Repairing an OLD TI video monitor

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
Alrighty, you may have seen my post about the junk I got, well in that junk was an old Texas Instruments video monitor, model 942 video display terminal.

I don't know if this gives an idea of how old it is, but the only control on the outside of it whatsoever is a brightness dial, the keyboard input is a phone jack, theres no serial port (just the old wide printer type), theres row after row of IC's, and I'm pretty sure that it only displays green since I don't see any other pixel color on the front, just kinda looks like green phosphor.

Getting to the point, when I plug it in and flip the switch, all I hear is a click and nothing happens... so here I am.

I opened 'er up, and other than general dust (surprisingly little) and a bit of rust on the clip holding the flyback ferrite together (it's a cute little one :D), the only thing I see that stands out as bad is what looks like it might be a fried 1/2 watt resistor. However, I don't have enough experience to determine whether or not it is legitly smoked or just well used.

I included a pic of it, along with a few pics of the inside in general.
Does anyone know if this resistor looks like it is fried, and what might cause the resistor to go bad like that, and what it would have taken with it? (It's in the power supply section)

This is the first time I've come across something I'd much rather keep around than just scrap, I think it'd be a great project to turn it into a simple scope so I can probe things over 20V without worrying about frying my little one.

Thanks!

[EDIT]
It's the resistor next to the cap, closer to the edge of the board, all the colors look washed out and the ares next to it looks like it got hot.
 

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debe

Joined Sep 21, 2010
1,252
Looking at the pictube neck its a monochrome probably green screen it will be realy Old Probably only scraping value. But fairly common for those resistors to be discoloured as they run hot, so unless you know wat its value shoud be it will be a bit hard to check with an ohm meter, it may be ok. When its switched on does the filliment light up inside the tube? If not then the horz O/P stage wont be working as its voltage is from that stage. So next check would be the powersupply this will probably be around 100V. If these dont register wreck it.
 

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
Looking at the pictube neck its a monochrome probably green screen it will be realy Old Probably only scraping value.
Yay, I've always wanted a green screen monitor :) (yea, I'm weird)
What do you mean by scraping value?

But fairly common for those resistors to be discoloured as they run hot, so unless you know wat its value shoud be it will be a bit hard to check with an ohm meter, it may be ok.
alright

When its switched on does the filliment light up inside the tube? If not then the horz O/P stage wont be working as its voltage is from that stage. So next check would be the powersupply this will probably be around 100V.
Will do, thanks

If these dont register wreck it.
:eek: :'(
 

Thread Starter

magnet18

Joined Dec 22, 2010
1,227
Alright, I got it turned on! :D
cleaned off some of the pins coming out of the power supply and that seemed to do the trick, the attached pic shows it displaying keyboard failure on the screen, which might make it more difficult to get a scope out of since I need at least one full axis.
I detect circuit bending in my future.
 

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Thread Starter

magnet18

Joined Dec 22, 2010
1,227
I should probably make a new thread for turning it into an oscilloscope, shouldn't I...
I'll go do that.
 
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