Trouble with calibration (C5 has no effect, bat test signal)

[jelinj8]

Hello,
I like the scope, but I have trouble with calibration (and usage).
The testing signal is OK on 3.3V, but the 0.1V square isn't at zero - it has about 3V offset (tested with a Owon 60MHz DSO).
I have tracked the test signal generation to voltage divider (R16 and R31). R31 is rated in the schematic to be 470R, but the SMD resistor on the board is 22R. I don't get where I'd get the 0.1V with 470R or 22R R31 on J8.
Setting input to AC and changing C5 has no effect at all, getting reasonable 0.1V test reading in DC mode isn't possible.

Thanks for advice.

[chris2u]

It's C3 that you have to adjust with the .1V signal..

I found that with the test signal at .1V (with couple switch set to AC) and with the sensitivity set to 50mV, I could adjust the waveform OK with C3.

With the test signal set to 3.3V and the sensitivity set to 1V, I could not completely get rid of the overshoot on the waveform by adjusting C5.
A 33pf cap paralleled across C6 remedied the problem..

[jye1]

@jelinj8:

Please use AC couple for the 0.1V adjustment. It is a bug in the firmware that caused the 3.3V offset. Will be fixed in the upcoming firmware release.

[Keichan2017]

Could you please tell me whether new firmware has been released?

[nunoit]

its been released last 3 055

[nunoit]

well got my 3 dollar http://www.ebay.com/itm/FTDI-FT232RL-US ... Sw-0xYVDs3 upgraded from 054 to 055 with out a hitch.

follow this
http://www.jyetech.com/Products/LcdScop ... rmware.pdf