Electohome G05's...again

Dude, hombres, hackers and the like...

<Joe Pesci mode on> Ok, ok, ok! So... but wait! <mode off, reselect thoughtful hat
mode> Ummmm. It's been, what?.... 10 mo.s since I had to track down a mildly
difficult X-Y monitor repair, so listen, I'm a little stupid right now. I don't
mean to be, but I have a brain like a sieve, and without proper refresh, it's all
gone back to long-term archival storage and I've forgotten the search keys.

But woah, let's get to it already. I got the spot killer on, which is kinda good.
I've got no blown fuses in the G05, this too is good. I've got a heating 3752
(-25v) on the "Y" deflection circuit... which is bad. CPU's good, (it's the Omega
Race, I've been hunting down), haven't checked the output levels, but the pot's are
way down to about 25%, and the picture on the 'scope at the output amplifiers is
good (could use some blanking of course...). More diagnostics... Swapped out the
("Y") 3716 and the 3752, no change. Swapped out the MPU-U07 ("Y" side), no change.
Checked (statically) all of the deflection X-istors, and MPS-U57/MPU-U07, they look
good. Oh, the +25 and the -25 check out OK, they seem stable.

Here's what I'm looking for some memory jibing on... I'm seeing at the base of the
"Y" deflection transistors, a waveform that looks like your basic audio excitation
signal that peaks and troughs from +25 volts to -25 volts. Remember this is at the
base. Conversely, at the base of the "X" deflection transistors, I might be getting
a real subdued waveform, that depending on the side of the diode you test on, looks
like a rectified version of this peak to peak about +/- 7volts.

And here's the question: "with head in hands, shaking slowly back and forth"; does
anybody remember what the levels at the base of the deflection X-istors should be
around? And if the "Y" levels are whacked (as I suspect), what is sending these
input levels spiking like this? Any thoughts?

Ace
(whose got to post the next few steps to troubleshooting the Omega Race CPU now!)
Received on Mon Jun 21 08:01:31 1999