Still have one of those lying around somewhere :-)

Minifig666, he won't even reply to common sense. So, don't even try and help him out.

I wonder what the science is behind the failure. Like is the phosphor depleted, or has it been poisoned and coated, because if it's the latter maybe reversing the current. They remove chrome plating by reversing the polarity.

I have a stereo that's at least 20, if not 30, years old, running 24/7. Its VFD is still easily visible in daylight, although it has slightly darker bands right under the filaments (so it's failure will be burning out the phosphor, not oxidation on the filaments). Maybe the HP devices are being driven harder to be brighter to be very visible in a lab environment (which should be a very bright workplace) and degrade faster because of that.

Sounds legit

Glowing the filaments only works if your filaments have been poisoned by DC bias. Every VFD I've dealt with specifies AC to the filaments to counteract this problem, I'd strongly suspect HP knew about this issue when designing this instrument. This unit had "phosphor fatigue" (easily identified by the phosphor segments looking dingy and inconsistent); there's no repair for that.

Cryo-EM microscopes have a similar issue with residue accumulation on the capacitor plates, which end up forming spark gaps and shorts. Preventative maintenance procedures are to run it hot to prevent catastrophic failure. (I mean, the electron source itself is a pain to deal with hah!). At Caltech, the cleaning procedure is to effectively do what what Shahriar was doing... but at longer durations. This is consistent with vacuum tubes restoration that use (unthoriated? IIRC) tungsten -- 110% standard voltage @ 30 minutes to burn off any aggregate material. Side-note, (no personal experience on this one..just remember someone mentioning it), on old fluorescent tubes (i.e. those ancient T5's), the single-ended ballasts would burn in unevenly. So much so that particulate from the electron source would be visible biased towards the emitting side (this is with a properly configured setup-- if other elements in the setup like your ballast are misconfigured/failing, then you have bigger problems than this). If you 180 them, you (in theory for sure, in practice, I believe as well) should be able to extend the mean time to failure

Also A+ Shahriar, great episode. This is definitely an "experiment' because you actually did experiment! This (personally) is an episode I would pay for, 10x over any sort of review. (In my personal opinion, the best episodes are the in depth "tutorials on non linear.." and "tutorials on ___ filters" (episode 9,10), then the "proper usage of obscure stuff' (episode 26), teardowns of things like the Agilent optical stuff most of us don't tend to use in our day to day lives. Repair videos like this where you experiment are great as well.

My thoughts exactly.

just need patience to rewind 200+ turns primary

Someone apparently did it: www.eevblog.com/forum/buysellwanted/hp-6632b-power-supply-replacement-oled-screen-(done)/

I've replaced an ancient LCD display in an old Fluke 8050A DMM with a graphical LCD display and STM32 micro that decoded the scanned display signals. It was a fun project..

+jolo0011 k You'd think. But that is not what happens. When you bring metal up to temperature the oxide burns off, and you are left with clean metal. I've done it many times with an oxy-acetylene torch on rusty hardware. Glowing metal up burns the rust away.

Looks like copper balancing to prevent bow and twist during manufacture.

Because the secondary side of the transformer was shorted together. The AC current at the secondary induces an AC current in the primary which was being measured by the isolation transformer.

He didn't remove the transformer, he removed the PCB (and rectifier) from the circuit. Electricity goes in through the back where it gets tapped off somewhere to operate some of the circuitry on the board (probably some low voltage devices like the fan and stuff) and forward to the primary of the transformer, which then goes through to the rectifier on the PCB. The rectifier was damaged so detaching the secondary removed the short and removed the current. Probably confusing is the fact that the transformer is near the front of the unit and not near the back, where it would be in a block diagram.

A Transformer is basically just a coil of wire, so a continuity measurement (wich measures DC-Resistance) would read a short circuit anyways (if the transformer is good or when some windings shortet together). If a transformer burns out (wich it would if the input fuse does not blow), it usually heats up from the inside outwards. That means that you have to unwrap a LOT of transformer wire to even get access to the fault. Also the melting coating on the wires tends to glue it all together. But if its a mechanical fault were for example the one end from the wire crosses the outside layer you could may be re-isolate that particular failure point with epoxy or kapton (-tubing). I surely wouldn't use electrical tape!

alfagulf think he said 90.

rapsod - in North America it is free or $8 Fedex flat depending on total of the order.

Lucky bastards :) For my country is $120.00 hehehe

no, that's his cat... she's got very nice nails :P

Electrocution is death caused by electric shock, electric current passing through the body. The word is derived from "electro" and "execution", but it is also used for accidental death.

Clearly he hasn't because the cat is still alive.

Justin Bell, next time you copy the definition from wikipedia maybe also read the next sentence. You'll find that it doesn't necessarily imply death. You pedants take the fun out of everything.

I'm fairly sure he's a Russian Blue. I have a fatter version of him :)

:)

steve c She has a masters in EE.

Oh how this reminds me of the article by Catherine Mohr: code.likeagirl.io/making-while-female-df4100658c13 "Often, I am informed that a tool like that is only “really needed” if you have [insert expertise level here], so I would be better off getting something else. Then there is the Mr. Hyde version of talking about the tool which is equally sexist, and more plainly aggressive. It comes as a, “What are you making with that?” delivered in a tone and manner distinctly pitched to express not-so-polite disbelief and more than a little disdain."