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Thread: Whence Alpha among the hobbyists?

  1. #41
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    I tried ^[^[ RMC and it echoed back just the MC which I believe from reading is something it will do, but I am not getting a RMC> prompt

    I am getting nothing on the front panel as the system won't power up at all (only the RMC PIC chip is running) and I am hoping the RMC can give me some idea as to why.

    Reading the manual, it talks about resetting the RMC, points to Appendix A which then only seems to tell you the default jumper setting.

    Might be on a hiding to nothing, but I think its worth seeing if the RMC can be accessed.
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  2. #42
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    Well

    Successfully got into the RMC, but apart from confirming the temperature sensor is fine, it doesn't tell me anything else and issuing a power on command just fails with a 'failed to power on' error.

    So where next, not sure.
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  3. #43
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    So looking online, the DS10's PSU is a modified ATX standard PSU with enough welly to drive a fully loaded box.

    That must mean it has a power on input that needs pulling down to ground, then a power good back from the supply to the machine.

    First job will be to remove the PSU and see if I can get it to run on its own.

    What I am missing is the pinout, I have found a vague reference to 'modified ATX pinout' but no actual drawings. Will need careful analysis.
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  4. #44
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    For what little it's worth, I have a Compaq PSU that looks just like a standard ATX model, but with very different pinout--and the "power on" has to be pulled up to activate.

  5. #45
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    Thanks Chuck. I could have been scratching my head with that assuming its a down and not realising it could also be a pull up.
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  6. #46
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    It's a stale memory, but I believe the soft power control in old Macintoshes is also a pull-up instead of a pull-down, so it's definitely a thing people did.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  7. #47

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    I don’t think the atx supply in my PC164 or PC164LX had soft power control at all. The newer system was all original and had to be turned on and off via the power switch. The PC164 I used a generic atx supply with a switch, and I connect green to black so that it was “always on”

  8. #48
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    There is/was a company supplying third party supplies for the DS10 and specify it as an intel EPS12V form factor and connectors as 'Motherboard Connector : 22 pin + 20 pin + 10 pin modified ATX connector'

    So I'm hoping it should be fairly simple to debug, but of course it could be tripping out on something within the motherboard but reading the writeup for the PSU, it does look as if they were a bit temperamental so that gives me a glimmer of hope.
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  9. #49
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    PSU removed and it fails to run on the bench, so it looks as if it isn't a short in the machine.

    It uses a TSM111 which is shutting down the supply. 3.3V, 5V and 12V all can be seen to rise then the Main Converter Control output goes high which stops the PSU running.

    Need now to observe the inputs to see if there are any valid reasons for the shutdown or if its the chip. Wondering if I could pull down the PWM output to get it to ignore the shutdown and see if the PSU will run, but that might release the magic smoke

    Oh well, in for a penny. PWM pulled down and PSU starts up !

    Voltages at the outputs

    3.3V = 4.3V
    5V = 5.3V
    12V = 12.3V
    -5V = -5.3V

    So it works but the 3.3V is too high and is probably why the supervisor is shutting it down. From the datasheet it looks as if Vvs1 is the voltage at which the PSU will shutdown if the 3.3V line is above it and the datasheet seems to state that is between 3.8V and 4.2V.

    So, into the main part next, but at least it works after a fashion, but not enough to actually risk connecting it to the motherboard.

    I do note that there are two connections labelled 3.3 sense, but I believe they are routed via the PCB and are used to tweak up the supply if load is causing a volt drop so shouldn't be my current problem ?
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  10. #50
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    Using a lamp as a load, the voltage fluctuates so badly the lamp flashes.

    Wonder if its capacitors not damping the switching circuit similar to the problem I had with the MZ80K.

    A couple are showing a small sign of bulging.

    Arrgh

    Why are there no drawings.
    Current fleet
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