Calibration using C3 and C5 not working

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shail
Posts: 3
Joined: Thu Nov 24, 2016 1:32 am

Calibration using C3 and C5 not working

Post by shail »

I've followed instructions and checked all voltages for DSO Shell 15001 kit.

I am unable to make a perfect square wave using trimmer c3 and c5 adjustment. Also noticed that test signal voltage level is very high. See the attached picture.
Test signal 0.1v appears as 9v signal. When I change test signal to 3.3V it goes up to 50v
Attachments
IMG_20161123_150827.jpg
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Calibration using C3 and C5 not working

Post by jye1 »

There might be gain error for the amplifiers. Please check resistors R5, R6, R13, R14, and R15.
shail
Posts: 3
Joined: Thu Nov 24, 2016 1:32 am

Re: Calibration using C3 and C5 not working

Post by shail »

jye1 wrote:There might be gain error for the amplifiers. Please check resistors R5, R6, R13, R14, and R15.
I've checked all resistors again.

R5, R6 is 620k when soldered on the analog board. I've also measured it after desoldering them it those are 1k.


Resistor values
Measured after soldering
R27 : 120
R26 : 120
R16 : 150
R14 : 1K
R15 : 680
R13 : 150
R6 : 620 (if measured after soldering to the board, otherwise 1k)
R5 : 620 (if measured after soldering to the board, otherwise 1k)
R12 : 15
R11 : 15
R10 : 30
R9 : 91
R8 : 150
R7 : 266

Voltage Check
Input : 8.10v
V+ : 7.17v
AV+ : 5.85v
V- : -6.53v
AV- : -5.31v
V1 : 0v
V2 : 0v
V3 : 0v
V4 : 1.44v
V5 : -0.96
jye1
Posts: 1228
Joined: Wed Feb 20, 2013 4:58 pm

Re: Calibration using C3 and C5 not working

Post by jye1 »

The numbers look good. Please try factory default restoration as instructed in the manual.
qu1ck
Posts: 24
Joined: Tue Nov 29, 2016 4:43 am

Re: Calibration using C3 and C5 not working

Post by qu1ck »

Judging by the picture you have C1 and C4 mixed up. The bigger one (0.1 uF) should be on the right.
shail
Posts: 3
Joined: Thu Nov 24, 2016 1:32 am

Re: Calibration using C3 and C5 not working

Post by shail »

qu1ck wrote:Judging by the picture you have C1 and C4 mixed up. The bigger one (0.1 uF) should be on the right.
You are right, Issue has been fixed :-).
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