Hello all, first post here. And it might be a bit long. Sorry for that.
If you don't want to read everything, I highlighted my question.
I'm Dioxaz, live in France and successfully AV-modded a Famicom before, with help of that guide (probably a bit outdated now, as it doesn't prevent the "vertical bars" problem).
I'm posting here because someone recently sent me a nonworking Famicom, having no knowledge about how to check voltages from the LM7805 and wanting to AV-mod it (no choice when you live in Europe). And also, because I didn't see someone yet having the same problem as the one I'm writing here or something similar on various forums or places. I may continue my research indeed.
As soon as I got the system in hands, I quickly spotted a blown fuse (it's a HCV-CPU-GPM-02 motherboard), as no 12V or 5V could be got from the LM7805. I shunted the fuse and, good news, the LM7805 wasn't blown itself as it did its job properly.
Unfortunately, things got complicated when trying to boot a game.
The first time I tested the system, I used a cheap center-negative power supply outputting 6V at 1A. Switching the Famicom on gave me a wavy picture* (but no hints of a game screen) and tuning to other close frequencies to get sound gave me a 50Hz hum so I quickly switched the system off.
Then, I tried with an ATX one with no better results (only a black screen). Finally, I got a proper one in hands, from a Mega Drive MK1.
But it didn't got any better. With three games, including a previously tested one, I only get a black screen when powering on, instead of snow. As if no cartridge was in. I tried every possible solution I knew, cleaning the cartridge contacts with alcohol, cleaning the cartridge connector with a toothbrush, etc.
Is it possible that I damaged the motherboard by using that cheap power supply in the first place and trying an ATX one? Even If I never did a reverse polarity?
Is it possible to determine what could have been wrong on the motherboard and if it is fixable?
Indeed there's the possibility that it was broken before (as I found the fuse to be already blown) but I'm not really sure if Famicoms are really that fragile.
I also tried to pick up the audio directly from the board (in case it was the RF part that were faulty), but this only resulted in a drop out when switching on and off the system (no sound of a game).
Regards
* French TV sets can't take NTSC though their tuner (only through SCART and AV inputs), but I knew I could get an out-of-sync picture by tuning my TV to 96 or 97 MHz and using the original RF modulator (for CH2, 91MHz for CH1). This is quick test to see if the Famicom works correctly before AV-modding it
Famicom refuses to boot a game
Moderators: B00daW, Moderators
Well if you supplied the console with +6V instead of +5V, I'm no expert, but it is perfectly possible that you did permanent damages to parts of the console. The CPU and PPU tend to heat a lot, and if you power it with a higher voltage, chances are that they could overheat and be subject to nonreversible damage. I can't guarantee that this is what happened either.
I live in europe and have imported a USA NES, I can use it with the R/F connector just fine as modern TVs accept NTSC singals. However, the sound doesn't work, loud white noise comes out of the speaker instead
I live in europe and have imported a USA NES, I can use it with the R/F connector just fine as modern TVs accept NTSC singals. However, the sound doesn't work, loud white noise comes out of the speaker instead
Useless, lumbering half-wits don't scare us.
How to decode Famicom RF into AV, if I remember correctly: Import an American VCR with a tuner, and connect it to a TV that supports NTSC through AV output. You should be able to see its menus on the TV. Set it to "standard cable" and look around in channels 95-99 for the Famicom video signal, as that's where channels 1 and 2 are stashed.
Re: Famicom refuses to boot a game
For some reason, Nintendo saw fit to not have any form of polarity protection on the fami, but did have a fuse. Unfortunately, the fuse rarely if ever protects the 7805 or anything else. I also have a fami that was blown up by using the wrong power adapter.Dioxaz wrote: As soon as I got the system in hands, I quickly spotted a blown fuse (it's a HCV-CPU-GPM-02 motherboard), as no 12V or 5V could be got from the LM7805. I shunted the fuse and, good news, the LM7805 wasn't blown itself as it did its job properly.
Unfortunately, things got complicated when trying to boot a game.
