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justajeffy

Power connector only 2 pins?

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I just picked up a TI-99/4A on ebay. (Never owned one before.)  It doesn't power on.  If I hold the power brick up to my ear, I can hear a faint humming which seems kinda normal-ish to me.  Looking at the power port on the back of the computer, I see only 2 pins where it looks like there should be 4.  Does this look right to you?

 

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Later versions of the connector only put two pins in, but they are the correct ones to pull voltage to the internal power supply board.

 

You may have an inoperative internal supply or there may be an issue on the motherboard. What is the symptom when you turn the power switch on? Is there a beep? Is there a long screeching tone and a black screen? The beige consoles don't give any visual clues that tell you they are on (the earlier, black and silver model has an LED). 

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No beeps.  No symptoms other than nothing appearing on the tv.  I'm using the original RF modulator set to channel 3.  I opened it up and took quick look inside.  Confirmed only 2 wires connected from the port to the internal power supply board.  The board looks like the QI board as per the photo at http://www.mainbyte.com/ti99/hardware/power_supply.html.  I don't know the voltages of those capacitors so I just closed it up for now.  Looks like this computer has just become a project.

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I'm wondering too, and I know this a loaded question, is this thing even worth trying to repair?  I'd like to play with it, but if it's going to cost a lot of time and money to get it going maybe I should keep a look out for another one in better condition.  Is it generally pretty straightforward to repair a TI-99 with some basic soldering skills and access to some testing equipment?

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It completely depends on what's wrong with it, and how deep you want to go. Consoles can be obtained for $20 with a little patience, so they aren't really rare yet. At the same time, if it's a common fault like the video chip, that's not hard to replace. Video RAM requires soldering to repair (or an F18A to bypass when they are available again).

 

It'll cost time, but I don't think any of the components cost much in terms of money. ;) 

 

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Isn't it possible the RF modulator is shot? There's no LED light on those beige TI-99/4A's, right? So no way to know if it's successfully getting power or not, short of an image on the screen. Maybe pick up a composite AV cable and see if you get anything with that. I get that you would normally get some sort of flicker or something even if the RF modulator is on its last legs with power to the computer, but not always. Worth a shot.

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That's a good idea and if I can get the computer working I'd probably rather use it with a composite cable than the RF modulator anyway.

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