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Papalapa

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About Papalapa

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    Barcelona, Catalonia

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  1. Well, I'm lucky today, mi Acorn Electron is already working 👍 Today the paint on the ULA was dry and and as you can see in the picture below looks not so good but anyway I installed the ULA in its socket. Before to do this I checked all the ULA tracks and as the last time that were checked all of them seemeed to be OK. Unfortunatelly when I turned on the Acorn I got the same screen pattern and it become frozen so, the malfunction still there. As "Plan B" was to replace the RAM I unsoldered the chips and soldered a good-quality sockets instead. Then I connected the new RAM chips and when I turned on the Acorn I heard a beep and I have seen the welcome screen on the display. I ran some small basic programs and all of them worked without hangs or erratic software behaviours so, the problem was located in the RAM chips (maybe only one chip, I don't know..). At this point I realized how easy it would have been to start by the RAM instead of the ULA and it's socket. What I noted is that the RF output has bettter quality than composite video output ¿? You can see in the pictures below that when the composite output is used a "ghost shadow" is shown over some characters while the RF output is clean. Anyway I will make a RGB cable and I hope that the image quality will be better. Composite output RF output Next step will be to completely dissasembly and clean the keyboard cap by cap (I do this will all my bought retro-computers), and the cabinet. There also some keys that most probably will need "contact cleaner" because they need a strong pressing to be detected. And finally I will upgrade my TZXduino firm to be able to load the Acorn Electron programs (actually it only supports ZX-81, ZX-Spectrum and Amstrad CPC-464)
  2. Well, after receive and carefully solder the new ULA socket the problem remains. As you can see the pattern on the monitor has changed but the CAPS light is not working and there's no "beep" during startup. I tried to clean the ULA pins with alcohol again and one track has gone and now I'm trying to restore this track using conductive paint. Also, some other tracks are small portions gone and other ones seem to have a bubble below the track so at the contact point with the socket, maybe they do not offer a good contact. You can see the pictures: Anyway, after the ULA repair I'll test again all the tracks continuity between the chip and the tracks edge. If all is correct I'll go ahead with the RAM chips replacement as planned...
  3. Thank you for your response. At the moment I released the ULA from its socket and carefully cleaned its pins. While cleaning the pins on the socket I have seen that there are some of them lower than the other so, probably they do not correctly conatct the pins of the ULA. When I tried to straigh a pin it was broken and I "repaired" it using a bit of cable, but later a second one was broken an therefore I ordered a new socket and actually I'm waiting that it arrives in order to replace the damaged one.
  4. Recently I got an old Acorn Electron that was stored in a loft for many years. Before to turn it on I checked the external transformer voltage and it was correct. I also opened the case and checked the internal power supply disconnected from the motherboard that was also OK, +5v and -5v voltages were present. Then I connected the power supply to the motherboard and once turned on there was not ot a "beep" sound , the keyboard not worked and the light on the keyboard was not illuminated . I only get this image at the composite and RF outputs: I'm aware that the Acorn Electron cannot be turned on with the keyboard disconnected so, I checked the continuity of the flat cable that connects the keboard to the motherboard and all the tracks have had continuity so, it seems to be correct. I measured the voltages at some points as explained in the Service Manual and all of them were correct. Unfortunatelly I don't have oscilloscope and I cannot measure the waveform signals (oscillator, clock, etc...). The only strange think that I detected is that the current compsumation on the -5v is only 3mA while the Service Manual says that should be 25mA. The current compsumation of the +5v is according to the Service Manual. Can be the ULA damaged? What else can I check? Thanks a lot.
  5. It seemed impossible but finally I found a 4K RAM cartridge and the FX-9000P is working now 👍 I'm surprised because the image on the screen is perfect. The TRC has enough bright and the characters are clean and without distortion nor vibration: Now is time to read the manual and type the programm examples on it...
  6. Yeah of course, "Before" one is S-Video output while "After" is composite video. In my VIC-20 composite was dreadful as you can see.
  7. I don't know if the American version video circuit is different from the European one (the modulator for sure) but if not you can convert the video composite output in S-Video. Im my case the quality difference was amazing: After Before Also, Pi1541 is really useful and even if do you have a Commodore 64 can serve both computers, VIC-20 and C-64.
  8. It's nice but as far as I remember is an HDD emulator, not a floppy emulator that allows to load floppy images it isn't? (maybe I'm wrong).
  9. This was the second reason and at the moment the shipping restriction was already gone, in fact I received my second unit after the Covid restrictions of the HK Post service. The first one was purchased on November last year when Covid even still "didn't exists".
  10. Yeah, I don't know why but usually these guys made a batch and then a lot of time passes until the next batch is available. When I purchased the mine time ago I contacted them by e-mail because the website always shown "Out of stock".
  11. Glad to know tha VGA output will be possible, even better than HDMI for me...
  12. Yes, ROM and GROM cartridge images on the SD Card.
  13. You can use wDrive. Last firmware version allows to copy an image directly from the wDrive (SD card) to a real floppy on the disk drive. It works like a charm.. Also maybe using ADTPro software but I don't tried this way...
  14. For me the best solution for the TI-99/4A is FinalGROM 99. I love it. For my Spectrum I have the DivIDE 2k14 and both work in the same way...
  15. No luck at the moment, let me insist.... 🙂
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