Background Information

The backstory of this receiver starts around 1977/78, with RBM (Rank Bush Murphy) sending this teletext receiver to the Rediffusion factory in the N.E. of England, where it was to be evaluated as a potential rental set. I’ve no idea how that evaluation went, or indeed if Rediffusion ever adopted it for their rental fleet.

The history of this particular TV is vague, basically it was never returned to RBM and ended up with a Rediffusion employee who had the foresight to preserve it. The receiver was subsequently wrapped up and put in his parent’s loft around 1983/1984, where it remained, until this year, 40-years later, a swap was done for a receiver I had, and this set then came into my collection. A smart move on my friend’s part was placing it in layers of cling film, as you can see the cabinet is immaculate, it’s an absolute time capsule waiting to be seen working once again.

The Rank Arena AC6333, not the Bush BC6333

The model is AC6333 and states T12A chassis on the rear label, but to all intents and purposes it looks identical to a Z718. Looking in those manuals, all the models listed in there are BC6XXX (Bush) or MCXXXX (Murphy), nothing relating to the AC6333. I did find mention of the AC6333 in the September 1977 Television, in the Teletopics section. They only mention evaluation being in the London area, so intriguing one made it up to the N.E.

Television September 1977

The Rank Arena Model AC6333 television receiver, which incorporates Teletext decoder,is now available to dealers throughout the UK,following initial market evaluation in the London area. Though Rank do not quote recommended prices, they comment that sets should be available at a price below £800.

I then subsequently found out some information from a member of our VRAT forum, who worked for an RBM dealership.  He believes the dealership he worked for were the first in the country to receive the production version (BC6333) of these TVs’s, and even recalls being asked to go to the showroom to set up the television to demonstrate it to the staff. He also thinks it was priced at around £900! That is an astronomical sum for the late 1970s.

Ultrasonic Remote Control of Receiver and Teletext

This set was missing its ultrasonic remote control, I had a plan in place to build one from scratch as I had the RRI Service engineer’s guide to Teletext. Within that book was to be found all the details required to do so, parts, circuit diagrams, frequencies and even a picture, this could all be used to enable the recreation.

However, this has proved unnecessary as the same member above, who worked for the RBM dealership, miraculously had in his possession the Rank ultrasonic remote. Not the Bush version, which was slightly different. If I never believed in fate before, I certainly do now!

Below shows the two versions, Bush on the left and Rank on the right. Below the next photo is an extract from the official RRI Teletext Guide.

The Bush version for some reason also had a physical split between top and bottom control.  I can’t say why they decided to do this, as it must have added to production cost, the extra bar across the middle adding complication. Personally, I much prefer the look of the Rank remote over the Bush. Just for clarity, the Bush remote shown below belongs to Michael Dranfeild, he also has this TV, the BC6333 in his collection.

The frequencies used by the ultrasonic remote

Tifax interface and remote Circuits

Tifax Decoder

Below is the standard issue 4 of the Tifax decoder.

Below is a sneak peek at the Tifax decoder that is strapped to the signals panel of this receiver. IC4 is unusual as it is not the standard IC which you see above in the production decoder. I’m wondering, is that an EPROM, if so it would be interesting to read the data within and back it up.

Missing Ultrasonic Remote Sourced

This will be a challenge, but one I’m certainly up for, I recall working on my first Thorn 9000 a Multibroadcast badged 773. That had been stored in a metal shed and had sweated away for years. Nearly all the silicon had suffered, as you can see from the link, especially the IC’s, but I eventually got that working and it gives a wonderful picture.

The IC may need changing, I will have to see, I don’t have any in stock and a quick look online reveals they pretty scarce. The tracks are badly corroded, but I believe they can be repaired, but I’m not sure how conductive the board as become. L1 looks OK, but we’ll have to see. My initial concern is the transducer, it’s heavily corroded, my gut is saying that is component looks toast!

Making a start on restoring the remote

Main board released from ribbon cables, and it’s hideous! They’re ready to clean, here are some pictures to document the process. Next ones will be after the PCB clean, and we shall then see what remains of traces. I’ll also try to measure L1, as I fear for the winding.

Both sides of the board cleaned, the traces seem to be OK with just the mask having flaked. A lot of components solder joints appear non-conductive even after cleaning. For example, I cannot read the left-hand resistors R3 -R7 top or bottom, these should all read 220K. The other side is OK. I shall remove all solder and reflow, will also replace all the resistors on the left side. The oscillator coil L1 seems OK giving ohms reading. The IC as expected, had experienced corrosion to its legs, continuity checked all lead-outs top-side to solder pad print-side, leg 13 seems troublesome, not sure if this is the solder pad. Hopefully, after removing all solder and reflowing, it all might improve.

The Keyboard PCB

The keyboard PCB, many of these keys are not going to function, needs a good clean-up. This is going to be a long process as each brass key actuator, will need to be carefully removed as the obvious battery leakage has leached under all the pads. As captain Oates once stated, ” ….. I may be sometime”, although unlike that instance I plan to be back.

To be continued…

Day two remote restoration

Removal of the crusty, acid encrusted solder to outer black ribbon connection, also repair of destroyed trace using track repair tape, and re-tin of traces.

I also swapped the position of the brass contact pad from button “Mute”, to the button “zero” pad, the sides of the original brass “zero” had disintegrated due to the acid, thus loosing rigidity. Zero will get much more use than mute ever will.

Removal of the old solder to the 12 pads for the ribbon cable was very difficult. The battery acid had changed the composition of the solder, it appeared non-conductive, very resistant to heat, and like a rock (see pic 3). Thankfully, with lots of flux, the Metcal could supply enough heat to dislodge it.

All the solder was removed as it has been infected with the battery acid, and its composition seems to have changed to rock! All the left hand side resistors are in poor condition. I also think the ic socket should be replaced, pin 14 of the ic does not have continuity through to the print-side. This could be due to solder, socket or i.c

The battery acid really did take its toll. As suspected, the IC socket had been damaged, corrosion through the pins. I’ve also lost two pads, 2 & 12. Getting the rock off, I hesitate to call it solder, was more like shifting excrement from a blanket. What’s worse, rat pee or battery acid? Both seem to change the surface of solder & traces.

After a couple of clean cycles in the ultrasonic tank, most of the resist had dissolved away in the cleaning fluid. I was left with little choice but to just tin all the traces. I’m looking into buying UV cure green mask that you can get on Amazon, I shall wait to if the remote functions, then decide.

New transducer installed, and I was not happy with the SAA1024, considering the damage to everything caused by the acid, the legs may have leached into the package. I therefore installed the M1024B5 from the same remote the transducer came from, I believe to be equivalent. Also, new IC socket, new 220K 1/2W 5% resistors, the rest were OK.

Remote Restore to working Order

TV now on the Bench

And so it begins…….The TV resurrection

First things first, Michael Dranfield has produced a fantastic video on the Z718 chassis, a really essential watch if, like me, you’ve not tackled this Bush chassis before.

Here are the detailed shots of the internals, another chassis baptism for me, I’ve never worked on one of these before.

The internals are absolutely minging, everything is caked in black muck, I wonder if this was due to coal fires. If I remember rightly, Malc mentioned he rented this TV out to a mate until 1984, then it was sealed in cling film before going in the loft. I doubt this is from 45-years in the loft as it was sealed, more like crud sealed in from 1984.

Reformed the main can on the Power unit, 7C1 & 7C2 both 300uF @ 325V and checked capacitance, both are OK.

After a clean up