Electrohome G08 Deflection Troubleshooting

I have a G08 deflection board that's driving me nuts...

Blew main fuses first, then while troubleshooting blew one of the deflection
fuses.

I have now been working on the deflection board with no deflection transistors
connected (keeps from blowing fuses).

The only thing I found wrong other than some cracked solder joints
(which I fixed before blowing the fuses) was one of the ECO jumpers
on the bottom was shorting to another trace through melted wire
insulation. Fixed that.

Have not reconnected to deflection transistors because voltages at IC600
are so wrong. Most voltages should have been near 0 except for a
couple a 4.2, one at 7.5, and then the +9 and -9 supply voltages.

The only correct voltages were the supply ones.

I removed IC600 (expecting that it is probably bad, shorted somewhere).
There are no shorts between the +9 or -9 supply lines and any other leads.

Rechecking the voltage at the pads for IC600, many of them are now at
0/near 0 like they should be. The supply voltages are still correct,
however pins 2 and 18 still measure -8V when they should be (in theory
with IC installed) at 4.2V. That's a total of 12V of difference...

I then wondered if something up with Q600 or Q700 could be "Backfeeding"
into pins 2 and 18... so I removed them. pins 2 and 18 still at -8V !

The only other voltage I see wrong is the collectors of Q600 and Q700
should be 34-35V, but they are at 60+ V.

I don't want to reinstall IC600 till I'm sure everything else is under
control, as if it is still good (???) I don't want to blow it.

Anyone got any ideas... I've stared at the schematic till I'm blue, and
I still can't understand why pins 2 and 18 are so far off in voltage.

the supply voltages of +63, -63, +9, and -9 all check fine with a DMM.

Hopefully someone out there has some ideas... I'm pretty baffled.

-- Curt

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Received on Sun May 12 20:20:16 2002