ChildOfCv Posted March 3, 2021 Share Posted March 3, 2021 37 minutes ago, hyuma said: @omf I followed this for 5v mod: https://console5.com/techwiki/images/c/c0/Colecovision-5V-RAM-04-2-L3-REV-D-Pads.jpg There is a NTSC rev D and a PAL rev D, and the revs have nothing to do with each other. But if you've disconnected -5V and -12V from the video memory and added +5V where needed, then you should be good. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 4, 2021 Author Share Posted March 4, 2021 There is a NTSC rev D and a PAL rev D, and the revs have nothing to do with each other. But if you've disconnected -5V and -12V from the video memory and added +5V where needed, then you should be good.Yeah, 12v and -5v are disappeared, now I will order ram kit! Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
omf Posted March 4, 2021 Share Posted March 4, 2021 15 hours ago, hyuma said: @omf I followed this for 5v mod: https://console5.com/techwiki/images/c/c0/Colecovision-5V-RAM-04-2-L3-REV-D-Pads.jpg this must be relatively new, when i needed it there was nothing, looks similar to mine to be honest 1 Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 4, 2021 Author Share Posted March 4, 2021 Today for fun I desoldered the BIOS and read the content to check all was in place. It was a really cool thing to do! Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
omf Posted March 5, 2021 Share Posted March 5, 2021 if you cant get anything useful out of this thing after replacing the video ram chips i have had trouble personally with the following components the two main ram chips after deciding to replace all the chips on the board because they were cheaper then the two ram chips, it turned out to be the ram chips or chip i think it was that was dead, not everything else ?♂️ the clock crystal on a ntsc board (one pin had broken so it was only attached with one. getting a replacement for that was an issue due to overpriced ebay shipping, had to get someone in the US to get it and send it to me so i could get it at a reasonable price. i still have an issue with my French RGB board (which is the one the ram chips were dead on) where it displays faint white vertical bars on the screen, i have replaced most of the video circuitry with new but it is stll doing it. most annoying, apart from that the machine turns on and functions. its not the vdp as swapping it into another pal board and testing the board it was swapped into the video is fine, so i have been stumped on that one for some time unfortunatley 1 Quote Link to comment Share on other sites More sharing options...
omf Posted March 5, 2021 Share Posted March 5, 2021 (edited) the switch is a known bad component, especially after 30 odd years being sat around. good practice is remove it, disassemble and make the internals shiny again with your preferred method, i use brasso then polish off apply dielectric grease and reassemble and solder back in failing that replace with a different switch Edited March 5, 2021 by omf 1 Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 5, 2021 Author Share Posted March 5, 2021 Yeah i polished the switch too [emoji106]Today I tested other sets of ICs, U30, U31, U32, U18, U19 and all are fine. I have ordered a set of 4164 then let's see next week if the issue disappear! Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 5, 2021 Author Share Posted March 5, 2021 if you cant get anything useful out of this thing after replacing the video ram chips i have had trouble personally with the following components the two main ram chips after deciding to replace all the chips on the board because they were cheaper then the two ram chips, it turned out to be the ram chips or chip i think it was that was dead, not everything else [emoji2357] If you meant the RAM chip 2114 U3 and U4 I tested with arduino code and they are ok [emoji106]Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 11, 2021 Author Share Posted March 11, 2021 Ok, RAM replaced, 4164 socketed, black screen with some lines on black screen but I can see PAL message on CEC. I have to test with some CRT and try some composite mod... Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 14, 2021 Author Share Posted March 14, 2021 Ok, with composite mod on breadboard i got on my LED TV the message "PAL" that appears on the top right of my TV. That should be the CEC. After a bit the message doens't worked anymore so i'm assuming that the VDP is not working well. When i wil receive my oscilloscope I will check the signals on it, and for now i just bought a new TMS9929ANL. Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 14, 2021 Share Posted March 14, 2021 On 3/11/2021 at 3:48 PM, hyuma said: Ok, RAM replaced, 4164 socketed, black screen with some lines on black screen but I can see PAL message on CEC. I have to test with some CRT and try some composite mod... That means your system clock works, as does the 10MHz resonator, and the 9929 is generating a picture. You should check the 74LS138's and the 74LS04 next. With everything else checked, if you still get nothing, then the Z80 could be the problem. You could also wire up your composite mod directly to the Y output of the 9929 to see if you at least get a B/W output. