Debranded Micsig handheld scope on sale on eBay

[mstck]

Mstck - are you sure your conductive pad is up to snuff? IIRC another member mentioned that the 1st one he tried didn't work. It looks like it has worked for everyone so far but two guys, did both of you try multiple pads or directly completing the circuit?

Thanks for the suggestion.  I was beginning to think along the same line since absolutely nothing happens when I press the "Meter" key.  I ordered these... https://www.amazon.com/gp/product/B017OIKGMW/ref=oh_aui_detailpage_o02_s00?ie=UTF8&p;sc=1 as recommended by mtdoc in post #68.  They install on the membrane, not the key. As such, I was wondering if there is a need to  place something in the hollow of the key which would push on the contact when the key is pressed.

I will open the unit again after xmas festivities, and see if I can energize it outside of the case to test if the pad works.

[mtdoc]

Mstck - are you sure your conductive pad is up to snuff? IIRC another member mentioned that the 1st one he tried didn't work. It looks like it has worked for everyone so far but two guys, did both of you try multiple pads or directly completing the circuit?

Thanks for the suggestion.  I was beginning to think along the same line since absolutely nothing happens when I press the "Meter" key.  I ordered these... https://www.amazon.com/gp/product/B017OIKGMW/ref=oh_aui_detailpage_o02_s00?ie=UTF8&p;sc=1 as recommended by mtdoc in post #68.  They install on the membrane, not the key. As such, I was wondering if there is a need to  place something in the hollow of the key which would push on the contact when the key is pressed.

I will open the unit again after xmas festivities, and see if I can energize it outside of the case to test if the pad works.

Yeah, those worked well for me. The resistance on the conductive pads I had salvaged from a calculator was too high. 

Yes, I glued one of the rubber bumps from the calculator pad on to the underside of the Meter button where the conductive pad had been. This provided the needed protrusion to push on the conductive pad.  It has been working very well.

[mstck]

Thanks mtdoc. That additional "filler"  is likely to be the source of  my problem. Do you know if  super glue would work on this material?

[mtdoc]

I used silicone adhesive.  Super glue (cyanoacrylate) might work but it can be brittle after curing - so not the best choice IMO.

For the "filler" any firm but rubbery material should work. One of those small, self adhesive rubber feet might be a good choice as well.

[eKretz]

In the scope section I also noted the DC offset seems to float quite a bit in the low mv range. Looks like I did get serial triggering actually - I was looking in the wrong place. Also in the system information tab it shows "Model HighRefreshRate"  "Model Udisk" (USB data recording) and "Model XY" (XY Mode) options installed.

The data logging looks useful enough and is pretty easy to use. It can log at different time rates and logs on a graph like a scope screen. While viewing the record you can use cursors to get exact voltages and time stamps, as well as graph slope.

I used a USB 2.0 stick for logging tests and it did fine with that. Inserting the USB also activates the Screen Shot button so it isn't grayed out anymore. Haven't played with that yet to see what it does though.

It looks like the disabled multimeter and neutered firmware have only got two negatives as far as I can see - no probe compensation and no external trigger. Both functions are tied to the multimeter and are missing from the neutered firmware.

[eKretz]

Sure would be nice if we could figure out how to "re-Micsig" the scope and be able to flash the firmware to restore the probe compensation and external trigger. I wonder what the problem was that caused them to disable the meter and discount these. My jacks were externally both perfectly functional and not smashed or bent at all.

[mstck]

Hi all. Success. I finally have the DMM section working, thanks to you. I have only done a quick check, but everything seems fine so far. I observed that the beeper used for the continuity check is virtually inaudible as mentioned earlier, and wondered if  anyone has identified a fix for this. Not a game changer, just nice to have.

Thanks again for your assistance.

[eKretz]

Mine has the "barely there" continuity beeper as well. I haven't played with it to investigate why yet.

I was doing some scope work today and found that I have what seems to be a faulty probe though. The trace jumps all over the place when the probe wire is jiggled even when the ground wire is shorted to the probe. The other probe's trace is stable with the same treatment. Swap the probes to the other channels and the jumpy behavior follows the faulty probe.

I also noticed that the DC offset float is quite a lot worse on channel 1 than on channel 2 - even with good quality probes installed.

[eKretz]

Have you other guys done anymore testing on your scope section of the meter? Just wondering about the DC offset accuracy - the manual says 2% - mine is way worse because it keeps jumping around - Channel 1 is worse than Channel 2, both seem out of spec. In the 20mV range with a LeCroy 10:1 probe I'm seeing mean voltage jump around like 6-8mV.

It also jumps around similar percentages higher ranges, some seem better than others. This makes it kind of tough to use cursors unless it's a one-shot or sampling is stopped. I've tried performing both the regular 'calibrate' function and the 'fast calibrate' function but almost immediately the voltage starts jumping around again.

I guess I'm wondering if everybody has the same issue or if I have a unit with a problem.

[TurboTom]

Did you run the calibration after the scope has warmed up? Mine had a pretty obvious offset as well that caused the trace to jump around when input sensitivity is changed. Moreover, there's also quite a strong temperature dependancy of the offset voltage, so depending on ambient temperature and warm-up time, the effect may reappear. Yet, the auto calibration function compensates the offset (at the then present temperature) quite well.

