Manna from Heaven: Donated Heathkit SB-650 Digital Display for K1T

Jim, you brought back a fun memory for me: About a dozen years ago, my wife and I worked for the same small company. During a company meeting our boss mentioned that while he had worked for NASA he had the opportunity of meet Werner Von Braun. I leaned toward my wife and said (louder than I thought), "Holy s$%t! He's the father of rocketry!" Our boss looked over at me with a grin and then looked around at no other reactions and said "I guess Scott is the only one that knows who that is."

 

Sometimes, with both you and Sue in a discussion in a thread like this, I often feel like a volleyball That was my initial intention... and not only one tube, but why not all of them?

That was my thought as well... if they can't draw current they can't light - even if there is very small leakage through the glue, I can't imagine it being enough to light the segment.

Haha!! No, I won't have it!

Dave
W7UUU

 

So I now have 170v (give or take) - all the 10k Nixie current limiting resistors are in place, and the 170v power supply parts (D5, R45, C21) (I ended up reusing the original 1 uF NP cap C21 - the new one didn't deliver 170v to the output - odd ... but the old one works fine so I cleaned it up and it's now soldered in place). All other parts are new

Going to just "let it burn" for a few hours, with just a 2W 10k resistor for a load - just make sure the transformer is OK, after all those years and all the water issues. Laminations are "buzzy" on the bench but when pressed by my hand they quiet down - pretty sure that once bolted back in position they'll shut up

Tomorrow I'll put voltage on a Nixie and ground a pin or nine And then another Nixie and another - may as well check all segments in all of them at this stage.

For tonight, just let it burn on the bench. This transformer hasn't been run in DECADES.

Dave
W7UUU

 

.....wait......

....you're going to let an ancient transformer, that hasn't been powered up in years, sit energized overnight, unfused and unsupervised?

What could POSSIBLY go wrong??

73 de Jim, N2EY

 

My thought is simply to provide a most-realistic test of the insulation - particularly since it has already been installed. Doing one tube is preliminary test - there are how many 10 K resistors in that thing?

Perhaps the best check is to do one Nixie, test it, and if it passes, install all the others, and test them.

The thing is, Nixies are essentially fancy neon bulbs (not sure what the gas is inside - probably a Penning mixture of neon-argon), and they have a minimum striking voltage, just like VR tubes. So if the resistance is on the order of megohms, not enough zotz may get to the cathode to cause it to strike.

But - a good dialectic will result in the choice of the best dielectric!

73 de Jim, N2EY

 

Haha! No, it won't run if I'm not in the room (as I am now). I check it every 20 minutes - it's "buzzing" in the background but if I put a hand on it, it shuts up - so once screwed into the chassis I think it'll be fine. Not hot - no issues - voltage stable - it's all good I think.

But no, I won't just leave it overnight - it's only 7:30 here so when I head up about 11:00 I'll be sure to unplug it.

Thanks for the concern though - appreciated

BTW, the "warning sign" is a result of the HW-16 restoration, when Anne N7ANN reached INTO THE RF CAGE AND TOUCHED THE MODIFIED TANK COIL (for the 20m mod) while the transmitter was powered!!! I didn't freak out and scare her, but gently (and QUCKLY!!) pulled her hand back and explained the situation.

Ever since then if I have ANYTHING with HV on the bench, my sign gets taped up.... just in case

Dave
W7UUU

 

Good idea. Tonight, since I can't do much else with it right now other than listen to it buzz, I'll fashion up a 6-pin cable, sufficient to light up a segment on all 6 tubes (I'll pick the 6 segment for obvious reasons - the project from HELL!) - just connect all Number 11 pins of the 7441 sockets with this cable to ground, with the 170v HV on the buss to the 10k limiting resistors - that will in effect put the full load on the HV system - that indeed would be a good check.

Gonna be a ton of fun fitting the Nixies - can hardly wait....

I'm going to have to take one at a time, and carefully bend the wires to fit the "socket" - and each is different - I'll have to "Sharpie label" each tube, as it will only fit the socket for which the wires are shaped. Can't build the rest of the board with the tubes on board, so I'll need a way to keep them straight - after forming their leads, they'll go in their own "muffin tin hole" until final assembly... wait - will there ever BE a "final assembly"??!!



Dave
W7UUU

 

Try tightening the screws in the lamination. You can also try spraying the lamination with hair spray, then let it dry for a few hours.

(That's lamination, not Lamentations. Trying to keep Kosher with the "Manna" theme.)

 

Good ideas!!

And yes - my choice of "Manna" has indeed morphed a tad through this process LOL!!

Will go see if I can "fix that blasted noise" (it's not all that bad really... just a quiet buzz - but good suggestion)

Dave
W7UUU

 

Jumper made for "7441 Pin 11 / Nixie digit #6 test, all 6 tubes" for tomorrow - will take at least an hour to fit each tube to the homemade socket, one at a time - but I feel like this is a very good test - full current load, power supply test, socket test. And of course, I can use the same jumper "test jig" to test all segments on all Nixie tubes.

For now, I'm just letting the transformer run in the background for good measure.

Dave
W7UUU