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

Have you decided which approach you’re going to take, retaining the original decoder or going RGB? The latter will be much easier to implement in my opinion and you can then sort out the tripler modifications. If all goes to plan and it works you could at a later date embark on the much more difficult option, constructing more or less everything after the delay line of the original G6 circuit. Some additional interfacing will be required, a lot of experimentation and trial and error will be needed.

Posted by: @jayceebee

Have you decided which approach you’re going to take, retaining the original decoder or going RGB?The latter will be much easier to implement in my opinion 

Not sure if I fully understand the scope of what this fully entails John, but I totally agree with you, let's go down the less complex route to start with. If we get it working, something on screen approaching a good account of itself, I'll be very pleased. As you say, the decision can then be made how to proceed thereafter, but to be honest If I get the G6 working with our mod, I'll likely leave it as I think it's highly unlikely a G6 S/S i/f will ever turn up.

With David fleshing out what needs to be done on the Tripler conversion, I'm hopeful the two projects will mean this G6 will live again. 👍 

Ok, going RGB means we’re going in addition to the signal stage we’ll need a decoder and RGB output ditching the G6 decoder with its colour difference stages. My thoughts are to use the G11 modules to drive, say a TDA3565 IC basically a simplified version of the TDA3560 feeding three output stages driving the CRT cathodes.

We’ll need a TBA120 for audio (could be left until later) and some IC to generate a sandcastle pulse for gating, blanking and clamping. All this so far should be a doddle, getting correct syncs for line and field will need experimentation. Beam limiting will need to be added but let’s see how we get on for now.

I shall attempt to get some circuit details drawn up ASAP so you can make a start.

Please note I am no designer and am not an expert at this, I used to just mend tellys so no guarantees that this isn’t going to be a total folly, I will need help from people much more knowledgeable than me for some aspects particularly syncs.

Hi John, I just checked my stores, and luckily I had just one TDA3565 (PAL Decoder) though I do have a TDA3560. Also, I have my last TBA120A (sound i/f) though I have dozens of TBA 120 variations (AS/B/S/SA/S4N/T/U) in stock. 👍 

Any idea what IC is needed to generate the sandcastle? I've got quite a large stock of various period IC's

p.s.

Without looking up the data sheets, anyone know what the variations on the TBA120 mean.

My choice for sandcastle would be TDA2576A but a number of ICs could do this. I can't remember which but one Thorn chassis generated the sandcastle pulse discretely, TX85?

Looks like a TDA2578A will do the job, I've just one of those in stock too. Hmmm this is starting to look like it was meant to be. So far so good, everything in stock here. 👍 

So far so good. The only doubt I have with the TDA2578A is it had a surprise for the unwary. Although we won't be utilising it, it has a field drive stage that just needs an external amplifier to drive the scan coils. Unless the drive stage sees some feedback back from the output stage it inhibits the drive leading to a chicken and egg situation. Caught a lot of people out that one, whether or not it affects the field blanking pulses on the sandcastle output we shall see.

Are there any specifics on delay lines using the IC PAL decoder? Sorry if that's a numpty query.

Any of the last very small glass delay lines will suffice, there are a couple of special inductors required but am sure you will have some scrap modules utilising a TDA356x from various manufacturers (K30/KT3 per chance?) which they could be obtained from. A nice big 12v 1W or better zener would be handy.

Posted by: @jayceebee

So far so good. The only doubt I have with the TDA2578A is it had a surprise for the unwary.

Yes, this will need some thought as if there is no feedback there will be no field pulses on the sandcastle. The TDA3565 will interpret this as field collapse and there will be no RGB output.

No Problem John, forget the 2578A, I have some TDA2576A, so we're OK 👍 

I also have plenty of delay lines to choose from and as for the 12V zener, that's covered too. I've BZX61 1W and for overkill we could use a 15W BZV15.

Unfortunately I've not KT3 or KT30 chassis' in stock to rob for inductors. Many tens of other manufacturers boards though.

Posted by: @jayceebee

special inductors required but am sure you will have some scrap modules utilising a TDA356x from various manufacturers

I kept this chassis, and I've never known why just have, perhaps for this very day. It uses the TDA3561A, maybe this has the inductors you reference.

5259 is an inductor, likely one of the inductors you mention?

CP90 chassis? Just the job, both delay lines, inductors, trimmer, everything you need bar the 8.86MHz crystal. 

