Project [Sticky] 1969 Philips G22K511 Missing I/F & LOPT, Conversion

I don't think it's an insane idea at all, saying that though I don't know how difficult it would be! Surely it would just be a case of looking carefully at the manuals, matching up what signals go in and out, and where, and what voltages are required, pick the IF board that matches the closest, and try it. It might be that you have to make some adapters, or even cut out bits of surplus circuitry.

Best of luck with it, I'll be following with interest!

Regards,

lloyd

An interesting project. Most IF boards potentially could  be made to work with additional circuitry to invert, amplify or attenuate the available host signals, but the Achilles heel is having to fabricate a decent video amplifier and sync separator (PFL200 and EF80) as a separate block.

Probably just as difficult to locate but simpler to modify a DS version?

Rich

Posted by: @marconi_mpt4

Probably just as difficult to locate but simpler to modify a DS version?

Yes, I contacted Mike Bennett, and he is going to rummage in his loft, but he doesn't think he has an SS i/f but might a DS. Then again maybe neither. Gary is also looking for me, if these two chaps can't help, then it will be the hard graft.

It's a mad crazy insane idea....  So it has to be worth a go. 😱 

You could end up with some grey hairs though Chris !

Here's hoping a board will turn up.

Comparing DS and SS versions highlight some significant improvements such as a black level clamp around the PFL200 luma amp, and a number of resistor value changes. The brightness control circuit is different. Do you have a DS schematic, I could scan my copy if required?

Rich

In the single standard G6 the chroma part of the vision signal picked off at the collector of the second IF amplifier transistor.  Separate bandpass circuits are employed at IF before being demodulated and passed on to the decoder board. Can "E" is the chroma bandpass module.

The BRC 2000 IF board works in a similar manner.

Till Eulenspiegel.

They did the chroma / luma split like that in the K9 as well. Reason was to avoid cross-modulation with the sound because of the diode demod. Then synchronous demod chips came along and made it unnecessary.

How about using modules from a G11? The biggest problem I see is although the G6 is apparently capable of excellent colour I believe it's also very difficult to get the best performance ie it's fussy. It could be quite difficult to interface with anything but the correct IF panel and not be chasing your tail, but could be the opposite as I've no experience with it. You could go the whole hog and convert it to RGB drive until a Philips original becomes available, I don't think that would be too difficult at all by adapting some of Luke T projects from PT mag using say a TDA3565. Sandcastle pulse generator and sync interface would be required but again don't think it would be too much trouble.

Hi John, thanks for your input, its very much appreciated.

I'm not opposed to trying anything as I seriously doubt I'm ever going to find a G6 single standard I/F panel. I've contacted probably the foremost collector in this field in the UK, Mike, and he's nothing which does not bode well, if anyone was going to have one it was him. Gary is also looking, but the chances are very, very slim. Philips G6's rarely turn up on e-bay and when they do, they go for huge sums and I would not dream of buying one for parts. Also, I've certainly never seen any G6 PCB's turn up and believe me I'm always looking for and buying vinatge PCBs.

I want this single standard G6 TV working therefore, I'm more than happy to do what is necessary to get it going. What's more it will be a wonderful educational opportunity. Way beyond my solo skills to figure out though, but with yours and others guidance I'm sure it's possible. Perhaps this project will even surpass "oddJob" the Baird 8724 I did many years ago now.

I've plenty of PCBs in stock from all manner of other manufacturers and do have many G11 parts, I think I've got I/f panels, I'll have to check.

It will be good when the world gets back to normal as then we could chew the project over, one-to-one in the workshop and a brew.

Still, it should be possible remotely, and I can even live stream the work to get "real-time" input, it would certainly make for an interesting series for my channel.

I have two G11 IF's in stock 👍

Hi John, just reading your post above again. Are you saying we just use the G11 modules U400 and U600, thereby not needing to use the entire G11 IF Panel?

If that is what you're saying, that would be pretty darn cool. If so, then I have some Paxolin sheet that I could fashion to replicate the g6 I/F board shape. I could then mount it in position on the G6 chassis and attach the G11 I/F modules to it. Then hard-wire from the modules accordingly to the rest of the G6 circuitry.

Just found a NOS U400 U600 modules as well.

Yes just the modules but designing and etching a custom PCB. Get out the Dalo pen and ferric chloride

Do you know if the timebases will run? Would be worth completing the heater chain to see before embarking on what could be a time consuming and difficult project. Fitting a polo mint section of around 75ohm would make up for the missing EF80 and PFL200.

Hi John,

I've no idea, I've not run it up. Another feature of this poor TV is the lopt cage cover is missing, so nothing to stop those testicle sterilising X-rays from belching out.

I have another plan to address this, that is to remove the 25kV overwind and convert it to tripler operation. The fact the over-winds are egg-shell fragile, the cage cover missing and coupled with spares being non-existent, it makes sense to do this modification. At least I won't be worried about running it and the overwind frying as they often do or irradiating myself. I’ve no idea how to do go about doing the tripler mod, but hoping this article will provide inspiration. https://www.radios-tv.co.uk/vintage-electronics-blog-forum/convert-decca-ctv25-to-tripler/

OK EHT regulation might not be as good as the full valve derived EHT stage, but again I'm not overly bothered. As I mentioned elsewhere, some folk may baulk at the i/f and lopt proposals, but this is not such a heinous crime considering lack of spares and fragility of the overwind.  What's better, being precious about originality and having a dead display TV or a functional one that took some ingenuity to get working again? I opt for the latter, besides It'll all be reversible.

Quite agree, what's the point in having an non working but all original set with a faulty unobtainable component or working set with a minor or major change of some form. All but the most drastic of changes can be reversed if said parts turn up. Each to his own I suppose. We'd better not mention the Philips K70 I fitted with a Thorn 2000 chassis in my youth 😱 

@crustytv
Nothing wrong in my opinion in modifying a set that spares are no longer available. It may as well be working.

When this argument is raised I always think about how the trade had to keep wireless sets working in WW2 with few spares available and nearly always had to modify the sets in some way to keep the sets working.

Hi Chris, when it comes to researching a replacement IF and video board for this set you will be working close to the EHT box over long periods of time.  Much better to convert the EHT system to a tripler or at least get rid of the shunt stabiliser valve and use a 25kv EHT rectifier stick similar to the device as used in the RBM Z718. A BRC 8500 EHT tray could also be considered.

After removing the high voltage winding we've established that is not just a simple matter of connecting a tripler to the top cap of the PL509, an additional winding is required to supply an 8KV pulse to the tripler input. The Ekco CT104 in the workshop is being used for the EHT tripler experiment.  I seem to remember a coil with 100 turns will provide the 8KV we need. When it comes to the flyback pulse it's matter of volts-per-turn in these transformers.

Till Eulenspiegel.

Hi David, I was hoping you might offer some of your sage advice. 👍 Embarking on these mods to the G6 are to be honest quite daunting, but I'm sure with John and yourself having my back with guidance I have every chance of making a good stab at it. 

Matrix board has arrived to build this G6 S/S i/f. I bought two sizes one 13x25cm, one 15X20cm. Not sure which will be more appropriate, guess we will see as the project progresses. The idea is to build a prototype on the matrix board, and if we can get it working then think about getting one etched or doing that myself.