Super Famicom that will not power on: the DC jack and the 7805

From the plug to the rail

A Super Famicom needs 9 to 10 V DC at about 850 mA with a centre-negative 5.5 x 2.1 mm tip. The Japanese SHVC-002 adapter and the US SNS-002 are not interchangeable in shape, and a generic centre-positive adapter will look exactly like a dead console. Check the polarity marking on the adapter before opening anything.

If the console runs only when the plug is held at an angle, the jack joints have cracked. If it never runs at all, work from the jack inward and find where the voltage stops.

Four measurements

The path is short: jack, fuse or protection diode, 7805, then the 5 V rail. Measuring at each point takes two minutes and tells you exactly which part to change.

The 7805 on a Super Famicom runs hot and is a known wear item on this console. A regulator that reads 5 V with no load and collapses under load is failing, not failed, and it will produce a console that boots some of the time.

1. Measure the adapter output at the plug with the console disconnected. Expect 9 to 11.5 V DC.
2. Measure at the jack pins on the board. A reading lower than the adapter output means the jack contacts are worn.
3. Flex the plug while watching the meter. A voltage that jumps means cracked jack joints.
4. Measure the 7805 input and output. Input should be 4 to 6 V above the output; output should be 5.00 V plus or minus 0.25 V.
5. Measure the 5 V rail with a cartridge fitted. A rail that drops below 4.75 V under load means the regulator is failing.

Jack joints, then the regulator

Reflow all three jack pins with fresh solder while holding the jack flat against the board. Do not stop at the one that looks cracked; the other two have been sharing the load. If the jack body itself is loose, replace it, because a loose jack will crack the new joints too.

If the regulator is failing, replace it with a 7805 in TO-220 and bolt it to the existing tab with fresh thermal compound. Add a small heatsink if the console is going to be used for long sessions; the stock tab runs hot enough to dry out the surrounding capacitors over a few years.

1. Reflow the three jack pins with fresh solder, holding the jack flat against the board.
2. Check the protection diode and the first filter capacitor for heat damage and replace if discoloured.
3. If the regulator is failing, desolder it and fit a new 7805 with fresh thermal compound on the tab.
4. Measure the 5 V rail with a cartridge fitted. It should hold 5.00 V plus or minus 0.25 V.
5. Run the console for twenty minutes and check the regulator tab temperature. Above 70 °C means it needs a heatsink.
6. Reassemble and flex the plug in every direction with the console running to confirm the jack repair holds.