Vintage HP weekend haul (Nixie tube content!) - Page 1
Forum section: electronics / testgear

author: willb
author_rank: Regular Contributor
timestamp: April 03, 2016, 10:55:36 pm
content: A few weeks ago, a co-worker of mine asked me if I had any interest in some vintage test equipment he had. It belonged to his father who past away last year. They were cleaning out his home and found a few pieces of equipment. I told him I was interested, expecting nothing really worth being excited over. I went over this weekend to look at it. I got interested pretty quickly. He had a 1958 HP 405AR nixie tube "digital" DC volt meter, a HP 130CR oscilloscope and a HP 400D. Every single item had all their tubes, most of which were the original HP tubes. This stuff was really dirty and dusty, probably sat unused for 20+ years. The 405A was by far the dirtiest. I threw everything in my trunk and got cleaning as soon as I got home!I did some very slow power ups with a variac, monitoring the current. The 405A did not work at first, it displayed garbage and the stepping switch was going nuts. I found the service manual for the 405D, which was close enough for my 405A. I cleaned all the contacts and switches and checked the power supply rails. The -150 rail was only -22 volts DC, a new .047uF 600V cap and 2 resistors later, the meter came to life. A fresh power cord completed the unit.Here are some photo!

author: willb
author_rank: Regular Contributor
timestamp: April 03, 2016, 11:14:19 pm
content: The 130CR came to life after a slow power up. The switches are extremely dirty, and the internal trigger does not quite work, but it will be a good candidate for a restoration, and will make for a cool project.The 400D however is completely dead. There is absolutely no needle movement. Main power transformer is good. It was extremely filthy inside, a lot of simple green cleaned it right up. Tested a few of the tubes, one of the 6CB6A has grid leakage, and 3 of the others measure quite weak. That's as far as I got with it for now.

author: rrinker
author_rank: Super Contributor
timestamp: April 03, 2016, 11:42:49 pm
content: Nice haul. I do love me some nixie tubes.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 03, 2016, 11:45:13 pm
content: Nice finds and nice work on the cleanup!

author: lowimpedance
author_rank: Super Contributor
timestamp: April 03, 2016, 11:50:13 pm
content: You were not exaggerating about being a bit dusty !Nice clean up. I particularly like the 405, I wonder just how many of those are still around and actually working!!.

author: Cubdriver
author_rank: Unknown
timestamp: April 04, 2016, 01:52:42 pm
content: Very nice haul you got there. It's nice to see that 405 come back to life, and it appears to have cleaned up nicely. The scope as well. Good luck with the 400D; no doubt with some more effort you can get that one back up and running as well.-Pat

author: willb
author_rank: Regular Contributor
timestamp: April 05, 2016, 12:54:06 am
content: Thanks!!! I've put a considerable amount of work into cleaning the 405A. I really wanted to get it looking good working again. I don't have any other test gear with nixie tubes, so the 405A was priority #1. There is very little information about them on the web other than some HP journals mentioning it. I was very happy to get it working again, they must be very rare these days...The 400D, sadly, needs a new front panel meter, the coil is completely open. I did check all power supply rails, the +450VDC rail is low at around +275VDC, the 6AX5 rectifier tube tests good. I noticed after that the filter capacitor for that rail gets extremely hot quite quickly, so the filter cap is obviously failing. However, unless I find a good working panel meter at a reasonable cost (eBay shipping prices to Canada are quite ridiculous), the meter will have to go on hold. Not sure what to do or where else to look for a replacement meter.

author: lowimpedance
author_rank: Super Contributor
timestamp: April 05, 2016, 03:07:49 am
content: Shame about the meter, perhaps pull it apart to see if the o/c is not in the coil itself (wishful thinking here!)The meter also reminded me of one in my junk box which was made be master instruments and it basically looks the same, so perhaps looking for generic old style meters from say Simpson or MI etc that you can then transplant the scale into. Off course it would help to know the meters sensitivity !.Good luck with the hunt.

author: crispy_tofu
author_rank: Super Contributor
timestamp: April 05, 2016, 04:40:53 am
content: Wow, nice restoration!

author: willb
author_rank: Regular Contributor
timestamp: April 18, 2016, 02:21:43 pm
content: I had a bit of free time Sunday morning so I fired up my Fluke 335D and decided to adjust the HP 405! Pretty pleased with the result. Not bad for a meter from the 50s!