Extreme TV bodgery!
Viewers of a nervous disposition should look away now... What you are about to witness is bodgery of the highest order, performed by a complete idiot, and should under no circumstances be attempted by anyone else!
Right, here goes! Back in 2008 I was given a little Ultra solid state TV, not sure what chassis it uses. It worked, for a very short while, with the picture snaking around the screen, I thought maybe smoothing was giving up, but then the picture began to bloom, smoke came from the LOPT, and a dark hole appeared in the picture and it faded away. So I was stuck with a telly with a duff LOPT. It wasn't one of Thorn's famous 'jelly-pot' types, it was encased in a brown resin, that was rock hard. The set still came on, and had sound, and there was some hissing in the LOPTY. A spark could be drawn through the side of the LOPT with a screwdriver! Clearly, there was still some life in it, and the insulation was a bit crappy too.
So with nothing to loose, out came the hammer! Well, after removing the overwind from the rest of the transformer, I guessed that there would be an EHT rectifier diode embedded in it somewhere, so started near the burn mark, on the flatter side of the thing. Sure enough, after a lot of bashing and bits of resin flying everywhere, I found the diode, and the end of the EHT winding.
I needed to see if indeed the transformer was working, and it was just the rectifier that had died. I needed a replacement rectifier in order to do this, a dig through the component drawers got me a handful of diodes to try, none of which worked, most went up in more smoke! It was then that I had a 'bright spark' moment... No, not from the TV! Well, not entirely... I had plenty of NOS DY86's in the valve cupboard, wouldn't take much to lash one in would it?
Well, the answer is no, it wouldn't take much to bodge one in!! So, with a few turns of EHT wire, stripped from a duff colour TV LOPT, wrapped around the core of the LOPT, and soldered directly to the pins of the valve, it was in. Time to power it up! I fired it up, and the uninsulated pins of the vale began to arc to the LOPT core, so it was switched off quick. A bit of plastic was placed between the pins and the core, and the set powered up again, this time without arcing! The valve heater lit up like a lightbulb, obviously too many turns for the heater winding, looking round the front of the set it could be seen working! There was a lot of hissing and crackling coming from the LOPT and valve, probably due to lack of insulation!
There wasn't any obvious way to make it safe to use, unfortunately! It would have been quite interesting to keep it with a valve EHT rectifier. I did still have that faulty LOPT from a colour TV kicking about, and then I thought, there must be an EHT rectifier diode in that, and it would more than likely stand up to the voltage of a black and white telly just fine! So out came the hammer again, and the EHT diode was liberated. I connected it up, and the set worked happily with it.
I 'potted' it with clear Araldite, after taping the plastic case of the LOPT back into place, which insulated it just fine, and returned the set to safe working order, no more snapping and hissing DY86!
Ps; sorry about the fuzzy pictures, they were taken from a video again! Don't know why I didn't take any proper photo's of the valve-bodge..
Looks like you enjoyed doing that. Not something to leave switched on unattended but top marks for the lateral thinking and getting it working.
A very interesting story there Lloyd and ingenious too.
You could have used a DY51 with flying leads, but it worked out well with the diode from the other LOPT in the end.
To understand the black art of electronics is to understand witchcraft.
Bravo, anything that saves it from the recyclers has to be a good thing.Nice reliable little sets, its a 6845 fitted with the 1690 chassis and the 14" version was the 1691. I modified the latter adding video in/out for use with a Shibaden monochrome reel to reel video recorder, a late 60s early 70s machine with no tuner or modulator fitted.
I also have an extreme TV bodgery tale from the 70s. A girlfriend of mine parents had a Philips K70 which was as unreliable as hell, I was also still learning the ropes (of the trade that is) and had no contacts with detailed knowledge of this chassis. I ended up removing the Philips chassis and grafting in a Thorn 2000 retaining the K70 varicap tuning, adding AFC and pincushion correction. Cue the mob
Now that is a good bodge! It would certainly have confused any TV repair guy who had later been called out to look at it!