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+150V DC Vacuum Tube Regulated Power Supply?
+150V DC Vacuum Tube Regulated Power Supply?
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Old 25th May 2018, 03:20 PM   #11
kward is offline kward  United States
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Also don't forget to bias up your pass tube filaments to the output voltage.

I think I would also consider biasing up the 6SL7 filaments. Since the pass tube filament circuit is biased at a different voltage than the 6SL7 filament circuit, it means needing separate filament secondaries. You might be able to "split the difference" so both heater-cathode voltage specs for both tube types are within tolerance, but I think that's a short cut measure. I would use separate filament circuits and bias each independently.
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Old 25th May 2018, 04:31 PM   #12
GoatGuy is offline GoatGuy  United States
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I'll make no bones about it: I like “sand-state” regulators for the simplicity of not having to deal with a significantly “raised cathode”. And the fact that unless they're thermally and/or electrically abused, they'll basically never “give up the ghost”.

Emitter follower (per Sodacose) or source followers (MOSFET, same service) do the job well. It is often a decent idea to have a back flow diode across the sand-state device so that if (like when "turning it off") there's more B+ on the output side than on the power transformer side, there is a way to safely bleed off the reversed potential.
Spend a nickel, save a buck.
Also, if you're willing to have a couple of sandy crystals working for you, then you can also implement either a slow-turn-on reference voltage, or a simple RC+transistor comparator delay of 15 seconds or so; makes for nice for the downwind vacuum tube amplifier.

Contrary to the advise of […] I prefer choosing higher henries than lower DC resistance when choosing random chokes for power supply purposes from my parts box. IF the power dissipation is within reason. Remember your friend: P = IR, so with a DC resistance of 141 Ω, a pass current of 110 mA (your numbers), then
P = IR
P = 0.11 A 141 Ω
P → 1.7 W

E = IR
E = 0.11 A 141 Ω
E → 15.5 volts
Not exactly an egg-fryer in dissipation! And the DC voltage drop is only 15.5 volts. Being “before the regulator”, the voltage drop is a GOOD thing. For Free.

Gotta run.
Goats to milk!
Cheese to make!

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Old 25th May 2018, 05:19 PM   #13
Merlinb is offline Merlinb  United Kingdom
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150V was a standard voltage for military equipment so you'll find a few such regulators in the NAVAER handbook of preferred circuits Part 1
Handbook Preferred Circuits Navy Aeronautical Electronic Equipment : National Bureau of Standards : Free Download, Borrow, and Streaming : Internet Archive
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Old 25th May 2018, 06:41 PM   #14
kodabmx is offline kodabmx  Canada
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I guess I'm old fashioned, I use non regulated power with more than 2200uF of capacity Gives a solid 150VDC from a 120V transformer.
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Old 25th May 2018, 07:04 PM   #15
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Sodacose View Post
Here's a simple hybrid that I did recently with 0D3 and a MOSFET:

Attachment 683054

You'd still have sockets left over. Maybe use a tube rectifier or a couple damper diodes to use them up. Or build the above for each channel?

edit: IRF820 was what I used, I think. Ignore the transistor symbol.
Yes, I'd use two of these, one per channel. I have plenty of IRF820 and IRF840. I even have a few heatsinks. Two 0D3s glowing would be doubly fun. They also don't make heat, which is a plus. I'd still have room for a 5V4 rectifier or something like that, if I really needed to fill that last octal socket. But I don't, really.

I also have a couple of vintage 500VCT 150mA transformers with 6.3V winding (but no 5V winding). I could use a choke input filter and get about +215VDC raw B+, then use this source follower-plus-0D3 after that, right? Okay, some questions about this:

- How much ripple rejection should I see from this circuit? If I set it up with +215VDC at the input with a 1.414VAC 120Hz sine wave riding on the DC. I see +145VDC at the output, but with only about -20dB of attenuation of that 120Hz sine wave. It does perform some voltage stabilization; it keeps the output voltage within +/-1VDC as the input voltage is varied +/-20VDC.

- This is with the IRF820 dissipating 3.5 watts, so a heatsink will be required. [Edit: It's labeled "Pdiss" on the schematic, but of course that should be Ddiss. Was thinking tubes again. Oops.]

Does this attached schematic look right?
--

Quote:
Originally Posted by Merlinb View Post
150V was a standard voltage for military equipment so you'll find a few such regulators in the NAVAER handbook of preferred circuits Part 1
Handbook Preferred Circuits Navy Aeronautical Electronic Equipment : National Bureau of Standards : Free Download, Borrow, and Streaming : Internet Archive
Hey Merlin! That's very helpful indeed. Preferred Circuit No. 1 fills the bill. The only problem is the need for that negative supply. I guess I can figure something out. Thanks for this; I'll be looking into it.
Attached Images
File Type: png Junkbox_IRF820-0D3_voltage_stabilizer_00.png (16.1 KB, 240 views)

Last edited by rongon; 25th May 2018 at 07:10 PM.
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Old 25th May 2018, 07:36 PM   #16
Sodacose is offline Sodacose  United States
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Looks correct! You might add protective zener to the source/gate or diode across the FET like GoatGuy mentioned, but what you have works.

The ripple rejection on this isn't as good as a feedback regulator like the series/pass ones earlier in the thread. Maybe a CCS feeding the VR is worth a sim?
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Old 25th May 2018, 08:12 PM   #17
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Would the CCS replace R2 (4.7k 5W) in the schematic?
(Edit: If you meant just replace the whole thing with a series CCS and shunt 0D3, then no, that doesn't work nearly as well. Much higher levels of pwr supply ripple pass through.)

Last edited by rongon; 25th May 2018 at 08:20 PM.
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Old 25th May 2018, 08:16 PM   #18
GoatGuy is offline GoatGuy  United States
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Here's circuit I'd use, incorporating the advice, and showing markedly improved ripple rejection.
Attached Images
File Type: jpg IFR-820-regulator-150-VDC.jpg (54.7 KB, 237 views)
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Old 25th May 2018, 08:30 PM   #19
Lingwendil is online now Lingwendil  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Sodacose View Post
Here's a simple hybrid that I did recently with 0D3 and a MOSFET:

Attachment 683054
Since these types of circuits work so well, I decided to work up a PCB with the option to run a stack of six Zener diodes as a voltage reference, and a pot/resistor in series across them for some voltage adjustment functionality. I've breadboard six so far, and wanted a nice board to be able to have them easily lashed up for future builds. I'm even working on a negative version. Assuming you used six 51 volt Zeners (like the 1N5262) you get just around ~300 volts out with an IRF820. Could easily run wire off board to a VR tube to use as a reference

Click the image to open in full size.

Click the image to open in full size.


It's still a rough draft, but if anyone has anything to suggest, go ahead and swing by my flea amp thread and let me know what you think. I'm wanting them to be a nice option for the DIY community.


(Note- I'm not actively selling anything at this time, simply throwing out the idea, and taking suggestions for anyone who has something constructive to add!)




Also, GoatGuy, check your PM inbox lol
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Old 25th May 2018, 08:34 PM   #20
Sodacose is offline Sodacose  United States
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Quote:
Originally Posted by rongon View Post
Would the CCS replace R2 (4.7k 5W) in the schematic?
(Edit: If you meant just replace the whole thing with a series CCS and shunt 0D3, then no, that doesn't work nearly as well. Much higher levels of pwr supply ripple pass through.)
Right, I was referring to replacing R2 but maintaining the MOSFET pass device.

Lingwendil's board looks good too. I recently made some boards that use an LR8 in place of the zener string (yet to stuff and test though). Only problem is these don't glow
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