Electronics > Projects, Designs, and Technical Stuff
It looks for me as stupid schematic (Oldtimers welcome!)
001:
--- Quote from: ArthurDent on September 29, 2019, 09:24:41 pm ---
--- Quote from: 001 on September 29, 2019, 04:37:36 pm ---Check ebay toy here https://www.ebay.com.au/itm/100-300V-DC-High-Voltage-Power-Supply-PSU-for-6P6-6N6-EL34-Tube-Preamp-Amplifier-/332777814374
It looks stupid for me
Why they bias transistor this way? :-// Is it good schematic?
--- End quote ---
The basics of the supply above are very similar to a supply I made decades ago using all tubes.
--- End quote ---
Have You some links to this project?
ArthurDent:
oo1 - "Have You some links to this project?"
Here's a post I made in another thread a while ago and that's basically all there is. Keep in mind I made this supply about 40 years ago and had to redraw the schematic recently. Like I said, it is very similar to the transistor version shown above
"When I made my 150-250VDC 100ma power supply I was trying to use parts I had in my junk box while still making a good regulated power supply. The case was from a military surplus magnetic amplifier and the case was the only part of that unit that was useful to me. I didn’t have one transformer that would work but I did have 2 identical smaller transformers that would fit perfectly in the back part of the case and give me the voltages and current I was looking for if I wired the HV windings in parallel. I did buy new meters and to give you an idea how old this is, I bought them from Lafayette Radio Electronics (kind of like Radio Shack) who went out of business in 1981! The circuit I used was one I modified from one I saw in an HP manual from about that time period.
The voltmeter was modified to have an expanded range by using a 150V Zener and using a series resistor to make the meter really read 0-100 volts and then marking the dial to read 150-250 volts. If you’re wondering why there is a 1N4007 between the output and the meter, that is to prevent meter damage if the output somehow dropped to zero, effectively putting 150 volts on the meter in the reverse direction. The milliamp meter is the same basic movement as the voltmeter with the series resistor removed and a shunt resistor in parallel and the scale marked in Ma.
One of the transformers 6.3 volt windings is used for the heater supply for the tubes and not referenced to ground to eliminate any heater to cathode voltage problems. The other 6.3 volt winding is connected to terminals on the back of the case to power tube heaters in devices I might be constructing.
The capacitor from the supply output to the pot wiper eliminates the D.C. component but sends the outputs a.c. ripple voltage unattenuated to the error amplifier. Instead of using a 5651 gas reference tube like the original design I used an 82 volt Zener that gets its supply voltage from the regulated output. It feeds the reference voltage to the error amplifier through the triode section of the 6U8A used as a cathode follower. Where I didn’t use the 5651, the triode might not be needed and the Zener could probably supply enough current to be connected between the error amplifier cathode and ground, then I could replace the 6U8A with just a 6AU6 pentode. The 6BX7 has a maximum plate voltage rating of 600VDC so it is used within its specs.
The HV rectified output from the two 1N4007 diodes is connected to the two 40 mfd electrolytics through a 10 ohm resistor that lessens the surge current and is also an emergency fuse. The two deck power switch is three position non-shorting and in the off and standby positions there is a 6.8K resistor connected from the two 40 mfd electrolytics to ground to safely discharge them. This capacitor has a 500 VDC rating because with no load there is about 450 volts on this capacitor. When the switch is in the operate position the 6.8K drain resistor is switched off and the HV center tap is connected to ground and the output is present."
T3sl4co1l:
No current limiting (aside from the impedance of the poor tube itself), and it'll explode if ever you should accidentally short the output. But yeah, that's about all you need for a basic dumb regulator.
Tim
Audioguru again:
I am also an oldtimer (74). Why are you playing with antique tooobs that soon wear out? I sold my tooobs tuner and amplifier about 55 years ago and the solid state replacements still work fine today.
ArthurDent:
T3sl4co1l - "No current limiting (aside from the impedance of the poor tube itself), and it'll explode if ever you should accidentally short the output."
As I said, I made that supply 40 years ago and I'm still waiting for the 6BX7 tube to explode, maybe in 50 years.:-DD I've never ever seen a tube explode but I have seen some tube plates glow bright red.
There is both a primary fuse and a 10 ohm resistor as protection in case you missed that. I also stated I wanted to build a supply out of parts I had in my junk box and I didn't intend to make a complicated supply that would have all the bells and whistles that my programmable precision bench supplies have today. You should be pleased I even put meters on the supply! 8)
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