Date   : Mon, 16 Mar 2009 11:35:25 +0100
From   : anders.carlsson@... (Anders Carlsson)
Subject: Dead BBC B

Mark Haysman posted the link to Sprow's webpage:

http://www.sprow.co.uk/bbc/howto.htm#powersupply

I also have a BBC B with a failing power supply. Last year I measured it and 
found it gives about 1.2V on the 5V lines when conneted, but close to 5V if 
unloaded. Based on the trouble shooting above, it sounds like fault #2, the 
BUA208 transistor which I'll try to replace.

However, do you think it would be wise to replace the 220uF electrolytic 
capacitor at C9 as well as the C2 and/or C1 capacitors while I'm onto it? 
The power supply didn't yet emit any smoke (that I can remember) but since 
all three faults are somewhat common perhaps it would be best to refurbish 
it completely?

It has been unplugged from the mains for a half year, so I expect most high 
voltage capacitors have discharged by now or would one still need to take 
extra measures before digging into it? I realize high voltage circuits 
shouldn't be fixed at all by unqualified people but perhaps if one is very 
careful?

Best regards

-- 
Anders Carlsson