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Old 25th Mar 2007, 5:38 pm   #1
Tazman1966
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Default Philips G8 G22K551/05. Help needed.

Hello everyone.

I am currently in the process of restoring one of these sets. Apart from a couple of dry joints on the convergence panel and a general set up, again mainly convergence it is a runner. It's got a very new looking LOPT and a pretty good tube as well although the red guns a little bit lazy. I am left with one problem though and although I seem to have read about it somewhere in "Television" I can't for the life of me remember the solution. I wonder if anyone can remember. I haven't got a diagram for it so I'm working from memory

The fault is that in the red channel somewhere there is a reduction in frequency response of the luminance signal which causes a smeary effect of the red with cyan trails following black objects which is easily seen in monochrome. I know that it is NOT the tube as I tried swapping the leads to the green and the red drives over and then the fault (in mono of course) became smeary green with magenta trails after dark things. I've taken a few screen shots to illustrate what I mean and if you open the thumbnails up it really shows up well. You can see that as an example in green(with the leads back round the right way) it's fine. I've changed the BF337 transistor and also C292 as it looked a bit dodgy. Other than this it's quite a tidy set and makes a change from the usual plain old 550 version.

Thanks in advance,

Tas
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Old 25th Mar 2007, 7:01 pm   #2
Steve_P
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Default Re: Philips G8 G22K551/05. Help needed.

Well I've not seen this one - if any of the others do, please post the details so we can all write it down for future reference. This is where the diagram (attached) and your scope are worth their weight in Gold!

Anyway, simple things first! Dry joints, clean the spark gaps (always a good idea) and soldering all the dry joints and checking the wiring. The diagram is below by the way.

Put a stationary picture up (crosshatch if possible) and compare red with the other colours. The output stages are BD115, and check the outputs, the outputs and inputs of IC202 (TBA 530 I think) and the outputs of IC201 (TBA 520). I personally would change C343 and look round the LC passive networks between the two chips.

On the RGB panel, there are 2 electrolytics, C586 and C589. Change these too.

Hope this helps!

Cheers,

Steve P
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Last edited by Mike Phelan; 21st Dec 2007 at 10:51 am. Reason: Unnecessary capitals
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Old 25th Mar 2007, 8:51 pm   #3
Tazman1966
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Default Re: Philips G8 G22K551/05. Help needed.

Hello Steve.

Thanks for the suggestions and the diagram although I have a feeling that your diagram refers to the two panel type whereas mine is the the long combined panel. I notice that the output transistors are different types. Still, it's something to be going on with and at least I'm not in the dark now.

Cheers.

Tas
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Old 26th Mar 2007, 5:51 pm   #4
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Default Re: Philips G8 G22K551/05. Help needed.

I heard about a Decca Bradford which had a similar fault. C262 (470pF) in the red output emitter circuit turned out to be o/c.

Possibles in the G8 could be C7343 (10nF) or C7340 (33pF)?

Just a guess.

Great picture!
Cheers,
Brian
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Old 26th Mar 2007, 11:08 pm   #5
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Default Re: Philips G8 G22K551/05. Help needed.

Hi Brian and Steve.

Try as I might I cannot get the circuit diagram to save clearly. If I try to zoom in it just goes blocky. Maybe I need glasses or a better internet connection . I tried the tiny cap in the emitter of the red output transistor...no change but it didn't correspond with the ref number you gave Is the diagram the same for the one long panel?

Look forward to sharing your thoughts.

All the best,

Tas

PS The output transistors on my panel are BF337's not BD115's
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Old 27th Mar 2007, 8:44 am   #6
Mike Phelan
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Default Re: Philips G8 G22K551/05. Help needed.

Tas
Later G8s did have BF337s - they are interchangeable with BD115s. Could be the TBA530?

It looks like poor HF response in the red channel. Is it possible to disconnect the coupling caps between the TBA530 outputs and bases of the BF337s in the R and G channels and swap them, to prove whether the fault is in the output stage or earlier?

Next thing is colour bar genny and scope.

HTH
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Old 27th Mar 2007, 10:50 am   #7
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Default Re: Philips G8 G22K551/05. Help needed.

Hi Tas,

The circuit I referred to looks the same as supplied by Steve, although as you say the component reference numbers do seem to differ. Unfortunately I couldn't make them out either. I referred to the circuit in Mike's excellent articles in 1978 issues of "Television".

