PIL - Colour fringing

[FERNSEH]

GEC-McMichael C2089 series of television receivers are equipped with a Hitachi chassis using 560EGB22 and 510VSB22 CRTs. From the service manual information about the purity adjustments on these PIL tubes.

DFWB.

[Nuvistor]

Thanks David.

I knew there was at least one Hitachi PIL crt that was setup has explained in the GEC instructions.
I don’t know if the CTP 213 set uses a similar set up or the scan coils are fixed when manufacturered.

I think the advice about leaving well alone is the best.

[Maarten]

Despite the lack of specific convergence instructions, it's often possible to converge such a set better, but you will need to study and practice instructions for similar tubes and possibly have to use permalloy assy's from scrap monitors or trinitron sets.

Edit: the two posts above also mention instructions for similar tubes. I think we're all on the same track here.

[Welsh Anorak]

From experience I don't think you'll improve on the existing setup. If you can, select a red raster and if it's not blotchy the purity's OK. Converging a tube on a picture is virtually impossible. Early sets with real controls you could twiddle are capable of excellent results and can be better than they were on leaving the factory as forum members have proved (hi Tas!). However the early PIL tubes were always something of a compromise to set up. I won't be the only one to have thought I could improve on the settings and many hours later realising the tube was at the limits of its tolerance and I was getting nowhere. If you must adjust things, make sure you mark the rings first as you may well need to return it to where it was.

[Pfraser]

Originally Posted by 19Seventy7

Hi,

I don’t just rely on the set being switched off for some time. This is just one of the things I do beforehand. When I did have the back off, i’d never touch the CRT for my sake, and its own sake. I have only had the back off once with power applied to the set as I had to see what happened to the screen. I followed the hand-in-the-pocket rule, rubber soled shoes, too.

I’d think that there is more steps to take before i get my hands in a set again, but i’m not to sure of what to do, and if i can do them (discharging - I don’t know how to do that) Looking back to when i first opened it up, I realise how much more I should’ve done, I guess I was lucky that I didnt get shocked.

Don’t worry, I haven’t taken this the wrong way at all. I’d much rather be told what to do and what not to when it comes to something like this, again for my sake and the set in question.

Thank you for your concerns, and also for your help! Again - I really appreciate it!

The hand in pocket is a wise procedure. The rubber soled shoes sound good too.

Re. discharging: I'm not a qualified engineer myself, just a former engineers' assistant (in radio) and a lapsed tinkerer. It would be best for you to get further advice from a better source than myself, ideally an engineer near you who either restores vintage TVs or used to be in the trade.

Or could other members here help?

You may find some TV servicing guides from the relevant era at your local library. If it hasn't been closed, that is!

There's a servicing guide by Eugene Trundle, a well-regarded author, on Amazon:
https://www.amazon.co.uk/gp/offer-li...3189576&sr=1-3

If you're interested in technical information generally, there are old issues of the magazine 'Television' on http://www.americanradiohistory.com

Loads of other technical documents on that site. It's a goldmine!

Have fun!

[hans]

I once had a good set with a defective PIL-tube. I couldn't get a correct replacement. I had a tube where the yoke had different impedance but the "glass" was the same. I tore off the yokes and swapped them. I put the yoke against the wedges and the picture was perfect. I might have been lucky...

[19Seventy7]

Originally Posted by Maarten

it's often possible to converge such a set better

Would it be possible, if you had the time and patience to do so, but get an almost perfect convergence, if not perfect? Of course I don't know the full ins and outs, but I'd have thought if you could adjust the positioning of the DY/Scan coils, couldn't you get perfect convergence?

Originally Posted by Welsh Anorak

From experience I don't think you'll improve on the existing setup. If you can, select a red raster and if it's not blotchy the purity's OK. Converging a tube on a picture is virtually impossible.However the early PIL tubes were always something of a compromise to set up. If you must adjust things, make sure you mark the rings first as you may well need to return it to where it was.

