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  1. I just edited my post with a bit of further...

    I just edited my post with a bit of further information - but a good clean never did anyone any harm either :-)!

    Dave
  2. It looks like two additional signals on top of...

    It looks like two additional signals on top of the VIDEO ON pulse.

    CB1 should be an input. It appears to be (erroneously) shown as an output on the Commodore schematics?

    Therefore, with UC7 IN...
  3. Might be worth having a look at the VIDEO ON...

    Might be worth having a look at the VIDEO ON signal at UC7 pin 18 with both UC7 installed and not.

    Dave
  4. Yep. There are only three (3) devices: Sheet...

    Yep. There are only three (3) devices:

    Sheet 2:

    UC6 (6520)

    Sheet 3:

    UC5 (6522)
    UC7 (6520)
  5. +1. UC7 is the beastie... Dave

    +1.

    UC7 is the beastie...

    Dave
  6. Look at the CPU /IRQ line with an oscilloscope...

    Look at the CPU /IRQ line with an oscilloscope whilst the cursor goes mad. Does the /IRQ line go mad at the same time?

    I suspect the problem is the keyboard PIA/VIA or whatever device it is. Not...
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    Yup. I suspect the RAS signal we are seeing is...

    Yup.

    I suspect the RAS signal we are seeing is the refresh but there is no RAS for the memory access. That's as I understand the two halves of the 7474 work at any rate.

    And one of the duff...
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    Yep, The last two bits of the 164 shift...

    Yep,

    The last two bits of the 164 shift register appear to be stuck at '0' and '1' respectively.

    Having changed the inverter in the output of 164 QG, things didn't improve, hence it is not...
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    That's what I said. I think the 164 is kaput -...

    That's what I said. I think the 164 is kaput - hence swapping any other device other than the 164 won't cure your problem (although I think there is a small probability that the 74S04 may have been...
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    You can turn it on. Remove the NOP generator...

    You can turn it on.

    Remove the NOP generator and see what my PETTEST does...

    Don't be surprised if it fails in the same way though...

    Since we may have fixed one problem (the potentially...
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    I like those signals better - as UH2 pins 13 and...

    I like those signals better - as UH2 pins 13 and 12 are now acting as a 'proper' inverter!

    I think you ought to get a replacement 74164 to replace UH3 next.

    Dave
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    Hi, Just got back from my walk - after...

    Hi,

    Just got back from my walk - after watching the Japanese F1 GP.

    I did suggest waiting for Dwight and Dave_m but...

    Yes, measure the points identified in post #354 again.

    Fingers...
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    I would guess the 74F04 should be an OK...

    I would guess the 74F04 should be an OK replacement. Just put it in a socket though...

    Perhaps wait though until Dwight and Dave_m 'wake up' to double-check the results first?

    Dave
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    A quick thought before swapping chips... Can...

    A quick thought before swapping chips...

    Can you just check the PCB tracks around UH2 and UH3 checking for any obvious short or open circuits.

    Dave
  15. Hi, I keep forgetting how good the Tektronix...

    Hi,

    I keep forgetting how good the Tektronix terminals actually were. You keep posting image files that are extremely good for the time period.

    We had a PET and a Tektronix 4051 in our...
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    You are getting consistent results. The...

    You are getting consistent results.

    The problem could be either UH2 (74S04) or UH3 (74164).

    I deliberately chose pins that were either end of a couple of copper tracks - and the results from...
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    A few minutes spare before lunch... I suspect...

    A few minutes spare before lunch...

    I suspect that your reading for UH3/8 is OK. This signal should be 16 MHz. I suspect this is well in excess of the frequency that your logic probe will probably...
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    Nice job Peter. I especially like the thorough...

    Nice job Peter.

    I especially like the thorough commenting in the WinCUPL source files - an excellent example for everyone reading them!

    Question, is anyone going to make kits of parts - or even...
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    Thanks for that. There are some interesting...

    Thanks for that.

    There are some interesting results there!

    Let me print out the schematic after lunch and superimpose your readings on it.

    I will probably come back to you and ask you to...
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    Using your logic probe... Note: I use H to...

    Using your logic probe...

    Note: I use H to mean HIGH (no pulsing), L to mean LOW (no pulsing) and O to mean oscillating.

    UH3 (164) pins:

    1 = O
    2 = H
    8 = O
    9 = H
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    What Dwight is saying sounds more complex than it...

    What Dwight is saying sounds more complex than it is:

    1. Purchase a 1 MHz 5V oscillator module.
    2. Solder 3 wires onto the clock oscillator module. One pin is 5V - wire it to the +5V supply line....
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    Learn from the experience and keep yourself well...

    Learn from the experience and keep yourself well away from the 'action'! If you need to be close, put a piece of Perspex/plexiglass between you and it.

    Dave
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    That's a similar part to the Mouser part that I...

    That's a similar part to the Mouser part that I referenced.

    If you can wait until I get my friend's dead 8032 here I will see if I gan get some traces of the /RAS and /CAS signals for reference....
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    it sounds like your preference is to replace...

    it sounds like your preference is to replace parts until you get it to work. This will work, but you could end up replacing 49 working parts and it is the 50th that is faulty. As long as that is your...
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    How have you tested the four '153's? Dave

    How have you tested the four '153's?

    Dave
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