Transformer question - HELP ME FIND ONE !

[MartyMart]

EDITED:

I need a 230v pri 1 x 15v sec 2VA PCB mount transformer and can't seem to find one anywhere in the
UK !
Everyone I find is 2 X 15 volt sec connections ! ... it wont fit my board unless its a single secondary winding

I've tried :
ESR
RS
Farnell
Bardwells ....

Thanks  MM




http://aronnelson.com/gallery/Martys-layouts-and-photos/L201568_10

Here's the pin diagram from a new 230v 2X15v 2VA transformer.
I'm replacing one in a mic-pre, which was only "single 15v" secondary.
However this pin diagram looks like I can use the "centre two" pins
for a 15v connection ..? ( S1 on diagram ) I thought that I'd have to exchange it, to me it
looked like the two "outer most" sets of pins ( S2 on diagram ) would be a set of 15v connections,
one set of secondaries at each edge.
The two inner most pins are the only ones that would "match" my board "holes"

Any ideas .... or should I just change it  ?
Thanks in advance ,
MM.

[Paul Perry (Frostwave)]

Yeah, you have two pairs of 15V AC windings. Use either the top two, or the bottom two.
(you can check with the resistance range of a meter while the transformer is unconnected, to check that the windings are like that).
It doesn't suprise me that the pins don't match the holes you already have

[MartyMart]

Thanks Paul .... as I suspected, the "middle set" has no reading .... change time !!

Marty.

[MartyMart]

Please look at the top post ...

[Paul Perry (Frostwave)]

Here's a workaround, if space is tight:
Get a 2A 15V AC wallwart & then the transformer is OUTSIDE the box!

[MartyMart]

Here's a workaround, if space is tight:
Get a 2A 15V AC wallwart & then the transformer is OUTSIDE the box!

HA HA .... unfortunately, I need it to give me,  15v ---> 230v ---> 100k ---> plate of tube... so its reversed !

Still lookin ....

MM.

[gez]

I'm flicking through the Rapid catalogue and it's full of 230/240 to 15V transformers.

Hint: The rating can be higher than 2VA (it's desirable even)!  The primaries to most of them are are split, which may be confusing you, but quite a few of the 3VA ones aren't.

Couple which might do you:

88-3519
88-3545

There are many others (with higher ratings), all fairly small.  I'm sure you can find something...

www.rapidelectronics.co.uk

Try Maplin too.

Edit:  Whoops, I take it layout is critical?  If so, you can probably bodge something (cut traces etc).

[MartyMart]

Sorted ... spoke with "Block" UK and they very kindly offered to send me some free samples
of the correct transformer, with a single 15v secondary winding and correct pin connections  !!

Superb  !!

MM.

[gez]

Glad you got sorted, but it just occured to me you could have used one with two 7.5V secondaries and taken the output from the outer lugs!   

[MartyMart]

Glad you got sorted, but it just occured to me you could have used one with two 7.5V secondaries and taken the output from the outer lugs!   

Thats right, I could have used these, only the "pin" connections were way off !
I need a pair of central pins for the 15v to fit this mic-pre board and also "size" of
the block was critical ! 34mm X 25mm X 44mm
The ones coming are perfect 

Cheers,
Marty.

[A.S.P.]

glad you found one;

the rating is critical in this case!
not so much in the sense of what power it can handle,
but how high the final output-voltage (HT) will be...

[MartyMart]

glad you found one;

the rating is critical in this case!
not so much in the sense of what power it can handle,
but how high the final output-voltage (HT) will be...

Thanks ASP, that is a slight problem and forces a question :
The original PCB mounted transformer was a 15/250v 2VA rating
I can only find a 15/230v 2.3VA version, so ... will the 1/2 watt 100k plate
resistor need to be adjusted, as the rectified original at this point was 300v,
I'm guessing that I'll have a bit less , perhaps 270v - 280v ..  ?
or will a slight reduction not change the bias enough to worry about ?
Marty.