Faulty regulator

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fredfit
Posts: 12
Joined: 17 Jun 2020 12:50

Faulty regulator

Post by fredfit »

Hi all,

While I was doing some tests with my Z-Uno on a breadboard, I accidentaly short circuit the 5V pin to the shield of the USB socket (which I believe is connected to the ground). My Z-Uno doesn't work anymore, no LED goes on ...

On the bottom side of the Z-Uno, I see close to the 5V pin a component that I believe is a 5V regulator. It's marked with "RHD 117-5" (red arrow on the attached picture. Click to enlarge).
I think it's an equivalent of the LM1117-5 (or AMS1117-5) 5V regulator in a SOT223 package.
Very easy to find, I plan to replace it, there is enough place around to desolder it.

Before placing my order for this regulator, am I right with the LM1117-5 reference ? Do you think it can be the cause of the failure I'm now facing ?

Thanks !

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PoltoS
Posts: 6086
Joined: 26 Jan 2011 19:36

Re: Faulty regulator

Post by PoltoS »

To check it first connect 3 Volts to 3V3/Gnd and see if Z-Uno works as expected. 3V3 goes directly to the chip. It most cases the LDO regulator goes out in case of short circuit, but LDO usually protects itslef agains short circuits, so it had to survive.

The big one is for 7-18 > 5. You need to check another one. Please refer to: https://z-uno.z-wave.me/technical/power-supply/
fredfit
Posts: 12
Joined: 17 Jun 2020 12:50

Re: Faulty regulator

Post by fredfit »

Thanks a lot for your help PoltoS
Z-Uno seems to be working well when powered at 3V.
So the LDO regulator seems down. Is IC2 (MCP1700) the LDO regulator you are talking about ?
If yes, it's a very small SMD component but I will try to replace it.
The problem is that Z-Uno is no longer powered by the USB's 5V while being flashed. Can I power it with 3V to program it ?
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PoltoS
Posts: 6086
Joined: 26 Jan 2011 19:36

Re: Faulty regulator

Post by PoltoS »

yes, you can use 3V power when flashing.
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