• [Not] Ready Player 1...

    From David Savery@21:1/5 to All on Wed Dec 8 10:11:16 2021
    Greetings all. I wonder if anyone can provide technical advice regarding a Vectrex fault?

    The backstory:
    When the Veccy' first came out, I bugged my parents for one without success. Indeed, the phrase "can I have a Vectrex" became somewhat of a running joke in our house as it was uttered so often. Eventually of course the Vectrex died and my dad plumped for
    an Amstrad CPC464 which he figured was a safer bet as our first home computing experience.

    Then, about five years ago, my mother decided to actually get me a Vectrex for Christmas, even though I'd long forgotten about the thing. Thus the joke came full circle and much mirth was had by all.

    Unfortunately, mother didn't perform her due diligence too well, and the example from off eBay has seen better days. It had a fault from day one - Minestorm would appear on power up unless another cart was already inserted. I assumed that's what it was
    supposed to do, it was only later I learned there was a menu screen I'd never seen.

    After a good pounding on Minestorm, Star Ship, Bezerk, et. al., the novelty wore off a little and it went a few months sitting quietly in the corner. After a while, it was fired up again where I now found to my dismay that a new fault had developed and
    Minestorm, or indeed any game inserted into the cart slot, hangs on the Player 1 screen.

    Attempted remedy:
    I'm an electrician by trade and an electronics dabbler as a hobbyist - or I used to be, I don't have much time for hobbies anymore. Anyway, that means I'm not completely clueless when it comes to soldering and I have some components and test equipment
    such as scopes, bench power supplies and meters at my disposal. There are no signs of obvious failure on the PCBs and the power board seems to be putting out 12V, 5V and -5V which is nice, so I think my problem lies wholly with the logic board. I've
    replaced most electrolytic caps (the ones I had ready spares for), run the soldering iron over every joint in case of dry jointing, re-seated the ICs in their DIL sockets where applicable and checked many of the traces for continuity, but all to no avail.

    The shit sandwich
    The screen works just fine, the sound works, the cartridge slot identifies the game loaded in, but on power-up I cannot get (and have never seen) the menu, and any game comes to a stop at Player 1 immediately after the requisite title screen. This
    happens whether the controller is plugged in or not. That it can read carts, play into tunes and display legible information about the game before coming to a halt means, I assume, that things like the processor and timing are good.

    Does anyone have any experience of this kid of fault or any suggestion of where to go from here? I've been scouring the interwebs and I've found suggestions that the AY-3-8912 could perhaps be responsible. I still have two Amstrad 464's in the loft - I'm
    wondering if I should crack one of those open for some donor parts as I believe they used the same chip (and may even have one in a DIL socket for easy extraction), but I thought I'd ask here in case someone had any information that might save a wild
    goose chase!

    Model serial number is U003942A and the logic board shows manufacture in 1983, week 26.

    Any advice appreciated! If I manage to crack it on my own, I'll post an update here if it helps anyone else.

    Cheers,
    David

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  • From Computer Nerd Kev@21:1/5 to David Savery on Wed Dec 8 21:35:25 2021
    David Savery <djsavery@gmail.com> wrote:
    The screen works just fine, the sound works, the cartridge slot
    identifies the game loaded in, but on power-up I cannot get (and
    have never seen) the menu, and any game comes to a stop at Player
    1 immediately after the requisite title screen. This happens
    whether the controller is plugged in or not. That it can read
    carts, play into tunes and display legible information about the
    game before coming to a halt means, I assume, that things like
    the processor and timing are good.

    Does anyone have any experience of this kid of fault or any
    suggestion of where to go from here? I've been scouring the
    interwebs and I've found suggestions that the AY-3-8912 could
    perhaps be responsible. I still have two Amstrad 464's in the
    loft - I'm wondering if I should crack one of those open for some
    donor parts as I believe they used the same chip (and may even
    have one in a DIL socket for easy extraction), but I thought I'd
    ask here in case someone had any information that might save a
    wild goose chase!

    Holding down controller buttons at the game title screen and not
    releasing them seems to have this effect, so the theory about the
    AY-3-8912 would be that, as the chip that reads the controller
    buttons, it's reading one as pressed down all the time and that
    prevents the game from starting. Swapping it over seems like a
    good starting point. Another possibility is that one of the
    capacitors (C214 - C221) on the logic board that connect to the
    controller input signals has shorted. Check the resistance over
    them with a multimeter.

    Finally, it could also be an issue with one of the address signals.
    In that case, given that it happens with both cartridges and
    Minestorm, that would most likely be a problem with the 68A09 CPU.
    That might better explain the problem you had before with not
    seeing "PLAYER 1" at all, because there was an address signal issue
    which made the game jump ahead of that part. It could also be that
    a faulty AY-3-8912 used to always pulse button 4 during start-up,
    but odd that the same behaviour wouldn't continue once the game had
    started.

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  • From David Savery@21:1/5 to All on Wed Dec 8 23:54:08 2021
    Thanks for the speedy update and confirmation that I may be on the right track with the AY-3-8912. I'll pull those Amstrad's out of the attic and see if there's a ready doner. I'll also take a closer look at the specific components serving that IC in the
    coming days.

    Regarding the address signals, my apologies if I wasn't clear in the original message; I've always seen the Player 1 screen on any game, it's only the main Vextrex menu screen that I've not clapped eyes on. But that fits too with the theory that a button
    signal is jammed and perhaps forcing the menu to skip either starting Minestorm whatever other cartridge is loaded. It's my suspicion that the CPU is okay based on that behaviour.

    My aim is to make or break by Christmas. Either I'll have figured it out (or, more accurately, muddled my way through to a solution), or I'll still have the fault (or perhaps even have made things worse), in which case the lil' fella will rest in pieces
    up in silicon heaven!

