On Mon, 21 Feb 2005 14:37:32 +0000, wb
wrote:

It does cut out when no battery is connected but doesn't when I
disconnect either wire going to the black box from the transformer.
So, hopefully, a new bridge rectifier will solve my problem. Is this
the sort of thing I can get at Maplins - I've had a look but none has
the same markings as mine: AC BR354 A 38
I'd be grateful for any pointers on this one. Many thanks for your
help thus far.

Hi,

Looks like a 'BR354' is a 35A 400V spec:

http://www.alldatasheet.com/datasheet-pdf/view/RECTRON/BR354.html

Maplins do a 'KBPC3504' which has the same spec, for £1.29:

http://www.maplin.co.uk/Module.aspx?ModuleNo=19088&TabID=2&WorldID=&doy=21 m2

Looking at a data sheet it's the same size with the same type
terminals too:

http://www.alldatasheet.com/datasheet-pdf/view/SEMTECH/KBPC3504.html

When fitting the new one be sure the AC terminals marked '~' are
connected to either lead from the transformer, and the DC terminals
'+'/'-' are connected to the appropriate outputs of the charger.

If you take the old one off and measure the resistance each way across
adjacent terminals, you should find that 3 of the 4 diodes only show
resistance one way, but one doesn't show resistance either way which
proves it's defective.

cheers,
Pete.