Master 128 PSU schematic

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dominicbeesley
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Joined: Tue Apr 30, 2013 11:16 am

Master 128 PSU schematic

Postby dominicbeesley » Tue Sep 26, 2017 10:03 am

The PSU is playing up in the Master (slow startup) before I take it for a recap does anyone have a schematic for the Master PSU or a run down of what caps? I've got one for a Model B, but without component values, it would be good to know what caps to bring...

Cheers

D

duikkie
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Joined: Fri Feb 07, 2014 3:28 pm

Re: Master 128 PSU schematic

Postby duikkie » Tue Sep 26, 2017 10:41 am

Not the same as the bbc b one ? Bbc b one somewhere on this forum

dominicbeesley
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Re: Master 128 PSU schematic

Postby dominicbeesley » Tue Sep 26, 2017 11:25 am

The one I found has no component values on it, the question is whether its the same or not i.e. is C9 on the BBC the same C9 as the Master....I'll have a go without a schematic as I should be able to work out which is the startup cap...

Thanks

D

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danielj
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Re: Master 128 PSU schematic

Postby danielj » Tue Sep 26, 2017 11:50 am


dominicbeesley
Posts: 401
Joined: Tue Apr 30, 2013 11:16 am

Re: Master 128 PSU schematic

Postby dominicbeesley » Tue Sep 26, 2017 12:54 pm

Thanks daniel, I had seen that but it doesn't specifically say Master.

Anyway, I replaced C9 and the two main reservoir caps (I left the X2's as they look to be non-RIFA parts and I find I've run out of suitable X2's).

It's still slow to start up though...around 3.5s cold around 2s for a off/on cycle...that's until the keyboard LEDs light and the cassette relay clicks. Am I just being impatient?

Ottly
Posts: 111
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Re: Master 128 PSU schematic

Postby Ottly » Tue Sep 26, 2017 1:32 pm

Hi.

I had a similar problem. Turned out to be a resister. I can't remember the one it was right now but can let you know if your interested. It's apparently quiet a common fault.

Scott.

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1024MAK
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Re: Master 128 PSU schematic

Postby 1024MAK » Tue Sep 26, 2017 1:54 pm

Ottly wrote:Hi.

I had a similar problem. Turned out to be a resister. I can't remember the one it was right now but can let you know if your interested. It's apparently quiet a common fault.

Scott.

One of the 100k ohm ones?

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
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dominicbeesley
Posts: 401
Joined: Tue Apr 30, 2013 11:16 am

Re: Master 128 PSU schematic

Postby dominicbeesley » Wed Sep 27, 2017 9:48 am

Thanks, I've got something with component values (Service manual scan with scribbled in numbers) and though it's for an original BBC seems to match the Master closely enough. I'll try the R2/R3 which look to be part of a tickler to get the osc started...

D


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