Dynatron CTV63 problem

[Snarf81]

Hi all,
Yesterday I acquired the above set and it needs some adjustment.

The sharpness/focus needs to be tweaked as there's a sort of blurry halo effect around the edge of the screen and the rest of the picture isnt very sharp, and also when images with brightness appear on the screen such as the sky, white banners etc the white seems to glare and flash very badly, especially when a scene changes from outside to indoors then the picture jumps a bit.

I'm no expert on these old tv's at all, so if anyone knows whereabouts inside the tv the adjustment pots are I'd be very grateful.

It's a Philips G11 chassis apparently.

Many thanks
Richard

[ben]

Start by checking the various supplies to the line , RGB and frame stages are rock solid.

[Snarf81]

Thanks for the reply Ben.
I'll delve into it on the weekend and let you know.

Thanks again
Richard.

[Welsh Anorak]

To expand on Ben's good advice, check the HT is correct at the top left fuse (on the print side) of the power board - should be 157V (I think) and shouldn't vary with picture content. Then move to the IF panel and check the 12V rail stays constant - the regulator is on a heatsink on its own. G11s did tend to have the characteristic of picture flutter - in fact there was a Television article on modifying the beam limiter to reduce this effect. What CRT have you got in there? Could be a little soft by now, though use will certainly help it.
Cool cat, by the way...

[Snarf81]

Hi Glyn,

Thanks for the reply and information.

I have no idea what CRT is in there, but I'll have the back off later today and have a careful nose around in there. I'll take some photos of inside too and post them on here.

The cat is cool, haha, his name is Zippy ��

[Welsh Anorak]

The CRT is a Mullard 20AX type and will be A66-500X (early version) or A66-510X which was a modified type. They enjoyed quite a long life, so hopefully you have a low voltage somewhere. I'm assuming it's a 26" set - the 22" versions were prefixed A56.
As a matter of interest, the G11 was one of the few sets to use the 20" 20AX tube that had the EHT connector at the top right. Most other manufacturers used a 90-degree 20" CRT.

[Snarf81]

I've not had the time to take the back off yet, but another thing I've noticed is that the picture is askew. I've taken a picture of it.
It's very noticeable when watching a widescreen programme as the black bars at the top and bottom are at an angle.

[Snarf81]

Hi Glyn.
It's a 22" screen.

I have to admit that I know absolutely nothing about these old crt tv's. I only got it because it to use with my old vcrs, and it was only a few miles away to pick up.

I've had it turned on all day so far just to let everything warm up or whatever it does as it was stored in a shed and I don't know if the previous owner had done any work on it etc.

Thanks again
Richard.

[toshiba tony]

What signal are you feeding into it. I notice a 3v22 on top. I had forgotten how grotty the pictures were until I dragged one out of hiding. But yes, the picture is tilted which will be corrected by a twist of the scan coils. I always liked G11 pictures, more than the TX10, both of which I had out on rental. But I have to admit G11's were less reliable. Check your main smoothing cap, if it's red change it, or hammer the rivets, URGENT!

[Maarten]

The picture looks a bit bent instead of really askew. Any strong magnets around?

[Welsh Anorak]

I remember some 20AX CRTs did have loose scan coils. With the set switched off, you should be able to see that they're off centre, and can be twisted back into place.
Perhaps you might be puzzled by Tony's advice as you're new to the game. TV off and unplugged, with the back off, swing open the right circuit 'door' as you look from the back (latch on the top). Look at the lower board and there's a big round capacitor at the top centre - it's the only big one on the board. If it's red or green it needs changing pronto. A dull pale blue is OK. If you're unsure, paste a photo.

[toshiba tony]

Message for Glyn, yes, I'd forgotten about the green ones, fond memories of them though. I'm sure he will sort it.

[Snarf81]

Hi.
Thanks for the replies both.

I'm not at home tonight (Tv is unplugged), so tomorrow I will have the back off and take some photos and post them on here.

The old Baird 8922 on top isn't connected to the tv yet as there is a problem with picture output on it. It's just for decoration at the moment. Haha.
I've got a humax freeview hd box connected to an ITT vhs and then the vhs connected via rf as there is no a/v input on the tv.

Regarding scan coils....I have no idea what they look like. I'll Google it and see if there is a photo online of them and I shall check the capacitor as a matter of urgency.

Thank you for your help with this.
I really appreciate it!

I'll post some photos of the insides of the set tomorrow afternoon.

Thanks again.

Richard

[dazzlevision]

This is what a G11 chassis looks like with the back cover removed. The scan coils are the big cream coloured plastic assembly that is pushed right up against the "cone" of the picture tube (cathode ray tube - Mullard 20AX type). If you look at the top of the scan coils, there is a "V" notch in the plastic, which should be aligned with a small raised mark on the CRT's cone glass above the notch. The clamping ring that secures the scan coils in place on the neck of the CRT is near the board that pushes onto the neck of the CRT (with the cream plastic cover and warning label - over the copper tracks side) in the first photo. Don't tighten the clamp up to tightly, else the CRT's neck glass might crack - disaster!

The power board is the bottom right hand one (coloured red in my set). The second photo shows the component side and the big capacitor in question (top centre) is sleeved with blue sleeping in my set (and so NOT the unreliable type). The unreliable type is usually branded PYE.

The third photo shows the CRT with scan coils and the neck circuit board removed and you can see the scan coils alignment mark on the cone - immediately underneath the thick white plastic (degaussing coil).

[Welsh Anorak]

That's comprehensive!
Just a word of warning. Removing the CRT base (with the white cover and warning label) should be done VERY carefully if you've not done this before. It needs to come off straight - don't bend either way more than a fraction. It's a tight fit, and it would be good (though perhaps not practical) to find an old junk TV and practice with that first.

[Snarf81]

Wow.
Thanks Glyn.

I shall try to be extra careful whilst I look inside, and I'll post photos of the insides tomorrow.

Thanks again.

Richard.

[jayceebee]

Be aware of the warnings printed on the CRT base. When switched on the metal work of the G11 chassis is at half mains potential and is a shock hazard, if you don't posses an isolation transformer do not switch the set on with the back removed. Best to unplug it altogether.



John

[Snarf81]

Hi John.

Thanks for the heads up. I won't have it plugged in at all.

Cheers
Richard.

[jayceebee]

Have a look at the sticky at the top of this section and if you have the means burn yourself a copy of the downloadable test card DVD. You could use your 8922 or any VCR to modulate the output of a DVD player onto a UHF channel to feed into the TV.

Looking at a test card will give you a better idea what's going on and what needs adjusting.

John.

[Snarf81]

Hi all.

I've just had the back of the set (the first time ever I've looked inside a crt tv)

I'll paste the photos that I took as I don't really know what I'm looking at.

Thanks again for all your help.

Richard.