My Leader LMV 89 AC Millivolt Meter - Page 1
Forum section: electronics / testgear

author: Henry Finley
author_rank: Regular Contributor
timestamp: January 30, 2022, 04:08:11 am
content: This is my Leader LMV89 Millivolt meter. Note that it is not a LMV189, where internet information and manuals can be found. This is the 89, where nothing at all can be found on it. Lacking the correct 89 manual I was able to famaliarize myself to some degree in tape recorder work, using the 189 manual. But questions remain. Firstly, it has banana jacks, which are approx 20mm apart, center-to-center. This translates to 25/32 of an inch. Will the dual banana to BNC adapters I see on ebay have the correct spacing for the plugs? And lacking a proper 50 ohm probe of any kind, is there no reason i can't use a cheap Chinese oscilloscope probe as my cable? Noteworthy is that there is a calibations sticker from 1981 on this LMV 89, which might help date it. I sure would like to know or find all I can on it. I've had it about 6 or 7 years and have come to prize it. It works quite well and seems accurate.

author: commongrounder
author_rank: Frequent Contributor
timestamp: January 30, 2022, 01:42:00 pm
content: I’m certain a dual banana to BNC adapter will fit the meter just fine. At audio frequencies, cable impedance matching is not critical. I actually adapted my meter through to RCA jacks to facilitate connections with audio gear on my bench using decent shielded audio cables. A scope probe can work, but it needs to be a 1x probe, or switchable to 1x. I just made some cables that were BNC to mini-clips if I needed to probe inside devices. Just be sure not to exceed the maximum input voltage on your meter. There’s nothing like an analog display for certain trending or comparative measurements!

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: February 07, 2022, 11:24:04 am
content: Really nice piece of kit - I have a dual-needle Kikusui which I too am fond of.My Kikusui is also a model for which no manual is available - it is just a little different also to the 'A' and 'B' models that were alongside it.The notable difference being that the chassis is lifted from the input grounds by 50Ω, whereas some of the similar models had switches to completely cut the input ground from the chassis (and thus each other too).Probably an obvious caution but given that you have a mains-powered meter, which may have grounded inputs, do watch for creating shorts when probing other mains-powered kit. Or, better still, resort to the DUT on an isolation transformer.The 'standard' for 4mm separation is 3/4" and so your 25/32" sounds like it probably is in fact that.I would also check any 'scope probes for series resistance - most x1 probes will have about 500Ω in series.

author: Henry Finley
author_rank: Regular Contributor
timestamp: February 08, 2022, 02:51:33 am
content: Thank you for that. I had assumed everything was on the secondary side of a power xformer. I gather 1x means 1x plus whatever unknown resistance the Chinese had that day while they were making these probes in their rat infested bathtub.Looks like my next purchase of necessity should be an isolation transformer (vintage American made). I don't want to fry my LMV-89. It is good Japanese gear, all-the-same.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 08, 2022, 03:20:13 am
content: It is not a defect. Typical scope probes are deliberately made with special resistive coax to cut down on reflections you'd get with regular ~50 ohm coax terminated into the 1 million ohm oscilloscope input. In other words it's just shielded, not a transmission line. Since scopes are not precision volt meters nobody cares if there's a few hundred ohms on top of the scope's 1 meg input impedance, especially when more often than not there's another 9 (10x) megs in the probe.

author: Henry Finley
author_rank: Regular Contributor
timestamp: February 08, 2022, 03:38:10 am
content: Quote from: BrokenYugo on February 08, 2022, 03:20:13 amThaks for the enlightenment. Obviously I am jaded by the amount of counterfeit crapola coming out of that country. 1.5 billion peasants with a computer taking 300 million here of their hard earned money to fill up American landfills. Too bad China can't filter out the fine goods made there, amongst the fake junk being peddled to suckers here. I've been bilked my last time on that worthless junk.