Date : Wed, 15 Nov 2006 22:15:24 +0000
From : splodge@... (Richard Gellman)
Subject: Master 128 Power Supply
Thanks for that Sprow, Robin. I'll probably get onto it at the weekend,
and just leave the machine switched on in the meantime.
Robin, believe it or not, replacing a capacitor is easier than digging
out the spare PSU. Aside from being inside a cupboard which has mount
Pilojunk in front of it, the M128 is buried under Morjunk Valley, and
thence I'd have the great fun on extracting the thing from the "other" M128.
The M128 in question is shamefully relegated to the cupboard due to its
somewhat cannibalized nature. While it does work, the keyboard is
missing 6 keys, and thence part of the keyboard circuit (a modern
printed-on-plastic variety) is torn in the upper right corner, thus no
LEDs are present (let alone in any kind of working state). The
motherboard has had various wires hacked into it at various stages, and
so the whole thing just looks nasty.
The tears in the keyboard circuit also cause a sort "auto-fire"
concerning the "1" key. Making typing in programs somewhat difficult.
You either spend 10 minutes trying to get a single "1" or you press it
and you can't stop the thing.
As I say, its the spare, so I'm not in a hurry to get it repaired.
-- Richard
Robin Commander wrote:
> Ah, you beat me to it :-)
>
> One point I forgot to mention, and is also not made on your excellent web
> page Sprow, is that these capacitors have to be installed the right way
> round, so if replacing one make sure you orientate the new capacitor
> correctly. Depending on their location (in an electronic sense as opposed to
> a physical sense) within the PSU, a capacitor which is incorrectly
> orientated may explode when power is applied.
>
> Regards,
> Robin
>
>
> -----Original Message-----
> From: bbc-micro-bounces+robincommander=blueyonder.co.uk@...
> [mailto:bbc-micro-bounces+robincommander=blueyonder.co.uk@...
> ] On Behalf Of Sprow
> Sent: 15 November 2006 20:25
> To: bbc-micro@...
> Subject: Re: [BBC-Micro] Master 128 Power Supply
>
> In article <455B7428.1080307@...>,
> Richard Gellman <splodge@...> wrote:
>
>> Flick the switch... nothing. Dead. Take machine apart, all the 5v lines
>> read 0.1 volts on the voltmeter. Try powering up supply separately, 5v
>> lines now read 5v. Try reconnecting PSU to M128, switches on fine. Looks
>> of confusion abound. Drink consumed, though sadly no alcohol present.
>> Reassemble M128, and slide it back into position. Power on. Dead.
>> RAMPANT looks of confusion now. Go to unplug unit, M128 suddenly powers
>>
> on.
>
>> Its almost like the PSU has developed a random time delay before it is
>> willing to provide power to the system.
>>
>
> A known problem. It's just taking a long time to startup, the larger the
> load the longer it takes (which is why in isolation it starts up instantly
> and appears to work fine), due to dry capacitor.
>
> See
> http://www.sprow.co.uk/bbc/howto.htm#powersupply
> along with a host of other frequently asked questions,
> Sprow.
>
>
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