need help with a dead SNES, replaced fuse still NO POWER

[slikrick8923]

hey guys I recently picked up a snes yesterday although I had success with replacing the 1.5 amp fuse on the original snes and the redesign model, this seems to stump me. After replacing the fuse I still get NO POWER, any ideas on what else could be wrong with the motherboard. I have two of em doing the same thing and cant figure out whats wrong. all help appriciated thanks

[Sunnyvale]

Both of them doing it? Did you check the power cord?

[slikrick8923]

yes I have its a working power supply I'm currently using and I know works on my other super nintendo

[Sunnyvale]

Maybe the power switch. If not that... If I were you, I'd go to next deptartment up.

[slikrick8923]

well I did test it for continuity and yes it works tried a power switch from a working console still the same result

[Sunnyvale]

Yup, sorry. Back to the help desk, or get a schematic on the interwebs and start working.

[FABombjoy]

Do you have 9-ish volts in and 5V out at the regulator?

[slikrick8923]

unfortunately im not that great with repairing electronics lol and by the way I came across a snes schematic but I dont understand how to read these things seems a bit complicated. I ruled out most of what could go wrong bad power supply, power switch, fuse, controller port. and then I found this tread

http://www.digitpress.com/forum/showthread.php?t=38390

it says to replace the D1 but its really tiny and if I do replace that what should I use?

[FABombjoy]

Before you do that, you'll wan to test the voltage regulator first. It's the 3-pin deal that's screwed into the side of the heat sink on the inside. It's easy:

1: Obtain voltmeter
2: Connect negative voltmeter lead to perimeter ground of circuitboard
3: Set voltage range to 20v
4: Turn SNES on
5: Touch positive lead to leftmost pin - should be around 9V
6: Touch positive lead to rightmost pin - should be 5V
7: Post results

[slikrick8923]

quick question on that when I test it should I plug in the AC adaptor on no?

[slikrick8923]

nevermind got the readings with the AC adaptor

[slikrick8923]

Before you do that, you'll wan to test the voltage regulator first. It's the 3-pin deal that's screwed into the side of the heat sink on the inside. It's easy:

1: Obtain voltmeter
2: Connect negative voltmeter lead to perimeter ground of circuitboard
3: Set voltage range to 20v
4: Turn SNES on
5: Touch positive lead to leftmost pin - should be around 9V
6: Touch positive lead to rightmost pin - should be 5V
7: Post results

okay I tried the following tips above turns out the voltage regulator was bad on both motherboards. After I replaced em I now have this other problem. The system now turns on but on the tv screen I get like a snowy picture with rolling bars which is completely odd, I know its not my AC adaptor because it works on 3 other SNES systems I have. Could I need to get another AC adaptor for this specific SNES or is something else wrong?

[slikrick8923]

could this be that I used a 7812 voltage regulator instead of the stock 7805 inside the snes?

[jb143]

could this be that I used a 7812 voltage regulator instead of the stock 7805 inside the snes?

Most typical digital electronics can't handle much more than 5 Volts and the 7812 is a 12 volt regulator...more than twice the needed voltage so hopefully you didn't fry anything else. Since there's only 9 Volts going in though, you may be safe(I don't remember what a regulator does on undervoltage). Either way, if there was originally a 7805 in there, then that's what you want to replace it with. They are very common and even Radio Shack is bound to carry them.

[bust3dstr8]

You might of just cooked two SNES. The 7812 will probally deliver about 8V into the pcb and chips. Most commercial grade TTL chips start going pop over 5.5V......GL

[FABombjoy]

edit: Just re-read the discussion about 9v in on a 12v regulator (doh!). As long as it's already probably cooked, might as well measure the output voltage on the 7812 and see what it's output is. It probably overvolted everything, but you never know. I can't seem to find a chart for input->output voltage on the 7812.

[bust3dstr8]

edit: Just re-read the discussion about 9v in on a 12v regulator (doh!). As long as it's already probably cooked, might as well measure the output voltage on the 7812 and see what it's output is. It probably overvolted everything, but you never know. I can't seem to find a chart for input->output voltage on the 7812.

A 7812 has a 2V dropoff. So through an unregulated SNES psu that outputs 9-11V the regulator will output 7-9V.

[slikrick8923]

well I have high hopes that it will work again I only tried it on one snes and not the other board all im going to do is return the 7812 that I bought yesterday for a 7805 regulator so ill post my results when I get back from RadioShack

[FABombjoy]

A 7812 has a 2V dropoff. So through an unregulated SNES psu that outputs 9-11V the regulator will output 7-9V.

Thats what I had assumed, but you know what they say about assuming...