Gravitar board issue

Area69

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I just picked up a Gravitar project and the board has this smoked cap (C110). The schematics say its a 2.2 uF 35v Tantalum. Is this a common issue, should I try to replace it or is it caused by some other issues on the board?

gravitar_cab110.JPG
 
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Not what I would call a "common" issue, C110 is an input filter for one of the 15V regulators, a momentary reversal of power could take it out but it might also have just reached it's natural demise, tantalum caps seem to short when defective more than standard electrolytic caps which often just start to lose value as they age.
Dick
 
Not what I would call a "common" issue, C110 is an input filter for one of the 15V regulators, a momentary reversal of power could take it out but it might also have just reached it's natural demise, tantalum caps seem to short when defective more than standard electrolytic caps which often just start to lose value as they age.
Dick

Thanks for that, I'll just replace it and see what happens. I guess it cant hurt. I'll replace the other caps while Im at it. Are there any other parts I should "shotgun" while I'm working on this board?

And thanks again for repairing my Pole Position II board. =)
 
I replaced the shorted tantalum cap today. I went to a local electronics shop and was able to find replacements for the axial caps as well.

When I power up the board, the spot killer comes on still. So I checked the x y and z outs. Y seems fine but the X was around .6 v and not fluctuating, so I'm ordering the TL082cp's and sockets from Bob Roberts. It worked for my Asteroids board, so I guess it's worth a shot.
 
The TL082s didn't help. The x out is still really low and not moving. Spot killer is on, and both LEDs are solid. y out looks to be good, and fluctuating. Could anyone point me in the right direction? Also I have a working Space Dual and Asteroids if either board will help me diagnose this one.
 
Also make sure you've got + and - 15V on the board itself. The test points are in the vector section of the board (silver area)
 
It's the 40 pin chip all by itself on the other side of the Board from the ROMs. Do you have a manual for the game? While you're there, check the +5 on the board too. The next thing to do is to use your finger to test the temp of all the chips while the board is powered up. Let it run for a few minutes and then lightly touch each chip after having first grounded your finger on the ground tab. Pay special attention to the RAM chips (2114/9114s). If any chips are significantly hotter than others, they're immediately suspect. Be careful not to burn yourself!
 
It's the 40 pin chip all by itself on the other side of the Board from the ROMs. Do you have a manual for the game? While you're there, check the +5 on the board too. The next thing to do is to use your finger to test the temp of all the chips while the board is powered up. Let it run for a few minutes and then lightly touch each chip after having first grounded your finger on the ground tab. Pay special attention to the RAM chips (2114/9114s). If any chips are significantly hotter than others, they're immediately suspect. Be careful not to burn yourself!

Swapped the AVG and nothing. Tested it on the Space Duel board and its working fine, so that's $35 dollars you saved me. The +5 checks out as 5.02 and the +15 is 14.98 -15 is -14.88. I checked all the chips and made note of all that were over 100 degrees. But I don't know which are 2114's and 9114's. I'm looking at the manual and they have names like LS244, and LS161?
 
Could it be that the -15V is too low at -14.88? The -15v regulator sets right beside the shorted cap that left a burned spot on the board. Spot killer stays on, I assume because the x out is 0.64? What else controls the x out?
 
If test mode isn't running then the game program likely isn't running and you're just seeing garbage on the output anyway. Next try grounding the WD/DIS pin and see if that will allow either the game to run or test mode to work. The manual will tell you where the RAM chips are if you can't read the markings on the chips. On SD there are two above the socketed ROMs at the edge of the pcb without the edge connectors and a bank of them above the two socketed vector ROMs near the middle edge of the board. Next question is do you have a logic probe?
 
The 6502 is good, I swapped that with the Space Duel. The manual shows only two RAM chips. I have one ROM that has a chunk missing from the top side of one end. I don't own a probe, but if it will help diag this and other boards I'm ready to try it. Can you recommend a good one Maxstang?
 
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