PSU 5v issue

PCB problems and fixes
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vholfx
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PSU 5v issue

Post by vholfx » December 2nd, 2019, 9:18 pm

Hello,

I'm having issues with the PSU on my Pana Custom Supergun, specifically the 5v line. I'm measuring in two spots, at the PSU and after a fuse (250V 1A). The reason why I measure after the fuse it's because that's where the first voltage drop is (goes from 5v to 4.6). This voltage drop happens only under load (testing with a Neo Geo MVS1).

Here's a picture of where I'm measuring the voltage. Is this normal? Isn't .4v too much of a drop right after the fuse? I tried increasing the voltage on the PSU to the max, and then after the fuse it reads 4.9 (5.4 before the fuse), so the Neo Geo boots but resets after a few minutes, I'm guessing because of the undervoltage. The 12 volts line works fine under load before or after its fuse.

Any help is welcome!
20191202_174633_2.jpg

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cools
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Re: PSU 5v issue

Post by cools » December 2nd, 2019, 9:57 pm

You need to be measuring the voltage on the connected game PCB
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vholfx
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Re: PSU 5v issue

Post by vholfx » December 2nd, 2019, 10:10 pm

Well, right at the end of the JAMMA connector is pretty much the same as right after the fuse above, around 4.6. Same at the PCB.

I should mention the Supergun was working fine before, but at some point it blew up all 3 fuses, so I replace them (triple checked they are 250V 1A) and now I'm having this issue so I fear the PSU might have gone bad, but I'm hoping something can be done about it.

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thegreathopper
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Re: PSU 5v issue

Post by thegreathopper » December 3rd, 2019, 7:53 am

Sounds like your power supply may either have a dry joint or caps going out of spec, I would inspect the board and have a look for any obvious faults first.

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