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repetto74

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Posts posted by repetto74

  1. Ok moment of truth...

     

    It was indeed the Pokey chip unfortunately. Swapping it with my own unique good spare has just fixed the problem 🙄.

     

    Bad luck and it is very difficult to source this chip at a decent price (especially the version that works with the Atari 8bit line of computers).

     

    Are there any open source projects for an FPGA Pokey in progress recently?

     

  2. 48 minutes ago, Beeblebrox said:

    Probably pokey. 

     

    Edit: @repetto74 BTW if you do find it's the pokey chip and you remove the old faulty one... Don't throw it. They can often still function as a secondary pokey chip in a stereo pokey upgrade. 

    Noted I will put it aside then :-). Hope to see one day an open source FPGA replacement for it. Actually the replacement Pokeys are quiet pricey!

  3. HI,

     

    I was playing on my Atari 800XL and suddenly the video turned to garbage. Since then there is no normal boot to the prompt. I just get a weird brown screen and a humming sound.

    I checked the power supply voltage at the pin connector with no load and oooh damn I read 15v!! 😑

    I checked the 800xl with another PSU I have and miracle the machine booted again!

    This post is just to tell users to not freak out if the original PSU fails. In my case it was the internal BD303 transistor who failed and was probably outputting less more that the 5v required under load.

     

    Better anyway to stay away from those old PSU and prefer a din-usb cable to be used with a standard usb phone charger 😄

     

    It was close!!

  4. On 7/17/2023 at 4:37 PM, marauder666 said:

    I've had a bad crystal in a couple of PAL machines I've picked up, both black screen.

    Check pin 6 on the Z80 with the oscilloscope, should be about 3.5mhz clock signal

     

    Thanks I'll pick from there and start the troubleshooting. There is although a change. I tried to hook the console to the composite output and now I do see an image but very very distorted which let me think that at least CPU, VDC and RAM should be fine.

    I think something is wrong on the video circuitry and maybe the TMS-RGB board is fried which may explain the total absence of an RGB signal.

     

     

     

    IMG_5175.JPG

    IMG_5176.JPG

    IMG_5177.JPG

    IMG_5178.JPG

    IMG_5180.JPG

  5. Hi,

     

    Some progress 😇

    I have hooked the Colecovision to the composite mod just to test if that was making any difference and indeed I do have a very scrambled picture in a loop with a black screen.

    With the RGB mod I just get nothing as I said, no video sync.

    Could this be a dodgy videochip? I am measuring only +4.6v on the board pcb so wonderign if the insufficient voltage can cause this.

     

     

     

     

    IMG_5176.JPG

    IMG_5177.JPG

    IMG_5175.JPG

    IMG_5176.JPG

    IMG_5180.JPG

    IMG_5178.JPG

  6. When you say a "blank screen" do you mean black screen or white noise (snow), as the former would generally suggest the video output stage is operational (creating a video singal) but the unit is not producing any video graphics, while the latter would generally suggest that the video output stage (i.e. RF modulator) is not working and so there is no video singal being produced. 

    It is a blank screen not black screen, meaning that my TV is reporting a "no signal" so there is absolutely no video generation from the circuitry (either the clock is missing or either the VDC is fried).

     

    I will start to troubleshoot and check all ICs voltages (I want to bypass the power switch for that first as on the Coleco it is a well known issue that power switch just fail with time and do not provide correct levels of voltages required by some ICs).

    Next will be to check the clock and reset from the CPU.

    Is there a place where I can find a good schematic for the Coleco?

  7. Hello,

     

    Drama 😨. I was having some graphical glitches recently on my Coleco and decided to desolder and give a good service to the infamous power switch.

    After cleaning and mounting the switch back, glitches where still there. I started to wobble the switch and noticed indeed weird graphic things happening on screen leading to the conclusion that he switch is very flaky and may need to be just replaced.

    Unfortunately I suddenly noticed a weird graphic pattern on screen and all turned to black. Since then, the console will not boot anymore. The video signal is not hooked up by the TV, just nothing (referred as a blank screen).

    I checked voltages at the power Supply connector and we have steady +12v and +5v. I randomly checked voltages on the video ram and notices +4.6v which seems to be a little bit low (+12v and -5v looks ok)

    I though that the power supply did fail completely but there are voltages when switched on.

    Where can I start to look at? I do have a logic probe and an oscilloscope even if I am not a super expert on hardware troubleshooting but any advice would be appreciated. I do have also some spare 4116 and 2114 rams in case but wondering how much they could be the cause in a total absence of video signal.

    Hope I did not fry the VDC or the crystal?

