ESI RV722 - verification (and repair?) - Page 1
Forum section: electronics / general

author: Rax
author_rank: Super Contributor
timestamp: February 24, 2023, 08:54:35 pm
content: I just acquired this KVD and, as the seller has had as much respect for this when packing and shipping (and likely owning) as a doorstop - this was essentially wrapped in packing paper with some faint signs of intention of padding - it seems it's been tumbling across the US from NE to SW and it arrived to me with a wrinkled face and I have no idea what other damage inside and maybe on the knobs and whatnot. The knobs were set to rest "shut" (plus minus a few insignificant inches) against hard foam and carved into it as the thing traveled.I'll need to assess its condition and make a decision I keep it or not. The manual doesn't go into a basic functionality check.Does anyone have some thoughts on some basic, cursory checks? Obviously, OK to go into more detailed ones, but I'm for starters looking into basic functionality vs. abused to be broken.Thank you.

author: Rax
author_rank: Super Contributor
timestamp: February 24, 2023, 08:55:51 pm
content: Oh, well. I wonder if the admins could (please) correct the model number in the title. Obviously, this is an RV722. I don't think I can once I posted. My computer keyboard's been acting all morning.

author: TimFox
author_rank: Super Contributor
timestamp: February 24, 2023, 09:08:07 pm
content: That corner is most at risk in badly-packaged shipping, but may not have spread its damage to the interior of the box.What equipment do you have available to test it?Simplest test would be to apply a 9 V battery (or, better, a precision 10 V power supply) to the input and check the output on a good DVM as a function of setting.The best DVM for that purpose would be one with a "high impedance" mode at the full-scale setting needed to measure the voltage from the battery/power supply.Resistance measurements are not very useful.

author: Rax
author_rank: Super Contributor
timestamp: February 24, 2023, 09:10:46 pm
content: Quote from: TimFox on February 24, 2023, 09:08:07 pmI have a Data Precision 8200 calibrator, and a bunch of 10Gohm on input meters (8840A, 8502A, etc.).Good points, thank you!

author: TimFox
author_rank: Super Contributor
timestamp: February 24, 2023, 09:12:28 pm
content: That should work.Check the DVM manuals to clarify which full-scale ranges have the high impedance mode.

author: Gyro
author_rank: Super Contributor
timestamp: February 24, 2023, 09:17:46 pm
content: Quote from: Rax on February 24, 2023, 08:55:51 pmYes you can, you have to edit it in your original post.

author: donlisms
author_rank: Frequent Contributor
timestamp: February 24, 2023, 09:59:55 pm
content: I don't have one of those, but I have lots of dekastats and dekaviders and dekapots and such.The resistors are the usual wire-on-mica-card things, yes? They seem pretty sturdy, physically, unless you breath too hard on the edges, when the mica cuts through the wire like a knife and all is lost. Do not bump the edges, and make sure you do not bump the edges. And of course too much current us a thing, but the results of that should be either fairly obvious, if serious, or part of the thing's personality, if minor.So I might just measure across each individual resistor, and look for obvious decrepitude, just on general principles. There is, effectively, a big parallel resistor across each one, and the switch is in the wrong place at the moment, the values will look wacky, so give it a twist. "Slightly low, but consistent" seems like a good goal. Still, I would expect a low probability of the resistors being affected by the shipping badness.I would guess the probability of physical damage would be more in the switches, yes? And they come apart pretty easily; lots of little doo-dads and long screws and posts and so on. Maybe just a little unsoldering, which is a bit scary, because they might be the cadmium stuff. But even so, with a bit of care, you would probably survive the attempt of undoing and doing, not breathing any of it, and maybe... I don't know... some flux to reuse the original solder? Or maybe they don't need any such attention. You've no doubt already twisted them to see how they feel.In general, those switch contacts, if they're the ones I expect, tend to have a bit of silver tarnish here and there, and you end up with noisy readings on certain settings. I'm not sure if vinegar or electrolysis is the best answer for that. My personal goal would be perfection... somehow. But that's not a shipping thing, that's an age thing.

author: bdunham7
author_rank: Super Contributor
timestamp: February 24, 2023, 10:28:23 pm
content: Yikes! I hope the seller is willing to cough up considerable compensation if you do decide to keep it. I have no mercy anymore on negligent shippers, I've received so much smashed stuff that it is just sickening to think about.With 10.00000V in on the right and your 8502A on the left, you should be able to dial in any value you want. I'd check each decade separately and then take the cover off and inspect if for any loose, broken parts inside. If that's all good, then get some money back and keep it.

author: Gyro
author_rank: Super Contributor
timestamp: February 24, 2023, 10:51:34 pm
content: The best way to take out a bend like that is to clamp the panel between two thicknesses of sturdy man-made board (maybe with a sheet of greaseproof paper at the front for further paint protection) and then apply squeezing pressure by clamping it up tightly in a sturdy bench vise. Hopefully you will have sufficient space to span the entire width of the bend once the rear box is removed. Don't just try to bend the corner straight by hand, otherwise you will cause a bend in the opposite direction further in, damaging the connections between the switches.

author: TimFox
author_rank: Super Contributor
timestamp: February 24, 2023, 11:34:16 pm
content: If you have a voltmeter that supports a ratio measurement, the K-V can be measured very quickly for proper ratios.

author: BradC
author_rank: Super Contributor
timestamp: February 25, 2023, 01:14:57 am
content: Mine came broken :https://www.eevblog.com/forum/metrology/esi-kvd-wafer-repair/As far as verification, I bought an SR-1010 and then built a bridge to "calibrate" it (given I have no standard to calibrate it against I was really just calibrating its linearity). Frankly for what it had been through and its age it is in pretty good nick.I used it a few times and was just getting used to the calibration->measurement process when life got in the way and it went into the cupboard.

author: Swainster
author_rank: Frequent Contributor
timestamp: February 26, 2023, 04:00:47 pm
content: Not much help, but in the spirit of commiseration, I know just how you feel. I bought the General Resistance version (similar enough that the 2 dividers share the same army manual) - think it's called the GR 4107x where x is the version letter. On arrival, it exhibited some very puzzling behavior. Opening it up revealed that one of the mica wafer resistors had broken off at one end. There was enough of a stub to solder it back on, but I doubt it's done the instrument much good. I suspect that rough handling was the cause. At some point I will have to have a go at calibrating it (keeping half a eye out for an SR1010).

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 26, 2023, 04:09:27 pm
content: Many years ago I wanted a KVD and after talking to Julie Research they sold me their prototype of the VDR-307, serial number 1. It's different than the production units, with a different chassis and a large number of banana jacks on the rear for additional pick-off points. Here's the test sheet that shows what points they measure. It's quite faded but I boosted the contrast as best I could. By using the points they did, you avoid having to test all 1 million settings!

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 26, 2023, 08:53:37 pm
content: Hopefully nothing got smashed when the panel was bent. If you need photos of anything, I can open my RV722. Meanwhile, I scanned my Julie instruction 307 manual, which may have some useful info. There's not a lot of difference between the different makes.

author: Rax
author_rank: Super Contributor
timestamp: February 27, 2023, 04:33:21 am
content: Quote from: Conrad Hoffman on February 26, 2023, 08:53:37 pmThank you, Conrad, I appreciate this. I may ask for pictures of the inside, but haven't gotten that far yet. Thank you also for those instructions.