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Author Topic: Famicom issues - no picture, no sound and getting very hot quickly!  (Read 8065 times)
ScoreAddict
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« on: December 16, 2014, 09:02:31 AM »

Hi!

So I bought my first Famicom some weeks ago. And since the guy selling it to me basically ripped me off, I put it in a cupboard waiting for my anger to subside. And now I want to finally fix it!

Issues:

- No picture, no sound, no gameplay.

The console is connected to my old television via antenna cable and channeled through a vhs-recorder. (This works fine with all of my Atari consoles.)

- Lots of heat on the shielding around the rf-modulator.

No idea if this is normal or not. Power is supplied to the Famicom via a Sega Genesis model 1-power supply. According to most faqs etc. this should work just fine.

Let's have a look at it!



It's yellow, it's old, it's mine!



Worn like old shoes. But the insides of the controller pads still look pretty good and without much wear and tear. So at least no worries there.



The backsite of the Famicom shows some damage which is due to heat from the pcb underneath (see picture 5) and the plastic getting brittle.



The main-pcb was pretty dusty, but once cleaned looks ok to me. Some re-soldering was done to the flat cable  which connects the main-pcb to the power/rf-modulator-pcb by the previous owner.



Here are some issues. Red marked is the "pin" which connects the inner section of the rf-socket to the pcb as it had no connection whatsoever! It almost looks like somebody deliberately (?) bent it back! Resoldered it, no difference. The shielding also gets very hot very quickly. The big 1000uf capacitator looks pretty new to me, maybe it was replaced by the previous owner.

So, here we are. Any ideas where to begin? More pictures needed? Just ask me!

The cartridge slot was properly cleaned by me and the Famicom game I use for testing works just fine on my NES (with an adapter).

_____________________________

ADDENDUM:

Having a closer look at the backside of the power/rf-PCB!



Looks to me like some bad (re)soldering going on?!?
« Last Edit: December 16, 2014, 09:56:59 AM by ScoreAddict » Logged
number47
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« Reply #1 on: December 16, 2014, 01:07:44 PM »

The current power/RF PCB is pretty much dead. The 7805 voltage regulator and the big capacitor have been lately replaced very messily. On top of housing the melted region suggests a short in RF module. I suggest to make a new PCB from scratch and not create RF part - only power regulator with filtering capacitors and AV-mod Cheesy
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zmaster18
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« Reply #2 on: December 16, 2014, 01:55:05 PM »

A lot of Famicom Power/RF PCB's have that old orange-brown goop around the power jack and voltage regulator. If you haven't already, try to reflow those spots with a high temp soldering iron and apply new solder. If it's getting that hot moments after turning on, something around the voltage regulator may be bridged and shorting, creating the heat. Be careful around the voltage regulator, I sometimes accidentally bridge the points when soldering there because he solder pads are so close to each other. I also recommend doing the AV mod to eliminate the other technical issues you may encounter with your video. 
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ScoreAddict
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« Reply #3 on: December 16, 2014, 03:52:37 PM »

The current power/RF PCB is pretty much dead. The 7805 voltage regulator and the big capacitor have been lately replaced very messily.

OK. That much I figured out myself. The previous owner had messed around without knowing (a lot) what he was doing and messing the pcb up badly that way.

Quote
On top of housing the melted region suggests a short in RF module.

Which must have been an issue for some time! I wonder how long it took the previous owner to figure out that his "fix" was not working properly.

Quote
I suggest to make a new PCB from scratch and not create RF part - only power regulator with filtering capacitors and AV-mod Cheesy

Well. If you have a tutorial for that I'd be very much obliged. If not... it's a bit beyond my capabilities to be very honest. Wink

But thanks for the great advice! Very much appreciated! Smiley

Post Merge: December 16, 2014, 03:56:47 PM
A lot of Famicom Power/RF PCB's have that old orange-brown goop around the power jack and voltage regulator.  If you haven't already, try to reflow those spots with a high temp soldering iron and apply new solder.

This is what I'm going to do next!

Quote
If it's getting that hot moments after turning on, something around the voltage regulator may be bridged and shorting, creating the heat. Be careful around the voltage regulator, I sometimes accidentally bridge the points when soldering there because he solder pads are so close to each other.

OK. Maybe I'll find and fix the short near the vr that way.

Quote
I also recommend doing the AV mod to eliminate the other technical issues you may encounter with your video.

Yes. Most certainly! Any recommendation for a good tutorial to do that? I'm getting better with a soldering iron these days, but I'm still most certainly no electronics expert.


Post Merge: December 17, 2014, 12:19:36 AM
After doing some research I decided to go for this tutorial:

http://jpx72.detailne.sk/modd_files/fc/avmod.htm

Looks easy enough to me.

I also tried reflowing on the power/rf-pcb but to no avail. Sad

Post Merge: December 17, 2014, 05:32:56 PM
No success with the AV-Mod! Black picture. Sad

The previous owner obviously attempted it too, since I discovered the cut on the video line of the pcb. Thanks for not telling me.

The voltage regulator is still shorted out!

Is there a way to substitute the power pcb? Just the bare essentials to get the other pcb up and running?

Post Merge: December 17, 2014, 10:00:35 PM
Done some measuring to the AN7805! 10-14V are delivered from the (Genesis model 1) power supply's side and about 5V come out on the other side.

I'd say the voltage regulator works just fine. So where to look next...
« Last Edit: December 17, 2014, 10:00:35 PM by ScoreAddict » Logged
80sFREAK
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« Reply #4 on: December 26, 2014, 04:32:07 AM »

 Clean the slot.
 No, you don't need to make new PCB.
 Do AV mod and reflow slot.
 Check temperature of CPU and PPU - they shouldn't be very hot.
 If you don't have oscilloscope, use sound input to check HSYNC and VSYNC on pin21
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jpx72
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« Reply #5 on: December 26, 2014, 04:14:24 PM »

Check P3 on the schematic - thats the pinout of the connecting cable between main PCB and the small PCB. You can deliver power directly there, audio and video - follow AV mod instructions. No need for the small PCB.
http://jpx72.detailne.sk/modd_files/fc/schematics/schematics.png
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jake74
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« Reply #6 on: December 07, 2016, 05:13:36 PM »

Hi all,

Revisiting this old post, as I have a Famicom that's got no picture, no sound, and the 7805 heats up super quick. I've AV modded the FC (I've done about 20+ mods now, so am fairly confident there's nothing amiss with the mod.)

I've replaced the capacitor, the 1.5A fuse and the 7805, and it's still doing the same.

Is there any chance of seeing that schematic for rebuilding the PSU board? Link is now dead.

I'm also interested in making it run off a USB 5V plug, if anyone has any info on that, I'd be interested!

thanks
jake
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