Broke another famicom

[fredJ]

I broke another famicom right now when I was modding it, fiddling around with the capacitor on the PPU. Now there is just a white picture, no sound. Quite sure it is broken. Anyone knows what is the first to blow in such cases?

[2A03]

If you were fiddling around with that, I'd probably say you fried your PPU. Have you replaced the cap yet?

[fredJ]

Oops that's not good.
It should give a picture without the cap (cap between pin 40 and pin 21).
Maybe I'll go back to it later, or more likely use it for spare parts...

[Xious]

One of these days I'll get back to making this mod (to remove the lines). I made some decent progress on it during the winter, but I'm occupied with other projects at present. For what it's worth, the capacitor mod isn't really that useful.

The problem exists on the ground-plane from all I've discovered: If you remove the PPU and re-configure its grounds, being sure to ground your A/V mod to the revised PPU grounds, it will help a great deal.

It is likely that you damaged the PPU: Possibly shorting it out in the process, but more probably damaged by overheating it. I've killed a couple PPUs due to overheating them and I have to remember to throttle my de-soldering pencil temperature... I advise buying a temperature control for your tools to prevent this.

[fredJ]

Actually I thought the cap mod helped a great deal. First I tried 220 uF, then 470 and with 1000 uF I feel quite satisfied with the result.

I have done a slightly different mod then jpx72 described though.

Problem is that when I attach wires to the capacitor to make it fit inside the famicom, the result gets worse again. Should I try different wires, or a stronger capacitor?

I have learnt not to fiddle around with it now though. Just solder, test it, and desolder...

[133MHz]

The capacitor must be soldered as close to the PPU as possible. If you extend its wires you'll inevitably lose its effects. You should get the smallest capacitor in terms of physical size with an acceptable voltage rating and/or get creative with the mounting.

Try the WCF (Well Calibrated Finger) test on the PPU. Let the Famicom run for a minute or two and then touch the PPU chip with your finger. If it's too hot to hold your finger in it for a couple of seconds it's definitely shorted out.

If the PPU and/or CPU chips are gone, suitable donors could be found on a junked NES, since they usually die of cartridge connector disease.

EDIT: Just noticed you're from Sweden, which means you'd end up with a Franken-PAL Famicom.

[fredJ]

I will try that once I put every modd-component back again. I alredy removed them.

A friend told me that the famicom might just need to rest a litte while.

[Drakon]

pin 40 is 5v.  Pin 21 is video out.  You wired a cap between 5v and video out?  There's plenty of pictures/guides on the internet on the pinout of the ppu chip



If what you said is correct then you sent voltage to the video out pin of the ppu without any grounding.  This would be your problem.

[fredJ]

I actually put the cap between pin 20 and 40.

[2A03]

I actually put the cap between pin 20 and 40.

So you were mistaken before? You may have either sent 5V to the video output without knowing it, frying the chip, or you left your soldering iron on the PPU for too long, which would've also fried the chip.

A friend told me that the famicom might just need to rest a litte while.

Your Famicom might be "resting" for a *long* time if you don't replace the PPU.

[Drakon]

So you were mistaken before? You may have either sent 5V to the video output without knowing it, frying the chip, or you left your soldering iron on the PPU for too long, which would've also fried the chip.

You can leave the soldering iron on the ppu pins all day and the chip will still work fine.  Maybe he just connected 5v and gnd somewhere without realizing it.

[2A03]

So you were mistaken before? You may have either sent 5V to the video output without knowing it, frying the chip, or you left your soldering iron on the PPU for too long, which would've also fried the chip.

You can leave the soldering iron on the ppu pins all day and the chip will still work fine.  Maybe he just connected 5v and gnd somewhere without realizing it.

I wasn't aware the 2C02 was that resistant to heat. In most cases if you apply heat to a chip for too long it'll fry the chip.

[133MHz]

I've seen my share of 2A03 & 2C02 fried by electrostatic discharge, so I wouldn't consider them to be resilient chips.

[Drakon]

I've built a lot of rgb systems.  I desoldered the ppus and the ppus all worked fine after being desoldered.  Heating up each pin for extended periods of time to remove solder doesn't effect chips.  I've never seen a ppu or cpu fry unless someone wired the power and ground pins together or something retarded

[fredJ]

As I said, I was fiddling around with it, by which I mean that the cap was loose on one end and I put in on the pin manually, then removed it back and forth, to see if I could see the difference in white bars. Hope you understand.

So yes, I might well have touched on the wrong pin or something restarted.