Iwatsu SC7403 bench multimeter manual or schematics, anyone? - Page 1
Forum section: electronics / testgear

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 02:37:02 pm
content: So a fellow enthusiast offered me anIwatsu SC7403benchtop multimeter recently, that has an issue with one of the current ranges. And I'm tempted to buy it from him under the (bold) assumption that I *maybe* can fix that issue (or live with it, I guess), but as much as I tried, I couldn't find any user manual, service manual, or schematic of this device. There doesn't seem to be a lot of information about any of the Iwatsu multimeters of that family, in factThe closest I found was an Iwatsu multimeter selection guide, with the specs and differences between the SC7401, SC7402and SC7403(attached).I feel like if there's any place on the internet with information about this device it has to be this forumSo if anyone here have more information (ideally the service manual or schematic) of this instrument I would really appreciate it.Maybe this device is similar to a different device from another brand for which there's more information?I'll leave here a picture of the multimeter too, in case that helps identify potentially similar models.Thanks in advance

author: Kleinstein
author_rank: Super Contributor
timestamp: July 21, 2022, 03:04:10 pm
content: If the problem is only with the current ranges one could probably fix it even without a schematics: the current part is usually not very complicated and pretty standard with most meters, especially if range switching is manual only.One may still run into problems with broken old switches that are no longer avaiable.

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 03:21:28 pm
content: Quote from: Kleinstein on July 21, 2022, 03:04:10 pmYeah, I assume it's probably a broken trace, or a burnt component or something (because it's the highest current path), but I'd still love to have the schematics or service manual in case I find other issues or run into other problems in a future.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 21, 2022, 03:56:53 pm
content: Especially the higher current path should be relatively easy to follow, as the wide traces are obvious and not hidden vias or such at high current. A broken trace, solder joint, fuse holder or switch are the likely causes. So relatively easy to locate, but the switch may be difficult to source if needed.A service manua l would be nice, but not all meters have this and for the 4 digit range there may not be one.

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 06:55:00 pm
content: Quote from: Kleinstein on July 21, 2022, 03:56:53 pmMaybe I got extremely lucky but the last multimeter I bought (also with issues) was an LG 20000 counts bench multimeter. I still haven't fixed the issue it has, but at the very least I have the service manual for it. I'm tempted to buy the Iwatsu, but I never feel at ease buying vintage gear if I don't have a service manual for it. Especially if they already have problems (although in this case it *looks* like it's probably easy to solve).

author: Zenith
author_rank: Frequent Contributor
timestamp: July 21, 2022, 07:10:01 pm
content: I've bought some obscure test gear only because it came with a service manual.I've turned down other stuff at reasonable prices, such as a faulty 100MHz Iwatsu scope, because the service manual seemed to be unobtainable. With no service manual, it would have been doubtful if had been fully working, but faulty and with no manual it was a non-starter.IMHO, used test gear with no service manual is only worth having if it's free or silly cheap.

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 07:25:21 pm
content: Quote from: Zenith on July 21, 2022, 07:10:01 pmI feel pretty much the same.Out of curiosity, now: What would be "silly cheap" for something like this multimeter?

author: Zenith
author_rank: Frequent Contributor
timestamp: July 21, 2022, 07:38:52 pm
content: £10 / €10 / $10, that sort of price. The cost of a few beers.But I'm not looking for one.

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 07:41:25 pm
content: Quote from: Zenith on July 21, 2022, 07:38:52 pmI see. I was just asking because I've not bought the instrument yet. I could make an offer if I want it. The seller wants like $80 for it. I wasn't going to pay that, but maybe I could do a counter offer if it was reasonable to buy this instrument without service manual.

author: Zenith
author_rank: Frequent Contributor
timestamp: July 21, 2022, 07:51:41 pm
content: I don't know what prices are like in Chile, or what $100 dollars feels like there in terms of purchasing power. It's hard to compare from country to country.If I wanted a bench multimeter, I'd be prepared to pay more to get a less obscure one with a manual available, and a community of people on here familiar with it and ready to help with problems. Old test gear can fail. Often it's simple problems, but with not even a circuit diagram, it's at least very hard work to fix.

author: battlecoder
author_rank: Regular Contributor
timestamp: July 21, 2022, 08:59:46 pm
content: Quote from: Zenith on July 21, 2022, 07:51:41 pmThis is in fact my concern.It's not like I need the multimeter though. I have equipment already. It's just the temptation of getting another vintage 4 1/2 digit DMM. But I would definitely like to have the service manual and/or schematic for it before getting it (which is the whole reason for this thread), for the same reasons you outline. We are pretty much in complete agreement there.