From: Chris on
>Before I take a look inside (or bin the thing) I just
> wondered if anyone had an idea what might have gone kaput.
>

I guess you old charger contains nothing more than a big transformer and a
bridge rectifier. The rectifier contains 4 diodes to convert the AC from the
transformer to the DC for the battery. If one of the diodes goes short
circuit then you will get the effect you are seeing.

If you really want to resurrect the charger you could probably replace the
old bridge rectifier with a new one from Maplins for couple of quid (AR84F
looks suitable). But as modern cars and batteries are more susceptible to
mistreatment I would be tempted to just get rid of it.

Chris


From: redwood on
"Chris" <nospam(a)nospam.com> wrote in message
news:LC%bh.2673$I6.1836(a)newsfe3-gui.ntli.net...
> >Before I take a look inside (or bin the thing) I just
>> wondered if anyone had an idea what might have gone kaput.
>>
>
> I guess you old charger contains nothing more than a big transformer
> and a bridge rectifier. The rectifier contains 4 diodes to convert the
> AC from the transformer to the DC for the battery. If one of the
> diodes goes short circuit then you will get the effect you are seeing.
>
> If you really want to resurrect the charger you could probably replace
> the old bridge rectifier with a new one from Maplins for couple of
> quid (AR84F looks suitable). But as modern cars and batteries are more
> susceptible to mistreatment I would be tempted to just get rid of it.

Thanks for the quick replies. I have now taken the back off and yes it
does look very basic inside. I can see the rectifier which has 4
connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield). It has writing on the rectifier which says;

S4VB
10 (Hole) 84

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.

From: Duncan Wood on
On Fri, 01 Dec 2006 20:15:54 -0000, redwood <help(a)nooos.com> wrote:

> "Chris" <nospam(a)nospam.com> wrote in message
> news:LC%bh.2673$I6.1836(a)newsfe3-gui.ntli.net...
>> >Before I take a look inside (or bin the thing) I just
>>> wondered if anyone had an idea what might have gone kaput.
>>>
>>
>> I guess you old charger contains nothing more than a big transformer
>> and a bridge rectifier. The rectifier contains 4 diodes to convert the
>> AC from the transformer to the DC for the battery. If one of the diodes
>> goes short circuit then you will get the effect you are seeing.
>>
>> If you really want to resurrect the charger you could probably replace
>> the old bridge rectifier with a new one from Maplins for couple of quid
>> (AR84F looks suitable). But as modern cars and batteries are more
>> susceptible to mistreatment I would be tempted to just get rid of it.
>
> Thanks for the quick replies. I have now taken the back off and yes it
> does look very basic inside. I can see the rectifier which has 4
> connectors and a hole in the middle screwed into a thin sheet of metal
> (or is that a heatshield). It has writing on the rectifier which says;
>
> S4VB
> 10 (Hole) 84
>
> I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
> looked at the Maplin code for AR84F and that is 25A. Would it cause any
> problems using a higher amp or is it best to keep with a 10A? Cheers.


Nope, that'll be fine.
From: John Rumm on
redwood wrote:

> connectors and a hole in the middle screwed into a thin sheet of metal
> (or is that a heatshield).

That wil be a heat*sink* - deisnged to help cool the rectifier. You will
need to fit something similar to the replacement part.

> I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
> looked at the Maplin code for AR84F and that is 25A. Would it cause any
> problems using a higher amp or is it best to keep with a 10A? Cheers.

Bigger (in this application) will be fine.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
From: Andrew Gabriel on
In article <4tbgu5F1357gnU1(a)mid.individual.net>,
"redwood" <help(a)nooos.com> writes:
>
> Thanks for the quick replies. I have now taken the back off and yes it
> does look very basic inside. I can see the rectifier which has 4
> connectors and a hole in the middle screwed into a thin sheet of metal
> (or is that a heatshield). It has writing on the rectifier which says;
>
> S4VB
> 10 (Hole) 84
>
> I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
> looked at the Maplin code for AR84F and that is 25A. Would it cause any
> problems using a higher amp or is it best to keep with a 10A? Cheers.

S4VB is a 4A bridge rectifier, and the 10 means 100V working.

A 10A or higher (50V or higher) bridge rectifier will be fine.
(A 4A bridge rectifier was obviously inadiquate.)
I would also get some heat sink compound to smear between the
new rectifier and the heatsink.

--
Andrew Gabriel