ESI RV622A Resistor Repair - Page 1
Forum section: electronics / general

author: gmilliorn
author_rank: Contributor
timestamp: April 27, 2024, 02:41:53 am
content: I have an RV622 that fails if standing on end, or if bumped laying flat. I traced it down to oneresistor that has a "bond wire" detached. It's hard to get a good picture, but the circled areais detached from the resistor.All these resistors look like the leads were spot-welded. I don't have such a tool, is it safe to tryto try to solder the wire? The end cap is pretty large and I don't want to melt anything.

author: scopeman
author_rank: Frequent Contributor
timestamp: April 27, 2024, 03:17:30 am
content: That wire is probably manganin or something simiar.https://en.wikipedia.org/wiki/Manganin#:~:text=Manganin%20is%20a%20trademarked%20name,the%20Bushy%20House%20physics%20laboratory.https://www.isabellenhuette.de/fileadmin/Daten/Praezisionslegierungen/Datenblaetter_Widerstand/Englisch/MANGANIN.pdfI am not sure what flux to use but when you find out please post. I saw on YouTube (search soldering Magnanin wire) where it looked like regular tin/lead solder was used but there were no other details available. I do know that once you fix it you need to coat the solder joint and the exposed wire with a conformal coating to seal out oxygen.SamW3OHM

author: gmilliorn
author_rank: Contributor
timestamp: April 27, 2024, 02:12:16 pm
content: It seems Manganin can be soldered, based on web searches plus comments from Edwin G. Pettis andothers such as here:https://www.eevblog.com/forum/metrology/manganin-zeranin-enamelled-wire-availability/From the close up of another resistor, the Manganin appears to be soldered while the lead is welded.Even though they look quite different, I assume the end-caps must be Manganin as well, or else theTCR would be affected?There are cheap spot welders on ebay, used to weld batteries. It might be interesting to try one, it'san inexpensive experiment and would prevent desoldering the manganin wire connection, perhaps.

author: gmilliorn
author_rank: Contributor
timestamp: April 27, 2024, 04:31:59 pm
content: Reviews of those cheap spot welders aren't very encouraging, and require an expensive LiFePo batteryor such. The lead wires are about 1mm thich at least.However, while searching, I found this comment from Earle Rich which discusses making just thesetypes of resistors:https://hackaday.com/2021/06/16/review-battery-spot-welders-why-you-should-buy-a-proper-spot-welder/#comment-6357273A bit too vague to replicate, though.

author: gmilliorn
author_rank: Contributor
timestamp: April 28, 2024, 10:30:28 pm
content: I could not find out if the wires inside are Manganin/Constantin or just copper. Since the point of a KVD is to eliminatethe effects of low-ohm switches, as I understand it, then I assume the wires are the same? All the internal wires aresoldered to the switches.Little info I could find on soldering manganin, other than a weird pair of youtube videos doing nothing.In any event, I cleaned the area w/1200 grit sandpaper and cleaned again with IPA, and was able to solder itrelatively quick with no issues. Either I was luckly or there's no issue soldering it.3x cleans after soldering with IPA and it seems to be fine.I can dial in any voltage within limits of my uncalibrated Fluke 8842, below reads as 1.0000V so I guess it isoff about 70mV.

author: gmilliorn
author_rank: Contributor
timestamp: May 01, 2024, 06:18:17 pm
content: Incidentally, in all my searches I never found any manuals covering the RV622A - only for thebigger RV722 which is larger values + trimmable, therefore a bit "fancier".If anyone knows of one it would be appreciated.

author: meandeev
author_rank: Regular Contributor
timestamp: May 01, 2024, 08:26:09 pm
content: I have a RV722, which is for sure not trimmable (but has a hidden secret ;-) seehttps://www.eevblog.com/forum/metrology/kvd-why-1-1-value-on-first-decade/), it depends on the age

author: gmilliorn
author_rank: Contributor
timestamp: May 02, 2024, 01:23:49 am
content: Hmm, I was basing the adjustment comment on this info in the RV722 manual:Perhaps they changed over the years...

author: Kosmic
author_rank: Super Contributor
timestamp: May 02, 2024, 04:04:13 am
content: Quote from: gmilliorn on May 02, 2024, 01:23:49 amThis is the newer version from IET (https://www.ietlabs.com/esi-rv722-dc-voltage-divider.html). The original RV722 from ESI can only be calibrated but not adjusted.