So, for a laugh I thought I'd try the tripler from a 2006 14" colour TV I had lying around. Ignore the vertical height, that was the line hold going off whack.
The width gives an idea of the lack of kV here. To paraphrase Jaws, "You're gonna need a bigger tripler..." I think the Mullard Panoramic needs something like 19kV.
Wayne, contact Malc Scott (ex rediffusion) via the pm system. Malc has loads of doublers which will do the trick. see here. Agree with Andrew, a CTV tripler as we know it, is going to be give way too much EHT.
Malc like us, is based in the N.E about 5-miles from me.
It does appear that the DY802 rectifier diode will quite happily supply 20kV as long as the incoming EHT doesn't go above 30kV, although the closer to 20kV the better. I may end up making my own doubler as I've learned a lot about them over the past few days.
I'm going to use a "sacrificial" 00s TV with the EHT deactivated for experiments.
So, for a laugh I thought I'd try the tripler from a 2006 14" colour TV I had lying around. Ignore the vertical height, that was the line hold going off whack.
The width gives an idea of the lack of kV here. To paraphrase Jaws, "You're gonna need a bigger tripler..." I think the Mullard Panoramic needs something like 19kV.
Be very careful here. Assuming that the width is low because the EHT is low is wrong. As EHT rises, more energy is required to deflect the beam and quite often an indicator of high EHT is a small, bright picture.
@wayned No, not at all. The amount of energy required to deflect the beam falls with EHT - this is why a set with a failing EHT rectifier not only produces a dim picture, but one that is often greatly over-scanned and "blooms" (i.e. expands) when you turn the brightness up.
As EHT rises, the amount of energy required to deflect the electron beam increases - this is why line output stages got more and more powerful as EHT rose in line with producing brighter images, as well as the need to deflect the beam over ever-wider angles. If you go right back into TV history, some pre-war sets just needed a medium power triode to deflect the beam across the tube face as the EHT was low and the scanning angle narrow.
Attempting to rewind the outer winding. Unfortunately I have no idea how many windings this requires but I do know the original had an inductance of 1.7 Henries and the resistance was 119.5 Ohms.
Even if it doesn't reach the required 19kV for the EHT at the very least this should give enough that I can add a doubler in.
@pye625 ah no. It's not going so well here either.
Actually, you might be able to help me, what is the inner winding on the secondary for? I've just managed to break one of the wires on it. I know it doesn't do anything when in 405 line mode. The schematic isn't exactly clear on it.
@pye625 Hmm... looks like I'll have to rewind that too.
Good luck there 👍
Take care of your primary section because it is highly likely that an overwind and tuning winding from an A774 chassis LOPT will fit and work perfectly, if all else fails. That is what I did with mine.
I now need a primary section to get mine working again lol !
To understand the black art of electronics is to understand witchcraft. Andrew.
So, LOPT secondary rewind take 2. Luckily I've managed to find out the number of turns from someone who repaired these back in the day. The inner winding is 22 turns:
After epoxying the two halves of the "bobbin" together, a good winding of 3M Temflex:
A makeshift bobbin winder:
Works surprisingly well!
The outer winding requires 980 turns according to the chap mentioned above. That means approximately 17 layers. I'm doing one layer, taking a really close photo and then counting the turns and I'm getting between 52-58 turns per layer.
Also note that I've made the inner winding connections exit the bobbin at the opposite end to the outer winding.
