Hmmm, I didn't write that particular piece, not sure where the detail even came from now? Given the low value of resistance, they're probably series resistors in the power supply to something as part of an R/C filter. The A3000 has a separate 5V supply for the video section, they were probably trying to minimise digital noise on the analogue video output. Personally I would have just designed an adequate filter, but that's another story...
The 5V video supply is the violet wire in the corner of the power connector. Forget which pin is it now. Just measure the supply randomly on some of the video logic (e.g. U450 pin 19) and it's immediately obvious if the video supply is working. The computer will boot without it (and you should hear the floppy drive "ticking"), but of course you'll have no video output.
To answer your other post...
I have a pin information diagram for Gary on
this page, about 2/3rds of the way down. It's for the A4000, but it's the same part.
Schematics for the entire computer
here. The internal operation of the gate array (Gary) is semi-complicated. Don't expect to be overwhelmed with detail from the schematics.
Since the ROM Output Enable is never going low, it kind of suggests one of:
- Bad CPU
- No CPU clock
- CPU in reset state
- Something holding up the address bus
- Faulty address decoder in the U110 gate array (Gary)
- Damaged U110 socket (check for cracks in the corners)
This kind of problem isn't very easy to track down. In the case of address bus problem... well nearly everything in the computer sits on the address bus. So any of these could be what's causing the problem.
One approach to this sort of problem is to monitor each address bus line in turn with the scope, just after you set then release the reset line (keyboard reset should also work for you). You should get a quick burst of bus activity on most of the lines before it freezes. If not, it's probably a CPU related thing (bad or no clock?).
Look out for logic output clashes on the data and address bus. That's where the peak value of the waveform is around 2.5V as opposed to the normal 5V. This happens when you have two logic outputs trying to drive a single line in opposite directions. That kind of fault could be a problem on the data bus chip/fast bridge, so around the U251 - U258 area. Yuck.
