Announcement

Collapse
No announcement yet.

Sprint 2 /Indy 2 Repair Log newbie

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Sprint 2 /Indy 2 Repair Log newbie

    Hi everyone, My name is Ben.

    I'm new here and new to arcade repairs, though not new to arcade machines. I had a collection some 20 years ago;. Defender, Asteroids, Time Pilot. Moon Patrol, Pheonix, Gyrus, Donkey Kong plus others of this vintage. The games I played in the 80s. I stupidly sold them all when moving interstate (Perth to VIC).

    One Machine I aways wanted but remained elusive was Atari Sprint 2. Many of hours spent battling my older brother on this one. A few weeks ago an Indy 2 appeared on FB Market place for $300! not going but it was nearby. It has ignited a revival for my love for these classic games, but now with a deeper interest in the restoration and PCB repair side of things.

    I've had it few weeks and have been doing lots of research, and think I'm having some progress, but now reaching out to see if anyone has more insight. This is my first attempt at PCB repair!

    Progress to date: To start the power was not good to the board. I tested back to the Power supply and found it a little low on the 25V side. Possibly completely unnecessarily, I re-wound the transformer with fresh copper. I couldn't find another for sale that had 16.5 CT and a 25V CT. It now has great even voltage... my first rewind , hopefully my last.

    Click image for larger version

Name:	LM323.jpg
Views:	1
Size:	242.4 KB
ID:	1913191Click image for larger version

Name:	Sprintpowersupply.jpg
Views:	1
Size:	224.8 KB
ID:	1913190Click image for larger version

Name:	Sprintrepair.jpg
Views:	1
Size:	368.0 KB
ID:	1913189

    I setup a work-station with the board, power-supply and the Motorola CRT. The CRT looks to be good. Very little burn, and a nice set of lines. The board still showed low voltage: 4.65V. Not great, but the clock appeared to running. I swapped out the LM323K with a modern cool running replacement. 5V across the board now. Still no game running.

    I'm getting 12.096mhz from the clock and all derivatives across the board are looking correct.

    I'm suspicious of the reset/watchdog circuit. There was no reset button on the board so I fitted one. At PIN 40 of the 6502 I get a floating signal. I believe this should be watchdogging up and down? Or High? A logic probe shows a red light and a very weak green. My Oscilloscope shows a very fine square wave.

    At present I suspect the decade counter 7490N at C6/7 not functioning correctly. By chasing the Timer Reset I see an intermitted lows (then inverted) across the board until the IC 7490N before the CPU there is nothing. I'm wait on a new SN7490N to arrive from the UK!

    Anyone with ideas? Keep in mind I didn't know how to use a logic probe or Oscilloscope until this month..

  • #2
    Pin 40 reset should be active high. If its toggling high low then the watchdog is barking and something is wrong. If its floating which means nothing happening at all then that's where I'd start.
    Also check your clock at pin 37.

    Comment


    • #3
      It will likely bark away until it has some video cos the “I’m happy so you can reset the counter” signal comes from the video system

      Comment


      • #4
        Originally posted by Arcade King View Post
        Pin 40 reset should be active high. If its toggling high low then the watchdog is barking and something is wrong. If its floating which means nothing happening at all then that's where I'd start.
        Also check your clock at pin 37.
        Cheers for your replys.

        I'm getting a nice clock at PIN 37. At about 755. khz

        I managed to get a watch dog signal briefly then back to a weak high. I'll keep plugging and poking away.

        I'm getting my hands on a Fluke 9010a and 6502 pod. I'll do some investigation with it and let you know my findings

        Cheers
        Last edited by BorntoFly; 13th August 2019, 10:40 PM.

        Comment


        • #5
          lol .. dropping 2k on test gear to fix a $300 game .. sounds like the sort of thing i would do

          how did you go with the ebay pcb? no better?

          Comment


          • #6
            That's a cracking start in board repair, from zero to Fluke 9010 in a matter of weeks - love it.

            Reach out if you need a hand driving the Fluke, they are a great bit of kit but the learning curve is quite steep.
            Sic transit gloria Atari!