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 16, 2021 Author Share Posted March 16, 2021 That means your system clock works, as does the 10MHz resonator, and the 9929 is generating a picture. You should check the 74LS138's and the 74LS04 next. With everything else checked, if you still get nothing, then the Z80 could be the problem. You could also wire up your composite mod directly to the Y output of the 9929 to see if you at least get a B/W output.Yeah 74LS04 and 74LS138 tested and working good. I've used the TL866IIplus programmer. Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 16, 2021 Share Posted March 16, 2021 How many channels does your logic analyzer have? You could hook them up to the data lines of the CPU to see if it's alive. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 17, 2021 Author Share Posted March 17, 2021 How many channels does your logic analyzer have? You could hook them up to the data lines of the CPU to see if it's alive.It have 16 channels, Data lines on z80 are pins 7,8,9,10,12,13,14,15? Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 17, 2021 Share Posted March 17, 2021 9 minutes ago, hyuma said: It have 16 channels, Data lines on z80 are pins 7,8,9,10,12,13,14,15? Inviato dal mio CLT-L09 utilizzando Tapatalk Yep. And address lines on A0-A15. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 17, 2021 Author Share Posted March 17, 2021 Yep. And address lines on A0-A15.Ok, I'll check both and I post resultsInviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 18, 2021 Author Share Posted March 18, 2021 (edited) @ChildOfCv I recorded two videos: one is Data lines and the other ones is Address lines of Z80. Next monday I will receive the oscillope that i bought and maybe the signals will be more clear. 1.mov 2.mov Edited March 18, 2021 by hyuma Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 18, 2021 Share Posted March 18, 2021 I see a lot of dead lines in those analyses. It strongly suggests that the CPU is dead. At least A0,A1 ought to be doing something, since execution of instructions requires a lot of sequential reads. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 18, 2021 Author Share Posted March 18, 2021 7 minutes ago, ChildOfCv said: I see a lot of dead lines in those analyses. It strongly suggests that the CPU is dead. At least A0,A1 ought to be doing something, since execution of instructions requires a lot of sequential reads. I have a Z80 from a Sega Mega Drive that I know is working that I will use as replacement there Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 24, 2021 Author Share Posted March 24, 2021 Oscilloscope arrived, Z80 seems really have serious issue, ordered a new one, waiting it for arrive Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 24, 2021 Author Share Posted March 24, 2021 @ChildOfCv New zilog in place but I noticed that the clock is different... Maybe I made a mistake buying the zilog?? Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 24, 2021 Share Posted March 24, 2021 Do you mean that your replacement can't handle the speed? TIL, the original Z80 had a 2MHz limit. The Z80A can clock up to 4MHz, and the Z80B can clock up to 6MHz, and so on. Also note that pin-compatible clones exist. My CV has a NEC μPD780C-1. (note that the -1 is important in this case) Looks like you have the SGS-Thompson version. Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 24, 2021 Author Share Posted March 24, 2021 (edited) @ChildOfCvI just notice that i bought Z80 PIO and not Z80 CPU, check the image, there is written Z80 PIO on the chip... I didn't read well the ebay acution... now i found a seller here near my city that have Z80 but it's 8MHz.. is this a problem? Should i have to use a strict 4mhz cpu? thanks! Edited March 24, 2021 by hyuma Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted March 24, 2021 Share Posted March 24, 2021 (edited) 1 hour ago, hyuma said: @ChildOfCvI just notice that i bought Z80 PIO and not Z80 CPU, check the image, there is written Z80 PIO on the chip... I didn't read well the ebay acution... now i found a seller here near my city that have Z80 but it's 8MHz.. is this a problem? Should i have to use a strict 4mhz cpu? thanks! 8MHz can run at slower speeds (even 0 ) so that shouldn't be an issue. If you can find the full part number, the datasheet will tell you if there's a minimum speed. But when Z80 went to CMOS, they eliminated the minimum speed. Looks like Jameco has the actual CPU you need in stock though. https://www.jameco.com/z/Z80A-CPU-Major-Brands-IC-Z80A-4-8-16bit-CPU-N-Channel-Silicon-Gate_35596.html?CID=MERCH Edited March 24, 2021 by ChildOfCv Quote Link to comment Share on other sites More sharing options...
hyuma Posted March 27, 2021 Author Share Posted March 27, 2021 Ok, New cpu Z80 in place, address line now are good with activities and not stuck hi or low as before. Composite mod in place but still black screen and some green lines or dot sometimes with PAL message top right of TV that appears when I turn on the console. As I have ordered a new tms9929anl and waiting for it that arrives, just for study I should check in the old one pin 35-36 and 38?Inviato dal mio CLT-L09 utilizzando Tapatalk Quote Link to comment Share on other sites More sharing options...
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