Car Guy Posted March 25, 2018 Share Posted March 25, 2018 Hey guys i just recently started picking up electronics since i baught a house in the city, now i have thrift stores and space haha Anyway i got a ti 994a today. Its my first pc older than windows 95. It was 30$ I played with the rf modulator and figured i could wire rca style plugs to the cable, i used 25 foot subwoofer stereo cables to reach my flatscreen It seams i have video and can hear beeps when i press keys, but i all i get is the color strips at the title screen, then i press a key and the color bars dissapear. No text like i see on youtube videos Any ideas? Ide appreciate some, Thank you! Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted March 25, 2018 Share Posted March 25, 2018 (edited) It would be helpful if you could post some video, taking pot-shot guesses can be time consuming. For instance, the first thing that came to my mind was... Is it hooked to an older CRT monitor? Sometimes on older sets the picture adjustments are set too tall and wide giving that effect as one possibility. Hard to tell without more feedback. -- edit -- Never mind, in re-reading your message I see you specified flatscreen. Also with no text at the color bars... that sounds like another issue, that others would be better able to help you with. I have a standard answer for most video questions, but it's a little more spendy and not currently available. Edited March 25, 2018 by --- Ω --- Quote Link to comment Share on other sites More sharing options...
ti99iuc Posted March 25, 2018 Share Posted March 25, 2018 (edited) @Car Guy, Are you from USA or Europe ? it is needed also for understand which kind of TI-99/4A are you using... NTSC or PAL and which kind of RF modulator, if PHA2036 or the USA one. Edited March 25, 2018 by ti99iuc Quote Link to comment Share on other sites More sharing options...
ollopa Posted March 25, 2018 Share Posted March 25, 2018 I think the problem is not with the RF modulator but with the console freezing just before loading the main menu after the title screen. He posted a screenshot on the 99er forums: 2 Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted March 25, 2018 Share Posted March 25, 2018 I think the problem is not with the RF modulator but with the console freezing just before loading the main menu after the title screen. He posted a screenshot on the 99er forums: Wow, that is weird... first time I've ever seen that one. I don't think my standard answer for a fix would apply here. Quote Link to comment Share on other sites More sharing options...
fabrice montupet Posted March 25, 2018 Share Posted March 25, 2018 It looks like some defective VDP RAM chips. 1 Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 (edited) Thanks ollopa I posted a video to youtube, in it i turn it on and press some random keys And heres my cord i made Edited March 25, 2018 by Car Guy Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 It looks like some defective VDP RAM chips. Damn. Are they the small removable chips i found lined up inside? Btw its an american (canada) machine Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 25, 2018 Share Posted March 25, 2018 See https://www.ninerpedia.org/wiki/Troubleshooting Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 (edited) Good link found my issue. Number 3 vram chip is toast i guess? i think anyway chip TMS4116 https://m.ebay.ca/itm/10pcs-TMS4116-15NL-TMS4116-IC-Chip-DIP-16/253164284180?hash=item3af1c46914:g:EqwAAOSwhYdZwh7l Edited March 25, 2018 by Car Guy Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 25, 2018 Share Posted March 25, 2018 Not quite, as I saw on a closer look. You have yellow and white fields in your color bar. Seems as if we need to do more experiments... Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 I turned it back on to make sure the camera got the colors right. it did. Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 If i was working on a car ide re melt all the solder point. Could the computer get cracked solder points from rough handling? Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 25, 2018 Share Posted March 25, 2018 This is a bit difficult to find out. I tried to apply some stuck-at-0 and stuck-at-1 masks in the MAME emulation of the video processor RAM, but I could not reproduce this pattern. Are the bright fields more like gray or more like white? Did you use a flash? (have to turn it off) Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 (edited) The white feilds are grey fuzzy upclose No flash, 3480x2160 HD The latest picture is as true as a picture of a tv can be This is a bit difficult to find out. I tried to apply some stuck-at-0 and stuck-at-1 masks in the MAME emulation of the video processor RAM, but I could not reproduce this pattern. Are the bright fields more like gray or more like white? Did you use a flash? (have to turn it off) Edited March 25, 2018 by Car Guy Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 25, 2018 Author Share Posted March 25, 2018 Thanks for the help By the way! Quote Link to comment Share on other sites More sharing options...
