HP 711A High Voltage Tube Power Supply 

Marc, I'm not sure how the meters are mounted in the casing, but try loosening a couple (or all) of the mounting screws or bolts a bit, if applicable. You need to reduce the backplate pressure. There is probably warping in the frame of the meter causing the movement to rub against the frame/bracing. I have seen this many times on old HiFi equipment. Cheers!

My father had the scariest metal rectifier battery charger I’ve ever encountered. It could charge 100 lead acid cells in series and was full of asbestos resistor mats. Non isolated croc clips for bonus points! I think it was originally used for charging tube radio filament batteries back in the day where the customer would swap their flat battery for a freshly charged one.

Gotta admire the foresight of the designers, providing those handy covers for hiding future replacement capacitors!

Hello Marc: I recently fixed an old Simpson 260 VOM with a similar sticky meter. The cause was some small (iron?) dust particles in the meter magnet's gap... these snagged the meter's needle armature. I used a can of flux cleaner and gentle compressed air to remove the "dust"... it now works great. Great channel... Steve ( another HP buff!)

CRT you need to give it grid and accelerator voltages as well. 1M resistor from the 500V rail to all other pins, one resistor per pin, and it will accelerate the electrons enough to make a faint glow, which is what you need. That small a CRT will run off 500V, not bright, but you do need to bias it hard on, and the 1M resistors will at least keep any flashover current down. Use high voltage resistors, or 3 330k 1/4W in series.

Growing up in the 70's and getting ham licensed in the 80's I toyed around a lot with tubes. From E85CC and EL86 to QQE06/40, 2C39 and 4CX250. Wonderfull years of experimenting. And an occasional hard reset if you forget to put bleed resistors onto the main high voltage capacitor.

I have one of those that I got at a garage sale for $10. A wonderful score. It worked kind of flakey when I first got it. I replaced all the bumble bee .1 uf caps with modern caps and it just started working fine. I will probably go through it and replace all the electrolytic caps with cheap PC-mount caps, mounted on a board I will fab and install. About $10 worth of new caps. I also cobbled together a bias supply by taking a little filament transformer and running it backwards from the 12.6 heater supply. It's in a separate little chassis and drives an 0A2 regulator in a completely ordinary fashion. Makes up to -90 volts. It's really a nice piece of gear, it's cute like a little puppy. Make sure you replace those bumble bee caps!! There is no way they are still good. You are chasing your tail unless and until you replace them. They are known to leak in their old age (like most of us) So those caps are going to have 500 volts on one side and they are going leak out volts on the cold side which will make the control circuitry go bananas. You really should not even have to think about this, there is no way those crappy old caps are still good. No way. Don't test them, just blast them out of there.

Thanks for the video; I just picked up one of these in very dirty shape. Great to see John Atwood and Bob R! BTW, the Sprague black body with red printing (6TM series) and the Cornell Dubilier avocado green (PM series) capacitors are mylar and almost always are fine. I've used a number of these in vintage restorations and I've never found a bad one. Save them! They are great for vintage repair. Now, on to get my 711A as clean as yours! Cheers, Kent

(Reposting this as RU-vid removed my comment for the link I guess). The use of the microswitch S1A/S1B for rough regulation control was clever! I also like how the capacitors are used for voltage control, from the manual Section III Page 3: "Any ripple in the output voltage is coupled by capacitor C4 to the grid of control tube V4B." "Any ripple in the output is coupled to the grid of V3B by capacitor C7." If you want to be get this perfect you should install your new film capacitors with the foil side right way around else they could also couple noise back. Mr Carlson video "Are Your Capacitors Installed Backwards?" goes into using a scope at the 8:00 minute mark to test for it. Looking forward to your next video! :)

Don't ever get rid of the elevator music, it's fantastic!!!

Mr. Carlson's body form rhymes perfectly with several of his tubes.

often times on old meters, the magnet will flake, and small pieces can flake off and get stuck between the moving coil and the magnet, can cause odd sticking. sometimes you have to disassemble the meter and use some painters tape to remove the flakes

I truly enjoy your channel, I understand enough of how most circuits work, I'm not an electronics guy, but you spell things out so well I learn more and more watching you work.