As I said, I did make the slight improvement by adjusting the brightness, colour and contrast and toning them down equally - which is probably better for the set, anyway.
The purity seems to be OK. I was watching Film 4, and the bright red ident was solid, I didn't notice any blotches, that's the closest I can get to a solid Red, green or blue, until tomorrow.
Of course it's not too much of an issue as the colour fringing isn't noticeable when on a full screen, but when something has the black bars down the sides and a graphic, like BBC, or ITV is when it's noticeable, but of course, that's not the focal point.


I think I'll take other people's advice and leave it alone, it's good enough as it is, I'm just being a little OCD with it, after all.

Thanks

Originally Posted by Pfraser

You may find some TV servicing guides from the relevant era at your local library. If it hasn't been closed, that is!

There's a servicing guide by Eugene Trundle, a well-regarded author, on Amazon:
https://www.amazon.co.uk/gp/offer-li...3189576&sr=1-3

If you're interested in technical information generally, there are old issues of the magazine 'Television' on http://www.americanradiohistory.com

Loads of other technical documents on that site. It's a goldmine!

I'll have to pop in tomorrow or something to see if they have any (It hasn't been closed down - yet)

I'll have a look at the links and have a read, thanks for linking them!

Thank you for your help, It's appreciated!

[simpsons]

I have found the static and dynamic set up instructions for pre converged PIL tubes.

In order to give you as much information as possible, I will need to scan from several documents; no problem just takes a little time.

In respect of the wedges, these are unlikely to have sagged, it could be the CRT is being driven harder to compensate for reduced emission or just that the original alignment was a question of compromise.

You will though need a cross hatch picture before any adjustments are made because,as stated earlier, trial and error is a recipe for disaster.

Chris

There are lots of "TV Test Pattern Download"s on the internet, simply burn to a DVD and play.

[19Seventy7]

Originally Posted by simpsons

In order to give you as much information as possible, I will need to scan from several documents; no problem just takes a little time.

In respect of the wedges, these are unlikely to have sagged, it could be the CRT is being driven harder to compensate for reduced emission or just that the original alignment was a question of compromise.

You will though need a cross hatch picture before any adjustments are made because,as stated earlier, trial and error is a recipe for disaster.

Chris

Hi,

Are you sure, I don't want to cause any trouble for you. I'm very grateful but I don't want to put you out in any way. Of course, i don't know how the set performed back in the 70s when it was new, so i cannot compare it. It's very bright when the brightness is turned all the way up, so it doesn't seem to reduced emission, or not a great deal anyway. But this is my guess.


I will have to find some blank DVDs, as Merlinmaxwell said, to burn onto from the internet.

There is no rush for the instructions, as i will need to get the DVDs from somewhere. (I've been looking around for a while and cannot find any?? Will probably have to order some online)

Thank you for your help, i really appreciate it!

As an aside, I do remember a good delta tube and convergence circuits could be aligned to within one phosphor dot and straight and level. Took ages to do and was rather satisfying.

[19Seventy7]

I bet it's very satisfying when it's perfectly aligned, with the nature of CRTs. I hope I can improve mine, if even slightly.

Thanks

[Sideband]

Originally Posted by hans

I once had a good set with a defective PIL-tube. I couldn't get a correct replacement. I had a tube where the yoke had different impedance but the "glass" was the same. I tore off the yokes and swapped them. I put the yoke against the wedges and the picture was perfect. I might have been lucky...

It could be done....we used to sell a lot of refurbished sets and we also saved good tubes from scrappers. We have swapped scan coils over from one tube to another with very good results. Others just wouldn't give acceptable convergence. Mainly 30AX types though rather than 20AX types.

[hans]

The 20 AX had to be converged and was "fully adjustable". I used to swap these tubes in the Telefunken sets with Philips tubes. The Telefunken and Philips tubes had different yokes. I swapped the yokes and adjusted them up. Didn't take long set these up and get a good result.

