Using a Zener Diode to drop B+

[Structo]

Hi, I was looking into some schematics where the builder used a Zener diode on the HT center tap to drop the voltage down to a manageable level before the first filter cap.
The one example was on a 18 watt amp but I amp thinking of using it on a tube rectifier circuit using a 5U4 rect.
I
I haven't measured the B+ off of the 5U4 yet so I'm not real sure what I am dealing with.

I have read about the bucking transformer method but that sounds like a bit more work than I want to do.

Is this a safe practice and do you use the stud mount type zener so the chassis acts as a heat sink?

Or also using a zener to drop filament voltage by using one on the heater wire center tap to drop it a bit.

[skyboltone]

Hey Tom.
Me again. The zener will not work on the filament circuit. There is too much diode loss. They won't allow you to just drop a few tenths. You might see if you can find a Shottkey diode that will carry the current, but I still think the drop will be too much. The other solution, as I mentioned before is a .1 ohm 5 watt resistor in series with the filaments. It really does work well and cost's 50 cents.

Paulster has a superb circuit board for regulated DC filaments off of a nominally 6.3 volt winding. I'm telling you it is a fantastic solution.

As far as the zener on the HT center tap, it's common practice and works pretty good. Select the zener wattage for the amount of voltage dropped times the total current on the HT. You may want to PM Dana, (UR2) and think about his board for voltage scaling. He can set you up for a fixed amount of voltage or adjustable. That way you get to play with the voltage and get it where you want. Now that you've invested what you have, you may as well go for it. BTW, that OT is rated at 11 watts but I've used them for 20. They will saturate pretty fast but still sound great.

[drz400]

Hi, I was looking into some schematics where the builder used a Zener diode on the HT center tap to drop the voltage down to a manageable level before the first filter cap.
The one example was on a 18 watt amp but I amp thinking of using it on a tube rectifier circuit using a 5U4 rect.
I
I haven't measured the B+ off of the 5U4 yet so I'm not real sure what I am dealing with.

I have read about the bucking transformer method but that sounds like a bit more work than I want to do.

Is this a safe practice and do you use the stud mount type zener so the chassis acts as a heat sink?

Or also using a zener to drop filament voltage by using one on the heater wire center tap to drop it a bit.

I used a chassis mount large Zener 25V on a Boogie once (by their suggestion), Expensive part and needed to be chassis mounted for heat. I have done the Buck transformer, it is actually easier than one would think.