VC8145 thread ... It's here, finally

[k2teknik]

Vichy VC8145 or Victor 8145? Which one to choose?

It is most likely not the same instrument, the Vichy is a 80000 count the Victor is a 33000 count, Victor seems not to have RS232
Victor 8145A: http://www.chenxiulian.com/ArticleShow.asp?ArticleID=839
Victor 8145B: http://www.china-victor.com/english/en/product_data.aspx?ClassID=173&ID=160
Vichy 8145: http://www.vicimeter.com/en/productshow.asp?sendid=8

[pascal_sweden]

So although the build quality is not that good on Vichy, it has much better specs than Victor (higher count and RS232 interface). Good to know!

Did somebody already do a tear down of the Vichy VC8145 bench multimeter and inspect the build quality and input protection on the PCB board?

Are there HRC fuses (High Rupture Capacity) or glass fluses?
What about MOVs (Metal Oxide Varistors)?
What about input protection PTC thermistor and large input protection resistor?
What about 10A current shunt?

[nctnico]

Look at the pictures here:
https://www.eevblog.com/forum/testgear/vc8145-thread-it%27s-here-finally/msg174988/#msg174988

[electronicnoobblog]

Hello,

I have question for owners of VC8145:

Does back-light can be enabled all the time or You have press button every time You want to see something?

(i came across some bad design, clone from handheld where You have to press it every time...
it was crazy...
maybe You save planet but meantime you end up in mental hospital for long treatment witch electric shock so basically it does not pay-off...)


If someone saw any video review it will be nice -> Sharing is caring!
Sometimes it's hard to base only of chines description.
I mean i saw some pictures in this topic from inside... looks nice at that price range, but sill that does not give overall expression abut measurements.

150 usd is a wired price range, to expensive to buy "just like that and thrown away if not nice like a 1 dollar crap" and to cheap to expect working like fluke or hp.

If someone could tell me, like a friend how does it goes in everyday working scenario.

Im asking something like this:
it have lot of buttons, does it for example need to make some multiple stupid clicking to just change from resistance to volt meter ?

Im please ask for that kind of comment abut this multi-meter

Regards

[nctnico]

The backlight if off by default but somebody posted a modification (a wire) which makes the backlight go on by default.
You can select between various modes with one button press. Only for the temperature measurement you need to press the select button to show the temperature of the probe. Otherwise it will show it's internal temperature.

[Dave92F1]

somebody posted a modification (a wire) which makes the backlight go on by default

That was me. But I ended up removing the mod, and I don't recommend it.

Turns out that it only works about 90% of the time. The other 10% you turn it on and it stays dark; if you did the mod then the button doesn't work, so you have to turn the meter off again, wait a few seconds and try again. I found that worse (1 in 10 times) than having to press the button each time.

I looked into installing a PIC to wait 500 mS then push the button, but the levels inside didn't seem to make that easy (I forget the details).

So I just removed the mod and now I press the button for the backlight.

I really like the meter, tho. It's accurate and has a very good UI (easy to use), other than the backlight thing. 

It does beep a lot. If that bothers you, don't get it. It doesn't bother me very much.

[electronicnoobblog]

The backlight if off by default but somebody posted a modification (a wire) which makes the backlight go on by default.
You can select between various modes with one button press. Only for the temperature measurement you need to press the select button to show the temperature of the probe. Otherwise it will show it's internal temperature.

somebody posted a modification (a wire) which makes the backlight go on by default

That was me. But I ended up removing the mod, and I don't recommend it.

Turns out that it only works about 90% of the time. The other 10% you turn it on and it stays dark; if you did the mod then the button doesn't work, so you have to turn the meter off again, wait a few seconds and try again. I found that worse (1 in 10 times) than having to press the button each time.

I looked into installing a PIC to wait 500 mS then push the button, but the levels inside didn't seem to make that easy (I forget the details).

So I just removed the mod and now I press the button for the backlight.

I really like the meter, tho. It's accurate and has a very good UI (easy to use), other than the backlight thing. 

It does beep a lot. If that bothers you, don't get it. It doesn't bother me very much.

Thank You, that's informing, i think i got everything what im asking for.
Pressing button once is not a problem.


Regards

[dev26]

I looked into installing a PIC to wait 500 mS then push the button, but the levels inside didn't seem to make that easy (I forget the details).

So I just removed the mod and now I press the button for the backlight.

Remove R70; then connect IC8, pin 12 with base of Q11 using resistor about 10k. Now the backlight is default ON, but the button can be still used.

It does beep a lot. If that bothers you, don't get it. It doesn't bother me very much.

Use the duct tape, Luke!

[pascal_sweden]

You could probably get in touch with the factory and ask them for a firmware update.
Is there a JTAG connector to the main processor?

