Technical and Repair Assistance

[guineapig64]

Okay, I'll be sure to order a voltage stepdown transformer.

I have decided that I'll send my Famicom to you so I'll have to get everything ready.  I will also pay for the return shipping.

[Pulse]

Hello, I'm Pulse, prolly shouldn't be asking for help on a first post but oh well  

anyway, long story short, finally found a FDS that was cheap enough for me to buy, but it doesn't work (moral of the story: don't buy something that says "untested"). I either get a grey screen, or a bunch of flashing blocks that just scramble around in no particular order

I thought i was making some leeway into this problem when i wiggled the part of the RAM adapter cord closest to the cartridge end and the colors would start flashing again, so I opened up my RAM adapter and it looks like all the wires are connected properly. Since then i haven't been able to get the flashing colors t come back, nothing but grey screen...

any ideas?

[ericj]

Clean the connector with rubbing alcohol and try it again. It's possible that the ram adapter is faulty, but I haven't personally found a bad one yet. Also, are you testing it on an official Famicom or a clone console?

If you're interested, I have 2 extra ram adapter parts, but if you got one you'd need to unplug the cable from yours and plug it into mine since I used the cable to make a FDSLoader dump cable. PM me if you're interested.

[Pulse]

i tried cleaning the contacts with rubbing alcohol before taking the RAM adapter apart and that didn't work, now that i took it apart an scrubbed a little better, i get sound and garbled graphics, but its a step in the right direction! Thanks!

this marks the first time I've actually cleaned a cartridge and it worked...

EDIT: It lives! now i just have to wait for my Disks to come in, thanks again!

[gonzalo]

Greetings from Argentina.
I just bought an original japanese Famicom (HVC-001). Due to Argentina's customs regulations I had to buy it without its power adapter.
I bought a power adapter at a local electronics shop with the following specs: 10V 2000mA. The guy at the shop told me 2000mA should work OK.
Also, the adapter can change its polarity.

I tried the adapter on my Famicom but didn't seem to work. I think I may have put it in the wrong polarity 

Can reverse polarity and over 850mA damage a Famicom in any way?

Also, TVs down here are PAL-N (I've got an LCD one that can work on NTSC), so I'm not sure what channel to try (tried 2 through 10 and 96,97).

Thanks in advance for your help.

[ericj]

Can reverse polarity and over 850mA damage a Famicom in any way?

¡Bienvenidos!

Yes, you can damage the Famicom with reverse polarity. Most likely it will damage the voltage regulator and maybe fuse and capacitor in the power supply. Either way, any damage done by it should be a quick and easy fix. Only way to know for sure it to take it apart and test it.

[gonzalo]

Yes, you can damage the Famicom with reverse polarity. Most likely it will damage the voltage regulator and maybe fuse and capacitor in the power supply.

Ouch! OK, thanks for the info. I'll give a shot at testing it this weekend. Any useful guides/links on that matter?

[ericj]

There aren't any guides AFAIK, but all you'd need to do is first look at the voltage regulator, if it looks broken, then it's bad. If it looks okay, test it with a DMM and see if it's okay. Check the fuse for continuity with a DMM, and visually inspect the capacitor. When a cap is blown, they will typically bulge and/or leak electrolyte.

[amurphy245]

Can someone tell me what tool i need to open a famicom ac adapter?

[Dioxaz]

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 page.

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).

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, as I didn't have an appropriate power supply, I used a cheap center-negative one outputting 6V at 1A. Switching the Famicom on with that power supply 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.

While waiting to test the system with a proper power supply (a Mega Drive MK1 one with negative tip), I tried with an ATX one with no better results (only a black screen). Finally, I got the MD power supply in hands.

But it didn't got any better. I have three games with me, including a previously tested one. All do the same black screen 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 but no change.

Is it possible that I damaged the motherboard by using that cheap power supply 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

[ericj]

Are you sure the voltage regulator is outputting the correct voltage? I doubt you damaged the motherboard.

[Dioxaz]

Thank you for the reply.
Well, according to my multimeter, 5V was read on the output. I even checked several times, just in case.

[Lochlan]

I bought a Twin Famicom on eBay with bad audio.  It causes a "buzzing" sound, which (thanks to the posts a few pages back) I was thankfully able to diagnose as being a bad 2P controller.

There are some replacement controllers on eBay right now for $40 shipped, but I'd rather repair the 2P controller and save $40 if I can.

1) Any advice for repairing the controller?  (Or at least diagnosing it further.)

I tried cleaning the linear potentiometer (volume slider), didn't help.  I tried sliding the slider all around, and weirdly it only seemed to fix itself when I was sliding it around with the controller disassembled, with the contacts at the *highest* volume level.

I could also get the sound to be ok if I left the controller totally disassembled (slider not making any contact), turned on the Famicom, and held the 2P controller PCB in a certain way (this made me think bad solder joints, but they look nice, could be bad cable?), but only after the famicom had been on more than 10 seconds or so.  If I turned the system off and on at this point, the sound would be bad when I turned it on and then gradually get better, and after about 10 seconds it was ok again.  (Capacitor issue?)

Any advice would be appreciated.

2) The microphone was literally falling apart, so I desoldered it from the controller PCB.  I thought this might stop the buzzing, but no such luck.

Where can I get a replacement microphone?  Mouser?  Does anybody know of an equivalent part number?

(Alternatively, if somebody has a cheap 2P controller with a functional microphone, or a cheap broken famicom, I'd buy it in a heartbeat.)

Thanks.

[jpx72]

The buzzing comes from the slider in the II.p. controller for 99%.  1% from the bad cable connecting controller with the famicom. How about disabling the slider completely? I was also thinking about using the microphone sometimes, but I never did it. There's no point having it functional (if you don't have FDS and Zelda for example).

[chazbc24]

my gamebit screwdriver won't fit  in the shafts of my av famicom! i can't reach the screws. http://cgi.ebay.com/Game-Bit-GameBit-Magnetic-Rubber-Grip-Screwdriver-New_W0QQitemZ270692569732QQ


What the hell should i do