AOIP seven decade resistor box, 0.5% - Page 1
Forum section: electronics / general

author: tatel
author_rank: Frequent Contributor
timestamp: February 13, 2024, 12:24:48 pm
content: Not sure if 0.5% accuracy really falls into metrology, but I thought somebody could be interested in these pictures... I've unable to identify these resistors, RS68Y now appears to be some vishay sfernice high stability metal film resistors. Yet these look as wirewound to me? Perhaps some of you will be able to say what they are.I got it on eBay last month. While looking for any documentation, I found a german cal lab that cites this exact model as one of the resistor boxes they are willing to work on. So I bought it.Unfortunately, seller did a very bad packaging job. 5-way connectors isolation broke. Not sure about what could be used for replacement. Should I go for Pomona copper-gold? Wouldn't that be overkill for a 0.5% accuracy thing? Perhaps some Hirschmann brass-gold would be good enough? What do you guys think?

author: bastl_r
author_rank: Regular Contributor
timestamp: February 13, 2024, 12:59:31 pm
content: HiI think, pomonas are overkill.If you have a decade with 0,01% you can think about optimations.I has a 8 decade Resistorbox that has aprox 0,01% with no pomonas...

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 13, 2024, 01:40:24 pm
content: Those are almost certainly wire wounds. Any decent banana jack should be fine. I'd probably remove all of them and put the panel in a mill or drill press, then gently straighten out the bend with the edges resting on some vise jaws or parallels. Naturally there's some risk of cracking, but you can probably get away with it.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 13, 2024, 03:53:24 pm
content: For most uses normal banana plugs are good enough. The main difference is with thermal EMF that also depends on the plugs and cables used, not just the therminals. With low thermal gradients (e.g. cover the coneectors even brass terminals and cheap cables can be OK. It needs both different materials and a thermal gradient to produce a voltage.There are quite some extra terminals to have access to the decades separate, so not just the sum. This is a nice feature. Not all of the terminals are equally important.I would not take it appart and apply the extra stress to the resisstors and switches more than needed to replace the broken parts. For the most part the slight bend in the front panel is a minor cosmetic issue.

author: tatel
author_rank: Frequent Contributor
timestamp: February 13, 2024, 04:07:37 pm
content: Yep, just thinking about replacing the broken ones. I think this damage could be more than cosmetic? I will probably also (try and) make that bend straight again. I see first attachment in the previous post is missing, don't know exactly why. So there it goes...

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 13, 2024, 05:28:34 pm
content: A fairly important reason to fix the bend is that the 3/4" spacing of banana jacks is critical if you use dual plugs. Having the tops tilted in will damage the plugs. If you straighten it in a mill or drill press, you can put a rod in the chuck to apply pressure and not have to remove anything. Keeping in mind that mills and drill presses weren't designed to be arbor presses, but they usually do OK with lighter jobs.

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 14, 2024, 12:43:32 pm
content: HelloAOIP plastic are quite cheap even on a 5000 Euro calibrator and brittle , can be a good idea to replace them or lathe turn part in PEHD or even PTFEOn Ebay there is Pomona gold plated at 10 Euro each ( Spain seller )AOIP is a french company , quality is very good can be compared to Time Electronic in UKsome time on Le Bon Coin or Ebay France you can locate AOIP quite cheap to recover spares parts as AOPI factory spares parts are $$$$$check :https://www.leboncoin.fr/bricolage/1941392471.htmhttps://www.leboncoin.fr/collection/2359657593.htmRegardsOS

author: trobbins
author_rank: Frequent Contributor
timestamp: February 14, 2024, 10:50:35 pm
content: Tatel, do you have the ability to measure resistance steps to better then say 0.05%, to identify what the tolerance spread is among each of the decade steps ?If you have some outlier steps, and can confirm those are due to individual resistors and not the switch contacts, then remedial work may be well worth it. You may even be able to confirm a much tighter tolerance than 0.5%.

author: tatel
author_rank: Frequent Contributor
timestamp: February 14, 2024, 11:56:06 pm
content: Well, this weekend I'll be back to where my workshop currently is, and I hope I'll get a first glance. Having just a week or so each month to be there, this isn't going to be a fast process, but at least I will get things going forward.

author: tatel
author_rank: Frequent Contributor
timestamp: February 15, 2024, 01:37:02 am
content: Quote from: Overspeed on February 14, 2024, 12:43:32 pmOui, j'ai trouve cet gadget en eBay France. Merci beaucoup de ces renseignements sur leboncoin que je met sous le coude.

author: Overspeed
author_rank: Frequent Contributor
timestamp: February 15, 2024, 04:39:49 pm
content: HelloIf you need shipping to Spain I can help you , as Le Bon Coin don't manage international shipping and most sellers dont ship outside FranceRegardsOS

author: tatel
author_rank: Frequent Contributor
timestamp: February 16, 2024, 12:57:04 am
content: Thank you very much for your offer. Happily une amie que habite a Hendaye can manage deliveries for me. Just a little problem, she won't be at home on delivery hours, so we have to make sure she can go to get the package somewhere. I guess the easier thing will be the post office.