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Showing content with the highest reputation on 06/05/23 in all areas

  1. This was quite often done to stop other manufacturers or competitors cloning the product. We did it at JPM with a video roulette machine, well we encased them in epoxy, trouble is they cooked themselves and I had to go across France to repair them all.
    5 points
  2. It's been a fair while since I posted about MPU1's so I thought I'd share the one I just fixed as it was one of those that was confusing but so simple once I'd found the reason why. It came in as a no boot but firing triacs and lamps on switch on. I'd had this one before and it had the PSU section serviced. On switch on it would RESET ok but then would sometimes switch a few triacs or lamps on and other times not at all? The funny thing was everything appeared to be working, the CPU was putting out signals on the address and data lines but it just wasn't booting? After trying a new CPU, which made no difference, it was out with the big guns. Scoping the outputs and again everything appeared to running but no code was being read from the ROM and the CPU seemed to be running a NOP mode. After a fair while of head scratching and thoughts of jumping in the Thames (well the weather is nice) a bit of sanity started to dawn on me. On checking the clock it was reading 1.5MHz and I know it should be 1MHz but surely that wouldn't cause an issue......could it? Well yes is the simple answer. Apparently the 1st version of the 6800 only runs at 1Mhz, version 2 will run at 2Mhz but not sure if that's a 'B' version? So, the question is why is the clock running at 1.5MHz? The clock in this board is based on the 8602/9602 chip and the timing by two mica 100pf caps and two high stability 11K resistors. From a visual perspective all looked good so I tested the resistors which were OK and then decided to remove the caps and test them. I don't think I've ever had a mica fail so I wasn't holding my breath. On removing one of the caps the pad came off with the iron so there must have been a hairline fracture where the track joined it. Putting in a rivet and soldering everything up I was greeted with a good boot up and all the diags running.
    3 points
  3. I remember reading that before! Ace did the same with their Sidewinder boards if I remember correctly. Nice to see you posting again. Will you be posting more memories of JPM, Astra etc soon?
    1 point
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