DSO138 troubleshooting - AV+ is negative (no trace)

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KeaganJ
Posts: 3
Joined: Sat Apr 07, 2018 1:14 am

DSO138 troubleshooting - AV+ is negative (no trace)

Post by KeaganJ »

The device boots and has the screen come up but no trace appears. I went through the AV- (no trace) guide but didn't see any issues. Using the voltage reference guide I measured AV- at -4.95V, AV+ at -2.1V, V1 at -1.29, V2 at -1.22V and all other voltages were correct (the voltages with a single star were all lower than the shown voltages). Any Ideas what the problem is?

Thanks
MNTech
Posts: 59
Joined: Wed Sep 13, 2017 2:23 pm

Re: DSO138 troubleshooting - AV+ is negative (no trace)

Post by MNTech »

If the display works you have 3.3V and the 5 volts that feeds the 3.3V regulator.
The 5 volt supply is connected to +AV through L3.
Check L3 with your ohmmeter and resolder its connections.
KeaganJ
Posts: 3
Joined: Sat Apr 07, 2018 1:14 am

Re: DSO138 troubleshooting - AV+ is negative (no trace)

Post by KeaganJ »

The inductor was bad and is now replaced. AV+ is now around 5v but still no trace.
MNTech
Posts: 59
Joined: Wed Sep 13, 2017 2:23 pm

Re: DSO138 troubleshooting - AV+ is negative (no trace)

Post by MNTech »

You may have the same problem as in this post
https://www.jyetech.com/forum/viewtopic.php?f=18&t=1658

If not provide more details.
KeaganJ
Posts: 3
Joined: Sat Apr 07, 2018 1:14 am

Re: DSO138 troubleshooting - AV+ is negative (no trace)

Post by KeaganJ »

All better now. Thanks for the help.
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