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shoestring

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Posts posted by shoestring

  1. Posted

    Last month I picked up a C-64 which powers (red LED) yet nothing comes up on the screen. After looking into units on eBay I've noticed the C-64s seem to lack the staying power of other retro computers. Most of the C-64 systems on eBay are listed as "not tested but powers up.." (aka Broken)

     

    Seriously, to me the C-64s seem to have excessive failure rates. I'm coming from TI-99/4 background where most everything ancient still seems to work.

    You purchased a "non tested" c64 and expected it to be working, that was your first mistake. I know someone who purchased two untested a8s recently and both were DOA. Having said that and in defence of Atarians, my first two Atari purchases ( 600xl & 800xl ) were untested but both arrived working. So you can have some pretty good luck sometimes.

     

    When you buy "untested" it's a lottery and that goes for any computer system especially on eBay.

     

    My experience with c64s tends to differ. The early PCBs were built very well, sockets were of the high quality machined pin type, not the cheap single wipe friction design used in some of the more expensive machines like in my Apple //e.

     

    I logged countless hours on my unit from 1986 with no problems. The early ones did have high failure rates, I think as high as 30%. If some users were more responsible and allowed air to circulate under the machine instead of playing on the lounge room carpet then perhaps they would have had the same experience as me.

  2. Posted

    I don't think the electronics are any more important than the cabs. Probably equally as important but that's a matter of opinion really. There are a lot of guys on KLOV who go to great lengths to restore their old or converted cabs.

     

    As for keeping old electronics in these games running, it isn't easy. Popular arcade games experienced significant longevity throughout the 80s and some ran into the early 90s. They practically ran 24/7 often exposed to cigarette smoke throughout the years. The situation is a little bit different compared with our Atari 8bits which were made from high quality components. Compare a Namco or Midway Galaga pcb to one from any 8bit Atari model and you'll see what I mean.

  3. Posted · Edited by shoestring

     

     

    There's a "feel" to the original hardware that the FPGA's and emulators are lacking for me. I would think people completely new to the Atari 8-bit would be fine with it though.

    I'm not sure what you mean by feel in this context. But it's unfair to compare or put emulation and FPGA in the same category.Emulation only gives us an approximation. FPGAs give us the ability to re-implement the original hardware design in this form.

     

    The only problem I can see is that the schematics for the chips in question haven't been published or are lost so a lot of the work involves reverse engineering and maybe some creativity too.

  6. Posted · Edited by shoestring

    Check reset circuit first. You said nothing happens when you press reset but look & listen carefully, there should be a pop sound or some indication on the screen.

     

    You really need at least a logic probe to see that. And it should be a transition from low to high ( and it should stay high ) on the RST pin of the 555 timer or from Sally. With reset broken your CPU just sits there with its address outputs stuck high and nothing at all happens on the screen. If reset is good and CPU address outputs don't toggle then you probably have a bad CPU or clock dividers. With the latter case, it's time to check Freddie and the address decoder as well.

  8. Posted

    I have a Digitech desoldering station, it's one of the cheaper brands but I haven't had issues with it so far. There are a lot of options in the US but if I had the money to throw away then I'd probably go for a Hakko FR-300, very expensive. There are more affordable options in the $60-$150 USD range.

     

    To be honest if you're going to be doing a lot of soldering you'll need one. But if you're only doing this to fix an 800xl and desolder 8 chips then I can't justify dropping that much cash for a small job like that.

     

    Get yourself a Goot desoldering pump, they're around $14 USD,practise on a junk PCB board. You might have a tough time removing the remaining solder on some chips. Remember that some pins will have excess solder on the parts side, solder often pools up through the plate through hole in manufacturing during the soldering process.

     

    Also a good habit to get into. Add solder to pins before trying to desolder. I find that it's easier to reflow / add some solder to stubborn pins before attempting to remove it with a pump otherwise there's a chance of only removing some of the solder. I kinda do the same thing now with my desoldering gun by tinning the tip with solder. The idea behind this is to minimise exposing the pads to excess heat which can screw a good board. Atari PCBs are good quality and can take some of that abuse but an arcade board won't stand up to the same abuse.

  11. Posted · Edited by shoestring

    Well after a few weekends of desoldering attempts, I think I'm about ready to throw this thing back up on ebay. I removed solder off all the pins for all 8 chips, but I still can't remove a single one. There still seems to be some solder on them, but I'm having a hard time seeing it. It must be on the top side, however the plunger is too big to get in between the chips and the wick doesn't seem to be sucking anything up.

     

    I don't see how people do this stuff. Youtube videos make it look easy!

     

    You need a good,clean tip and a temperature controlled soldering iron is ideal for this stuff. Years of soldering taught me not to use bad quality equipment because then I risk doing damage. Also make sure your tip is tinned with solder before you apply it to anything.

     

    Wick works well but its a slow process, I used a Goot desoldering pump for removing chips until I got a proper de-soldering gun, it's fast and easy. Also important to make sure the pin isn't connected with a tiny bit of solder when you attempt to pull the chips out or you risk ripping up traces and the plate through-holes with it.

    • Like 2

  13. Posted

    Thanks for letting me know, would have never guessed.

     

    That might explain not being able to get the computer to boot when I had half a chance.