[k2teknik]

Remove R70; then connect IC8, pin 12 with base of Q11 using resistor about 10k. Now the backlight is default ON, but the button can be still used.

Well seen, Q11 is a 4013 (Dual D-Type Flip-Flop) with a Q and an inverted Q output, so just switch to the inverted Q and the display light function will be reversed.
I was lazy and just lifted pin 13 and then shorted the pad under pin 13 with pin 12

Use the duct tape, Luke!

I desolder the buzzer.

[Dave92F1]

Remove R70; then connect IC8, pin 12 with base of Q11 using resistor about 10k. Now the backlight is default ON, but the button can be still used.

Thanks! I'll give it a try.

Use the duct tape, Luke!

I can't. I need the continuity beeps.

[dev26]

Use the duct tape, Luke!

I can't. I need the continuity beeps.

That is the idea - the beep is still here, but is much softer and quieter.

[Dave92F1]

Remove R70; then connect IC8, pin 12 with base of Q11 using resistor about 10k. Now the backlight is default ON, but the button can be still used.

I confirm it works great.

Even easier, just turn R70 by 90 degrees, then connect the loose end with a wire, as shown.

(BTW, be sure to clean the keyboard contacts on the other side with alcohol before reassembling, if there's any chance you touched them with your fingers.)

May I ask how you figured this out? If you have a schematic for the VC8145, could you please post it?

[dev26]

No, I have no schematic. I just followed wire from the button and saw it ends on clock pin of a 4013. Then looked to other pins - Q is connected with base of some transistor which controls the backlight's LEDs.

It's known way to use a flip-flop - "!Q" to "Data" (via R67), "Clock" to a button (R39+C8 for anti-bounce, R40 - push-down) , a delay circuit (R69+C36) to "Set". Result may be taken from Q or !Q.

[Dave92F1]

OK, thanks.

Unfortunately I backed out the mod - it vastly reduces the LCD contrast when viewed from straight-on or below. (It was bad to start with; with the mod it's worse).

[Dave92F1]

Hm. Replacing R41 (68k ohms) with about 30 ohms vastly improves the LCD contrast.

I don't fully understand why it needs to be such a low resistance. It seems to have more to do with the current flowing thru R41 (into the display controller) than the voltage.

[nctnico]

That is probably the contrast adjust voltage for the LCD display.

[pascal_sweden]

Does the manual document a procedure to calibrate the multimeter yourself using an accurate source?

Most expensive multimeters can be calibrated yourself using a detailed and documented procedure.

Or do you need to send it in to the factory?

[k2teknik]

Does the manual document a procedure to calibrate the multimeter yourself using an accurate source?

No, my version do not.

Or do you need to send it in to the factory?

That will most likely cost too much compare to the cost of the instrument it self.
Contact a calibration service near your place and ask them if they can calibrate it for you.

But maybe you do not know the difference between calibration and repair?
Calibration is a check if the instrument is within it's spec. the result is a yes/no, and maybe a more detail report.
Repair is what you do to make it return to spec. if it fails in the calibration process.

[pascal_sweden]

Are there many trim potentiometers on the PCB board?
Do they have a text marking?

Who has an email address to the manufacturer? Maybe we could contact them and ask for the detailed calibration procedure.

[k2teknik]

Who has an email address to the manufacturer?

Here you go: http://www.vicimeter.com/en/contact.asp

Maybe we could contact them and ask for the detailed calibration procedure.

Do not expect too much, I had tried a few times to contact them no response so far.

[torch]

Hm. Replacing R41 (68k ohms) with about 30 ohms vastly improves the LCD contrast.

Earlier in this thread you indicated that the light mod affected the contrast and therefore you reversed it. So in the end, did you re-do the light mod after swapping out R41? How did that work out?

[torch]

Way, way, back in this thread, someone asked about the >80Mohm measurement range. Today I tried measuring the 1090 Mohm 2% resistor in a recently acquired Heathkit 336 VTVM HV probe. Obviously neither the accuracy of the Vici nor the accuracy of the ~50 year old resister can be assured, so the following should not be accepted as canon!

The reading tends to wander up and down the scale a bit. Even breathing on the resistor changes the measured value. However, the wandering did generally stay within the supposed 2%, centered around 1092 - 1094 Mohms or so most of the time, dipping to 1078 if held a certain way and climbing to 2011 if held another way. The most stable and closely centered method seemed to be laying the body on a piece of wood with either end hanging in free air, connecting the probes with alligator clips.

[gatoazul]

Hi,

im interested in this meter.
How is it going over this years in terms of accuracy?
Could someone who owns this bench multimeter do some accuracy tests?

[nctnico]

Earlier this year I checked both my VC8145s against a Keysight 34461A and both where within spec. The VC8145 has a decent voltage reference inside so I don't expect it to wander off much.