     

    I would like to make a test and bypass the power switch. But before hooking any wires at the back of the switch vias I want to be sure that I will not short anything. The switch has 6 pins, left side is the +12v and right side +5v. Where I should bridge to power the board? If I refer to the schematic below I should bridge top pin with the center one on both +12v and +5v rails.

     

    Just as extra information, this Coleco has 2 video mods, one is the composite mod and the second is the TMS-RGB mod (both working good). I was hooked up on the RGB connector when troubles started and did not had a chance to try to connect to the composite circuitry (the pcb was on the test bench and not connected to the RCA jacks mounted on the Coleco case). I am willing to try to hook it up with composite although I do not think this will make any change.

     

    Sans titre.jpeg

  8. Hello,

     

    Drama 😨. I was having some graphical glitches recently on my Coleco and decided to desolder and give a good service to the infamous power switch.

    After cleaning and mounting the switch back, glitches where still there. I started to whobble the switch and noticed indeed weird graphic things happening on screen leading to the conclusion that he switch is very flacky and may need to be just replaced.

    Unfortunately I suddenly noticed a weird graphic pattern on screen and all turned to black. Since then, the console will not boot anymore. The video signal is not hooked up by the TV, just nothing (referred as a blank screen).

    I checked voltages at the power Supply connector and we have steady +12v and +5v. I randomly checked voltages on the video ram and notices +4.6v which seems to be a little bit low (+12v and -5v looks ok)

    I though that the power supply did fail completely but there are voltages when switched on.

    Where can I start to look at? I do have a logic probe and an oscilloscope even if I am not a super expert on hardware troubleshooting but any advice would be appreciated. I do have also some spare 4116 and 2114 rams in case but wondering how much they could be the cause in a total absence of video signal.

    Hope I did not fry the VDC or the crystal?

     

    I would like to make a test and bypass the power switch. But before hooking any wires at the back of the switch vias I want to be sure that I will not short anything. The switch has 6 pins, left side is the +12v and right side +5v. Where I should bridge to power the board? If I refer to the schematic below I should bridge top pin with the center one on both +12v and +5v rails.

     

    Just as extra information, this Coleco has 2 video mods, one is the composite mod and the second is the TMS-RGB mod (both working good). I was hooked up on the RGB connector when troubles started and did not had a chance to try to connect to teh composite circuitry (the pcb was on the test bench and not connected to the RCA jacks mounted on the Coleco case). I am willing to try to hook it up with composite although I do not think this will make any change.

     

    Sans titre.jpeg

  9. On 3/27/2021 at 10:28 PM, webdeck said:

    Success!  I followed the instructions in Post 28, namely:

    1. Disassembled the console
    2. Removed the 9918A with a chip puller
    3. Soldered a ribbon cable to the TMS-RGB
    4. Soldered the TMS-RGB (ordered from Mobius Strip Technologies) under the VDP socket on the back side of the board
    5. Soldered a wire to the sound output
    6. Desoldered the video connector and removed it from the board
    7. Desoldered the one resistor that was where the bottom 560 ohm resistor goes
    8. Added and soldered the three 560 ohm resistors
    9. Soldered the ribbon cable and audio cable to a mini-DIN 8 jack following the XRGB wiring diagram (using this helper board)
    10. Bent back the shield near the mini-DIN jack to make enough space for the new connector + wires
    11. Attached the mini-DIN jack (upside down) to the board with solder and hot glue, using a nut as a spacer (otherwise it is too low for the opening)
    12. Double-checked continuity between the pins of the mini-DIN jack and the TMS-RGB and checked for shorts
    13. Cleaned off all the old thermal paste from the shield
    14. Inserted a TMS9928AN (purchased a used one pulled from a working system on eBay) into the VDP socket
    15. Applied new thermal paste to the VDP
    16. Covered soldered wires with electrical tape
    17. Put electrical tape around ribbon cable where it comes near the shield to go around the board
    18. Put everything back together
    19. Connected the mini-DIN jack to my OSSC's SCART connector via the recommended cable
    20. Set the OSSC for AV1 (SCART) RGBs

    I powered it up and got the most beautiful crisp title screen.  Audio works fine with the SN94624 sound chip.  My TI has never looked this good!

     

    IMG_6053.thumb.jpeg.d01d2fcfefc66f4c175726a3fd820ae6.jpegIMG_6054.thumb.jpeg.86a01c3bb21d9954da99dfa2efc8e37b.jpegIMG_6056.thumb.jpeg.a93c511e80bdfb68142eb83942c2fb64.jpegIMG_6059.thumb.jpeg.6e63b7b5b90d0613c2ba28fe6741d1cf.jpeg

    Hi,

    I made the same mod with the TMS-RGB board and the Mini Din 8pin. 