[Welsh Anorak]

You could often get surprisingly good results swapping yokes. Very often 30AX types that had been regunned came back with convergence rings added. Results were often mediocre, though, as a good regun wouldn't need them.
I used to swap yokes from those Orion 14" TVs - the ones with the wedges that ate through the copper wire and damaged the winding beyond repair. I had a load of broken Philips tubes and with some adjustment they could be made to work.

[Maarten]

Originally Posted by Sideband

It could be done....we used to sell a lot of refurbished sets and we also saved good tubes from scrappers. We have swapped scan coils over from one tube to another with very good results. Others just wouldn't give acceptable convergence. Mainly 30AX types though rather than 20AX types.

Since the 30AX tube had integral multipole magnets, they were mated with their yoke during the final stage of the production process in the tube factory, before magnetising the multipole (20AX tubes came with separate yokes and external multipole rings).

This also explains that reguns sometimes came with external multipole magnets, as the integral multipole would have been part of the gun.

[simpsons]

Attached are instructions for adjusting static and dynamic convergence of a PIL CRT similar to the one used in the Hitachi CTP213.

The use of a cross hatch is preferred but you might be able to use the Freeview Test Card, a wide screen Test Card F, as described in the sticky note "Displaying a test card on Freeview".

You will note that the dynamic (yoke) adjustments described adjusts the position of the red/blue convergence at the crt circumference. To make this easy, for this prceedure, the green video output is disabled.

I am not famiiliar with the inside of the Hitachi and so you you will need to either remove the "green" video by disconnecting the video out Tr852 on the crt base, turn down Green Background R859, having noted its position or short the base to emitter connection on this transistor.

Whilst, quite correctly, attention has been drawn to the high voltage on the yoke, it was after all adjusted during manufacture by a human being. I wear cotton gardening gloves when doing this, take note of the connections and keep my hands clear of them.

Good luck

Chris

Instead of turning off guns you could use coloured glasses.

[julie_m]

If you can get hold of a working ZX Spectrum or BBC Micro, I could easily recreate my old "convergence test" program in an emulator and post the BASIC here. It was necessarily fairly quick to type in.

[19Seventy7]

Originally Posted by simpsons

Attached are instructions for adjusting static and dynamic convergence of a PIL CRT similar to the one used in the Hitachi CTP213.

The use of a cross hatch is preferred but you might be able to use the Freeview Test Card, a wide screen Test Card F, as described in the sticky note "Displaying a test card on Freeview".

You will note that the dynamic (yoke) adjustments described adjusts the position of the red/blue convergence at the crt circumference. To make this easy, for this prceedure, the green video output is disabled.

I am not famiiliar with the inside of the Hitachi and so you you will need to either remove the "green" video by disconnecting the video out Tr852 on the crt base, turn down Green Background R859, having noted its position or short the base to emitter connection on this transistor.

Whilst, quite correctly, attention has been drawn to the high voltage on the yoke, it was after all adjusted during manufacture by a human being. I wear cotton gardening gloves when doing this, take note of the connections and keep my hands clear of them.

Good luck

Chris

If you can get hold of a working ZX Spectrum or BBC Micro, I could easily recreate my old "convergence test" program in an emulator and post the BASIC here. It was necessarily fairly quick to type in.

Hi,

Thank you so much for attaching the instructions, I shall get to reading right away! I'll have to find a suitable pattern, as I have a "YouView" box and cannot get Test Card F on it, unfortunately. However, if I could take up Julie's offer of the BASIC programme, please? I'd be grateful as I could use "Beeb Emulator" to programme it in and I'll get a suitable adaptor/cable to connect my PC to the TV.

I was thinking about wearing gloves, myself actually. Would dish washing gloves be okay, being thick-ish rubber? I could get some gardening gloves easy if need be.

Thanks all for your help! I really appreciate it!