I had one of those IBM modules at one point when I was a teenager. I didn't know what it was back then so I used parts from it to build my first tube pre-amp that is still working and still floating around in the family somewhere. If I had known what it was back then I would have never destroyed it.

Marc a colab with Mr Carlson in your Lab would be amazing 🤩

I worked at a Nabisco factory in the 80s. We had a cake mix packing line that used 110 VDC. It had a bunch of relays and solenoids. It used selenium snubbers. I replaced one with a silicon diode. The next day someone replaced it with selenium.

I learned to keep one hand in my pocket when working on high voltage ⚡️

Great! Loved the smiley mouth on the PSU at the end lol

I love stuff like this :) I'm not even big into tubes, but it's neat to see old analog test gear come to life and still be useful.

I fully expected a surprise 'guest appearance' by a certain Canadian tubester in future episodes.

Not flying to the moon with this one? No problem, it's still lovely stuff that will last for ages. I like your way of replacing the electrolytics' innards more than Paul just adding new ones under the chassis. A black beauty is a joy never.

I love me some hollow state stuff, awesome job Marc and crew!

Thanks for more of the tube stuff! I can practically smell the old electronics.

I'm a simple man, i see a new video from Marc, i hit like.

Very neat to see this. One of my prized pieces of equipment is a John Fluke, yes John still had his name on it back then, 407D power supply. 555V at 300mA, with -250V bias and a few 6.3 filament outputs. It has multiple taps and the main selector is in 50V increments and is accurate enough to calibrate a meter. The control circuit is way more complicated and uses 3 807s for the output. I spent a lot of time restuffing the can caps and replacing anything questionable in it. I was blessed to get it in exchange for an ancient scope I got for $20 and a 8 hour drive to make the swap.

Never get tired of the capacitor dissections on the lathe. Great!

@1:00, that fellow who likes tubes and throwing bricks into dryers would like this bit

I could smell this video. Aaah, nice.

Aah, 500v. Where life starts to get interesting! and where not paying attention will give you a very bad day.

1:48 Hey, I had one of those soviet rocket lamps when I was a kid!

I was frowning a bit when the crt didn't light up, but the thought of a future 3kV PS restoration video turned my frown upside down! Thank you, Marc!

I like messing around with tubes. The voltages demand respect though. One hand in your pocket, insulated work area, etc. ;)

I’m ocd enough to drop a bit of epoxy on to reattach the vintage cap casing to hide the new caps (then the paper covers. Super interesting. I just brought back some valve based test equipment from my dad’s apprenticeship in the 50’s. This video gave me a little courage to take a look knowing there are locals that know what to suggest.

CRTs need a variety of voltages. 6.3V for the filaments, 500-600V for the video and brightness grids, -100V for the cathode, 10-15kV for a black and white anode, 24-30kV for color anode. You need a bit more voltage to drive that display... The flyback transformer is primarily the one that generates the anode voltages, but it is often tasked to generate the other voltages as well.

You can get the phosphors on CRTs to glow with a UV light. This at least works on green monochrome tubes and color tubes with ~400nm light. Of course if you can do it with electrons that's even better!

Coming from an old fart that started playing with this tube stuff as a teenager in the 1960's, the Navy into the '70's, then radio and television for the rest of my life, I found this video very satisfying in today's silicon based world.

You must love the mix of technologies from so many different eras in this video.

Another great video Marc!

Great video Marc! Always an inspiration

You are now ready to find a beam penetration color CRT. The drive circuit should be interesting. A Transmitter triode tube is normally used to regulate the drive voltage to the CRT. The color of the trace depends on how hard you hit the phosphorus and you can't have blue only red through to green.

On this channel, if you are "a crazy friend", it's a big compliment.

Interesting old instrument. Always good to have some geeky tube friends helping out. Great video!

Thanks for the show! I've had one of these for a long time. It developed some hum a while back which I traced to a genuine, original, HP factory-installed, passed-all-inspections No-Solder-Joint on one of the electrolytics!

