lloyd » Fri Apr 29, 2016 9:00 pm

Good grief! Why are these transistors so rubbish? I thought AF117's were bad...

Hope you get it sorted :aad

Regards,
Lloyd

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Fri Apr 29, 2016 9:40 pm

Turns out the instability is from the tuner Gary kindly supplied. I've refitted the original for now. What's the betting there's a lock fit in the decoder stopping the colour??

Place your bets :aaj

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Fri Apr 29, 2016 10:03 pm

I better post what led me down this blind alley... Here was my train of thought...

No sound or vision. Blank raster and no sound. Nothing from the sync Sep...

So, surely the fault must lie in the if stages shared by the vision and sound channel....

But all those checked ok.... Hence my incorrect diagnosis of the tuner itself.

The defective transistors are all after the commoned IF. Both the first sound I.F. And the ratio detector , and the video IF emitter follower. I hate being led down a garden path. Glad I've got it though...

Now back to finding the fault in the reference oscillator.

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by crustytv » Sat Apr 30, 2016 9:14 am

Lloyd wrote:Good grief! Why are these transistors so rubbish? I thought AF117's were bad...

I'm going to be controversial, stick my head above the parapet and no doubt get it kicked but here goes.

There is no doubt the Lockfit transistor has a reputation but like the AF117, not all are found to be bad but right or wrong they all get condemned. The following posts intent is not denying what others may have experienced but only to report what I have found and experienced, in the interests of bringing a balanced view.

As you may or may not be aware I tend to repair my sets rather than restore, meaning I only do what is necessary to get the set up and running, no shot-gunning. That does not mean I leave my TV's in a poor quality state of repair, far from it as I'm too fastidious for that. It means I replace what is needed to be replaced, to get the set up and running so it gives a very good stable quality picture. This is not to say I have not found bad Lockfits because I have. However equally I have many and I mean many sets, where Lockfits are working perfectly well. I've even removed tested and refitted lockfits that continue to function well, the trick is not to pull but push equally from beneath.

In reality I've had as many T092 packages fail as Lockkit if not more. Consider my latest set the HMV 2703, all the transistor failures were T092 packages none were Lockfit. The set is still packed full of them on the IF, Video, decoder etc. Is the picture crap, is the set unstable? No Its working and working well.

If the HMV were just an isolated example then fine but its not . Walk through my collection albums on the main site and you will find not one but many sets, most if not all have Lockfit transistors installed and working fine. As I say I can only speak as I find, I'm not saying Lockfits are without fault as they clearly do have a reputation, I just wonder if like the AF117 some are good and some are bad but not all are bad.

OH and I have many NOS lockfits and don't hesitate to fit them when required.

Well there I said it, I'm a heretic burn me at the stake and let the kicking commence. :qq1

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by PYE625 » Sat Apr 30, 2016 9:42 am

An example of the lockfits working well are in my Pye CT72. There are quite a number dotted around.

Yet another excuse to boast about the picture quality?

Sorry chaps :ccg
Attachments
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Sat Apr 30, 2016 12:43 pm

CrustyTV wrote:
Lloyd wrote:Good grief! Why are these transistors so rubbish? I thought AF117's were bad...

I'm going to be controversial, stick my head above the parapet and no doubt get it kicked but here goes.

There is no doubt the Lockfit transistor has a reputation but like the AF117, not all are found to be bad but right or wrong they all get condemned. The following posts intent is not denying what others may have experienced but only to report what I have found and experienced, in the interests of bringing a balanced view.

As you may or may not be aware I tend to repair my sets rather than restore, meaning I only do what is necessary to get the set up and running, no shot-gunning. That does not mean I leave my TV's in a poor quality state of repair, far from it as I'm too fastidious for that. It means I replace what is needed to be replaced, to get the set up and running so it gives a very good stable quality picture. This is not to say I have not found bad Lockfits because I have. However equally I have many and I mean many sets, where Lockfits are working perfectly well. I've even removed tested and refitted lockfits that continue to function well, the trick is not to pull but push equally from beneath.

In reality I've had as many T092 packages fail as Lockkit if not more. Consider my latest set the HMV 2703, all the transistor failures were T092 packages none were Lockfit. The set is still packed full of them on the IF, Video, decoder etc. Is the picture crap, is the set unstable? No Its working and working well.

If the HMV were just an isolated example then fine but its not . Walk through my collection albums on the main site and you will find not one but many sets, most if not all have Lockfit transistors installed and working fine. As I say I can only speak as I find, I'm not saying Lockfits are without fault as they clearly do have a reputation, I just wonder if like the AF117 some are good and some are bad but not all are bad.

OH and I have many NOS lockfits and don't hesitate to fit them when required.

Well there I said it, I'm a heretic burn me at the stake and let the kicking commence. :qq1



Likewise. I had a couple in the Keracolor that were bad, but none in the Decca 30. My GEC 2028 continues to give faultless service, I'm yet to change one on that. The BF196's and 197's in this set are faultless... Just the 194's. I've had a nice walk into town this morning and returned with a bag of nos 194's. On with the work!

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by rob t » Sat Apr 30, 2016 1:03 pm

Like wise i dont condemn lockfits on sight .
there are some places for example thorne 3k/3k5 decoder boards where they do seem to cause problems .but would others fare any better?
experience an different sets give an indication of what transistors are likely to cause problems what ever type they are.
Rob T

 
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Re: 1971 GEC 2103: 2040 Series Chassis

Post by Doz » Sat Apr 30, 2016 5:03 pm

meanwhile, back at the GEC....

Scoped up the reference oscillator, and it's fine. 4.43MHz bang on.

So the colour killer is disabled, and I've still got no colour at all...

Checked the colour pot ! It's OK.

Checked each of the chroma transistors either side. TR318 and TR319.. both open circuit.... BF194!

Checked every other BF194 on the board.... and found TR 324 open too!

I'm now here....
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