#6 - Mastech 5308 LCR Tester Update

This is a follow up to the Mastech MS5308 review and talks about the external power module

[globin]

I am shopping for one of these and note (3 years later) that the unit no longer comes with an AC power supply and any photos I can find have the top view edited (markings brushed out)

[jwrelectro]

Sorry to hear about your unit failing. I made a longer comment to your posting over on Dave's forum. I have almost completed a schematic diagram of the power supply and may post some more follow ups.

[xydo]

Thank you for your video on Mastech 5308. Very helpful.

About this PSU - it seems to me like a not very good PCB design for a switching power supply. Thin long traces, etc. They have a 2-layer board anyway, why they didn't put a solid ground plane(s) on the back? Hence EMI and different effects from oscillocsope connection.

[jwrelectro]

Your absolutely right and sorry for left channel only. When I edited the video I forgot to copy the left to right channel (making it mono). I use a wireless microphone and the reason the audio was not very good is I didn't notice the battery low indicator. Again I am sorry for the poor audio and I promise to check things better in the future.

[DanFrederiksen]

I kept wanting you to zoom in on the signal on the scope but you never did...
An inductor prior to the output capacitor might fix the problem. Likely.
A common mode choke on the output might also. It could be radio frequency interference. Grounding a single lead shouldn't otherwise make a difference in a circuit as I understand it.

[uKcvPAq]

The lack of Y capacitor is probably to prevent leakage current on the output.

[jimviau]

If a user must make his own power supply to get his instrument running it may not be too bad considering the price. What bugs me most is IF the instrument is that much sensitive on power supply signal I just cannot trust it. For me it would be a NO NO. After all, a testing instrument must be trustable at all levels.

[DLTX]

lol massive noise, i guess the LCR meter does not read weirdly once the ground is shunted away, maybe it's because the LCR meter is floating and the PSU is not.
Oh and i heard high frequency components throughout the video

[freeradical]

Get rid of the cheap Chinese CHENG cap and use an actual Low ESR cap which is what should have been used there. A Panasonic FM or FR should be good enough.

[pecocoa]

You speaking only on left audio channel is super annoying with headphones, better to have just mono audio than that...

[GaRbAllZ]

It doesn't look like they spent a penny on noise suppression. What a piece of junk.