Interesting flashback. I had its big brother, the HP 712, for a while in the 1970/80s I bought it at a hamfest. Haven't done anything with tubes in years so sold it long ago.

high voltage you have to have a lot of respect for it more than fear

When i started playing with tubes i made my own power supply, it was a nice project 😀 specially with that level of tension.

nice supply, i have been trying to locate one myself for a while

Very nice video, I have similar PSU on my bench (has outputs of 600V 40mA, 60V 80mA and 12V 2A) and also adjustable 1-7VAC 5A heater supply. All transistorised though. Btw when restuffing the capacitors, I would leave the tops of the cases in and glue them on the cut bases. When restuffing, if you want to preserve the whole can, put it in a lathe and just take off the bottom ring. The cap will just slide off then and you can reuse it later.

It's always good to check the filament to see if it's "filamenting".

for future reference, the black beauties with the red writing are di-film caps, i have a lot of NOS ones and they all test fine on capacitance and leakage, they are rarely bad even after all these years. i would not hesitate to use them, same with the electrolytics, i've still got gear running on 1940's filter caps! The ones with the bands (commonly called bumble bee caps) and the black beauties with yellow writing however are paper and foil caps, they are usually very bad by now.

The difference between meter sticking when tested in the equipment but not on the bench is probably due to the orientation. When vertical the frictional forces on the bearings may be greater than for the horizontal orientation or the pointer may be deviating and dragging against the glass.

Excellent.

When those Selenium Rectifiers go bad, they emit not only "magic-smoke" they also emit quite a pungent smell too.

Sprague OEM electrolytic caps cost an arm and a leg nowadays...I recently fixed a vintage HP 80 MHz counter and wanted it to stay as it was...$40 for the Sprague and it was, but I don't regret it. 73 - Dino KLØS

Enjoyed the video. These are quite beefy supplies for your small CRT. Might be easier to test it with a 555 timer driver and flyback transformer if you value the tube. Stationary spots can burn the phosphor surprisingly fast if the beam current is high.

Beautiful PS

The ragtime for this beauty is little bit on the ironic side, yet appreciated.

3KV power supply ? i can't wait anymore .....

That is a nice little tube power supply . Much easier than the Sorensen I have it a bit heavier at 70 pounds thou 200ma and 800 volts all day it is a bit of a space heater. You good luck to get John Atwood to help is a bit of very fine luck for sure.

Thanks for sharing. 😉👌🏻

Thats a really nice power supply, i have domething similoar made by a local company Tesla it is 0-400V at 2A and has some preset vacuum tube heater voltages like, 6.3V, 12.6V (one of the reasons the thing has three separate trasnformers) one of them takes care of the preset voltages and the other two take care of the 0-400 variable voltage output as that is devided into two settings 0-200V and 200-400V. I happen to have two of them only tested one so far as i had trouble finding the connector for the mains cable anyways so far the first doesn't work as the only working output is the 12.3V one.

These two gentlemen are in the league of shango066 in my opinion. Great stuff!

Next restoration, tube based computer restoration!

Now that the super small high voltage capacitors arrived, the Interocitor will soon be assembled and another space adventure begins!

Perhaps the mounting panel is slightly warped, and the meter is tightening down unevenly. That might result in binding. It's also possible there is something magnetic nearby, though that is a little unlikely. BTW, it looked like one end of the cap terminal strip was missing a #6 mounting screw. I know you mostly only collect Tek and HP equipment, but if you want to play with tubes, I'd suggest looking at a Hickok PS-505 or PS-5505 supply. These have 0-400V @ 100ma, 0-30V @ 1A, 0 to - 100V adjustable grid supply, 6.3V filament, and 12.6VCT filament supplies. They also have a 1A Variac and a plug socket on the front panel. The filament supplies are isolated form each other, and the 30V supply (if I recall correctly) is isolated from the 0-400V and 0- -100V supplies. The 400V and -100V supplies share a common lead. They show up on eBay periodically, though there aren't any there at the moment.

