HP 3440A Digital Voltmeter Nixie 3444A plugin 1963 test teardown

here is a Hewlett Packard 3440A Digital Voltmeter with Nixie tubes, the plugin module is 3444A so this makes in Volt, Ohm, Amp meter, initial design is from end 1963, it had a few loose connections, and it was quite dirty, but a deep clean solved it it, so now it works fine again, and looks nice too.
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#teardown
#restoration
#hewlettpackard
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I use auto generated subs, I go thru them my self, but i am far from perfect at finding all errors, so if you find errors worth fixing, please comment (or PM) with the TIME in the video you saw the error, i will be happy to fix it. This also apply to the Danish version.
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[@twipsy2047]

This channel makes me extremely happy - beautiful, ancient test gear on display 🙂

[@TeardownOZ2CPU]

then i am extreamly happy too :-) i love comments like this

[@patmx5]

Nice overview of a fine piece of hardware! I have both a 3439A with a 3445A AC/DC Range Unit plug in and a 3440A with the 3444A DC Multi Function Unit like yours on my bench; they get plenty of use and are fantastic instruments. Love nixie tubes - so much more personality than seven segment displays. Here's an interesting bit of trivia I read about the 3440A some time ago - when they were in development, HP wanted them to be fanless, but were having overheating issues. At some point, one of the designers tried leaving a gap between the chassis deck and both the front and rear panels. This permitted the air within the cabinet to start convecting within the enclosure, and this small amount of circulation turned out to be enough to let the heat radiate through the top and bottom panels and keep the internal temperatures within limits. Clever bunch of guys! Based on the date codes I could make out on the components in your video, yours appears to be 1964/1965 vintage. I have another one that I bought years ago from a surplus house in California in my repair queue; it has an asset tag from Bendix that says they bought it in summer of 1965, about three or four months after I was born.

[@Edisson.]

Hi, that's a beauty, I love these old HP meters, it's amazing how accurate they've been (if they work). As long as the green slime is slime, it's still good, it's worse when it becomes a crust, it's difficult to clean, but usually the contacts are very damaged. Those capacitors from SPRAGUE are incredible, I recently wrote this in another comment - during the restoration of the HP3400 I checked all the electrolytic capacitors and I didn't understand at all - I measured better parameters for some capacitors than for those newly bought for replacement. Those capacitors are maybe forty years old and that's why I want to replace them, I never know when they will fail. It's a great pity that the person in question who did the adjustment of the circuit connection didn't leave a note in the device as to why - that's how I do it. Thank you for the opportunity to look into another beautiful piece of technology. Nice day 🙂 Tom

[@patmx5]

I've found the electrolytics used in old HP and Tek gear to be pretty high quality devices that are usually still good. I'm certainly not inclined to shotgun them like people do with old audio gear and radios - the nice thing about these older test instruments is they were typically NOT 'value-engineered' by bean counters trying to squeeze every last cent out of the parts cost.

[@michaelturner4457]

The "green slime" is called verdigris. Which is oxidation of copper or brass.

[@Conlan0215]

Do you know what kind of contact cleaner might cause something like that? I'm a frequent DeOxit user, but if it has any chance of causing this...

[@michaelturner4457]

It's the same age as me. :)

[@frankdahlin]

Very big diodes, resistor and so on. Opposite of SMD components. :-)

[@Conlan0215]

Thanks for posting this. I've got a 3444A to restore myself- Luckily doesn't appear to have been modified at first glance, but it's got some clear thermal damage to the MFU, necessitating a replacement resistor (managed to find one with the right specs in a TO-220, good enough I guess...) A question for you: Have you taken a closer look at the plexiglass window that sits in front of the nixie display? It looks to me like it's made of laminations, which have started to fail, giving it that smeary/dirty look. I'm going to fabricate a new one out of orange plexiglass stock. PM me if you want one while I'm at it...

[@TeardownOZ2CPU]

you are right, the window is laminated, it is easy to replace with thinn red acrylic when it fails, mine is still in an ok state, so i like to leave it as original as possible, for as long as possible, the best of luck with your restoring.