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 Post subject: fc twin snes not working
PostPosted: Mon Mar 16, 2015 2:39 pm 
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I have an fc twin here that isn't working no lights or anything and I was having a look around and found out that the voltage regulator could be the problem. When plugged in and powered on if I measure the left pin and ground I get about 12v showing but when I measure the right pin and ground it's 0 or 0.01v. I'm not the best with electronics but does this point out a faulty regulator that needs replacing and if so how many volts? Thanks.

The required adapter is 10v 850ma centre negative and I'm testing with a master system adapter.

UPDATE: I managed to get it to work by bypassing the voltage regulator but the snes part isn't working it just gives a black screen.


Last edited by steocullen91 on Tue Feb 07, 2017 6:53 pm, edited 2 times in total.

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 Post subject: Re: fc twin no power
PostPosted: Mon Mar 16, 2015 9:00 pm 
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Someone might have plugged in the wrong polarity supply, if there's no protection that will take out the regulator. I don't know about the FC Twin specifically, but it almost certainly should be 5V, so you'd use a 7805. There should be a capacitor connected to the input of the regulator, it should also be replaced.


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 Post subject: Re: fc twin no power
PostPosted: Tue Mar 17, 2015 5:41 am 
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As a test I took a regulator from a dead snes and used it on a broken famiclone showing the same results on the multimeter and it actually worked, the console powers on again however the regulator gets really hot after a couple of minutes it has a little heatsink on it and it gets so hot that you can't touch it. I don't know if that's normal or not and I still used it for over an hour but at least now I know it's the regulator in the fc twin too and that has a much bigger heatsink. Will try to get my hands on the parts and try it out. Thanks for the help I'll be back on with the info.

Edit I had a look and this yobo fc twin doesn't have a capacitor on the line just a trace directly to the regulator input.


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 Post subject: Re: fc twin no power
PostPosted: Tue Mar 17, 2015 12:07 pm 
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It's going to get rather hot... even just a plain NROM cart would be ~350mA × 5V = 2W, so probably 40°C rise.

If it seems conspicuously more than that, see if anything else in the console is particualrly warm: it could be damaged.


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 Post subject: Re: fc twin no power
PostPosted: Wed Mar 18, 2015 4:56 am 
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It's just too hot to put your finger on and leave it there but the console functions properly. There are other chips on the board that warm up but not as hot as that.
It didn't seem as hot when it was powered on for a few hours but I might be imagining things and it definitely only reaches a certain temtemperature. I have another couple of 7805 regulators ordered so I can try one on the fc twin and the other broken famiclone.


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 Post subject: Re: fc twin no power
PostPosted: Wed Mar 18, 2015 8:01 am 
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Location: NE Indiana, USA (NTSC)
Long-term, is there a good replacement for a 7805 that doesn't generate so much heat but isn't quite as expensive as one of these $15 switching regulators? Is there say, a 5 buck converter?


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 Post subject: Re: fc twin no power
PostPosted: Wed Mar 18, 2015 11:54 am 
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First off, http://www.famicomworld.com/forum/index ... pic=6933.0 says that the FC Twin ran on 7.5V, not 10 or 12. Those extra volts will make the 7805 get a lot hotter.

The most efficient replacement is to remove the original regulator and power adapter and just use a 5V switching adapter (like any standard commercial USB-shaped charger). But this is potentially error prone, because unless you remove the original barrel connector, you could plug the wrong adapter in and blow everything up. OTOH, using a (ordinary/mini/micro)USB B connector is pretty unambiguous.

The next best thing to do is to get a 7-7.5V switching (not just standard "transformer, diodes, capacitor") adapter. Lower would be nicer, but the famicom (and NES) don't use a "low dropout" (LDO) regulator, just an ordinary one. This will minimize the voltage turned into heat by always emitting the smallest voltage to keep the 7805 functioning correctly.

This implies a 3rd option, cheaper than the switching regulator and still lower power than just using a 7.5V adapter with the existing 7805, and yet also safer than removing it altogether: replace the 7805 with a LDO regulator (such as the LD1117) and then use a 6V switching adapter.


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 Post subject: Re: fc twin no power
PostPosted: Thu Mar 19, 2015 2:58 am 
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Thanks for all the info I think I'm starting to understand a bit about it now. Like when the motor burned out in our cooker hood it's because it seized up and all the energy was dissipated as heat and the motor burned out. Basically regulators are doing the same kind of thing to use up the excess energy.

Thanks for the suggestions I'll get back to you if I've any other problems.


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 Post subject: Re: fc twin no power
PostPosted: Thu Mar 19, 2015 5:16 am 
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Wow thanks a lot I found a 5v switching power supply and bridged the input and output points on a famiclone that was missing the regulator and it works absolutely perfect thanks a million I'll have to try this on the fc twin now.


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 Post subject: Re: fc twin no power
PostPosted: Thu Mar 19, 2015 11:31 am 
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The FC twin might use the unregulated voltage for the FDS drive itself? Don't know, though, since I haven't found any schematics for it.


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 Post subject: Re: fc twin no power
PostPosted: Fri Mar 20, 2015 5:22 pm 
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I removed the regulator on the fc twin and bridged the input and output and used a 5v switching adapter and nes games are working. The fc twin is ntsc and I'm in a pal country so music is higher pitched and the games are faster (my games are pal) but snes games aren't working on it. I was wondering is it because it's ntsc and my snes games are pal. I know the nes part is playing them but I'm not sure what way the snes works and I don't have any ntsc carts to try.


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 Post subject: Re: fc twin no power
PostPosted: Fri Mar 20, 2015 5:35 pm 
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:oops: ... FC Twin ≠ Twin Famicom.

Hard to say; the SNES (although I have no idea about the FC Twin) uses its unregulated voltage for a bunch of random things in the analog path. Without some kind of flash cart or oscilloscope, it'll be hard to figure out where it's going wrong.


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 Post subject: Re: fc twin no power
PostPosted: Fri Mar 20, 2015 5:49 pm 
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I do have a flash cart if that could help.


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 Post subject: Re: fc twin no power
PostPosted: Fri Mar 20, 2015 5:54 pm 
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... Surely you don't mean a SNES flashcart? Otherwise, why not just try an NTSC SNES game?


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 Post subject: Re: fc twin no power
PostPosted: Fri Mar 20, 2015 6:29 pm 
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Yeah a snes flash cart but it doesn't boot, maybe I should program an ntsc game to it and try it. I don't have an original ntsc game cart though to try.


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