Regulated Power Supply using 6550

[Ketje]

Originally Posted by denny9167

So I should probably stick with the transistor,and only use half of the 12AT7,and use separate windings? I won't need to worry about lifting my heaters either?

Yes you can do that,or use any other triode with 5mA/V (more or less).
The heaters can be left floating but some prefer connecting them to the cathode.
Don't forget,you need a neg.tension (stable) as a reference voltage.
The neg.out in the original is wrong,is connected to the base of the transistor,has to be the emitter.
Mona

[denny9167]

I don't really need the negative bias supply, as I will
Be just using this for a general bench power supply.
I could go ahead and add it for testing power amp curcuits using fixed bias.

[denny9167]

I think I've decided to go a different route,I found an article in AudioXpress on regulated supplies and found one that's a better performer,and has been tested. I've re-drawn the schematic for expresspcb. The author didn't mention lifting the heater on the pass tube,so I will do that if it's needed.

[tomchr]

In the original schematic, it looks like V2 (EC92) is supposed to work as the error amplifier. However, it doesn't have any voltage reference and will always operate with a positive Vgk. Not what you want...

The 0~-70 V output isn't regulated either. I honestly don't see the point of the emitter follower T2. Why would you take the supply output off the base but run the meter off of the lower impedance emitter?

There are better ways to build tube power supplies. Have a look at Designing Power Supplies for Tube Amplifiers by Blencowe for example.

You can also look at this thread: High Voltage Regulators (Maida or zener)
I went through quite a few regulator topologies before landing on the two I have on my website.

For a variable supply, I use a high-voltage transformer fed from a variac. Works great. No thermals to worry about. No regulation either, but good enough for most experiments.

~Tom

[tomchr]

Sorry... Didn't see Post #13 until I after I'd written my post above.

Originally Posted by denny9167

I think I've decided to go a different route,I found an article in AudioXpress on regulated supplies and found one that's a better performer,and has been tested.

With the dual differential pair, it's a very "semiconductor" approach to a tube regulator. I don't see any reason it shouldn't work, though.

Originally Posted by denny9167

I've re-drawn the schematic for expresspcb. The author didn't mention lifting the heater on the pass tube,so I will do that if it's needed.

You'll need to check the data sheet for your pass tube of choice to figure that out. You'll have to select a voltage that ensures the pass tube doesn't have its Vhk violated at any output voltage.

~Tom

[grommeteer]

To use the 12AT7 at 6.3V you need to connect Pins 4&5, not 4&9. In your schematic half of the heater is shorted.

[denny9167]

Originally Posted by grommeteer

To use the 12AT7 at 6.3V you need to connect Pins 4&5, not 4&9. In your schematic half of the heater is shorted.

I've worked on several Dynaco Fm3's and it has a mixture of
6 and 12volt tubes, this is I believe a parallel connection.

[SY]

Pin 4 and 5 short together, 6V between 4/5 and pin 9.

[denny9167]

Originally Posted by tomchr

In the original schematic, it looks like V2 (EC92) is supposed to work as the error amplifier. However, it doesn't have any voltage reference and will always operate with a positive Vgk. Not what you want...

The 0~-70 V output isn't regulated either. I honestly don't see the point of the emitter follower T2. Why would you take the supply output off the base but run the meter off of the lower impedance emitter?

There are better ways to build tube power supplies. Have a look at Designing Power Supplies for Tube Amplifiers by Blencowe for example.

You can also look at this thread: High Voltage Regulators (Maida or zener)
I went through quite a few regulator topologies before landing on the two I have on my website.

For a variable supply, I use a high-voltage transformer fed from a variac. Works great. No thermals to worry about. No regulation either, but good enough for most experiments.

~Tom

Thanks for the suggestions, I'm glad you mentioned the book, I bought that
Book a few months back for my iBooks app, I haven't finished it yet
But it is a marvelously well written book, as soon as I get my new iPad I will try and finish it, it's hard to read on an iPhone!! I also have Morgan Jones' book.
On Kindle that is an in depth read.

[grommeteer]

In the later schematic it says 6V3 heater for both double triodes and the tubes are in parallel. That's ok. But connecting pin 4&9 on each tube is not ok. Pins 4&5 connected together are one pole of the 6V3 heater, pin9 is the other.