CITAC backup batteries

[Jimmyhaflinger]

Hello,

Is it a good idea to replace 2.4v CITAC backup batteries with modern supercapacitors? (i have a bag full of 0,47F 5v supercaps)

I have a couple of sets waiting for a new CITAC battery, one is a 1978 Philips K11, the other one is a 1983 Philips KT3

[murphyv310]

Hi.
I don't think that the supercaps are such a good idea, the caps will run down quite quickly. I would stick with the battery.
Trevor

[Steve_P]

Agreed. Stick with a battery! If you can't get the right one, then pick any 3v battery and put it somewhere safe.

Cheers,

Steve P.

[Tractorfan]

Forgive my ignorance but what's a CITAC?
Cheers de Pete.

[Sideband]

Originally Posted by Tractorfan

Forgive my ignorance but what's a CITAC?
Cheers de Pete.

I think it stands for Computer Interface for Teletext and Analogue Control. Philips used the term waaayyyyy back in the 70's.



Rich.

[Welsh Anorak]

Hi there
Nothing to forgive - it stands for Computer Interface for Tuning And Control. It was developed by Philips and uses the SAB series of ICs. It is easy to spot as it uses a 1.2v back-up rechargeable battery, and could be said to be the forerunner of the now familiar clock and data analogue control interface.
As CMOS technology is used, the current consumption is small and the set keeps its memory when switched off - until the battery fails, when all tuning and analogue information is lost.
Other sets to use the CITAC syatem were the Rediffusion Mk4A, some Hitachi G7Ps and a Panasonic U4 (I think). Oddly, the batteries in these used to last much longer than in the Philips.
Strictly speaking, the KT3/K30/CTX used a VST system with a Toshiba IC, the CITAC system proper being featured in the 2A, 2B and 3A. I think Philips' CP110 television was the last to use a back-up battery, though again this used a Toshiba IC.
I suspect I'm not alone in finding it a little unnerving that a system I remember spending a good while learning about and repairing now features in Vintage Television!
Glyn

[Brian R Pateman]

Originally Posted by Welsh Anorak

I suspect I'm not alone in finding it a little unnerving that a system I remember spending a good while learning about and repairing now features in Vintage Television!
Glyn

Me too Glyn!

In fact when I saw this thread yesterday lunchtime I almost shifted it to "Modern Technology" but then I realised how old these circuits are.

I've probably got all the manual supplements for them somewhere.

The basic circuit was pretty reliable as I remember with the battery being the main source of problems. Having said that I did once manage to destroy all the chips in one set by discharging the tube to chassis with a meter lead instead of the resistor discharge lead. And it was one of my own rental sets!

Regards,

[gec2110]

The CITAC was very robust circuit
these were the good old days of common problems and easy earners

[GMB]

I think there are a number of difficulties with using capacitors to replace batteries in this kind of situation:

The capacitor voltage drops continuously whereas a battery holds up to near the bitter end. The circuit will have a minimum hold voltage and I think that may be quite close to the battery voltage.

Capacitors self discharge quite fast. I checked one spec. sheet and that example would only last a few days.

The energy storage of these capacitors is usually much less than the same sized battery.

[Welsh Anorak]

Hi
To go back to the original question, I have seen all sorts of weird and wonderful "modifications" to the original circuit with batteries hanging all over the place, rarely with any success! I think for the amount they cost it's best to stick with the original spec battery - and to check periodically for leakage as I've had that ruin several PCBs.
Glyn

[Jimmyhaflinger]

Ok, i'll stick with batteries...

I'll try to mount them off the CITAC board with a lenght of wire so that they won't ruin the PCB in case of future leakages... maybe with a coaxial wire so that it wont pick up interferences

[Jimmyhaflinger]

Originally Posted by Welsh Anorak

Hi there
Nothing to forgive - it stands for Computer Interface for Tuning And Control. It was developed by Philips and uses the SAB series of ICs. It is easy to spot as it uses a 1.2v back-up rechargeable battery, and could be said to be the forerunner of the now familiar clock and data analogue control interface.
As CMOS technology is used, the current consumption is small and the set keeps its memory when switched off - until the battery fails, when all tuning and analogue information is lost.
Other sets to use the CITAC syatem were the Rediffusion Mk4A, some Hitachi G7Ps and a Panasonic U4 (I think). Oddly, the batteries in these used to last much longer than in the Philips.
Strictly speaking, the KT3/K30/CTX used a VST system with a Toshiba IC, the CITAC system proper being featured in the 2A, 2B and 3A. I think Philips' CP110 television was the last to use a back-up battery, though again this used a Toshiba IC.
I suspect I'm not alone in finding it a little unnerving that a system I remember spending a good while learning about and repairing now features in Vintage Television!
Glyn

The philips CITAC chipset (SAB3055 and MAB8461P) was also used on many K40/KT4 sets made after 1985, earlier versions of this chassis had the Toshiba VST chip and a non-volatile memory which did without a backup battery

On continental Philips sets you can tell the kind of chipset used in a mid 80s Philips set by the front panel.

If it says "computer controlled TXT" then it has a philips CITAC chipset
If it says "super selection" then it has a Toshiba VST chipset

this was cutting edge technology for a telly back then... now it's definitely vintage technology... and is probably the last example of "interesting" TV engineering...

[Welsh Anorak]

Hi
Slightly different over here - I've never seen a 'super selection' badge on one, though 'computer controlled teletext' is common, and that usually has a 2A chassis and the SAB3037 IC.
The KT4/K40 in Britain used the MSM5840H as a micro which needed a 2.4v nicad cell - plus some white thick-film units that occasionally failed. They were never that popular here so there may have been some CITAC controlled versions - it's just I haven't seen one! All Philips sets I've seen up till the G110 used a back-up battery with the exception of the GR1-AX and NC3-R.
As you say, it was an introduction to the bus and data lines that we now take for granted.
Glyn

[Tractorfan]

Ta for the info. I left the TV trade just when solid state colour tellies were making their appearance & my boss did the technical bits while I made the tea, which is probably why I'd never heard of a CITAC.
Just a thought, if the TV in question belonged to a builder or plasterer, then why not just strap a PP9 to the back with black insulation tape?
Cheers de Pete

[Maarten]

Originally Posted by Welsh Anorak

All Philips sets I've seen up till the G110 used a back-up battery with the exception of the GR1-AX and NC3-R.
As you say, it was an introduction to the bus and data lines that we now take for granted.
Glyn

Philips 3A and late model 2B used a 24C02 EEPROM.