OSSC issues: One overvolted & Second no HDMI out?

[Caspian]

Hey, I got two OSSCs and sadly have issues with both. (these were bought around 2020)

The first one overvolted because I used the wrong power adapter. Expecting the board shows me that I was right:

As you can tell it’s dirty but if you look above C31 there seems to be a leak? While I have soldered some mods in the past, I’m not too verse in multimeter testing (I do have one so some suggestions would be nice.)

 

The second unit turns on, says it syncs with RGB like normal use but won’t output a picture from the HDMI.

Here are some photos

• This topic was modified 5 months ago by BuckoA51. Reason: moved to dedicated OSSC forum

[Morpheus_79]

For the first one:
Check if F1 has continuity and if the voltage regulators aren’t shorted. You can check the voltage regulators as described here:

https://github.com/marqs85/ossc_pcb/assembly/assembly_tips.txt at

Before turning on power (DC 5V / center positive / min. 1A supply), it’s a good idea to check that power supply lines are not shorted to ground. It can be done easiest by checking all the regulators:
-on bottom side, there are 8 small regulators in SOT-23-5 packages (U6, U7 etc.). Verify with a continuity meter that only the middle pin on the side with 3 legs is connected to ground
-on top side, there is one larger regulator (U5) behind the display. Verify that only the middle pin (on the side with 3 pins) and the heatsink pin are connected to GND

For the second one:
Do you get the gray test image without any input source? If not, U3 may be damaged.

[Caspian]

Thanks for the reply. I’m not great at testing in multimeter and still learning. So it seems it beeped via continuity and couldn’t really figure it out that way, so I decided to do a voltage check and it seems I get a voltage reading near the pins for the connector and a voltage reading for F1, but when it gets to D5, I don’t get a voltage reading and can’t get it in the caps (can capacitors give you voltages?) after.

I’d assume its an issue with D5? What is the name of the chip and is there a list with the name of the components used/

Ill check D3 on the other tomorrow.

[Morpheus_79]

I don’t think it’s an issue with D5, since (as far as i know) D5 isn’t necessary for the OSSC to work. It is a transient voltage suppression diode. It doesn’t do anything under normal workload, but provides an alternativ route for high voltage ESD pulses (to protect the ICs from damage). It’s a protection device and under normal circumstances the OSSC should work perfectly fine without it (same for D3 and D4)!

You can get a BOM (= bill of materials) for the OSSC here:

https://github.com/marqs85/ossc_pcb/raw/v1.6/bom/bom_full.xls

It should list all components and their markings.

If you are not even sure how to check for continuity via multimeter: maybe you should ask someone with some more experience in electronics for help!?

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