4 Jan
2008
4 Jan
'08
2:05 a.m.
1) The 1488 gets the right input signal(s)
2) The 1488 gets power
3) THe 1488 is working correctly
4) The output must bot be shorted to something else
You have checked (1) -- or have you. The 1488 contains 4 drivrs. One is an
inverter ,the other 3 are NAND gates. _Often_ the inputs on the latter
sections ae strapped together turning them into inverters too. But is
that the caser here? Have you made sure there's not another signal being
fed into the other input?
I checked the pins on the 1488 according to how they were shown on the
schematic. There are no pins "tied" according to that schematic.
Now as for (2), check there's +12V and -12V on the
right pins of the
1488. And that the ground pin is, indeed, groudned. Remember a supply
might be misisng because osmething is overloading it. Maybe a 1488 or a
dcoupling capacitor has shorted.
It's showing -0.60v for all the -12v test points.
I'll know for sure whether or not the converter is good once I can pull
and test it.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.