Restoration of an ITT-KB model SV041 (VC100 chassis)

[dazzlevision]

Hello,

I was given this 20" set many years ago and have only recently got around to restoring it. The ITT-KB price list of December 1969, shows this model costing £71 15s 0p (retail).

The date stamp on the cabinet is 25th August 1969, the year BBC1 and ITV moved over to UHF 625 colour (in November). This chassis is clearly a single standardised version of the preceding VC51/52/53 series of 405/625 “hand wired” chassis that ITT-KB made much of in their advertising and publicity literature!

I think I can safely say that no other UK manufacturer offered a hand wired chassis construction UHF/625 only monochrome TV; they were all based on printed circuit construction. Of course, ITT soon moved on to PCB construction with their rather nice VC200 series, which I believe was based on the design of their German sister company Standard Elektrik Lorenz (“ITT Schaub Lorenz”).

The Philips/Mullard AT6382/40 four push button UHF tuner is basically the same as used in the preceding dual standard range, but with the addition of an IF preamplifier PCB (VMK10) to make up for the (625) IF gain provided of the VHF tuner’s PCF805 mixer stage in the dual standard version.

ITT did make a VHF/625 version of the VC100, designated VC100/2, for use with VHF/625 communal distributions systems. The UHF tuner was replaced by a rotary turret valve VHF type.

The top of the main chassis looks, at first glance, much the same as its dual standard predecessors but upon closer inspection, you can see that there are a few less IF cans and no 405 contrast or 405 width controls.

When you look at the underside of the main chassis, the absence of the long 405/625 slider type of system switch is obvious, together with quite a few other components.

The main chassis is in good condition, not badly corroded. A light dusting out was all that was required.

As a matter of course, I replace all the mixed or paper dielectric capacitors in the line output stage with modern polyester or polypropylene types, to ensure correct operation and avoid any extra stress on the line output transformer.

Fortunately, by 1969, a lot of the previously short lived “dodgy” types of capacitor and resistor had given way to Mullard C296 “mustard Polyester film and Iskra carbon film resistors (the ones with the cream coloured body). However, there are still plenty of carbon composition resistors from Erie and Morganite and I replaced the usual suspects, such as the frame output pentode cathode bias resistor and several high value ones in the set width and boost HT circuitry.

Again, by 1969, ITT were using modern synthetic encapsulation materials for the two LOPT windings and the LOPT has proved to be reliable after several hours of running.

As you can see from the pictures, the set displays a very satisfactory picture on its original Mullard A50-120W/R CRT.

The cabinet needs a bit of work. I’m not sure what has caused the many small white streaks on the teak veneer. Maybe it just needs some teak oil applied?

Regards,

Dazzlevision

[Tazman1966]

Very nice Dave. You mentioned a VC200 - this was one of many different sets I had as a young teenager. The styling was very similar to this VC100. It too worked very well indeed. I sold it in the end to a mate for twenty quid for his bedroom. Bargain eh?!!

[Welsh Anorak]

Hi
I've never seen one of these - I assumed the single standard sets were all the VC200 series which was like a mini-CVC5.
That small preamp looks suspiciously like the one fitted to its big brother, the CVC2.
It's interesting how the development of ITT's mono sets proceeded from the VC1 to the VC100 while keeping the family resemblance. Does yours still use a PL36? If so that must have been the very last outing for the valve.
It looks nice - I expect a good rub down with fine steel wool and some Danish oil will bring the cabinet back.
Glyn

[dazzlevision]

Hello Glyn,

Yes, the VC100 IF preamp is similar to the one used in the CVC2 but I think there will be a few differences due to the fact the main VC100 chassis uses a valve 1st IF amp stage (EF183), whereas the CVC2 is a transistor. If you look at the picture carefully, the PCB has screen printing and component holes for slightly different versions.

The VC100 does use a PL36, see: http://85.92.85.233/forum/forum/showthread.php?t=41542

I shall try your suggestion in order to renovate the cabinet finish. Is Danish oil the same as Teak oil?

Regards,

Daz

[FERNSEH]

In the sixties and seventies I had a large number of the KB VC1,2,3,4 and 51/2TV sets on hire but only one VC100.
Most of the sets were branded as RGD, later KB and ITT-KB. The RGD sets were supplied from another TV dealer in Newcastle. It made sense to for him to supply me with TV sets at trade price, the more sets he sold, then better quantity discounts could be had.
Back to the VC100. If the circuit diagram is to hand it will be interesting to see how AGC is applied (if it is) to the first transistor in the UHF tuner.
The question is: is the RF amplifier transistor part of the AGC system or is it supplied from a fixed bias?
It always poses problems for the designer when mixing transistor and valve technologies in the same circuit.

DFWB.

[Hybrid tellies]

That's a nice looking set, and the tube looks very bright as well. I take it they dropped mean level AGC for sync tipped AGC. I know I RBM did this with the single standard version of the A640 chassis.

