Here's something you don't see everyday! A Rediffusion MK4, 22" colour TV with teletext and remote control. It also has an AV input on the back, with a switch hidden behind a flip down panel that also conceals the headphone socket. Unlike most sets of the time, the channel display is on-screen, not on a separate LED display. Tuning the set is done by little push buttons hidden behind another flip-down panel, which come up on screen telling you what UHF channel each preset is tuned to. All the other controls are behind this panel too, the only non-hidden control being the power switch. There are also 2 green LED's on the front panel, one to tell you the remote signal is being received, and one to tell you the set is muted. The remote control is almost the size of a brick! it uses a 9 volt battery (PP3), and has all the controls for teletext, as well as the other user pre-settable controls.
I came across this set at the NVCF, left out in the car park not far from my car, with a note on it saying 'free to a home', it didn't specify that it needed to be a good home, so I thought I'd better take drastic action, and put it in the car... It did look like it was about to rain, and chipboard doesn't fair well in the rain, better to move it out of the possible rain, or it would turn to a horrible pile of mush and ruin the car park! I did ask 2 guys nearby if they knew anything about the set being there, but they didn't know who left it! I thought I'd not be able to get any picture on it at all when I saw it, as I thought all Rediffusion sets were cable only sets that required some odd signal, but closer inspection revealed it was a UHF set, so would be fine with nothing more than a modulator.On getting it home, I was hit with the reality that there was no room in the workshop for it! Nor was there for any of the days purchases...
I opened the set up in the kitchen, just to see what was in it, to my surprise, I found the mains lead coiled up inside, with a plug fitted. I also noticed some odd green goop on one of the PCB's, and some strange white powdery stuff growing on all the little black pots. I eventually got the set to the workshop, where it lived in the doorway on it's side. I checked for shorts on the mains lead, and plugged it in. When I finally got enough courage (or should I say distance between me and the set!) I hit the switch, there was a 'POP' and a 'BEEP' from the speaker and a crackle of static, and it came to life! Once the CRT had warmed up there was some very out of focus snow on the screen. Once the freeview box was connected it was obvious there was a problem with the picture focus, much like a Bush TV22 with a low emission EY51, the picture would bloom when the brightness was turned up. With the back off I wound the focus control from end to end, but could not focus the picture. I decided the set was a dud, so left it alone for a while. Then I saw mention on UKVRRR about a MK4 with a duff tripler, causing bad focus, this all sounded familiar! I then kept an eye out for a new tripler on ebay, but never found one, mostly because I didn't really know what I was looking for... I did come across someone selling a load of Rediffusion remote controls, so I bought one, and asked if he happened to have any triplers for the same set, to my surprise, he said yes, he had one left!
With the new tripler and remote, I set about making some space to work on the set. Off came the back, unclipped the timebase panel, and removed the screws holding in the tripler. De-soldered all the wires after making sure the new tripler had the same connections, one was missing, from one end of the focus pot. It looked like the piece of wire from here had broken off long ago, there was just enough pad left at the end of the track to attach a new wire to. The new tripler was then fitted to the set, and that funny looking white powder brushed off the pots. I left the green goop in situ since it seemed fairly solid after poking it with a stick. I powered the set up whilst standing well back! This time when it came on the EHT rustle sounded a bit more violent than previously, and once the tube had warmed up a nice bright and not too out of focus picture had appeared. A quick tweak of the focus control bought a good sharp picture. The back was re-fitted and the set tested for a good few hours with no more problems.
One remaining thing to do is to find a way of testing the teletext decoder, as when text is selected it does some funny things! random stuff appears whenever the signal is interrupted, either by turning off the modulator, or selecting the test pattern. I did try to get some off a VHS tape, which I had managed previously, even though most of it was garbled, you could actually get some info from it. it would certainly be enough just to test it anyway. This TV also has an interesting party-trick, when the remote is used to turn off the TV, it operates a solenoid somewhere behind the main power switch, which unlatches it. On an old worn set like this, the power switch cap can come a little loose, and the effect of the rather violent unlatching of the power switch causes the button cap to get fired out the front of the set! I had hours of fun with this...
I haven't cleaned the set out yet, it's a bit disgusting, but since it's now being packed up ready for a house move, it'll have to wait until I get a new workshop! This will be the last TV repair I do in my current workshop!
Thanks for reading