Cheers,
Thomas

[eKretz]

Yes, I did indeed. I tried waiting half an hour the first time, and varying times up to 2 or 3 hours. No matter how long I let it warm up, either calibration routine brings it back to zero momentarily, then it starts to float up and down again all over the place within less than a minute. I don't mean a slow drift either. More like an oscillation. This happens  whether I have no probe connected, have a probe connected and grounded, and even when displaying a signal.

This is running on battery also, and no stray signals around - again this doesn't happen on my bench scope when they're sitting within a couple feet of each other.

[eKretz]

Here's a video, this was after a couple hours warm up time:

http://s240.photobucket.com/user/eKretz/media/Pub/TRIM_20161231_013516.mp4.html

[eKretz]

Just been doing some more playing/checking. Discovered that if I ground couple Channel 1, it still fluctuates about 0.4mV - more than my Tek when DC coupled (but probe grounded). Oddly, after reverting to DC coupling it also seems to reduce the DC offset wander by a decent amount - before being ground coupled it wanders near 8mV in the 20mV range - after ground coupling then switching back to DC coupling, the wander drops to more like 3mV. Still outside the rated 2% though. In 1V range before ground coupling it was wandering 350+mV, after ground coupling, a little over 100mV. After a few minutes it starts going back up again. Hoping some more guys will check in so I can see if it's just my unit doing this - I know blackfin? was it? mentioned something about this too.

[rpress]

I see a similar offset problem, only on channel 1.  On the 100 mV range I see a jump of -18 mV, which is consistent.  It will change to -18 mV offset for a while (up to a few seconds) and then jump back to zero.  In 2 mV range the jump is 0.4 mV.

Ground coupling seems to give a nice steady trace with no jumping of the offset.

[eKretz]

Thanks for checking in. Sounds like yours is quite a bit better than mine. Mine goes both above and below zero, and quite a bit more in magnitude than yours. I just uploaded a video showing how it starts doing this immediately after a full calibration. Should be able to post it today, been having difficulty with my upload being viewable on Photobucket so I just switched to YouTube.

[rpress]

I decided I would try to fix the offset problem.  I started by swapping ICs from the AFE of channels 1 and 2.  The first thing I noticed is a ton of flux residue, a lot of it under the ICs as well as around them.  As I swapped them I cleaned things up with isopropyl alcohol.

Just swapping/cleaning the ICs mostly fixed things, and the problem did not move to channel 2 so I don't believe the ICs themselves were a problem.  I still saw an occasional offset wander so I cleaned the discrete amplifier stage just before the VGA.  This is the group of components just above the QFN component (the VGA).  After doing this it has practically eliminated the problem.

https://youtu.be/o34ETXZH-yg

Sorry I don't have a before video.  Maybe you could try cleaning yours (without removing ICs) to see if it has an effect.

[eKretz]

I will give that a try as long as they don't have a problem with it. Thanks!

I assume AFE = analog front end, and I know what to look for as far as the QFN package VGA. So the AFE will be the isolated boards connected to the BNCs, right? (I remember from Dave's teardown video of the similar scope). You swapped ALL ICs there?

[rpress]

Once open, remove the single screw holding down the metal cover near the BNC and take it off.  Make sure you are on the correct channel. 

I swapped the LMH6518, AD706, and OPA4872.  I did not swap the transistors.  I do not recommend you do this, these parts are quite expensive and the LMH6518 is challenging to solder.  Try a thorough cleaning first with a fine bristled nylon brush (toothbrush?) and alcohol.  Apply heat to dry.

[cdev]

Make sure to remove the battery and all power before cleaning and drying it.

Does the Windows application run under Wine?

[rpress]

Does the Windows application run under Wine?

I plugged the USB into my Fedora 25 desktop.  It detected the device but no driver was loaded.  Because there is only a 32-bit Windows driver I am thinking it is a custom device and not some USB-serial converter chip that could be used with Linux.

[cdev]

What does "lsusb" say?

[rpress]

lsusb:
Bus 003 Device 005: ID 3955:1956 

dmesg:
[68476.341130] usb 3-1: new high-speed USB device number 5 using xhci_hcd
[68476.509840] usb 3-1: New USB device found, idVendor=3955, idProduct=1956
[68476.509846] usb 3-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[68476.509849] usb 3-1: Product: Microscope C
[68476.509851] usb 3-1: Manufacturer: Microscope Co., Ltd
[68476.509853] usb 3-1: SerialNumber: M

[eKretz]

OK I think the issue has been found. I tried doing the flux residue cleaning and swapped the 706s and 4872s from channel to channel with no results. Then I went ahead and swapped the 6518s and the unstable offset problem changed from Channel 1 to Channel 2. Looks like faulty or damaged 6518s.

[Mikke]

Hello everyone,

After reading this interesting thread I bought one myself. So far I am happy with it, especially since I had no scope at all before.

However, I have one question to other owners of this scope:
Does the Recorder-function work in your units? It seems that mine starts recording from multimeter input, but using scope inputs recording just doesn't start. I haven't tried to fix the multimeter yet, so at the moment I have no recorder at all.

By the way, it seems that the selling price is now more than doubled.

[mtdoc]

Recorder function works fine on mine - both meter and scope.

It's crazy that they raised the price that much.