Date   : Sun, 28 Sep 2003 03:16:22 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: BBC Power Supply

In article <6A4F555CEA3CD5118DBD0002E30AC0912C0827@...
consultants.co.uk>, Andrew Hancock <Andrew.Hancock@...
consultants.co.uk> writes

>After reading some posts, recommended by a few on the list, I changed the
>dropping

chopping

> transistor for a BU208D

You did remember to solder the transistor pins in? (I've done this :)

> (I couldn't find a BU208A - but the BU208D
>after checking all the specs, is (maybe!) an updated version of the BU208A.

No, the BU208D has an inbuilt resistor and damper diode and is intended
for the line output stage in TVs and monitors.  I can't be sure from the
circuit diagram whether the additional resistor and diode would matter,
but do not think I would use it in this case.  An alternative to the
BU208A is the BU508A; that should be freely available in the TO3
package.

Have you checked the original transistor with a multimeter to make sure
there are no shorts between any pins?  If there are, check that the
fuse, L1, R2, R3, R5 and R12 are OK.

>I also changed C9 (220uf 25v 105C) on the primary side,
>and C18 (100uF 25v 105C) and checked all existing solder joints.

C18 is on the -5v line (low current).  Have you checked C19, C20 and
C21?  If in doubt, replace.

Is the supply making any noise at all?  clicks, ticking, squeaks, sighs?

Checked for breaks in the mains power cable?

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