Speaking of tube computers, someone in Usagi-Electric's comments said they had an IBM 604 they were willing to part with, maybe you can find them and see if it's still available.

Yay tubes! They make more sense to me than transistors do, electrons getting stopped by a charged grid? Naturally. Holes in a semiconductor? Uh ... There was a missed opportunity to pull out another DVM and use the thermocouple they often have, it would be fun to see the temperature rising in that poor underspeced resistor

That thumbnail smile will haunt me in my sleep.

Point to point chassis wiring, like an old TV! How anyone ever repaired stuff like that is beyond my small brain.

If you need to see the colour of the crt, shine a uv or regular powerful flashlight on it. On some screens the phosphor will lit up.

Well Mr Carlson does have a stern and direct warning at the start of all of his videos for a reason. I suspect calling him also prompts the same stern and direct warning. LOL.

god that video thumbnail is creepy! I love it!

If I changed all the parts at once like you I am sure it wouldn't have turned on anymore.

We have always been told that playing with 230 volt mains is dangerous. But playing with 500 volts is interesting dangerous.

bonjour, Marc super vidéo comme d'habitude personnellement pour l’échange de condensateur de filtrage électrochimique je ne m’embête pas à découper la cannette je laisse l'ancien en place je déconnecte les pattes et je soude proprement le nouveau dessous comme ça je ne dénature pas le design d’antan. Merci

500 volts is more than enough to light up an older oscilloscope CRT.

Great video (as usual!). Did you end up swapping the selenium rectifier(s)?

Ahhhh, I think I know what they are up to. Not only they wanna rebuild the Saturn V and Lunar lander, they also want to bring back the original astronauts with high voltage frankenstein tube technology! **x-files music ** 😉😁

The "future capacitors" make me think this is a real-life remake of the classic This Island Earth (1955). That's pre-Netflix.

The magic Cup in Action

orange phosphor is the coolest

Hi Marc - why do they put paper tubes on the capacitors - is it only for spark protection, or is there some other reason?

I'll bet Mr. Carlson wishes he had John L. and John A. on HIS speed dial…

I thought with a CRT you always have some electron acceleration in the gun (edit: "screen"/G2 in TV terms). The main anode at the face of the tube just speeds them up more. I'm not sure you'll get a spot at any anode voltage without some positive voltage on at least some of the gun elements.

Ooh there's nothing like the smell of a burnt out selenium rectifier....

What’s up with the Hakko holder? Made it yourself because it doesn’t look like the Hakko C1100 holder which they make for the 301.

I wonder if it started off since 1960 wall voltage would have been closer to 110 than 120V.

I'd have stuck the cans back on those caps, perhaps using some aluminium tape? Keep the look as much as possible. 🙂

Using a couple of 6V6's as a linear regulator... oof, they gonna get hot. A very nice design though. But complicated. Cheers,

Somehow I knew when you mounted the meter back it was going to intermittently fail again. Those 3KV supplies make me nervous.

That’s odd. The 6L6 tubes are rated at like 500 volts max. HP usually didn’t push parts past their maximum ratings.

kool

That power supply can power up 55 arduino boards connected in series.

Note to futur me : Take time to check if filament are filamenting !!!!

He's holding a bag of ITT branded tubes. I remember those from the late 60s and early 70s. Unlike Sylvania, RCA, and GE who were the primary suppliers at the time, the ITT branded tubes were very low quality. (no insult intended)

ooo is it ok to touch that capacitor's insides though? I'm always super paranoid about chemical hazards in old stuff like this. Isn't it possible that the capacitors from this era contained highly toxic polychlorinated biphenyls?

Mine make two nasty voltage spikes at power on, and one at power down, even if potmeters are set for 0v out, and I forget the output on/off switch, do you see this too?

I don't get why you didn't install those old capacitor cans back? Just fix them in place with aluminum sticky tape around and it will look pretty fine. I used such trick many times for restoring old tube radios and TVs.

This brings joy the diodes down my left side, what is wrong with me?

Just designed built my own switching 12->600V supply for a similar test. I'm jelous for this old beauty, but mine is waaaay smaller, and more efficient (but not by much sadly)