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Thread: Sprint 2 /Indy 2 Repair Log newbie

  1. #1
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    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.

    LM323.jpgSprintpowersupply.jpgSprintrepair.jpg

    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..

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    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.

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    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

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    Quote 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 at 10:40 PM.

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    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?

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    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!

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    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.

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    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; 4 Weeks Ago at 05:12 PM.

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    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.

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    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.

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