Re: help replacing an old ac power transformer.

On Sun, 09 Oct 2005 15:38:42 -0700, fotoobscura wrote:

> Hey John,
>
> Thanks. Yeah it is a color enlarger with the bulbs costing
> $30/each...yup...I am posting the picture to the
> alt.binaries.schematics.electronic group after this message.

Apparently my server is a little slow to catch up - what
subject line did you use, and did you sign it "fotoobscura",
like this one?

> The picture is of the old transformer on left and the new on right
> along with the box that houses the transformer and a power switch.
> Very basic little box.
>
> The specs of the new one are:
>
> 12.6v AC, 3-amp
> center-tapped secondary
>
> Its quite possible the new one I bought is just plain the wrong
> one...Maybe not enough voltage?

Well 12.6V is certainly not going to light up a 27V bulb!

> I do have a digital multimeter. But I'm a little sketchy on playing
> with AC unless I know exactly how to measure it safely. And (where) to
> measure :)

First, you put your meter on the ohms range, to find out which winding
is which; but an RS tranny should have stamped on it which is supposed
to be the primary. But I've never heard of a tranny with three black leads
- are you sure one of the black ones doesn't have some kind of stripe?

Well, I can be more helpful after I've seen the picture.

> I am not sure there are electronics between the transformer and the
> bulb. I can take it apart to check, though.

Might as well just take a look - as others have said, it could be one
of several factors. Did it just start buzzing recently? That could
be just a cheap transformer. Did it smell like something was burning?
Are you only replacing it because of the buzzing, or does the light
not light at all?

Thanks,
Rich

.

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