Frustrating when manufacturers do this during a long production run!

Cheers,
Brian
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Old 27th Mar 2007, 10:51 am   #8
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Default Re: Philips G8 G22K551/05. Help needed.

Hi Tas
I do have the manual but it's a bit chunky (i.e. in an A4 ring binder). I'll see if I have a single panel supplement I could send you if you're still in trouble.
Glyn
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Old 27th Mar 2007, 11:04 am   #9
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Default Re: Philips G8 G22K551/05. Help needed.

Hello again (so soon...)
The output stages from first to last are quite different in design as well as numbering!
On the single PCB the capacitors are 292 (which you've changed), 298 (82pF) and 297 (1n0). A remote possibility is 308 (18pF) - though check resistor 291 (39k). Luckily you have two other channels to swap with!
If you need a TBA 530 there's bound to be one here.
Look on the bright side, you could have the original panel with that legendary discrete component version of the TBA!
Good luck! If you want a scan of the circuit, PM me your e-mail address so I can send you a hi-res version.
Glyn
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Old 1st Apr 2007, 9:32 pm   #10
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Default Re: Philips G8 G22K551/05. Help needed.

Hello Brian, Glyn, Steve, Mike P, Michael M and of course Mikey B.

Ta-da!!! Good news - the Philips is fixed. I was starting to lose any hope of fixing it and started to even think that it may be the CRT loading the red output channel in some weird way but no and the lesson to be learnt is read your meter correctly. I think maybe I should wear my glasses more often! In addition to what I’d already done and using the manual very kindly lent to me from Michael Maurice and the scan of thee diagram from Glyn, I swapped over the coupling caps C298 with C318, no change….C297 with C317, no change. Now what, the IC? No! Although I had already checked the resistors in the output stage I thought I had nothing to lose by going over them again and on checking R291 it read 380k. I had mistakenly read this as 38k at first on my DMM. What a dunce! On piggy backing two 82k resistors, the LF response in the red was back to normal and initial thoughts that the red gun was lazy were dispelled as you can see in the attached photos.

Just a complete set up of the grey scale including the DC levels which were miles from 145V was all that was needed in that section.

Earlier on I had gone over some rather dodgy looking joints on the convergence panel as the red green verticals seemed to jump out every now and again but was now annoyed to see that the fault was back again. Just as I started to prod about they corrected themselves again….good grief! After some poking about I found that the fault could be made to come and go by wiggling the wires to the green static convergence coil around the tube neck. I thought that would be that….not so. It appeared that there is some sort of intermittency in the coil but wedging a thin sliver of wood has cured it hurrah.

I gave the cabinet a good clean up and scrubbed the grille and knobs clean and it now looks great as you can see. The LOPT looks very new indeed and the CRT has either been changed late in its life or has not seen much use as it is great – no flaring or problems with the grey scale so what a great set. Now all I have to do is convince SWMBO that it can stay in the dining room as it is at the moment!

All the best to you all and thanks,

Tas
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Old 2nd Apr 2007, 8:20 am   #11
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Default Re: Philips G8 G22K551/05. Help needed.

Well done Taz, I have very fond memoroies of the G8, it being the first set I got when I bought my house.

The set was donated to me, because the previous owner had an engineer out 3 times to fix a frame fault, when he couldn't, they gave it to me.

I fixed it in 10 minutes, the screws holding the frame O/P transistors on also act as a connection to the collector. They were loose.

I kept the set for about 3 - 4 years and sold it for £60.

The reason I sold it was because I got a nearly new B & O stereo set, the one with the 30AX tube.

In 1990, I sold it and got myself a B & O LX2802, which we still have.

I'm glad I was able to help you out Taz, I look forward to seeing it in the flesh.

Regards

Michael
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Old 2nd Apr 2007, 1:18 pm   #12
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Default Re: Philips G8 G22K551/05. Help needed.

Hi
Glad to be of help - especially when the end result's as fine as that! And I must admit I've rarely seen such good convergence....

Glyn
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Old 2nd Apr 2007, 1:33 pm   #13
Tazman1966
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Default Re: Philips G8 G22K551/05. Help needed.

Hello again.

Thanks once again for all your help and your very kind comments. I think it must have been lots of playing around with our Invicta (Pye) 693 convergence practising on that set that got the convergence so good

All the best to you all.

Tas

PS See you later Michael with the return of your manual.
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