Text 215, 122 rader
Skriven 2005-01-31 12:06:46 av Roy J. Tellason (1:270/615.0)
    Kommentar till text 214 av James Bradley (1:134/77.0)
Ärende: Monitors nee-But it's ec
================================
James Bradley wrote in a message to Roy J. Tellason:

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

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

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

 JB> So it's the plate-plate insulating material that provides the
 JB> component of pure resitance? ... Oh for just the degridation, and
 JB> you need to passivly test it? <Skatching head>

Not sure just what it is,  exactly,  in terms of the mechanism,  but something
in there goes bad,  the ESR goes up,  and the cap becomes effectively useless. 
Checks good on the usual kind of a cap checker,  too. 

 JB> ...I'm sure this is only NTSC, but maybe PAL too, but I doubt it. I

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

 JB> Turns out to be a "T.V. Post Marker/Sweep Generator" Model IG-57A.

 RJT> That's not a pattern generator,  it's one that's used for alignment of

 JB> I know that now. <D> Since I shoved it in the rack - some half
 JB> dozen years ago - that's the best recollection of the unit I came
 JB> up with. On the front it has an input for IF, 

That'd be an output,  I think.

 JB> and two channels of influence. (Yada-yada-yada...) I likely noted 
 JB> that it had a BNC on the front labeled IF, thought it was an 
 JB> output, then found a place for it on a shelf.

 JB> When I buy at auction, I try to go for the quantity deal. That box
 JB> came with the hospital's TV distribution system. Got a BIG pile of
 JB> stuff from that one!

I've managed to accumulate junk at a somewhat slower pace overall,  and haven't
resorted to that sort of thing yet.  :-)

 JB> Say, since you brought it up... <-; I purchased at gov. auction a
 JB> V-mA meter that displays via a swinging mirror assembly. Any ideas
 JB> what makes these work?

Same thing that makes any other meter work,  probably -- little coils mounted
on pivots...

 RJT> the IF  stages.  The "sweep" refers to a frequency modulation of
 RJT> the output,  the modulation also being used to provide 
 RJT> horizontal deflection input to a scope, and thereby 
 RJT> generating a response curve.  The "marker" part refers to 
 RJT> generating a slight intensity variation on the curve so you 
 RJT> know where certain frequencies of interest are.  In the 
 RJT> years that I spent doing tv repair,  I could never quite 
 RJT> justify the cost of such an instrument.

 JB> That's why the local hospital board absorbed the cost, and I got it
 JB> in a two-fer. <L-like a maniac) Now I need more storage space.
 JB> <cower>

Always.

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

 JB> You know, beside the wonkey pictures you can make with the unit, it
 JB> would be good for little else than to tax or deplete a subsystem?

Hm?

 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.

 RJT> Not a problem,  mostly.  The tricky part would be to find a video card
 RJT> to use  for generating that output that would have sufficient 
 RJT> flexibility to allow for a wide range of frequencies that 
 RJT> could be tweaked,  rather than a small number of discrete 
 RJT> ones to select from -- this is what one of my monitors here 
 RJT> can deal with,  and I don't recall the specifics on any of 
 RJT> the cards offhand.  I know that the one (ISA) card I have 

 JB> Capt. solder runs an ISA card! Eveybody... <LOL>

 RJT> in this box has several of those little oscillator modules
 RJT> on it,  and seems to generate a whole lot more in the way 
 RJT> of tv interference than the one I was using before that 
 RJT> died.  My antenna consists of a bit of wire,  and I guess 
 RJT> those modules radiate enough hash,  that mixes,  that it 
 RJT> messes things up.  Good thing tv reception in here isn't 
 RJT> that high a priority with me.

 JB> I think it was an old Osbourn lug-able, that I pulled a Herc.
 JB> TTL/EGA (If that's the one that used a low density D-plug?) card
 JB> out of. That I could use for test paturns. It's a full length ISA
 JB> board, but maybe only able to draw two colours.

Osborne (no u) made luggables all right,  but the ones I'm most familiar with
were the ones that pre-dated most of this stuff,  and ran cp/m for an operating
system.  Their clone machines were just before the end,  when they went out of
business.  The original machine had only one board in it (aside from the ones
on the floppy drives and in the power supply) and the Executive (which I have)
had a plug-in memory board,  that was it.  There was one later one,  but I
never got to see the inside of that model.

 JB> Ya... any day now. <-;

 JB> Me, I just plugged the capture card into a 21" monitor. That
 JB> sheilded cable comes in handy to take the reception elsewhere.

Capture card?

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