jdgabbard Posted May 12, 2015 Share Posted May 12, 2015 I was working on pulling the DRAM chips and accidentally broke a resistor. Color code says its a 120m Ohm, which I feel is a little higher than what I would get by about 100M... Anyone know for sure what this resistor's value is??? Quote Link to comment Share on other sites More sharing options...
Shift838 Posted May 12, 2015 Share Posted May 12, 2015 why don't you just put an ohm meter on it since it is out of the circuit to get the reading? Quote Link to comment Share on other sites More sharing options...
Fritz442 Posted May 12, 2015 Share Posted May 12, 2015 I believe that's a capacitor... Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted May 12, 2015 Share Posted May 12, 2015 I agree with Chris, put the DMM on it. Honesty, I'm not sure if the color is correct in that photo or not. It looks like a 5 band resistor code, but the numbers I got make no sense, so I'm assuming the colors are off. Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted May 12, 2015 Share Posted May 12, 2015 I believe that's a capacitor... Now that might make sense, but if it was wouldn't the temperature coefficient band be twice as wide? I also don't remember seeing any capacitors with the bumps on the end. Barrel capacitors are usually straight, right? Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted May 12, 2015 Share Posted May 12, 2015 I can't tell what the real colors are, the picture is crap, but I can tell you it's not 120OHM. Here is a bag of 120OHM resistors on my bench... Quote Link to comment Share on other sites More sharing options...
Fritz442 Posted May 12, 2015 Share Posted May 12, 2015 (edited) Look at almost all TI PEB boards.... Brown, Black, Red, Blue, Blue ( .01uf Cap ) | (center could be orange) Edited May 12, 2015 by Fritz442 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted May 12, 2015 Author Share Posted May 12, 2015 I don't have a means to test capacitance.... Should invest in that. The colors are brown black red blue blue... And sorry, that would be 102m.... The one I pulled isn't registering on the multimeter. Although in circuit that is about what it read. But it also reads that with this one pulled... Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted May 12, 2015 Author Share Posted May 12, 2015 So you think it's a cap? Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted May 12, 2015 Share Posted May 12, 2015 So you think it's a cap? I'm guessing that it MUST be, because with five bands, and even if you read it backwards as a resistor, the colors would not match for tolerance. Quote Link to comment Share on other sites More sharing options...
Fritz442 Posted May 12, 2015 Share Posted May 12, 2015 Yes....http://www.mainbyte.com/ti99/hardware/peb/32k_card.html 1 Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted May 12, 2015 Share Posted May 12, 2015 If the resistance reading changes with time, it is almost certainly a capacitor. ...lee Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted May 12, 2015 Share Posted May 12, 2015 Yes....http://www.mainbyte.com/ti99/hardware/peb/32k_card.html Weird caps, don't think I have ever seen these before. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted May 12, 2015 Author Share Posted May 12, 2015 Well, those are definitely the same ones. And you're right, they do vary over time, eventually not reading at all. So a .01uF is the rating? Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted May 12, 2015 Share Posted May 12, 2015 Interesting. http://www.tpub.com/neets/book2/3g.htm Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted May 12, 2015 Share Posted May 12, 2015 It is definitely a capacitor. It is 82pF at 1% tolerance with a Temperature Coefficient of +30, assuming I'm reading it correctly. http://fashions-cloud.com/pages/c/capacitor-color-code/# Here's a link to read the code. Note, it only makes sense if the Brown band is the tolerance band, which tells me how to read the rest. 2 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted May 12, 2015 Author Share Posted May 12, 2015 I replaced them with two .1uF caps. Seems to work...I think... Trying to get this old system working, thought the DRAM was bad, but replacing them didn't work. So I guess it's the 9918. Good thing I have a few of them on the way from China. Of course I guess it could also be the crystal. I'll have to check it with my analyzer. Black screen with just a constant tone. Quote Link to comment Share on other sites More sharing options...
Keatah Posted May 12, 2015 Share Posted May 12, 2015 Of course it's a cap. Each chip has one across +VCC and Ground. And there are "C" designators. Agree with post 16. Quote Link to comment Share on other sites More sharing options...
Stuart Posted May 12, 2015 Share Posted May 12, 2015 Could always try that age-old trick of looking at the component location diagram in the TI-99/4A technical data manual (on ftp://whtech.com/) to get the component ID, then finding that on the circuit diagram. If it's from the row of caps immediately above or below the VRAM, it's 0.1uF. Quote Link to comment Share on other sites More sharing options...
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