CTV [Sticky] 1974 20" Ferguson 3C03; Thorn 4000 ; Super Rare

Ah, that's the telly with the "Cat Shelf" on the front! I saw one in a shop in York, once, where it was to be repaired, or failing that, it was a very similar set.  The chap who ran the shop called it the cat shelf model on account of the owner's cat sitting on the ledge in front of the CRT, chasing footballers across the screen, or race cars, horses, birds, or anything that took Puskin's attention!

Posted by: @crustytv

I've now bought the 3C03 as well...

I had a gut feeling that you might, and a wise move too if I may say. 👍 

This is excellent news because not only has the set found a good home, you will be able to establish the working condition of both the set's now.

The 3C03 should be here tomorrow, hopefully I can then get started on the HMV.

Midnight and the 3C03 (4000) has just been delivered by Shiply. 😲 Collected and delivered in the same day. For now it's sitting in the storeroom, more tomorrow. Time for bed.😴

It looks very nice and very modern for it's time.

A plastic polish may help reduce the marks on top, but all in good time.

It’s come up quite nicely! Looks very well packed in the cabinet, and the whole set looks tiny once it’s on your bench!

if you decide the cabinet damage is too much you could always get some sticky backed plastic to cover it!! The stuff sold for vinyl wrapping cars works quite well!

 Regards 

Lloyd 

Posted by: @lloyd

Looks very well packed in the cabinet,

Apparently one of its failings, the 110 delta toroidal scan coils among other things generating a lot of heat from the vertical deflection. It has to supply 6A p-p output and consumes 40W in doing so. Not such a problem on the huge HMV 2726 cabinet, but on the 3C03 very much so. The tripler on the 4K failed not so much due to it being inferior, but the silly place it was located, heat being what killed it. I'm proposing to fit a fan to try and address that on both sets

Posted by: @lloyd

and the whole set looks tiny once it’s on your bench!

Yes, I'm glad I took the decision this time last tear to go for a very big bench. Even the HMV 2726 console, G6 and Thorn 2000 console, go on there with ease. Lifting them up though is an entirely different matter.

For the vertical module, most of the thick film units and the two output transistors can be replaced by a single LM1875.The vertical OP is just a power op amp with current feedback.

You can simulate the circuit in LTSpice to make sure it works the way it should before you build the hardware. And it's quite cheap to get prototype PCBs made in China these days. You just need the PCB cad software and someone with the skills.

Hi Ian, don't suppose any of your compatriots on the Oz forums have a spare vertical deflection PCB tucked away?

Posted by: @crustytv

Apparently one of its failings, the 110 delta toroidal scan coils among other things generating a lot of heat from the vertical deflection. It has to supply 6A p-p output and consumes 40W in doing so. Not such a problem on the huge HMV cabinet. The tripler on the 4K failed not so much due to it being inferior, but the silly place it was located, heat being what killed it. I'm proposing to fit a fan to try and address that on both sets.

Bit OTT, but a Peltier heat pump would at least be silent...

https://uk.rs-online.com/web/c/hvac-fans-thermal-management/electronics-heating-cooling-components/peltier-modules/

Posted by: @irob2345

For the vertical module, most of the thick film units and the two output transistors can be replaced by a single LM1875.The vertical OP is just a power op amp with current feedback.

I had the idea of possibly using the circuit from the TX10 Mk1 as some models were fitted with CRTs having toroidal field scan coils. I couldn’t see an easy way to implement N/S correct which is required on the 4000, the circuit used a TDA1044 field osc/output IC driving a couple of power transistors.

@jayceebee Well I know the LM1875 will do the job because I've used it to replace whole vertical amps when the transistors were unobtainable. My late mum's Pye T30C comes to mind, it ran for 10 years with the LM1875, and would probably still be running had it not been in that flooded garage. Made a horrible mess of the cabinet, which just turned to mush.

Actually, the T29 and T30 (we're talking Aussie Pyes here, nothing like any you've seen) used a very simple circuit to derive the NS correction, with discrete components. It worked well. I must dig up the circuit.

The T30C had a Toshiba 110 degree wide neck self-converging CRT that required no NS correction. Not so for the earlier models with the Toshiba RIS tubes.

OK! I found it and scanned it.

Q503 to Q508 and all associated parts can be replaced by the LM1875, although with this CRT you'd lose top and bottom vertical convergence adjustments. Q509, L501 and the parts around it provide the NS pincushion. The other 3 transistors to the right are for the side pincushion, using the Philips-style East-West Modulator circuit. But that's not part of the 4000 vertical module.

Pretty simple really. L501 is a centre-tapped adjustable pot core about 22mm diameter. The adjustment tilted the correction. Might have to experiment with that one.

With this level of simplicity you can see why these sets were rock-solid reliable. Most common fault was the connectors.

After I'd shut down for the night I realised that the book that had the Pye T29 would also have the AWA 4KA.

Sure enough, it did.

I've attached a scan of the appropriate page.

There is enough information to link the Pye circuit into the 4000. It looks eminently do-able.

If you can source the connectors the rest should be easy.

I have access to PCB design software and can easily get prototype PCBs made up.  If somebody can sort out a schematic I'd be happy to help.

Martin

Hi Martin,

Here is the circuit for the 4000 series vertical deflection. The PCB layout and the two thick film units that are also on the master PCB. Including a photo of the actual PCB.

Some internals of the 3C03, for your perusal. There would initially appear to be fewer repairs to this, than the HMV. The focus unit looks to have had a problem with the 5kV lead-out, it's taped up for insulation and some sheathing added to the chassis. Hope the unit is not duff! The focus unit is dated 51st week of 1976, replacement or original? As these TVs came out in 73/74 I would hazard a guess at replacement.

Seeing close-up's of some of the components, it has a continental look to it... ERO capacitors for one thing and the good quality resistors.