    I'll post results here. Fingers crossed for some festive Minestorm and my Veccy making it into 2022!

    Cheers,
    David

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  • From gtoal@gtoal.com@21:1/5 to djsa...@gmail.com on Tue Dec 14 01:49:04 2021
    On Thursday, December 9, 2021 at 1:54:09 AM UTC-6, djsa...@gmail.com wrote:
    Unfortunately, mother didn't perform her due diligence too well, and the example from off eBay has seen better days. It had a fault from
    day one - Minestorm would appear on power up unless another cart was already inserted. I assumed that's what it was supposed to do, it
    was only later I learned there was a menu screen I'd never seen.

    What menu screen??? There is no menu screen if there is no cartridge inserted. Just Minestorm. Your machine is indeed doing what it is supposed to do.

    G

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  • From David Savery@21:1/5 to gt...@gtoal.com on Tue Dec 14 14:01:18 2021
    On Tuesday, December 14, 2021 at 9:49:05 AM UTC, gt...@gtoal.com wrote:
    On Thursday, December 9, 2021 at 1:54:09 AM UTC-6, djsa...@gmail.com wrote:
    Unfortunately, mother didn't perform her due diligence too well, and the example from off eBay has seen better days. It had a fault from
    day one - Minestorm would appear on power up unless another cart was already inserted. I assumed that's what it was supposed to do, it
    was only later I learned there was a menu screen I'd never seen.
    What menu screen??? There is no menu screen if there is no cartridge inserted. Just Minestorm. Your machine is indeed doing what it is supposed to do.

    G

    Ahoy-hoy, some positive progress!

    Tonight I took out all the capacitors on the controller 1 and controller 2 inputs and replaced them. This schematic proved helpful:
    https://console5.com/techwiki/images/d/d8/Vectrex---Logic-Board-Schematic.png

    Caps 234 to 237 are 0.1uF which I had ready replacements for, however C214-221 and C230-233 are 1nF which I was lacking. I did have some 820pF among my spares which I figured may be close enough. I think these are just used for switch debouncing, but may
    cause problems if they fail. I couldn't get readings out of most of them using a capacitance meter while soldered in situ and they were pesky things to remove in one piece. Some tested good, but I just changed out the bally lot.

    Anyway, the good news is that she lives! We're no longer hanging at the Player 1 screen and both Minestorm and cart games are progressing into the playable (and they play juuuust fine). Thank goodness I didn't have to try to desolder that AY-3-8912...
    yet. That might still happen though as I still have the original problem of the splash screen not appearing. If I hard power it on, it draws very briefly before Minestorm takes over. It's still acting like a button is pressed somewhere causing it to skip.

    This wouldn't be a problem except I have the 72 game multicart which launches straight into Armor Attack (which plays without issue), but the selection screen on that too gets skipped. I can see it appear very briefly on power-up after the title screen,
    but something is causing it to launch straight into the first game on the list. The reset button just restarts Armor Attack; only a hard boot forces it to try to show either the splashscreen or cart menu.

    Anyway, one headache at a time. Thanks Computer Nerd Kev for the sage advice earlier; I'm so pleased it's playable again, at least with the limited games I have available!

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  • From Computer Nerd Kev@21:1/5 to David Savery on Wed Dec 15 21:51:58 2021
    David Savery <djsavery@gmail.com> wrote:

    Anyway, the good news is that she lives! We're no longer hanging
    at the Player 1 screen and both Minestorm and cart games are
    progressing into the playable (and they play juuuust fine). Thank
    goodness I didn't have to try to desolder that AY-3-8912... yet.
    That might still happen though as I still have the original
    problem of the splash screen not appearing. If I hard power it on,
    it draws very briefly before Minestorm takes over. It's still acting
    like a button is pressed somewhere causing it to skip.

    Good to hear! Strange that it didn't cure the old problem, but at
    least it's progress.

    I wonder if there might be some excessive ripple on the 5V power
    line, which is worst straight after power-on? The capacitor could
    then keep the voltage at the controller input below the (raised)
    HIGH voltage threshold when there's a voltage spike on the 5V
    power line. Just a thought. You'll need an oscilloscope to
    effectively view spikes/ripple on the 5V line, it would be caused
    by either failing filter capacitors or a failing 5V voltage
    regulator. But that's just one theory.

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  • From David Savery@21:1/5 to Computer Nerd Kev on Wed Dec 15 23:57:01 2021
    On Wednesday, December 15, 2021 at 9:51:59 PM UTC, Computer Nerd Kev wrote:
    David Savery <djsa...@gmail.com> wrote:


    I wonder if there might be some excessive ripple on the 5V power
    line, which is worst straight after power-on? The capacitor could
    then keep the voltage at the controller input below the (raised)
    HIGH voltage threshold when there's a voltage spike on the 5V
    power line. Just a thought. You'll need an oscilloscope to
    effectively view spikes/ripple on the 5V line, it would be caused
    by either failing filter capacitors or a failing 5V voltage
    regulator. But that's just one theory.
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    Thanks for the tip - I do have a scope so I'll go probing around the power lines next. I'll also take a look at the other components on the input lines as one curious thing I did notice was on Berzerk in that every time I used the stick to move the
    character left, right, up or down, he also fired his gun in that direction without my pressing buttons 1-4 which are all 'fire' buttons. I didn't know that was awry until I saw a YouTube video of someone else playing it where their little chap was
    running around without blasting away in all directions!

    That perhaps indicates an uncommanded input, or maybe just a fault with my Berzerk cartridge as it only happens on that game. Minestorm, Star Ship and Armor Attack all allow movement via the stick with no ill effects. Still, there's something else to
    find here, and I hope it's just a discrete component I can pin down!

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