Power Up Test DSO 068

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Re: Power Up Test DSO 068

Postby jye1 » Sun Jan 15, 2017 2:22 am

U2 is an opamp for analog channel. It is not relevant to the digital circuits. Digital circuits mainly include U4, LCD, and keypad. Please first make the digital circuits work then to look at analog problem. Here are some checking suggestions :

1 ) Have a look at C21 and C22 for correct value and good soldering. These caps are for oscillator of U4. If the oscillator doesn't work the chip won't work.

2 ) Replace the LED if you can in case the LED was a bad one. If no LED for replacement you can also probe (at pins of R26) the output of U4 pin 11 while applying power to see if you can read activity there.
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Re: Power Up Test DSO 068

Postby leonardmuresan » Mon Jan 16, 2017 9:09 am

Good morning !
I have checked C21, C22, for soldering and value. They seem to be OK. Xtal 1 as well. I measure over the LED 0,21 V. This value does not change by pressing SW12. Could it be that Xtal 1 is broken ?
Unfortunately I do not have any sophisticated equipment such as an oscilloscope.
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Re: Power Up Test DSO 068

Postby jye1 » Mon Jan 16, 2017 6:02 pm

If possible please try replacing the crystal. Frequency doesn't have to be exact 20MHz. Any 10 - 20M crystal can be use. Just to see if you can get LCD display.
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Re: Power Up Test DSO 068

Postby leonardmuresan » Sun Mar 19, 2017 8:05 am

Good morning ! After a long break because of an abroad course I have managed to resume yesterday the work. I have replaced the crystal a the scope is booting. All commands seem to work. I have now the problem of no trace. After the last power up test with the switches in the GND, 10 mV position and X1 i can get no trace With the switch in X2 position, 1 V, AC. a get a square signal. Any suggestion ?
Many thanks
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