Famicom Disk System issue

[Skawo]

I'd try to reflow that left leg, at least, but if it's making contact, shrug.

Do you get continuity between ground and 5V when power is not connected?
Try checking between these legs

[LaughingElfMan]

Yeah, it looks like there's continuity there. I guess that's the short you suspected?

[Skawo]

Yeah, there should not be any continuity there.

The proble is which component that short is in. It could be the chip itself, but it could also be any of the transistors or caps on the board :s

I guess I'd try taking out the chip next and seeing if the short goes away.

[LaughingElfMan]

Will do. I'll let you know once I get the replacement in place.

[Skawo]

I mean, you could check the short before you put the new part in.
If the short is NOT caused by the amp then it could even damage the new amp you put in.

[LaughingElfMan]

Haha, that would have been a good idea. The amp just got here and I just finished installing it. Guess I might have a spare. I'll check the short before anything gets power.

[LaughingElfMan]

Didn't find a short, but the issue persists. C2021, I guess?

[Skawo]

So, wait, you changed the part and the short went away, but it still acts the same, or is the short still there?

[LaughingElfMan]

The short went away, but it still acts the same. I quadruple-checked the switch (again) but it's working perfectly.

[Skawo]

Does it at least let the console start up now when connected to the AC Adapter?

And, well, yeah, I guess the next step would be the C2021. I hope the first transistor didn't get cooked by the short :s

[LaughingElfMan]

I didn't check whether the console sent anything to the TV, but I'll do so this evening.
Even if the chip DID get fried, no big deal. I bought 2,just in case.

[LaughingElfMan]

Still no display/audio with the ac adapter, but it has both with batteries.
My C2021s are taking forever to get here. Are there any alternative parts? I have an original NES that could function as a donor, if it has any parts in common with the FDS?

[Skawo]

BC107, BC171, BC183, BC207, BC237, BC547 are alternates of C2021, but they might be different packages;
you'd need to check datasheets for which leg is which.

For example, between the C2021 and BC547 two of the legs are swapped:




I am really confused why there would be no video now if the short is gone, though. Unless the legs on the chip aren't making good connection and there is still  a short, or the DC barrel jack itself is faulty?
:s

[LaughingElfMan]

Thanks, I'll check if I can find any of those outside of China.
I'll also redo the points on the chip and try to verify that the barrel is good. At this point I'm invested, and I've honestly enjoyed learning about this stuff.

[LaughingElfMan]

I finally received and installed two 2SA937-R in place of my 2021s, and I'm now getting audio and video when on the adapter!
Incidentally, does the "R" in that part number stand for reverse? It's powering on when the console is off, so... probably need to flip them.
All that aside, it's still trying to read when nothing's in the drive. I reckon the tall limit switch behind the header must be damaged, but I can't see anything wrong. Is there a good way to check it? Maybe while the machine is running?