Question about jumpers

[pychneag]

Hi. I'm working on my S-132.

• I would like the S-132 to be powered from the connected IMSAI8080
• I'm using the PS/2 connector

I'm confused about the jumpers/patch header. Document states:

For JP1 & Patch as required | Header Pin Shunts

I cannot determine how to set: JP1 5V or the Header Pin Shunts for my use-case above.

Thanks!

[dmcnaugh]

For the use case you describe you wont need any jumpers in place.

1. The S-132 is already connected to the IMSAI8080 for power
2. Communications between the IMSAI8080 and the S-132 doesn't require any jumpers

Note:

• JP1 is a bypass for the LM7805
  • you only fit this if you are using a +5VDC supply plugged into the DC Barrel Jack on the S-132
• The Patch header (4x2) on the S-132 simply reproduces the 8 pins of the original IMSAI Patch header used for patching Rx & Tx (1 &2) to the MAX3232 for the RS-232 DE-9 connectors

[cavaughankirov]

Okay, figuring this out. So I see that it's 7.5 at the source, but at the header there is no power.

[dmcnaugh]

What about on the output of the LM7805? That's the source of +5V for the rest of the board.

[cavaughankirov]

Ok, now I'm confused... Such a neophyte.... If I test directly on the output plug, I get 7.5. But if I test on the soldered sections to the plug, I'm only getting like just over 5v. Now only one of the LM7805 shows power and it's like 1v. And now it's hot as hell. Just burnt myself.....

[cavaughankirov]

This is weird. So I unplugged it. Let the LM7805 cool down. Plugged it back in, nothing across the LM7805. Actually, sometimes I get a slight movement, but then nothing. Ok, yeah, it's acting like a capacitor. Waited again. Touched a lead to the LM7805, got voltage, but dropped somewhat slowly to nothing. And it doesn't seem to be getting hot.

[cavaughankirov]

Ok, scratch that..... I unplugged it. Let it sit and plugged it back in. Now that the LM7805 is boiling hot, I know it's doing something. So using the soldered posts on the underside on the one end it's the same 5v, as for the power source, but on the other end it's only around 1v.