Text 213, 80 rader
Skriven 2005-01-29 20:06:49 av Roy J. Tellason (1:270/615.0)
    Kommentar till text 212 av James Bradley (1:134/77.0)
Ärende: Monitors nee-But it's ec
================================
James Bradley wrote in a message to Roy J. Tellason:

 JB> 01-27-05  12:06, Roy J. Tellason told James Bradley about Monitors
 JB> nee-But it's ec

 JB>  Well, how do, Roy?
 RJT> James Bradley wrote in a message to Roy J. Tellason:

 RJT> I'm thinking that it's probably some power-handling 
 RJT> component that's gone bad, and perhaps some electrolytics 
 RJT> as well.  Gotta get an ESR tester together one of these 
 RJT> days.

 JB> ESR? I hope you aren't depending on an Extra Sensory Receptors. <G>

Equivalent Series Resistance,  a common problem with capacitors,  particularly
electrolytics...

 JB> ...I'm sure this is only NTSC, but maybe PAL too, but I doubt it. I
 JB> can only see the South side, as it's in a rack that resides
 JB> bass-ackwards until I can get off my carcass to flip it around.
 JB> It's a Heathkit if memory serves. Nothing special, but it has quite
 JB> a selection of knobs on the front.
 JB> BNC connector on the back, with a Blanking, and Trace Rev. 
 JB> switches.

 RJT> Hm.  Let me know what it turns out to be,  just out of curiosity.

 JB> As I'll never remember to fill you in when the day comes, I made
 JB> the day come. Turns out to be a "T.V. Post Marker/Sweep Generator"
 JB> Model IG-57A.

That's not a pattern generator,  it's one that's used for alignment of the IF
stages.  The "sweep" refers to a frequency modulation of the output,  the
modulation also being used to provide horizontal deflection input to a scope,
and thereby generating a response curve.  The "marker" part refers to
generating a slight intensity variation on the curve so you know where certain
frequencies of interest are.  In the years that I spent doing tv repair,  I
could never quite justify the cost of such an instrument.

Sometimes,  with real early stuff,  the sweep generator and marker generator
were separate items.

 RJT> I remember hitting some web sites with "monitor databases" 
 RJT> and there was one heck of a lot of older stuff out there on 
 RJT> one or two of them.  I'm not sure if I still have those 
 RJT> bookmarks or not,  they seem to have gotten misplaced in 
 RJT> one or another upgrades.

 JB> Ya... That happens. Found a few specs myself, but the files tended
 JB> to concentrate on a specific monitor, or line.

There are a number of different sites out there,  some more useful than others
in this regard.

 JB> There's nothing like the smell of ozone in the morning. Smells
 JB> like... Teen Spirit! <-;

 RJT> I wonder how difficult it would be to take an old 386 or 
 RJT> something and stick an extra (!) video card in it,  use it 
 RJT> for a generator?  Linux would support this,  no doubt.  I 
 RJT> know it will support more than one sound card... 

 JB> The kernel would have to be an older ones, no? All I've seen
 JB> nowadays, is a i586, or above.

Not a problem,  mostly.  The tricky part would be to find a video card to use
for generating that output that would have sufficient flexibility to allow for
a wide range of frequencies that could be tweaked,  rather than a small number
of discrete ones to select from -- this is what one of my monitors here can
deal with,  and I don't recall the specifics on any of the cards offhand.  I
know that the one (ISA) card I have in this box has several of those little
oscillator modules on it,  and seems to generate a whole lot more in the way of
tv interference than the one I was using before that died.  My antenna consists
of a bit of wire,  and I guess those modules radiate enough hash,  that mixes, 
that it messes things up.  Good thing tv reception in here isn't that high a
priority with me.

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 * Origin: TANSTAAFL BBS 717-838-8539 (1:270/615)