Alda  M-838 multimeter teardown - Mastech M-838? - Page 1
Forum section: electronics / general

author: reagle
author_rank: Unknown
timestamp: November 15, 2012, 08:55:32 pm
content: Finally got around to take apart my old cheapo DMM. Purchased in the early 90-s for a few bucks!The thing still works, though the screens is starting to go. Looking around the input, I see no protection beyond the fuse. On the other hand they don't even claim any CAT ratings or agency certs for that matter, so at least they are being honestNotice a big Mastech logo near the UM7106 chip, and also M838-4 in copper under current sense shunt. Looks like a rebadged Mastech to me.

author: reagle
author_rank: Unknown
timestamp: November 15, 2012, 09:18:59 pm
content: And here is the schematic - can't vouch for the exact match, but looks close enough

author: steve30
author_rank: Frequent Contributor
timestamp: November 15, 2012, 11:05:45 pm
content: They've been making these things that long?Couldn't help but laugh at the 'Expression of quality' logo on the front, when I look at the placement of the components.Still, it strikes me as one of those things that will probably work fine despite being a bit dodgy.

author: reagle
author_rank: Unknown
timestamp: November 15, 2012, 11:17:21 pm
content: Quote from: steve30 on November 15, 2012, 11:05:45 pmAnd you would be right- the thing lasted me since 1994. Granted I did not subject it to any undue stresses and only measured low voltages

author: T4P
author_rank: Super Contributor
timestamp: November 16, 2012, 12:03:37 am
content: Expression of quality ... simply badged on the frontThe proper Mastech DT830s are simply much higher quality than any of the clones (Right ....)

author: reagle
author_rank: Unknown
timestamp: November 16, 2012, 03:26:15 am
content: Quote from: T4P on November 16, 2012, 12:03:37 amIsn't that how the boats are named? How it sails is a function of the name

author: amyk
author_rank: Super Contributor
timestamp: November 16, 2012, 07:12:43 am
content: That would be one of the infamous 830 series...Quote from: steve30 on November 15, 2012, 11:05:45 pmApart from the safety issues, they're as accurate as any other '7106-based DMM.Flukeused the same ADC chip long ago. The 830s nowall use a COBin place of the relatively expensive DIP40.

author: T4P
author_rank: Super Contributor
timestamp: November 16, 2012, 06:13:57 pm
content: Not when the 830B goes for 10yuan in local shops in china ... You can bet how many cents as cost to them

author: steve30
author_rank: Frequent Contributor
timestamp: November 16, 2012, 11:13:17 pm
content: So, did Mastech originally make the 830B and other cloned it, or are the similar ones just rebadged?Just wondering, as i have a Mastech M-830B and a SkyTronic 600.006 both of which are very similar, but the Mastech seems better quality.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 16, 2012, 11:35:11 pm
content: Quote from: steve30 on November 16, 2012, 11:13:17 pmI asked that a while back. Details athttps://www.eevblog.com/forum/general-chat/which-multimeter-or-company-started-830-design-case-that-is-so-widely-copied/

author: reagle
author_rank: Unknown
timestamp: November 17, 2012, 01:02:08 am
content: Unless the logo is fake, the board in this one seems to be Mastech