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Old 20th Mar 2017, 2:40 pm   #1
cashaw1972
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Default Philips G8 autopsy

Back in around 1976 my parents bought a new Philips G8 with touch control tuning and the "clicker" remote.

The TV performed well until around 1980 when it stopped displaying 'red'. The red would appear once in a while, once a week during switching on, but this got to be a rarer and rarer occurrence.

The TV repairman was called in a number of times and eventually the TV was sent to it's repair centre. It came back a few weeks later with a note that it's tube was bad and they suggested a re-gunned tube at £50.

My father was not convinced and even removed the back of the TV and switched the red/green video drive cables to demonstrate the red gun was fine. Even so, the TV was deemed not economically repairable and was soon replaced with a Ferguson TX in around 1983.

Ironically, the G8 got moved to the next door room and provided many years service as the TV connected to the computer.

Can any of you old-timers recognize the G8 symptoms described above ? There was always a feeling in the family that we had been ripped off and forced to buy a new TV instead of fixing the old.
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Old 20th Mar 2017, 2:53 pm   #2
Nuvistor
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Default Re: Philips G8 autopsy

Loss of one colour was quite common and could be due to a variety of reasons including the CRT. My experience of the standard delta 90degree CRT's was slow loss of emmision of one or more of the guns not intermittent loss of a colour.
I did have that problem with quick heat type CRT's but I don't think the G8 used that type.

Much too long ago to guess what the problem was in the TV, all evidence lost.
Frank
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Old 20th Mar 2017, 3:53 pm   #3
Philips210
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Default Re: Philips G8 autopsy

Hi.

As the tube has been ruled out as faulty then loss of red could have been due to the red video output stage being cut off so the red cathode voltage is high and the gun is also effectively off. The red G2 (A1) voltage could be going low intermittently possibly due to the switch playing up on the convergence board. The tube base socket is unlikely to be faulty though it's not above suspicion. It's also possible there could be a problem with one of the spark gaps on the CRT base board. Dry joints are of course a distinct possibility.

Seeing that the fault is present for most of the time it should have been easy to diagnose the problem by checking the voltage conditions on the CRT base board.


Regards
Symon.
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Old 20th Mar 2017, 4:15 pm   #4
Hunts smoothing bomb
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Default Re: Philips G8 autopsy

Does the G8 employ RGB drive?
If so then I would have plumped for a dry joint around the red output transistor leaving the tube cut off.

But after all this time it is only a guess.

Cheers
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Old 20th Mar 2017, 4:18 pm   #5
Welsh Anorak
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Default Re: Philips G8 autopsy

Old timers? Well really!
If swapping the red and green leads made the fault appear in green then we can discount an A1 problem or any trouble with the CRT or base, which leaves us with the large signal panel.
Just sounds like a dry joint, but I'm sure that would have been first stop for the workshop. I've had some of the RGB transistors go intermittent which would do this, ditto the load resistors. The TBS530 isn't above suspicion. The fault would have had to be near the output stage, with the rule of 'follow the heat' being your best bet here.
It does sound like you were being scared off with a quote for a regunned tube to make you buy a new set!
Glyn
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Old 20th Mar 2017, 7:37 pm   #6
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Default Re: Philips G8 autopsy

A new BF337 usually cured this one or dry joints to it's connections as Lee has suggested. Must have changed hundreds of BF337s back in the 70's and 80's. Very common fault. J.
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Old 20th Mar 2017, 7:42 pm   #7
System A
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Default Re: Philips G8 autopsy

Hi
I have repaired 100's of G8's in my time . The common fault would be intermittent RGB transistors , BF337 . A couple of years ago my nouveau 22 suffered the same fault.
Great sets.
Regards.
Gary.
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Old 20th Mar 2017, 7:51 pm   #8
Nuvistor
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Default Re: Philips G8 autopsy

I think quite a few makes of sets that used the RGB BF337 transistors had this problem, I don't think the CRT was the problem, dry joints and BF337 are most likely items, we cannot be sure though exactly the cause.
Frank
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Old 21st Mar 2017, 9:28 am   #9
cashaw1972
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Default Re: Philips G8 autopsy

Thanks for the replies ! And confirming what I have suspected for over 30 years.
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Old 22nd Mar 2017, 10:30 pm   #10
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Default Re: Philips G8 autopsy

Our G8 was also written off by a TV engineer (I was only about 13) who said it was the tube and we'd need a new set. The symptoms? A gradual narrowing of the picture height over several weeks. Quite obviously not the tube but who was to know back then!
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Old 23rd Mar 2017, 6:15 pm   #11
Welsh Anorak
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Default Re: Philips G8 autopsy

Well, the 'engineer' was to know, wasn't he?
Another urban myth - small picture means dying tube. Never quite knew where that came from.
Glyn
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