RXB Posted March 25, 2018 Share Posted March 25, 2018 I turned it back on to make sure the camera got the colors right. it did. GROM ZERO LOCK UP, seen this happen when I had the SOB and not seated properly or when GROM ZERO chip was defective. System shows part of screen and locks up in a loop, using a GRAM KRACKER I loaded a alternate GROM ZERO and it worked fine. It could be another issue but this is similar to what happened to me. 2 Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 26, 2018 Author Share Posted March 26, 2018 I lifted and lowered all the chips i could, which chip is grom? Quote Link to comment Share on other sites More sharing options...
Flottmann1 Posted March 26, 2018 Share Posted March 26, 2018 look here http://www.mainbyte.com/ti99/hardware/chips/main_board_big.html http://www.mainbyte.com/ti99/hardware/chips/grom.html 1 Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 26, 2018 Share Posted March 26, 2018 (edited) I did some more research using MAME ... have a look at the screenshot below. I got it by copying bit 4 to bit 3 (counting from the left): data = (data&0xef) | ((data&0x08)<<1);This means that the VRAM chip of bit 4 overrides the one of bit 3. It remains to find out how this could happen, though. [Edit: Ah, sorry, the blue and magenta do not match. Going to try a bit further.] Edited March 26, 2018 by mizapf 1 Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 26, 2018 Share Posted March 26, 2018 OK, this is my analysis so far. The color bar is created by writing character codes to the screen image table, and by setting color codes in the color table. Each bit has its own VRAM chip. If a chip fails, the bit at that location is always 0 or always 1. Character Color Error output 01100000 00000110 00000110 01101000 00000011 0000101* 01110000 00000001 00000110 01111000 00001011 0000101* 10000000 00001100 00001100 10001000 00001101 00001101 10010000 00001111 00001100 10011000 00000100 00001101 10100000 00000010 00000010 10101000 00001101 0000111* 10110000 00001000 00000010 10111000 00001110 0000111* 11000000 00000101 0000010* 11001000 00001001 0000100* 11010000 00001010 0000010* 11011000 00000110 0000100* The asterisks show that I am not sure about the color, judging from the photograph. Every row is a color field from left to right. Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 26, 2018 Share Posted March 26, 2018 Also possible is that the outgoing lines from the VDP have a bad connection. The schematics show that the VDP (video processor) has a read and a write data bus. The write data bus shares lines with the address bus. If there is a cold solder joint, then not only the respective bit is lost (although the VRAM is possibly OK) but the address is wrong. The VRAM address is transported in two parts (7 bits row and 7 bits column), so we have a 7 bit address bus. That is, unless D0 is affected (not shared), every lost data bit causes two address bits to be lost as well. @Rich: From the symptoms I tend to think it is more likely the VDP/VRAM, not the GROM. However, the lock-up is a point for the GROM theory. 1 Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 26, 2018 Author Share Posted March 26, 2018 Jees thats some great info. Just what i was looking for. Although iam nearly incapable of completely understanding. After work ill take it apart, then photos of the inside and we will highlight some solders to go over with the iron. I seen some wires that looks out of place ill highlight those too Quote Link to comment Share on other sites More sharing options...
Car Guy Posted March 27, 2018 Author Share Posted March 27, 2018 All appart Quote Link to comment Share on other sites More sharing options...
+mizapf Posted March 27, 2018 Share Posted March 27, 2018 I think it's not too likely to cause trouble, but maybe you should clean the 9918's pins from the white heat-conductive paste, but don't forget to apply some new on its top again before you assemble everything. It depends on whether the paste is also conductive for electricity. Quote Link to comment Share on other sites More sharing options...
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