Ac voltage regulator

[timmy]

I’m looking to build a small simple ac voltage regulator with an input of a 6.3v filament transformer for the ac . problem is I’m looking for a voltage of .55v With the currant around the same as the transformer .60 but is there a way to put this together it has to be ac not dc. I’m not sure of what would be used and I know the dc regulators can’t be used. Maybe a triac? Anyone knows how to put something like this together please post it. I don’t know if a triac or an scr can go to that low voltage, .55v

[old_tv_nut]

What runs on .55 v ac? Does it need to be a clean sine wave?

[timmy]

Originally Posted by old_tv_nut

What runs on .55 v ac? Does it need to be a clean sine wave?

Just needs to be .55ac it is for a d5-100 crt. It’s just for the heater.

[mrjukebox160]

The spec sheet doesn't specify AC or DC. Any reason why it has to be AC?

[timmy]

Originally Posted by mrjukebox160

The spec sheet doesn't specify AC or DC. Any reason why it has to be AC?

I tried dc but it affected the clarity of the picture ac is better

[mrjukebox160]

Ah I see.

[Electronic M]

If it doesn't have to be a clean some you may be able to use TVS diodes (think Zener for AC applications), but I don't know if they go that low....ISTR from the pilot TV threads on ARF that to clamp the 3KP4 heaters at 6.3V they needed an 8.2V diode so maybe the peak VS RMS conversion might push the .55V up closer to something a TVS can do.

[Yamamaya42]

There is no easy answer for this, since this is such a odd CRT, with a weird heater voltage, most likely made to be used with a wire wrapped around a FBT, for power, ac voltage regulator circuits are rather tricky and complex to get right, one mistake a FOOM, your heater is dead.
One thing you may try is a rather hefty adjustable power resistor hooked to a 6v filament transformer and adjust the wiper up till you got the needed voltage, tricky bit will be choosing the value of the resistor.

[timmy]

Originally Posted by Yamamaya42

There is no easy answer for this, since this is such a odd CRT, with a weird heater voltage, most likely made to be used with a wire wrapped around a FBT, for power, ac voltage regulator circuits are rather tricky and complex to get right, one mistake a FOOM, your heater is dead.
One thing you may try is a rather hefty adjustable power resistor hooked to a 6v filament transformer and adjust the wiper up till you got the needed voltage, tricky bit will be choosing the value of the resistor.

I already used a resistor with a 6.3v filament transformer but the transformer got extremely hot and I did get the .55v right on but the transformer won’t last.

[timmy]

I can’t use carbon resistors because there is no real load for the resistors to work .55v is nothing I used power resistors.

[Yamamaya42]

for example, a 1K Ohm adjustable power resistor 20-50w, should not load the transformer. hook it to the far ends, and the CRT to the adjustable wiper.

[Yamamaya42]

like seen here
https://www.google.com/imgres?imgurl...MygAegUIARDVAQ

[Yamamaya42]

You are basically using the adjustable power resistor as a voltage divider, that you can set to what ever point you need to.

[timmy]

A resistor with 20-50 watt it would have to get hot I don’t see how it wouldn’t load the transformer down as I can’t take a chance with this .55v like you said boom instant burn out. The voltage reading should show me .80v before I would put it to the heater which it would drop to anywhere from .450 to .530v

[timmy]

And the heater needs the current if not it won’t work I already had the perfect.55v but had no current to work