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midibob last won the day on January 22

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About midibob

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  1. midibob

    Tales from Midibob's workshop. MPU3

    Yep, spot on chaps. Not a difficult one really so I'm a bit embarassed I didn't spot it first time around. 'Should have gone to Specsavers' is the quote I think!
  2. midibob

    Tales from Midibob's workshop. MPU3

    Nope! Have a look on the first pic, should have said that before. It's a dead giveaway, unless you're me of course.
  3. midibob

    Tales from Midibob's workshop. MPU3

    Well, the new morning brought with it a fair bit of head scratching. The suspect lamp transistor T20 was fine but it had next to no voltage on it's collector. After chasing my tail for a while I couldn't understand why there was no voltage on the blue connector until I saw this. Not sure how I missed it on first inspection? Was that it, well not quite. Testing on my Cabaret machine, the 4th reel didn't spin. Another one I should have spotted on first inspection. Who's going to be first to spot the issue?
  4. midibob

    Tales from Midibob's workshop. MPU3

    Interesting one came into the workshop today. D.O.A. so there was no fault list. Once all the usual corroded bits were swapped out it was time for a switch on. It booted up OK and started running the test mode. That was a relief, however all was not well. Only one bank of lamps was working. Everything else was OK, switches, sound and Triacs. All the power transistors and drivers appeared to test OK so time to dig a bit deeper. Going back up the driver chain we come to IC20 (ULN2003). Some outputs were dead, and some inputs had high voltage on them! Not sure how high but my logic probe was glowing 'overvoltage'. This is bad news as it feeds directly back to IC4 (6821). As I was testing the pins on IC20 I could see some sparks around pin 8 and only because the sunlight was fading. On removal pin 8 stayed in the board! You can also see a carbon mark on the top. Once this was changed there was still no more lamps and as suspected IC4 had also met it's maker. It was running quite warm too. Good job I noticed IC20 first otherwise another 6821 would have gone up in smoke. So I now have lots more lamps, but not all? All the lamps in the lower user buttons are still out so that's one for the morning with a fresh head.
  5. midibob

    connectors for old molex type plug

    You have the manufacturers part number now so have a look on the TE web site and it will give you all the drawings and info for the part.
  6. midibob

    connectors for old molex type plug

    That's a better pic, same series I think? Must be getting close.
  7. midibob

    connectors for old molex type plug

    That's more like it. They could be these all be it they are not the same colour. https://uk.rs-online.com/web/p/pcb-connector-housings/7828937/ The pins.... Pins Getting closer maybe?
  8. midibob

    connectors for old molex type plug

    They all look too modern to me? There is the possibiltiy it may be obsolete. Still, early days as they say.
  9. midibob

    connectors for old molex type plug

    I still think we are fighting a losing battle here unless you can get some 'in focus' pics. The connectors may have an id. on them, but they may not so visual identification will be everything unless someone knows what they are already.
  10. midibob

    connectors for old molex type plug

    As you can appreciate there are literally thousands of different connector types out there so eliminating all the ones that it isn't is a good start. Probably a silly question but do you have a manual?
  11. midibob

    connectors for old molex type plug

    Still difficult to see from the pics as they are out of focus. Are you sure they are Molex and not AMP as Andrew suggested. They do look more like an AMP style to me.
  12. midibob

    connectors for old molex type plug

    Need to know what tech it is or failing that a picture of the Molex connector.
  13. midibob

    connectors for old molex type plug

    Unfortunately the pics a so far out of focus it's impossible to identify. When you say they are Molex what board are they from?
  14. Nice to see you got them going. Always good to see a result in the end. Cheers Bob
  15. midibob

    Tales from Midibobs workshop, Sys80

    Getting back to the workshop, here's the first viewing of the test rig in action. I won't post the code just yet as it's a bit of a mess. https://youtu.be/XMfS6CXOaIM