Part 1: Teardown Mastech MS8040 Bench DMM - Page 1
Forum section: electronics / testgear

author: med6753
author_rank: Super Contributor
timestamp: December 06, 2016, 04:17:01 am
content: Subject of this teardown is a new Mastech MS8040 Bench DMM. Can the average electronic hobbyist with limited funds get a decent bench DMM for around $150 USD? I will attempt to answer that question. Part 1 will be the teardown. In a few days I'll post another thread which will be Part 2 and I'll evaluate it's overall performance. So in keeping with Dave's motto.....”Don't turn it on, take it apart!”....we'll get started.The box it came in. Was purchased from Amazon but was actually sourced from Circuit Specialists.The contents. The DMM with power cord. An actually decent pair of test leads. DB9 cable, install CD for the PC Link program, instruction manual (copy attached below), and carry strap. Also an adapter for the temperature probe as well as the probe itself. First impression is that it appears to be solidly built. It actually has some weight to it. No cheap plastic. Large LCD display.The top of the case opens to reveal a storage area for the probes, etc. That also provides access to the input fuses without having to open the case.First look inside. The top of case comes off after removing 4 screws. Power supply top center. Battery compartment to the right. You can use one 9V battery or 6 AA batteries. Mains power transformer below the battery compartment. Then a switch for the mains power and RS232 connector. To the far left is the input fuse board.The linear power supply. Plus some circuitry for the RS232. Overall the soldering looks good. The capacitors are “Kehong” which could be a problem in the future. Never heard of that manufacturer.The backside of the front panel. Separate fuse board for the amp and ma fuses. It's bolted directly onto the front input connectors. Mastech claims CAT2 certification. I can't pass judgment on that because I'm not familiar with the standards. I'll let others chime in on that.Fuse board removed from main circuit board.Main circuit board removed from front panel.The “money” shot. LCD panel pulled from board revealing a large chip. It's a Cyrustek ES51922A 22,000 Count Auto DMM. I have included the data sheet below. What's very curious is that the date code on that chip is 1401. If that's correct this DMM could be NOS (New Old Stock) and might have been sitting on a shelf for as much as 10 years or more. In Part 2 I'll show some other things I found that lead me to believe that it is indeed the case. But for now that completes the teardown.As mentioned in a few days I'll start of new thread for Part 2 evaluation of performance.

author: TiN
author_rank: Super Contributor
timestamp: December 06, 2016, 04:49:34 am
content: It's a hard justify, given plenty of deals in same pricing region at 200$ for venerable 34401A's, which are lightyears ahead of this portable DMM plonked into cheap plastic caseThanks for teardown, no worries there.

author: djos
author_rank: Unknown
timestamp: December 06, 2016, 05:20:26 am
content: Quote from: med6753 on December 06, 2016, 04:17:01 amSurely 1401 means Jan 2014 ?PS, I look forward to seeing more on this DMM.

author: med6753
author_rank: Super Contributor
timestamp: December 06, 2016, 06:02:55 am
content: Quote from: djos on December 06, 2016, 05:20:26 amI read that as week 14 of 2001 or am I mistaken?

author: djos
author_rank: Unknown
timestamp: December 06, 2016, 06:16:59 am
content: Good question, I always thought they only showed year and month but I may well be wrong.

author: djos
author_rank: Unknown
timestamp: December 06, 2016, 06:28:18 am
content: Actually I think we were both half right, I think it's week 1 of 2014.

author: med6753
author_rank: Super Contributor
timestamp: December 06, 2016, 07:19:25 am
content: Quote from: djos on December 06, 2016, 06:28:18 amYep, I'm mistaken. It is week 1 of 2014.

author: djos
author_rank: Unknown
timestamp: December 06, 2016, 07:30:17 am
content: Quote from: med6753 on December 06, 2016, 07:19:25 amHehe, we got there in the end.