            Comment


            • #7
              The Ebay PCB was really rough. It's missing a few ICs and has some corrosion. I'm using it to swap out parts for now. Hopefully I'll get that one going too if I have any success with the first.

              Comment


              • #8
                Hi Womble, The Fluke and POD arrived and I've done my first ROM and RAM tests. The results:

                RAM LONG : RAM @ 0000-07FF err at Bit 7

                ROM @ 2000 - 27FF SIG B0FC - ERR DDCF NOT B0FC
                ROM @ 2800 - 2FFF SIG A197 - OK
                ROM @ 3000 - 37FF SIG O92C - ERR 575A NOT O92C
                ROM @ 3800 - 3FFF SIG EB50 - ERR C1DD NOT EB50

                Stabbing in the dark a little. Am I using the correct SIG codes? -

                UPDATE:
                So i found another source for the Fluke SIGs and ROMS are all reading correctly.

                I also tested the PROMs 6400-01 and 6401-01 these both came back with read errors at 0000-0000?

                Any thoughts

                Cheers

                Ben
                Last edited by BorntoFly; 23rd August 2019, 05:12 PM.

                Comment


                • #9
                  You can't test the 6400 and 6401 PROMs with the Fluke. How are you testing them and determining that they are bad? You would be missing the inputs to N2 which would affect the VBLANK*, /VBLANK*, VRESET, VBLANK, or VSYNC signals coming out of N2 if the 6400 PROM was bad.

                  6401 is the Address Decoding PROM and you can't read it either, but if you're able to access and read the PROGRAM ROMs successfully then it's working.

                  Comment


                  • #10
                    Great. thank-you for this advise. I was using the Fluke incorrectly. (Noob). The VBLANK*, /VBLANK*, VRESET, VBLANK, or VSYNC all appear to be showing correct signals. And I can read the ROMs.

                    I've ordered some new RAM, could the 0000- 07ff at bit 7 error cause no boot?

                    I'm still concerned about the high on PIN 40. A logic probe shows RED but on osciliscope, it looks like a floating or weak signal? Any thoughts would be greatly appreciated.

                    Comment


                    • #11
                      Originally posted by BorntoFly View Post
                      I'm still concerned about the high on PIN 40. A logic probe shows RED but on osciliscope, it looks like a floating or weak signal? Any thoughts would be greatly appreciated.
                      Until you get video the watchdog will bark. It’s how the board works

                      Comment


                      • #12
                        Originally posted by BorntoFly View Post
                        Great. thank-you for this advise. I was using the Fluke incorrectly. (Noob). The VBLANK*, /VBLANK*, VRESET, VBLANK, or VSYNC all appear to be showing correct signals. And I can read the ROMs.
                        Then those 2 PROMs should be fine.

                        Originally posted by BorntoFly View Post
                        I've ordered some new RAM, could the 0000- 07ff at bit 7 error cause no boot?
                        Yes. Since you can read the ROMs OK, your data bus overall (/DBUS0-7) should be fine. Focus on the RAM at K3 (/DBUS7 input and the output going through the 74LS04 at J5 - pins 5 and 6 then through the LS367 at pins 6 and 7 to the data bus)

                        Originally posted by BorntoFly View Post
                        I'm still concerned about the high on PIN 40. A logic probe shows RED but on osciliscope, it looks like a floating or weak signal? Any thoughts would be greatly appreciated.
                        If you're referring to pin 40, the CPU, you need to be concerned with the transition from low to high. the /RESET signal is active low - which is what the bar over the signal name means. It should stay low for at least 50ms when powering on the system the go and stay high when running normally. If the /RESET signal is pulsing repeatedly then the CPU cannot boot and the system is repeatedly activating the /RESET signal by means of a watchdog timer. This timer gets reset repeatedly by the CPU when it is running normally. You only see it in action when the CPU can't reset the timer and the timer hits its mark then resets the CPU.

                        Comment


                        • #13
                          Nice work. Clearly your approach is the way to go... my approach was logic probe/ttl based as my budget was about a third of yours. A lot of hair was pulled too!
                          Hope you smash it soon! Good luck!

                          Comment

                          Users Viewing Topic: 0 members and 1 (guests)
                          Working...
                          X