[Focus Diode]

What a nice rare set you have there! I've never seen one until the photos. Certainly much simpler without the VHF 405 circuitry. I don't think many were produced, rapidly succeeded by the VC200 chassis. Come to think of it I've not seen one of these either!

Certainly unique being a UK 625-line set with a PL36 line output valve.

Cheers,
Brian

[dazzlevision]

Originally Posted by FERNSEH

Back to the VC100. If the circuit diagram is to hand it will be interesting to see how AGC is applied (if it is) to the first transistor in the UHF tuner.
The question is: is the RF amplifier transistor part of the AGC system or is it supplied from a fixed bias?
It always poses problems for the designer when mixing transistor and valve technologies in the same circuit.

Hello,

There is a BC108 tuner AGC interface transistor stage on the main chassis (see picture - look below the large yellow "Plessey TCC Supamold" capacitor).

The VC100's main AGC system is identical to the dual standard version, so the BC109 stage only applies AGC to the UHF tuner's RF amplifier stage when the main IF stip's gain has been turned right down (i.e. only on very strong signals).

In answer to "Hybrid Tellies" question, the vision AGC system is still mean level and not gated/sync tip.

Regards,

Dazzlevision

[cmjones01]

That looks like the ultimate TV set for long-term reliability - modern components built on a metal chassis! No PCB to go crispy and fall apart, and no leaky capacitors. Very nice. Should last for ever.

Chris

[Heatercathodeshort]

Quite a rare receiver. I didn't sell many of these as they were always on 'allocation' from ITT who always had a full order book. [Thorn 1500's and RBM single standard mono were the popular receivers of the 1970 period.] Very well made and it was with some sadness on removing the back from the first delivery of the VC200 series. As it turned out it was quite a reliable model. I have a good example in my collection. Happy Days! John.

[dazzlevision]

Originally Posted by Heatercathodeshort

Very well made and it was with some sadness on removing the back from the first delivery of the VC200 series. Happy Days! John.

Hello John,

I'm not quite sure what you mean. We're you disappointed with the VC200 or the VC100?

Regards,

Daz

[ntscuser]

Originally Posted by dazzlevision

I think I can safely say that no other UK manufacturer offered a hand wired chassis construction UHF/625 only monochrome TV; they were all based on printed circuit construction.

I think they made the only hard-wired colour chassis to be sold in the UK as well?

[FERNSEH]

The VC100 was the last of a line of Kolster-Brandes Footscray UK designed TV sets dating back to 1948 with the CV40.
The VC1 dual-standard chassis was introduced in late 1962.
All the subsequent models from 1970 on are of SEL Lorenz origin. Starting in the UK with the VC200 and CVC5 colour TV.
The 1976 CVC20 and CVC32 series might be UK designed however.

DFWB.

[dazzlevision]

Originally Posted by ntscuser

I think they made the only hard-wired colour chassis to be sold in the UK as well?

Yes, the CVC1 dual standard and CVC2 single standard chassis.

[FERNSEH]

A follow up to my last post. The VC100 was the last true Kolster-Brandes design. The CVC20 CTV might have been designed in Britain, however, there was another that might have been designed and made in Britain, the excellent CVC40 colour TV of 1980.

DFWB.

[Hybrid tellies]

I think the VC100 has to be a unique and rare set. Not only the only UK S/S 625 line set not to use a pcb but being the only UK 625 S/S set to use an all valve chassis, apart from the tuner and IF pre amp, of course. Or its certainly the only UK 625 S/S set to use a valved IF stage.

[dazzlevision]

Hello Simon,

In fact the single standard Decca MS2000 series did use valves in the vision IF strip but an IC for sound IF and detection and an MJE340 for audio output! The UHF tuner also contained an IF preamp stage. Not one of Decca's better efforts IMHO.

Daz.

[Heatercathodeshort]

Similarities can be seen in the VC100 and the 1949 12" KB EV30 I brought back to life recently. There is no doubt who the VC100's daddy was. John.

[Hybrid tellies]

Originally Posted by dazzlevision

In fact the single standard Decca MS2000 series did use valves in the vision IF strip but an IC for sound IF and detection and an MJE340 for audio output! The UHF tuner also contained an IF preamp stage. Not one of Decca's better efforts IMHO.

I never saw that Decca chassis, what a weird line up, I only saw the hybrid Decca single standard mono set which bore more resemblance to the Baird hybrid dual standard chassis. I have still got my ITT/KB VC205 which is in very good condition it just needs the frame fault sorting and it will be perfect. Cabinet style very similar to your VC100.

[Studio263]

Originally Posted by Hybrid tellies

Not only the only UK S/S 625 line set not to use a pcb but being the only UK 625 S/S set to use an all valve chassis...

I think I can see another transistor in the under chassis view, at the bottom on a tag strip near a blue electrolytic. I don't have the diagram to hand, what does it do?