You know I'm not going to get any sleep tonight mulling all this over in my mind 🤣 🤣 🤣 

Posted by: @jayceebee

everything you need bar the 8.86MHz crystal.

Got that covered 👍 

Posted by: @jayceebee

you know I'm not going to get any sleep tonight mulling all this over in my mind

You and me both 🤓 

Posted by: @crustytv

I'm sure with John and yourself having my back with guidance I have every chance of making a good stab at it.

Plus, you have that added advantage that neither are very far away - Perhaps not too helpful just now, but as the pandemic subsides, and lockdowns are withdrawn, if the project runs that long?

Hi Chris, I'm still searching for a G6 IF board. No luck so far.   However, I'd be still keen on the idea of using the G11 board.   A metal plate the same size as the G6 board can be used to mount the G11 PCB. The valveholders for the  PFL200 video amplifier and sync separator valve and the EF80 sync inverter can be attached to the metal plate and conventional wiring techniques employed. I've got a few tag strips for the other components.  A B10B metal chassis valveholder might be difficult to find. A PCB mount B10B valveholder might possibly be the only type available.

Till Eulenspiegel.

Hi David,

John and I have pretty much decided on our approach, that is to start simple, you could say we're adopting the KISS project methodology. We're going to utilise only the modules from the G11, not the entire board. Which means the following:-

• G11 IF/Select/Gain module
• G11 I/F detector module

Perhaps controversially to some onlookers we're also ditching colour difference due to the complications of interfacing and going for RGB drive. As a result we'll not using the G6 decoder, well for now at least. Our aim is to get something on screen without introducing too much complexity for ourselves. If we achieve this then we will consider trying reintroducing the G6 decoder but at least at this initial point we'll have a working TV to break out from.

So what else? We will be designing/creating a pluggable board that can be easily removed, so nothing is irreversible. It will employ as stated above, the G11 modules and the following:-

• TBA120 for audio.
• TDA3565 PAL Decoder IC feeding three output stages driving the CRT cathodes.
• TDA2576A to generate a sandcastle pulse for gating, blanking and clamping

All the above I have in stock, other parts like the delay lines, trimmer and inductors etc have been harvested from a CP90 chassis which employed the similar TDA35xx IC. I had the 8.86 crystal and an overkill 15w 12V zener/heat sink and pretty much everything else needed in stock. Just waiting on john to come up with the circuit now.

As I mentioned above, if we get this far and get it working, and it's a big if, then we can decide what to do next.  Do we stick with it or then build another prototype board but this time reverting to colour difference and design that next level of complexity, so we can interface with the G6 decoder.  I'm taking as if I know what I'm doing, I don't. The approach we're embarking on it gives me options and should a G6 I/F ever turn up I can easily revert to spec.

I'm taking the lead from John here but welcome yours or any other folks input as does John. What I'm concerned with is that we don't get bogged down with too many designs, I really want to keep it simple and get started asap.

What I have been hoping for David, as you mentioned earlier in the thread, is that you might have some input and theories on the way forward to converting this G6 to tripler. As I said earlier in this thread, I'm not running it with the missing cage and I want the 25kV overwind gone, they're just way too unreliable and spares are non-existent and ones that have been pulled from dead sets die soon after being installed, so one way or another it's got to go.

The Matrix board with stand-offs and parts thus far.

P.s.

Also, due to this pandemic we cannot do what would be really need to do, which is get together at my bench. Therefore, I plan to live stream, so those involved can get stuck in and see what is going on in real-time as we hopefully progress.

Posted by: @crustytv

Just waiting on john to come up with the circuit now.

 

Working on it when I can, you'll probably notice I've been actively raiding the technical library stealing other peoples ideas as I say I'm no designer. I would welcome any comments from others pointing out any pitfalls which I'm may not be seeing. As I see it interfacing suitable syncs with the existing timebases is likely going to be the hardest part and possibly getting the grid bias right on the CRT, cue famous last words 🤣 

Please be aware this will not be a direct replacement as such but any changes will be able to be restored to as it was should an original surface. For a start we need to find suitable -ve and +ve line pulses for AGC and sandcastle generation.

John, I have the full service manual for the G22K511. I've not scanned it though the cct diagrams are in the data library However, if you do require anything else I can scan individual parts required as and when required. 👍