     

    With the PLD reprogrammed and installed nothing happens as I suspected. No consistent video sync or timing signals. Sometimes it will splutter video as I see it on the screen for second or two then it will stop.

     

    There are a couple FREDDIE chips floating around, I'll order one and let you know how I go. I looked at Best Electronics but he has a min order of $50 and I don't need that much stuff.

  16. Posted · Edited by shoestring

    Thanks for that. I'll take a look.

     

    FREDDIE definitely has an issue though, I forgot to mention that at times activity was nil on the said lines, nil video sync and measuring the Y1 crystal directly revealed a very weak sine signal ( 2.5v max ) in that instance.

     

    Now FREDDIE is completely dead and I just managed to accidentally snap a leg off the Y1. So I'm up for another ( c070034 ) to go with the new FREDDIE chip..

     

    I have a spare from a PAL Apple //e but I think the frequency is 14.25mhz and is a little off.

  17. Posted · Edited by shoestring

     

    If you own an oscilloscope, check the following points...

     

    - Pin 7 of the CPU (SYNC). Should be some transitions visible after RESET. Maybe flat line at 0V after some cycles (CPU hung up). If absolutely NO activity after RESET / Power-Up, no PHI0 clock is provided to CPU

    - Check OSC output of Freddie (Pin 37). This is the "master clock" for ANTIC, this one will generate PHI0 for CPU. OSC should be around 3,5xx MHz. If no transistions visible, Freddie is dead

    - Check pin 33 (RAS) and 35 (CAS). RAS must be constantly active, CAS also. Also no transistions = Freddie dead

     

    Without oscilloscope my Sys-Check might be helpful, but of course not in all situations.

     

    Good luck, Jurgen

    So I followed your tips and it seems I'm getting the right signals with my scope. See attached photos.

     

    I also followed the troubleshooting guide from the 130xe service manuals. Microprocessor operation and Clock and dividers. I couldn't find any issues.

     

    I'm going to remove these sockets again to see if I've gauged any traces or damaged any plate through-holes.

     

    CPU clock Phi0 - pin 37

    4ca4cbb965197939969afab99694fb06.jpg

     

    CPU sync - pin 7

    3b9898e991c88e1a77f6613f526f03cc.jpg

     

    Pin 37 - FREDDIE

    ee1a2518e0fed6b99c2fb28a87875628.jpg

     

    Pin 35 - CAS & RAS

     

    3065172bd97d9774a9446edea49c02b7.jpg

     

    55a29734f383f8d8996e94bc9583567a.jpg

  18. Posted

    Try a "switching adapter" solution. Salvage the 7 pin din DC plug from your power supply ( then chuck the ingot in the bin ) and use a 5v supply from a router or USB hub, splice the two wires and solder them to the end of your lead of your salvaged DC plug. You just have to be careful with the polarity if you do this yourself ( easy to screw up ).

    • Like 1

  20. Posted · Edited by shoestring

    Keyboard was the only way I knew how to play those games because in high school, there weren't any joysticks however, I do recall playing Choplifter on a joystick in 3rd or 4th grade.

     

    Most home systems with a standard Atari joystick port only had 1 fire button which made control difficult especially for arcade conversions. It's ironic that the C64 was used mostly for games whilst the Apple II was considered the more serious, educational machine and had a joystick with a second button.

     

    Usually space was often employed as an alternative means for a second button. Some programmers came up with an alternative control system on the standard joystick which either worked really well or not at all.

  24. Posted · Edited by shoestring

    Interesting weekend so far.

     

    So I socketed all the chips in the 65XE and did a little troubleshooting. ( By the way this is a PAL System )

     

    Here's what I found.

     

    Custom chips & roms tested by substitution in known working machine. ( A 600xl )

     

    7400/4000 series chips all tested good.

    Basic and OS rom tested good

     

    ANTIC: CO21698 Tested good

    GTIA: CO14889 Tested good

    POKEY: Good too

    PIA/6520: Also good

    The new 2x4464s: No problems

     

    6502 tested bad in the 600xl, brain farts an executes random addresses

    MMU tested bad ( red screen ) ( I have some spare GAL16V8s to fix this )

     

    With the good MMU & CPU installed in the 65xe from the 600xl still doesn't fix it.

     

    So that obviously isn't the only thing wrong with it

     

    I haven't trouble shooted FREDDY with the scope just yet, but I suspect it's dead.

     

    We will see.

     

    My 600xl has developed a problem whilst using it as a donor.

    Keys 6,7,Y,U & N aren't working now.

     

    Edit: KB fixed. Bent pin on the 4051 mux will do that :)

    • Like 1

  25. Posted

    @shoestring:

     

    It sounds like you had "The Ingot" supplies. The epoxy filled bricks should all be thrown in the bin before they do damage.

     

    I highly recommend the U1M for a RAM upgrade. Just put 64K back in and get a U1M. You should also consider the SIDE2 cart because of how it works with the U1M. It becomes a bootable PBI device which can load disk images from a FAT32 CF card. In other words, you can download some Atari stuff on your Windows system and directly copy it to the CF card. Very easy to transfer files.

     

    Thanks Kyle, I'll keep that in mind as well :)

     

    Pictures of the two power supplies from the auction.

    post-45355-0-97829900-1478150514_thumb.jpg

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