dphirschler Posted August 13, 2014 Share Posted August 13, 2014 (edited) I have three beige TI consoles. Two have bad keyboards, one has a good keyboard but looks like this when I boot it. I replaced the one chip that comes out of the socket (this is the one I removed for the eventual F18A mod) from another console. Didn't help. Can anybody else diagnose this from just a photo? Darryl Edited November 9, 2014 by dphirschler Quote Link to comment Share on other sites More sharing options...
Gazoo Posted August 13, 2014 Share Posted August 13, 2014 If I was to hazard a guess, it would be that the Grom 0 chip is bad. Gazoo Quote Link to comment Share on other sites More sharing options...
am1933 Posted August 13, 2014 Share Posted August 13, 2014 Well, I had a flick through some very hefty technical documents and after consultation and looking at your screenshot-I have diagnosed the problem, it does not work properly 3 Quote Link to comment Share on other sites More sharing options...
Stuart Posted August 13, 2014 Share Posted August 13, 2014 I'd say a bad video RAM chip. Very common problem. If you have an F18a, trying on this console would confirm whether its a bad video RAM chip or not as the F18a doesn't use them. 2 Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted August 13, 2014 Share Posted August 13, 2014 My money is on bad VDP RAM. TAKING ALL BETS! Quote Link to comment Share on other sites More sharing options...
+arcadeshopper Posted August 14, 2014 Share Posted August 14, 2014 Yeah when the video is fried like that its either the vdp or video ram.. F18a to the rescue! Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 14, 2014 Author Share Posted August 14, 2014 I don't think it's the VDP because I already swapped it out with a known good one (removed from another TI in preparation for F18A). I was very hopeful this would solve it, but it didn't. So that leaves video RAM then, right? Can I assume that the video RAM is #14 in the below picture? (picture from old-computers.com) I should point out that TI Invaders crashed shortly after entering the game. That seems to point to bad RAM too, doesn't it? Darryl Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted August 14, 2014 Share Posted August 14, 2014 Yup. Those would be they! ...lee Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 14, 2014 Author Share Posted August 14, 2014 So... Desolder old ships, solder in new chips? Next question. Does anybody know where I can get replacement RAM chips? Also, is this the oportunity to make it 32k? Darryl Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted August 14, 2014 Share Posted August 14, 2014 So... Desolder old ships, solder in new chips? Next question. Does anybody know where I can get replacement RAM chips? Also, is this the oportunity to make it 32k? Darryl The VDP only supports 16k, but you could do the 16-bit 32k RAM in-console upgrade. Quote Link to comment Share on other sites More sharing options...
gregallenwarner Posted August 14, 2014 Share Posted August 14, 2014 My suggestions is don't muck about with the video RAM chips. Just slap in an F18A. Much easier, and no soldering involved, so fewer chances for things to go wrong. It has its own RAM, so it doesn't use the faulty RAM on the board. You'll be killing two birds with one stone, as you also get a VGA upgrade! 1 Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 15, 2014 Author Share Posted August 15, 2014 (edited) I didn't realize the F18A had its own RAM. So it doesn't even use those bad chips after the upgrade. This post made my day! And now (after re-reading the thread), I see that Stuart said the same thing but I just missed it. Darryl Edited August 15, 2014 by dphirschler 1 Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted August 15, 2014 Share Posted August 15, 2014 On the screen you see "PPGQQ" instead of "PRESS". P is 0x50 (or $50 or >50, depending upon your assembly culture), R is 0x52, S is 0x53, Q is 0x51, E is 0x45, and G is 0x47. In bit-speak that is: P %01010000 Q %01010001 R %01010010 S %01010011 E %00100101 G %00100111 Just looking at "PRESS" we see this pattern: BAD GOOD %01010000 %01010000 %01010000 %01010010 %00100111 %00100101 %01010001 %01010011 %01010001 %01010011 This does not give a consistent dead or stuck state, but it does show that bit 1 is usually not what we expect. Looking around the screen, it is pretty consistent that bit 1 is often wrong, and wrong on the same characters: E->G, S->Q, N->L, M->O, etc. I do not know which chip is bit 1 of the VDP RAM byte, but I am sure someone else here does. If you are going to replace your VDP with an F18A then this is academic unless you want to save good RAM chips for other computers. Quote Link to comment Share on other sites More sharing options...
