Power / AV board replacement

Started by ChloeTigre, March 27, 2018, 02:40:14 pm

Previous topic - Next topic

ChloeTigre

Hi people, first public post!

So I'm working on a bunch of Famicoms,  buying them cheap and installing krzy's mod (works like a charm) when they're unmodded, or changing the mods to something nicer them when they're dead-bug-botched-modded.

Today I encountered a strange situation which almost cost me an eye (literal eye). This HVC-CPU-GPM-02 unit I had sitting there was bought as already modded. I just wanted a non-boxed Famicom so I could play games.

I identified a fried fuse (infinite resistance between the legs). Decided to short it just for tests. Plugged it to my TV, connected my usual power supply to it. Result just here  :-[



I'm not a good electronics worker and I have very little experience with a Famicom so I have a bunch of questions.

1/ Fuse has continuity (with the metal frame. Is it normal? I never asked the question and wonder whether this is OK.
2/ is a 7805 supposed to blow up this way? this is how I almost lost my eye. Part of it went flying around.
3/ What are the points on the PCB I should verify before changing a fuse? Like, to avoid short circuits and the like
4/ Are there replacement power PCBs on the aftermarket for this Famicom model? I'd love a basic one without the RF part so I could just put a audio/video jack on the back without drilling holes.

This unit was specially botched and when I received it there was an extra jack added to the metal carter. I suppose this is the reason for some of the other damages on the power board. The green coil on the board (the one with hot glue all around) is badly damaged and I'm pretty sure the coil wasn't this way.



Could this be a reason for the 7805 blowing up with a big CRACK noise and a spark?
-- ChloƩ - @chloetigrerouge

Pikkon

The metal frame is ground and the fuse should not have continuity to it.

Remove the fuse and 7805 and check for any shorts also it's not always the best idea to bypass the fuse as it can cause a lot more damage to the motherboard.

ChloeTigre

So, I fixed my 2 Famicom.

The continuity was an issue indeed, as the pad for soldering the fuse and the pad that goes to the metal shield solder.

I also found out after replacing the voltage regulator that the solder was not good and although it held in place there was a contact problem. Resoldering it (just melting it and letting it cool again) made the solder better and the contact was established.

I also gotta say that krzy's amps are just fine. He uses wrapping wire as input and output and I just added more wrapping wire to connect my output jack. This is clean and nice and works great. Only downside is the dual-sided tape he uses to hold the board in place doesn't adhere so well so I had to add more of it.

I'm modding my other Famicoms this week and will probably order more AV amps :)

Thanks for the advices and knowledge base this forum brings!
-- ChloƩ - @chloetigrerouge