Re: Electohome G05's...again

ddhumphr wrote:

> 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.
>

If you have 2N3752 transistors (unlikely, don't think there IS such a thing), replace
them with 2N3792, the correct part.

>
> 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?
>

Open yoke? Bad solder joints on the yoke connector?? Shorted R620 (should be
2 ohms, 10 watts, NON-inductive)? Blown F600 (or bad connection)---don't just
LOOK at it, use an ohmmeter on it!), 2 amp fast blow.

>
> Ace
> (whose got to post the next few steps to troubleshooting the Omega Race CPU now!)
Received on Mon Jun 21 13:39:19 1999