Re: Question on Commodore 720 PSU

Hi Rob,


Am 07.01.2012 22:33, schrieb Rob Clarke:
> Good evening gents,
>
> Thanks to Ruud and Jens, I have all the missing IC's for my 720. It 
> came with all the cables disconnected and I haven't been brave enough 
> to hook it all up yet but I have connected the PSU to check the 
> voltages and have a couple of questions.
>
> o Are the PSU's in the 6 & 700 series have any history of being flaky 
> or are they generally OK?
As far as I remember there were no problems, but last time I switched my 
700 on was several years ago.
>
> o There is a 4 way, in-line power connector cable tied near PSU with 
> gnd, +5v and +12v and I don't think it connects to anything on the MB 
> - anyone know what it's for?
This is the power for the (legendary) internal disks. See the inside of 
a 8296d for details.
>
> o If I connect the power to the monitor without connecting the video 
> cable from the MB, should I expect to get any sign of life from it? I 
> would of thought I would have at least heard the HV whistle (it's a 
> long time since I had a CRT( but it seems ominously quiet.
As the 700er series have a more modern monitor design, there is a 
protection circuit, that switches of the beam if V and H are missing. 
This is not the case with older monitors (early 8000 series), where you 
can see the dot from the beam, burning a hole in the phosphor, if the 
video connector is unplugged during operation.

>
> o There are earth straps with a ring connector from the monitor and 
> the PSU. Were these strapped to a screw on the motherboard or to some 
> other part of the case?
There should be a short bracket on the backplane with a hole for a self 
tapping screw.
>
>
> cheers,
>
> rob
>
>
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Regards,

Simon

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