TI99/4a issue

[8bitbricks]

I have a ti99/4a that gives a black screen, but does beep. There was also a damaged component that broke when I removed it that I believe is c602 on the schematic, but I don’t know what to replace it with. How would I fix this?

Edited June 5, 2022 by 8bitbricks

[AwkwardPotato]

If the damaged component is the black one, right of center, in between the two blue wires, I *believe* it's a 1uF tantalum capacitor.

 

Just to double-check: is the beep on your system a short tone, or one that continues as long as the system is turned on? If it's a short tone, check that your video cable is good, then try resoldering all the pins of the video connector on the motherboard. If you still don't have any video afterwards, it's likely that the VDP has failed.

[8bitbricks]

The beep was a short tone, and I am pretty sure it is the VDP. Where could I get a new one?

Yes, the component is the black one, what would a suitable replacement be?

[8bitbricks]

Would this work: 

https://www.ebay.com/itm/194051392661?epid=1818450792&hash=item2d2e5d4495:g:wXUAAOSwXeJYECgS

[AwkwardPotato]

Hard to say whether that VDP will work or not. While the listing photo looks like it could be a genuine part, finding working VDPs on eBay seems to be extremely hit-or-miss nowadays. May be worth a shot, and perhaps other members here will be able to share seller recommendations.

[AwkwardPotato]

Double-checked my TI's board and yes, the damaged part on yours is a 1uF 25V tantalum capacitor. A suitable replacement can be found here on Mouser, and it appears that the same part can be found here on eBay too (not affiliated with seller). Note that this capacitor is polarized, so the rounded-off/tapered side needs to face the TIM9904 chip.

[8bitbricks]

I got a video output using a RCA cable, and alligator clips and it worked. It didn’t need a new video chip, but I will replace the missing capacitor, though I don’t think it is vital for operation. Thank you for your help.