Here is the next piece of gear for show and tell. As I mentioned yesterday, I was given a Dana 5330 5 1/2 digit voltmeter by my buddy. He never turned the unit on and it sat in his basement stored away for probably close to twenty years. As I was carrying it in, tucked under my arm, I thought I heard something move around inside the unit. I gave it a gentle shake and there was definitely something loose inside. I figured some component fell out somewhere. I was curious and removed the top cover which was held by a single Phillips screw. At first I didn't see anything obvious, then noticed a vacuum tube box in the far left corner. Whiskey Tango Foxtrot ?
What's a tube doing in here ? Then I noticed another Westinghouse tube box on the right rear corner.
??
I picked up the box and nearly fell over. Two brand new ZM1000 replacement Nixie tubes in never opened boxes !
Never have I come across spare components inside any unit other than fuses. Whatever I had planned for the afternoon was "I'll get to it tomorrow"...
After further examination, I could not see any signs of repair. Either it never was repaired, or if it was, the repair person was very honest and left the tubes. They could easily
have been expropriated. I found a power cord and plugged it in. It powered up, but the display was jumping around. I set it to autorange and it settled down.
I was hoping it was a true multimeter, but it is just a voltmeter. That's okay, it's 5 1/2 digits. The next question was, how accurate is it at the moment. I hooked up
my AD688 precision +10.0000 and -10.0000 reference to it and it showed +9.9988 and -9.9852. Not too bad. Back in February this year, my good buddy gave me a
Weston Standard Cell. Up until the mid 90's the Weston Cells were the worldwide voltage standard. They were replaced by the Josephson Junction. You can read up on this stuff
on the net. A new Weston Cell was 1.01830 volts. The cell is only supposed to be guaranteed accurate for a number of years but I have read some are still good after many decades.
I don't know how old my cell is but I made the adjustment to 1.01830 as quickly as possible. The cell needs recovery time and the longer you pass current through it the longer it
takes to recover. If it shorts, it may take 5 weeks to get back to 1.01830 volts. Since I don't use it regularly, the next time it's used it will be okay.
I know this isn't the best way to calibrate the unit, but it is accurate enough for my purposes.
All in all, this was a good find. Cosmetically it is not great. The display bezel took a hit somewhere along the line and has a large crack in it. I will get some tinted plexi and
with a heat gun remove the Dana plate and reglue to the new one. A flat black paint job and maybe one for the top cover and its fully restored.
I am glad that it didn't need repair. It's old RTL technology. Repairable yes, but even the RTL devices are rare.
Here's a few pics. The inside is just RTL chips and normal stuff and the input module won't show you anything so I didn't take any pictures.
Edit for another typo...