out of screen trace , (large -ve offset,wrong test voltage

[Jobinjoseph50]

Hi,

I have Orginal dso shell 22uznavA with 113 firmware analoge board revision E with activation from jye ,iam not getting trace in middle of screen as there is a -ve voltage offset all time.

these are the test point voltage with sw1 set to GND
av+ ,5v
av-,-5v
v1,2.1v
v2,4.3v
v3,.183v
v4,.565v
suppy voltage is 9 v with shorted input diode

I have checked soldering on u1 and u2 along with resistor and ic soldering in analoge board.

The Input coupling selection and all works fine and gets refelected in scrren when changing position.

I have checked sense 1,sense 2 ,sense3,sense 4 status according to the logic level chart listed in faq and is functioning fine.

I have tried all functions to alinement and default restore functions.

Problem is the trace has to be scrolled to middle of screen all time. a -ve offset is shown when measuring in sw1 in gnd position ie @ 20 v scale vmax is -42 volt or -36 mv at 5 mv input setting.

With this scope i can only see waweform and frequency all voltage related measurments are wrong.

Can sombody help with a solution to correct this? my guess is tl087 is bad!

[jye1]

Have you tried VPos alignment? Please try it if you haven't.

[Jobinjoseph50]

YES i have tried vpos alinment .

I can move the trace to middle of screen .but as i said earlier the offset -ve voltage is there all time even i have selected gnd position.

[Jobinjoseph50]

Hi All,
i have manged to find the issue ,the ic tl084 was damaged ,replaced the same and now device working fine.

if someboday else have similar issue with non zero v1 , v2 and v3 (large offset like mine around 2 v at v1 and v2) it is possibily the tl084 (ic u1 in analoge pcb)is damaged

[ShahRc]

Hi, I am newbie in electronics, I just bought 2 weeks ago (Fully Assembled 15003) and now the shell trace went top of the screen. V1, V2, V3 is not 0; Manual PDF from JyeTech was slightly different board than mine. Do you think it’s the same chip that is faulty?

[jye1]

Can you post photos of your board please ?

[ShahRc]

After assemble to take the following snapshot the trace looks like the following.

[ShahRc]

After reassemble it went back to square one



The trace went back up

[jye1]

Please check connection of the 2x5 pin-headers.

[ShahRc]

So far I can’t see any connection issue other than the solder joints on the 2x5 pin was not a best solder joints. Will try to re-solder and see the result.