stfouill

Hello ! Some Videopac G7000 and G7400 were made in France. At the Time, lots of Philips plants all over Europe... Envoyé de mon M2103K19G en utilisant Tapatalk

Oh yes I did not realize it is so close to the feet ! Indeed we can see the pressure on the tracks now you point it out ! No soldermask on this old lady, reminds me the videopac I own which also failed. At least it is easy to probe and to repair !

Finally, I found the issue ! I want to give here my troubleshooting, it may help someone... I was quite sure the issue was related to how the image is generated after VRAM. If you check the schematic, VRAM is working by pair : one pair for odd column, one pair for even column. First I realized my Saba Videochanel is close to Luxor schematic from veswiki. So I pushed investigation on component E6 (74LS195, see schematic extract) which is a shift register that is mixing odd/even line for the foreground items (score, ball, pong bars, red contour). I was expecting on pin 9 some kind of square signal (this pin is used to load the register) but I saw what you can see on scope.jpg Clearly not good, not a signal expected on a logic component ! Then I checked the trace to find where it comes from and I found bridge ! See picture. What is strange is that this bridge seems factory (like the PCB was not correcly manufactured). Bridge removed and... tadaaa ! Thank you again for your help, especially the wiki/schematic. Hope this could help anyone... now let's play

Yep the 5V was faulty (7805 was bad), but the +12V/-5V are good. I don't think there is any chemical capacitor outside power supply but I will check again. I reseated every 40-pins DIN chips, nothing changed ! I checked every vertical/horizontal clocks (2H, 4H, 8H,... V, 2V, ...) all seems good. Also adress generator is working correctly I think, even if it is difficult to be sure without any logic analyser (I can confirm I can see writing sequences on every adress/data pins). So I think that the issue is after RAM, when image is generated by the 74LS195 (which is alterning between odd/even columns). I continue to poke around with the oscilloscope.... I will let you know if I find something.

Thank you all for your answers ! I only had the FVE schematic. I don't know yet which one is the closest to my Videoplay. I swapped the RAM by just interverting them. I guess that if one had failed, then I would have another issue. Indeed there is something about X coordinate as you mention, I think only one of the two VRAM banks is accessed correctly (when writing or reading). As I understand the schematic, one bank if for odd columns, one is for even columns. That would explain why one of the two vertical line is missing (it may be on an even column for instance) and the other has double the width (odd column for instance). I will try in the next days to clean the big DIP-40 chips, I keep you informed. Thanks again !

Hello AtariAge community ! I recently aquired a Saba Videoplay (first revision) that has some faults I try to repair. The first one was the +5V regulator which was dead and giving 3.5V. That's fixed. The second one is a video issue, attached what I get from the included videogame. I tried swapping the 4 RAM chips and nothing changed. I poked a bit around with the scope and I confirm all 4 RAMS get data in (when the microprocessor is writing) and give data out. It seems also all 6 adresses pins on the four chips are working. I have the schematic but limited knowledge on the architecture of the machine. I guess that all of these is working : - Pixel clock - H sync, V sync, Composite sync - Vertical adressing from µP - Vertical/Horizontal adressing from video generation I guess I have to check next - Horizontal adressing when µP is writing ? - RAS, CAS ? - Mixing Foreground/Background ? - ? Any idea ? Any clue would be much appreciated !! Stéphane

I just received and installed mine, result is just amazing ! I have to say it was quite easy even if I fought a bit to have all lines due to some dust. Thanks for taking this project to the end with such great value for our Microvision systems. It may be my favorite screen update because it really helps revive the console. Cheers from France !

I'll check the bodge and cross check with PAL schematic ! Thanks for the proposition, I'll try myself I think, I already have soldered Hi-Def NES, SOPHIA and such kits which require some solder/desolder skills also ? (or let's say I fear postal services more than my solder skills haha ?)

I don't know if I am attached to that specific 7800 but I want to give this grand'ma her chance to improve the video output - which is indeed totally crappy with the RGB encoder. My TV is compatible with S-Video so I will try to bypass completely the RGB encoder as you proposed. I have to check beside the encoder what bodges are done to the motherboard and if they are easy to undone...

Good news thanks ! The thread is huge now, I tried to read it quickly, I think the mod is compatible with French version (which is a PAL with an additionnal board if I understood correctly) am I right ? Envoyé de mon BLN-L21 en utilisant Tapatalk

Hi all !@juansolo you said taht maybe you will do a PCB for the modification, any news ? I guess I'm not the only one to be interested Envoyé de mon BLN-L21 en utilisant Tapatalk