Repairing my faulty F48

Mark_M

Annoying Elf
Generous elf
Joined
Dec 30, 2018
Messages
912
Location
Christmas Light world
Here's a write up and video about me fixing my F48 not powering on.

My light show was running fine December 4th 2023 up until 9PM.
At first I saw the network ports indicator lights were off and the OLED was displaying 'Idle'. On power reboot the board did not turn back on. Uh Oh!
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The next day I powered it on and saw two power indicator LEDs flickering. Some sign of life, which indicates it could be a thermal related issue (cold start).
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Probing around the board with a multimeter in DC voltage metering, I found that the input voltage from the PSU was indeed at 5v.
Next was measuring the voltage regulators. VR1 is a 5v to 3.3.v regulator. VR2 is a 3.3v to 1.2v regulator. VR1's output is wired to VR2.
VR1 should be receiving near 5v from the power input to the board, instead it was supplied ~2.4v.

Measuring up stream;
Q2 and Q1 are mosfets controlled by U2 chip. U2 is a over voltage, over current and reverse polarity detection device which will not bias Q1 & Q2 mosfets if there is a problem.
Q1 & Q2 won't work with or without U(2).

Measuring Q1 P-Channel MOSFET, there was very little voltage across drain and source.
However, Q2 N-Channel MOSFET had 2.6v drop across drain and source!

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Confirming on thermal camera, this component was hot.
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Now luckily this isn't the streets with no name and these components have a number!
And unlike U2, I have found what I'm looking for:
Here's the part numbers which David Pitts emailed to me:
Q1P-Channel MOSFETDMP6180SK3Q-13
Q2N-Channel MOSFETDMTH4007LK3-13

I didn't receive this email until after I ordered DMTH4007LK3Q-13 from Mouser Electronics.
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After waiting for a few days DHL shipping I received 10 DMTH4007LK3Q-13. On the 11th it was time for some really bad soldering with my under powered soldering iron.

View: https://www.youtube.com/watch?v=yuquTRQkcZ4



And it's a Beautiful Day! The fix worked. It's the Sweetest Thing!
(I'll stop with the U2 jokes now).

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Thank goodnes the controller was working for the rest of December!
I plan on taking my F48 into University soon and use their better soldering equipment.
 
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