Willsy Posted August 15, 2014 Share Posted August 15, 2014 If you're handy with a de-soldering tool (I'm luck, I actually have a Weller de-soldering station ) you could de-solder all of the VRAM chips, throw away the bad one, and sell the rest on eBay. They actually go for good money - they're getting increasingly rare. It could offset some of the cost of the F18A :-) Another benefit: Your TI console will pull considerably less power from the built in power supply board, meaning the whole console runs cooler - that's also good from a "stressing the hell out of vintage ~30 year old components" perspective! Quote Link to comment Share on other sites More sharing options...
Willsy Posted August 15, 2014 Share Posted August 15, 2014 Talking of old components, are there many electrolytic capacitors in the TI console? We're gonna start hitting a wall soon whereby those old caps are gonna dry out and need changing. It's already being seen quite a lot in the ZX Spectrum world (degrading PAL video output which is corrected by changing a capacitor). The components in our consoles are now 30 years old (32 years, and 31 years in my two consoles) - some of those caps are gonna we waaaaay off spec! 1 Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 16, 2014 Author Share Posted August 16, 2014 F18A fixed it! Check out this pic. Can I safely desolder the old video RAM chips? Darryl 3 Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted August 16, 2014 Share Posted August 16, 2014 F18A fixed it! Check out this pic. Can I safely desolder the old video RAM chips? TI Invaders.jpg Darryl Congratulations on the new F18A! You could go through the PITA of removing them, but why bother? Are they hurting anything? 1 Quote Link to comment Share on other sites More sharing options...
Ed in SoDak Posted August 16, 2014 Share Posted August 16, 2014 I was gonna suggest swapping a working motherboard and keyboard into one case but the F18A answer is no doubt better yet! If the RAM chips don't feel hot like one or another might be shorted, you may be better off leaving them in. It's a lot of desoldering that has its own risks of board/trace damage. Or just swap in one of the working boards, but you'd have to reinstall the F18A into it. -Ed Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 16, 2014 Author Share Posted August 16, 2014 Removing the chips will be a snap. My coworker has a professional desoldering station and wouldn't mind taking a few mins to remove those chips. My main concern is identifying the bad chips so I can throw them out. The good chips I want to keep on hand as spares, or possibly sell them on EBay. Darryl 1 Quote Link to comment Share on other sites More sharing options...
Ed in SoDak Posted August 16, 2014 Share Posted August 16, 2014 (edited) Some Timex Sinclair models use the same 4116 or compatible RAM, plus other vintage iron as well. Sometimes you can piggy back a good chip by hand, but not so sure how easy or reliable that test is. About the only way I know of testing in circuit other than a short check on the power pins or feel for heat is substitution with a known good chip. Which usually means having a working system with one chip socketed for testing the unknown chips. Maybe the hardware gang has something better. I have a Timex 1500 with bad RAM, so I'm watching this thread as well. -Ed Edited August 16, 2014 by Ed in SoDak Quote Link to comment Share on other sites More sharing options...
RobertLM78 Posted August 16, 2014 Share Posted August 16, 2014 Congratulations on the new F18A! You could go through the PITA of removing them, but why bother? Are they hurting anything? It would be a waste of time removing them. The F18A bypasses the VDPRAM. Quote Link to comment Share on other sites More sharing options...
Stuart Posted August 16, 2014 Share Posted August 16, 2014 Removing the chips will be a snap. My coworker has a professional desoldering station and wouldn't mind taking a few mins to remove those chips. Be aware that you'll probably find that two diagonally-opposite pins on each chip were folded flat against the board prior to soldering, so as well as melting/removing the solder you've also got to bend up a couple of pins that are soldered to the board. It's not just a case of melting the solder and the chips fall out ... Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted August 17, 2014 Share Posted August 17, 2014 Be aware that you'll probably find that two diagonally-opposite pins on each chip were folded flat against the board prior to soldering, so as well as melting/removing the solder you've also got to bend up a couple of pins that are soldered to the board. It's not just a case of melting the solder and the chips fall out ... Is that part of the wave-soldering process, to hold the chips in-place until they hit the tub? Quote Link to comment Share on other sites More sharing options...
dphirschler Posted August 17, 2014 Author Share Posted August 17, 2014 I am also planning on removing the a/v connector in the back left corner. I will put either an RCA there or a 1/8" audi connector. I might install a small amp and a volume wheel too. Darryl Quote Link to comment Share on other sites More sharing options...
+OLD CS1 Posted August 17, 2014 Share Posted August 17, 2014 I am also planning on removing the a/v connector in the back left corner. I will put either an RCA there or a 1/8" audi connector. I might install a small amp and a volume wheel too. Darryl I just built a 5-pin DIN connector with nothing but audio output. Quote Link to comment Share on other sites More sharing options...
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