Mastech 5908C Multifunction Tester (Lite)

[AndyD]

Mastech 5908C 'Circuit Analyzer'

Price; Under a grand ZAR.

Looks like this;



Tests performed;

• True RMS
• Ground to Neutral Voltage
• Peak Voltage
• Frequency
• 5A/8A/10A load for volt
drop test
• Socket test function
• RCD / GFCI test
Line Volts: 85 - 265V
Neutral/Ground: 0 - 10V
Peak: 121 - 374V
Freq: 45 - 65Hz
Volt Drop: 0.1 - 99.9%
RCD trip time: 1ms - 6.5s
RCD trip Amp 30mA
GFCI trip time: 1ms - 6.5s
GFCI trip Amp: 6mA

Has anyone got any first hand experience of this tester? I have a Mastech multimeter with logging that I use on my repair bench, it's a couple of years old, always been accurate and recently passed a calibration. The input stage on the multimeter isn't as well protected as a Fluke for example, it's classed as CATIII but lacks in physical separation and fuse quality. That said I'm aware of its limitations and only use it for electronics benchwork.

The 5908C does an impressive array of tests and given the price it would be rude not to buy one if it does what it says. Just wondered if anyone had any advice about whether it's fit for purpose.

MS5908C.pdf

[Dave A]

It looks like you'll have to be our tester, Andy.

I have to say it does look interesting...

[AndyD]

Already ordered last week, will keep you posted.

[AndyD]

Okay, as of this afternoon I'm the proud owner of a brand new Mastech 5908C 'Circuit Analyzer'.

Contained in the box is;
1x Zip pouch
1x Instruction booklet (identical to the pdf in the post above)
1x Mastech 5908C tester
6x AAA batteries
1x Test lead with a 10Amp IEC 60320 plug on one end (computer type plug) and a 16Amp Schuko plug on the other end.

Why it comes with a Schuko plug on the lead I can't imagine, as far as I know schuko sockets aren't even legal in South Africa.

[AndyD]

Removing the battery cover and another 4 screws on the reverse side of the tester the entire back easily separates to reveal the single circuit board inside.



A considerable spiral of plactic came out with two of the back panel screws which appear to just self-tap into the posts on the front panel and on later reassembly one of the screws didn't tighten fully.

The internal circuit board looks fairly neat at first glance, all the components are SMD with no through-hole components that I've seen in abundance on cheaper testers in the past. There's numerous empty solder pads scattered around the board along with a solid plastic blanking plug on the LHS of the tester where a button might go which suggests there's at least one more model available in this form factor with extra components and probably extra tests it can do.

The soldering on the input pins is borderline passable at best and there's no slots cut into the circuit board to create safety separation between the input area and the logic area of the board. The input fuse looks like it might be silica filled but it's small and of poorer quality than the HRC fuses you get in more expensive testers. Also there's only a single fuse and a very small surge arrestor by the looks of it and there's no containment panels molded into the back panel to surround the fuse and the MOV to contain any flash that might occur should they ever blow.

According to the literature the rating of the tester is IEC 601010-1, 300v, CAT III. I'd probably be happy to use the tester on single phase domestic circuits but the safety of the input stage doesn't instill much confidence and I'd be loathed to use it anywhere with higher than average PFC, anywhere where there may be high voltage transients or where there could be any chance the 300v limit might be accidentally exceeded.

[AndyD]

The input stage of the tester also has a large 5 Watt resistor which is mounted on top of a small chip. I'd guess the resistor is for performing the voltage test with a 5A, 8A and 10A load and the chip underneath it is for sensing over-temperature of the resistor which is going to heat up pretty quickly during this type of test. The resistor is sitting at an angle above the chip and there's a gap of a couple of milimeters between them. I'm not convinced about the effectiveness of this arrangement as protection against overheating, a thermal fuse would have been a nice addition here.




Under the microscope it's easier to see the angle and distance of the components relative to each other;

[AndyD]

A closer look at the board shows that there's several areas where the components were soldered on by hand. The quality of the soldering and the amount of residual flux and contamination is very poor.

This is the MOV surge arrestor on the input stage;





This is some of the SMD soldering under a microscope showing large amounts of contamination;

Gawd knows what all the black bits are...


I'd be interested to know if R16 is supposed to be there....

[AndyD]

So.....to sum up so far, I guess you get what you pay for.

On the down side it's got minimal, probably borderline passable user protection. The general build quality and ruggedness is average until you get down to component level on the board when it becomes unacceptably poor and it comes with a plug that's not relevant in this country.

On the up side is it's low price and wide range of tests it can apparently do.

I'll get around to doing some tests with it this weekend and report back again.

[SeanM]

Morning Andy

Thank you for the on depth feedback so far. Very interested in the update on the testing.

[Dave A]

Gawd knows what all the black bits are...

Flux?
(Kinda reminds me of my early soldering days )

[AndyD]

The photos were taken at around 20X magnification and the black bits aren't really visible to the naked eye.

The whole area is covered in residual flux and flux usually comes out of a syringe so it's clean, the black bits are something else entirely. Looking at the board they haven't reflowed using a hot air station so I'd guess it's a build up of burned crap that was on the soldering teezers or pencil iron they used. Maybe they scraped the shellac of the solder pads on the board using the iron or hot tweezers and that resulted in bits of blackened and burned varnish.

If it survives the testing regime I have planned for it and I end up keeping the tester I'll probably give the board an hour in the ultrasonic bath.

[AndyD]

Just a note to let you know I haven't forgotten I promised to post some test results. I made some initial tests and all did not go well. I'm in the process of some further investigations which are taking longer than I anticipated.

[AndyD]

Okay, a late update with this unit.

All didn't go well. The main reason I was interested in this particular tester was its ability to do 5Amp, 8Amp and 10Amp on-load tests. The tester I bought did none, or rather it did the tests and gave results with dubious accuracy but it didn't introduce a 5, 8 or 10 Amp load whilst it did them. I even tested it it using a high sample rate on an oscilloscope in case it was so fast it was outside the sample rate of my Fluke bench meter but alas nothing.

I returned the unit and exchanged it as faulty for another new one. The build quality of the new one was marginally better, it didn't have the black particulates on the board and considerably less residual flux but it still yielded exactly the same results.....or lack of results. I kinda lost interest at this point because I couldn't find any board-view schematics online and I don't have time to start from scratch reverse engineering the circuit to localise the problem(s).

This one was a bust unfortunately.

[Sparks]

Thank you Andy, your contributions are much appreciated.

[BobZA]

Thanks Andy. Was going to post a question on the build quality of Mastech … but I think you have covered that well. As you say I guess what you pay is what you get ...