Problem with SEN1 switch

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GCS58
Posts: 2
Joined: Tue Jun 16, 2015 11:01 pm

Problem with SEN1 switch

Post by GCS58 »

I just assembled and tested the DSO138 kit. The kit is working well except for the SEN1 selector switch. When switching from 1V to 0.1V to 10mV the waveform display changes properly but the sensitivity label on the LCD panel stays at 1V for both the 1V and 0.1V positions. It changes properly to 10mV when the 10mV position is selected. I verified the proper operation of the switch and double-checked to make sure all the associated components were properly placed and soldered. This happens independently of the SEN2 switch and the CPL switch positions. For example - if I select 0.1V on SEN1 and X5 on SEN2 the display should indicate 0.5V but instead it stays on 5V. By the way, trimmer capacitor C4 has been adjusted to provide a nice flat square wave per the assembly instructions and all TP voltages have been verified.

Does anybody have any ideas?
amb
Posts: 12
Joined: Sat May 09, 2015 3:43 pm

Re: Problem with SEN1 switch

Post by amb »

There's a post very early on http://www.jyetech.com/forum/viewtopic.php?f=18&t=452 that's about the firmware but he also had a problem with one of the SEN switches that should help point you in the right direction.
GCS58
Posts: 2
Joined: Tue Jun 16, 2015 11:01 pm

Re: Problem with SEN1 switch

Post by GCS58 »

Thank you!
After reading your post I examined the SEN1 switch and circuit. I was getting only 1.4 ohms across R21 (which is a 3.3K resistor). After reflowing the resistor and the pins on the SEN1 switch I am now getting 2.62K ohms across R21 which is nearly the same as the resistance across R24 which is the corresponding resistor in the SEN2 circuit.

Everything is working perfectly now!

Thank you again for the help.

These forums are invaluable.
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