    I have a nice and crisp picture but sound is very low and I can barely hear it.

    I connected both L/R audio cables to the pin 5 of the DIN connector. I have a PAL machine by the way.

    I am missing something to get louder audio output?

     

    Rick

    • Like 1
  10. Hi,

    I know this thread is old but I’ll try my luck. 

    I have mounted a Uno Cart but today with cip shortage, the stm32f407vet6 can be sourced more easily and at a better price. 

    This should be a straightforward alternative of the stm32f407gte6 (only difference is flash size of 512k i/o 1mb)

    I programmed the vet6 with a good checksum but all I get when I plug the cart on my 800xl is a red screen. 

    Is there a specific setting when programming the firmware on the vet6? Any specific block where to write the firmware?

    Many thanks.  

  11. On 7/26/2022 at 11:19 AM, Al_Nafuur said:

    Yes you can. The only technical difference between the VGT6 and the VET6 is the flash ROM size ( 1 MiB vs. 512 KiB) and of course a large difference in price and availability.

     

    The only drawback is that there will eventually be a bank switching scheme that requires the larger flash memory. Currently there is none supported by the standard UnoCart firmware.

     

    Which board do you want to use?

     

    You might want to have a look at @Andrew Davie's Unified breakout board (which should work with the v17 UnoCart firmware too) in this thread:

     

    I would like also to build the UnoCart2600 and use the VET6 alternative microcontroller. 

    If I understood correctly the firmware originally developed for the VGT6 is 100% compatible? Do we need to recompile or amend it before flashing it?

  12. On 8/29/2021 at 8:54 PM, zx-81 said:

    Hi Repetto74,

    You need to use a 1k resistor (10k is too high).

     

    Zx

    Hi zx-81,

     

    Indeed that was it!! Changed to a 1k pull-up and now the cartridge is working perfectly :-D.

    Thank you for your support and nice piece of hardware this one ? !

    Sorry for the late reply I had many things to sort out in the past months so not so much spare time to dedicate to the 8bit retro computing :-). 

    Cheers,

    Rick

  13. The Coleco will usually crash when trying to load a game stored into the first eprom. I'll get a garbled screen like this one enclosed or a freeze on the cart menu. 

    Pressing the reset will either load the same game stored into a certain position on the eprom (DK something) or show up the message to insert a cart into the module.

     

     

    image.thumb.png.10050ef529e6356ba30b7b816447354c.png

     

  14. If I swap the two eproms then the Coleco will load the game available on the first memory bank of the second eprom. As the menu is on the first eprom then i can only load this unique game but indeed it loads.

     

    It is maybe irrelevant but worth to mention. The 74LS688DW I have installed is marked 74LS688 and the package was not the good one (smaller then the pad positions on the pcb) but I managed to solder it properly without any shorts. Question is are pinouts different from one package to another?

  15. Hi 5-11,

    I have built this cart based on the gerber and schematics available for it. There are no bypass capacitors.

    I have made some extra testings after finally replacing the loose socket with a good one. Basically all games stored in the second eprom are working fine when selected from the menu (the pcb is making use of two M27C801 of 1024k each). If I select a game stored on the first eprom then the Coleco will either crash or load the prompt screen asking to insert a cart and reset will just do nothing. I have checked the first eprom with the programmer and it verified good with the original bin.

    Here is the schematic of this project.

    image.thumb.png.28a8681d9b0a7719b84e11e75c3e1a99.png

  16. Hi Guys,

     

    I have built this multicart and used the two bin files to program the two eproms. I can get to the menu but the loading is very erratic. Sometimes the game loaded is not the one selected from menu and other times it crashes.

    I have I think an issue with a socket where the eprom is not fitting tight but is loose. 

    Can someone let me know what is the value of the pull-up resistor? I put a 10K but not sure this is the correct value to use.

     

    Thanks and great project for our beloved Coleco :-)!!

  17. 12 hours ago, Al_Nafuur said:

    So it looks like the STM32 can talk to the ESP8266 but the response line is broken.

     

    You might try and solder a wire between these two pins (ESP8266 Tx -> STM32 Rx) or maybe you should first check all soldering related to these two pins.

    grafik.thumb.png.3d8d9192763bdd8bfd67bf962824bf1f.png

     

    That did the trick! Soldering a jumper wire has solved. I can connect now to the wifi and set-up the Plus Store account. I cannot really explain why there is a broken line here, I have checked the continuity and it looked fine. Bad PCB? Anyway it works that's the most important :-D.

    Thank you for your support, this cart is ra really nice piece of hardware :-). Let's put it in a cartridge shell now!

    IMG_2386.JPG

    • Like 4
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