The first time I tested the system, I used a cheap center-negative power supply outputting 6V at 1A. Switching the Famicom on gave me a wavy picture* (but no hints of a game screen) and tuning to other close frequencies to get sound gave me a 50Hz hum so I quickly switched the system off.
What usually happens is someone will get a famicom, think "oh it's the same power plug as my NES!" and then plug the NES adapter into the famicom, which blows up the 7805 and pops the fuse. The problem is the fami wants 10V or so DC with center negative, while the NES uses 9VAC. Whenever I fix one of these I remove that small input filter and substitute a diode. This prevents the wrong adapter from blowing it up again.
If the fuse is blown, I highly suggest you replace the 7805- it sounds like it is bad. Fortunately, it almost never hurts the system; the 7805 will sacrifice itself first.
The modulator draws power from the adapter input directly and does not use the 5V coming out of the regulator, so turning it on can cause a blank screen. The modulator is working, but there is nothing feeding it so you just see a black screen.
Replace the 7805 and your troubles will probably be over.
/* this is a comment */
Thank you for all the replies.
I doubt the LM7805 could be in cause because it seems to output straight 5V according to my multimeter. I did several tests when testing with those 3 power supplies. But I may change it, in case I can't access to the inside of the cartridge slot.
And no, I never bypassed the LM7805, thanks god. ^^
Well, according to what is said, chances that I damaged the motherboard are slim, this is good news. Appearently, the Famicom will not be damaged even if the voltage is not well regulated, right?
I also suspect the cartridge slot but I don't know how to fully access to its pins to clean them better, as I ignore if the previous owner had the bad habit of letting a cartridge in all the time or not, which can enlarge the space between pins and possibly cause that malfonction. Is there a way to remove the metal casing around it?
I doubt the LM7805 could be in cause because it seems to output straight 5V according to my multimeter. I did several tests when testing with those 3 power supplies. But I may change it, in case I can't access to the inside of the cartridge slot.
And no, I never bypassed the LM7805, thanks god. ^^
Well, according to what is said, chances that I damaged the motherboard are slim, this is good news. Appearently, the Famicom will not be damaged even if the voltage is not well regulated, right?
I also suspect the cartridge slot but I don't know how to fully access to its pins to clean them better, as I ignore if the previous owner had the bad habit of letting a cartridge in all the time or not, which can enlarge the space between pins and possibly cause that malfonction. Is there a way to remove the metal casing around it?
The Mega Drive "AC adaptor" I'm using is 10V 1.2A and worked perfectly with a previous Famicom I had in hands, so I doubt it could be that.
Meanwhile, I'll try another cleaning of the cartridge slot, to see if it helps.
This looks interesting. Is there any reseller who has that kind of thing? eBay doesn't seem to be the right place and for the moment, a quick Google search only suggested a link to a 72-pin replacement connector on Amazon.MottZilla wrote:I'm not sure about that but I am fairly sure you can get replacement 60 pin connectors. So if you can't clean it you can install a new cartridge connector.
Meanwhile, I'll try another cleaning of the cartridge slot, to see if it helps.
Thank you very much for the link. I wasn't aware Tototek was selling these replacement slots.
Unfortunately, I'm going to abandon here as my last attempt in tightening pins didn't improve anything.
But curious fact, I was trying to capture the sound from the motherboard to my soundcard and ended up recording from the mic on controller II. But no sound coming from a game.
Unfortunately, I'm going to abandon here as my last attempt in tightening pins didn't improve anything.
But curious fact, I was trying to capture the sound from the motherboard to my soundcard and ended up recording from the mic on controller II. But no sound coming from a game.
I have some spare connectors in my stash. Did you try cleaning it? I doubt you've damaged anything, but you should try bypassing the fuse with a small length of wire to check if it's faulty.
If the slot is dirty/corroded, then it may not be making a solid enough connection tot he games. In fact, clean the carts too! The FC will display a black or purple screen if 'tisn't getting a good signal from the ROM/Mapper (amongst other reasons).
If the slot is dirty/corroded, then it may not be making a solid enough connection tot he games. In fact, clean the carts too! The FC will display a black or purple screen if 'tisn't getting a good signal from the ROM/Mapper (amongst other reasons).