The Tripler Trick

[Laurdys]

How many KV's do you expect at the CRT?

about 10kv

[glowinganode]

You might need to play around with the value of the coupling cap for optimum output. Make sure you use a HV rated cap, around 2KV dc.
Rob.

[Billy T]

Originally Posted by Danny

Hi the overwind has been removed and it was connected directly to the line output anode . the lopt has since failed on the primary so have given up for now. Danny

The primary will go s/c as quick as look at you if you let the peak volts at the line-output anode get too high. We never had valve CTV in NZ, but I used the tripler trick often on rental monochrome sets and for impecunious cash clients (no guarantees).

To avoid destroying the Loptx you have to start off with a fairly large tuning cap at the anode and slowly reduce the value in stages while monitoring the EHT. Either that or use a variac to bring up the input volts and adjust the tuning cap value until the mains AC input volts and output EHT are compatible.

If the pix was a little under-scanned at optimum EHT, rather than risk destroying the loptx, some judicious variation in the S-correction capacitor value plus linearity tweaking would often produce a fully scanned pix with no visible non-linearity on program material. At its worst it was nowhere near as bad as some stock-standard Murphy sets we had, apparently linearity was not in that designer's dictionary.

With Philips loptx, particularly the EN67804, we could safely run the EHT up to 17.5kV and got some really excellent results with bright and pin-sharp pix, and reliability as well.

Cheers

Billy

[murphyv310]

Hi Billy.
Most Lopt's prior to 110 degree tubes were untuned, In fact i believe the Bush TV22 was possibly the firsrt here and others came a lot later, While I agree on adjusting the tuning cap, the LOPT should be tuned to the correct frequency rather than making the picture fit.
In effect though you are damping the line output by strapping a cap to deck from the anode of the line o/p valve.
Any tuning cap should be altered by ringing the lopt after the removal of the overwind, and the EHT adjusted by the addition of a bleeder network to feed the tripler, assuming its too high.
I have never distroyed a LOPT running it minus the overwind.
Cheers
Trevor

To ring the lopt you need to know if it has 3rd or 5th harmonic tuning this can be done via audio signal genny and you should be able to see the peak quite clearly, at this time you can alter the tuning cap to get resonance at the correct frequency.
As I have already said though only the later ones are tuned, and many sets dont have an "S" correction cap again more to do with 110 degree tubes