19 Aug
2010
19 Aug
'10
4:27 a.m.
Tony Duell wrote:
Good call --
there's a few areas that are obviously identical. The real
fun will be taking out the main PCB to work on it, this thing doesn't
have the most modular design.
Snagged a
Wavetek 1901C last week. This is a 12" oscilloscope display
(X/Y+intensity input), I was hoping to use it as a point-plotting/vector
display for a couple of little computer projects of mine. (Or maybe
just hooking an Asteroids board up to it... :). It's in pretty good
shape (has more screen burn than I think I've ever seen in a few spots,
though.) I fixed a couple of cold solder joints and it's now mostly
working, except something appears to be going slightly wrong in the Y
deflection or amplification (it's getting clipped/distorted depending on
the gain and input intensity).
Anyone have a service manual or schematic for this thing or know good
sources for such things?
Often the X and Y channels are very similar, if not identical, for
obvious reasons. I don;t know how it's constructed, but if you can
identify corresponding parts of the X and Y channels, then you might be
able to compare signals between them to track down the faulty part.
Does this unit use electrostatic or electromagnetic deflection?
I'm not sure
-- what are telltale signs of electrostatic vs.
electromagnetic? I'm fairly sure at this point that the actual
deflection is working OK -- I can use the vertical/horizontal
positioning pots to move the waveform anywhere onscreen and there's no
distortion as a result. The distortion seems to be related to
whatever's coming out of the amplifier (is that the right term in this
context?). If I input a sine wave with 1V amplitude to X/Y and set the
gain to 1V/Div the display is fine. If I change the gain to .01V/Div
the tops of the sinewave get oddly distorted -- past a certain point the
top of the displayed oval jumps up as if the Y value is getting forced
to some maximum value. It's difficult to describe. I have taken a
couple of pictures of an example, they're at:
http://yahozna.dyndns.org/scratch/osc/
Since I know your computing setup is not optimized for web-browsing,
here's an ASCII diagram (apologies for the crudity)
Good:
__
/ \
| |
\__/
Bad:
_
| |
| |
_/ |
/ |
| |
\__/
- Josh
-tony