A Confession

[Hagstar]

Originally Posted by tom.j.fla

Which tripler did you use? A D.C. input and D.C. ground will go BOOM! .

I used an NTE 523...hmmm...this has a capacitor in ground lead.....appears identical to 500A.

John H.

[Hagstar]

Here's the diagram of the NTE523 I used, I did order a 500A replacement, actually a bit cheaper.

[Hagstar]

I did a postmortem on the tripler and it appears to have arced from the unused Focus voltage pin to the cage. I thought the distance, shrink tube, and 200K resistor in series would eliminate that risk, but.....

[Tom Albrecht]

Originally Posted by dtvmcdonald

"You may find the tripler actually works a little better than a real flyback supply. HV stability may be a bit better, for better focus stability, etc. "

For those who would accept a bit of non-originality, tucked away, there
is a simple cheap, effective panacea for focus instability: Zener diodes.
Just install a long chain of 200V Zeners from the focus pot down to ground.
I did this and it works great. I measured the correct focus voltage and
set the total Zener voltage so that the focus control was about 1/4 or 1/3 of
the way up from the bottom.

In fact I also did exactly that when I restored my CT-100 a year or two ago. A bunch of 200 V zeners in series to make a 2 kV zener. Works splendidly!

[tom.j.fla]

If using a tripler with a built in focus divider, connect a 66 meg. H.V. resistor from the pot term. to ground, puts a load on the divider gets rid of arcs and you get a bleeder resistor on the H.V. All the best, Tom

[miniman82]

I probably have a few of those laying around if you need them. Also a few 100 meg ones, left over from the photo CRT experimentation.

[Hagstar]

Originally Posted by tom.j.fla

If using a tripler with a built in focus divider, connect a 66 meg. H.V. resistor from the pot term. to ground, puts a load on the divider gets rid of arcs and you get a bleeder resistor on the H.V. All the best, Tom

Thanks Tom. I believe you but how does this prevent arcs? Hair of the dog principle ? Bleeder resistor value principle I grasp....
EDIT - I see you must mean it would prevent arcing from the focus pin by providing a safe super high resistance path.

John H.

[Electronic M]

Originally Posted by Hagstar

Thanks Tom. I believe you but how does this prevent arcs? Hair of the dog principle ? Bleeder resistor value principle I grasp....
EDIT - I see you must mean it would prevent arcing from the focus pin by providing a safe super high resistance path.

John H.

Without the resistor the focus pin is at ~25KV and can arc to anything grounded within ~2-3"....With the resistor to ground that pin is at the designed value of ~4-6KV and probably won't arc more half an inch... That pin is meant to be the output of a voltage divider...Take away the bottom half of the divider and things go WAY out of design spec.

[tom.j.fla]

Tom C. thank you for clearing up my comment from post #50. I do better in face to face conversion, again thanks. Now if you loose the focus network in your CTC-4 use a 25 meg or maybe 50 meg focus pot from the control pin to ground and move the focus lead to focus pin on a tripler with the divider network built in, with a ECG500A use a focus control network from a CTC63 or CTC66 instead it has the top and bottom resisters built in. All the best, Tom

[Hagstar]

HOUSTON WE HAVE STABLE HIGH VOLTAGE AGAIN. Plus no blooming etc. with brightness control changes. A million thanks to this forum. "Neutering" the tire of the flyback last weekend took some worrying. Finally I just snipped through most of it and found the end again and unwrapped another couple hundred turns, securing the end in some shrink tubing and silicone.

This time I snipped off the unused Focus pin and buried the stub in a 1/2" mound of silicone.

One day I may find that NOS flyback but at least I have a working set and less hissing or to watch out for.....

John H.

[DaveWM]

Curious, did you consider using the tripler supplied focus voltage for the set?

[Hagstar]

Originally Posted by DaveWM

Curious, did you consider using the tripler supplied focus voltage for the set?

I saved that option by leaving a stub of the pin. But I wanted to keep the set as original as possible and retain the separate focus diode.

John H.

[DaveWM]

understood. Now you need to post a pic or better a video of the working set!!

[Hagstar]

Originally Posted by DaveWM

understood. Now you need to post a pic or better a video of the working set!!

Only static convergence here so far-

http://hagstar.phanfare.com/7138833

John H.

[Hagstar]

So when I did check the high voltage with the new tripler what is it? 22 thousand volts, just like before. It's stuck on that value. Does anyone get a 25 kV out of these? Not that it seems to matter too much.

But I do have to add a bleeder to stub of the focus pin- it manages a bit of corona for a moment under the RTV blob covering it to the cage as is, have 66 meg resistor coming.

John H.