I have an original famicom model HVC-002 that was working fine until a couple days ago, when I accidentally inserted the wrong AC adapter into it - oops! I'm not terribly knowledgable about electronics, but I've followed guides and done some soldering in the past. I read around the internet to find that I likely needed to replace the 7805 voltage regulator and the 1000uF capacitor. The capacitor looked fine, but I tested the 7805 voltage regulator on the psu and saw it was outputting 0 volts. Replaced the voltage regulator, still no go. Replaced the capacitor and then realized there's a fuse in this famicom model and mine was broken. Jumpered the points for the fuse, still no go. One of the things that confuses me is that I now see 16 volts coming into the voltage regulator, the famicom AC adapter I'm using outputs 10V, is something wrong here? Regardless, the motherboard is now receiving 5V from the PSU. Small complication: I tested and broke this thing while visiting family, and the HDTV I'm testing on now is the previous year's iteration of the same TV, (a Panasonic Plasma) so probably no difference. I've tried both Famicom and NES RF cables. I'd say I'm 80% sure that I would see a signal if it were working, but not certain. So I guess I'm wondering, are there any tests I should do on the motherboard to see if it's fried, and/or is there a way to test if the device is outputting signal without having a CRT TV to plug it into? Thanks!
NEVER DO THAT!!!! Ok, first thing, what AC adapter did you use to damage it? What specs? Second thing, replace that bridge with a proper fuse before you do anything else. The fuse is there for a reason. Third thing, since you read 16v at the input of the regulator, that means the circuit is open ( A connection is cut somewhere and the current cannot pass) This means there is no actual load on the AC adapter and it is normal that it reads higher than the voltage it is rated for. In other words, there might still be hope, but start by replacing the fuse.
Many thanks for the feedback, MaxWar! I don't have the exact specs of the AC adapter that broke it on hand, though I can try to get them. Offhand, I believe it was a 9v adapter running between 500 to 1500mA. There is a good chance the polarity was reversed. I anticipated disapproval about jumping fuse, but not quite so many exclamation marks! Clearly I don't know what I'm doing, so I'll follow your advice and replace the fuse first thing. Honestly, I searched for a new fuse but didn't know what to get. The local radioshack had a number of different types, none of them resembling the small opaque part to be replaced. Sadly, the staff was more clueless than me. So if the circuit is open, does that I mean I accidentally broke a connection somewhere on the PSU board? I don't know if this matters, but worth noting: the replacement capacitor I used is huge - 1000mF rated for 35v (the original is rated for 6.3v). Could that be a problem?
Might also have been an AC output adapter, which is even worse. I try to limit myself to 3 exclamation marks, seems I went over the limit here I think it is the cumulative effect of seeing so many people jumping fuses over time. Hard to say exactly. IIrc the firetruck famicom does not have a power LED, this is an easy way to see if the mobo is getting power. But then you said you measured 5v on the motherboard, where exactly did you measure? Assuming you mean uf ( microfarad ) and not millifarad (mF) it should be fine
No worries, point taken! Frustrating that I can't find a replacement fuse locally. Radioshack has 1.5a glass fuses but no fuse clips, argh. Indeed there is no power LED, which is frustrating. I measured 5 volts on the output of the voltage regulator, and also on the motherboard at the power switch points. Hopeless? ... yeah, microfarad
Might be good to test the switch but somehow I doubt it is that since it worked prior to the AC adapter incident. For the fuse, for testing purpose, You could purchase a wired fuse holder and install it on the points of the original fuse. Then you can use some standard fuse they have at your local store. This might be temporary but if you get the console working then you could order the proper picofuse replacement. For testing the 5V, test it on the chips on the motherboard, or in the cartridge slot or something. The chips pinout are easy to find on the internet. If you have no power to the actual circuit, that is the first thing to look for. Maybe a diode, resistor or something fried somewhere.
Yep, I tested the switch and it's fine. Took your advice and bought a wired fuse holder as a temporary measure. Afterward, Tested GND and +5v points on the cartridge slot and all chips - fine. This got me to the point where I felt I really needed a verifiably working TV. Last ditch effort, I played around with the TV settings and changed Antenna in to Cable in and ... fixed! Question: is there a way to test whether the original 1000uF cap is broken with just a multimeter or by reinstalling it? It doesn't have any visible signs of damage to my eyes. Reason being, the new cap I bought is huge, and makes it impossible to put the case back together without modifying the PSU shielding. Even then, I'm not sure it will fit. MaxWar and Pikkon, thanks for all the help! Can't wait to work on modding this guy!
Original cap is probably ok. If you need to desolder it you might as well put a new one but if you cannot get one of the proper dimension easily you might use the old one.
