LL/88 ASC transformers

I was wondering if you night be able to help me find out more about these Ex-BBC LL88/ASC transformers.

Back in 2008 there's a thread
http://www.groupdiy.com/index.php?topic=24105.20 which states they are ...

Ratio = 1:1
Primary Inductance = 10.6 Henries
Primary Resistance = 40 Ohms
Secondary Resistance = 65 Ohms
On mine the Red/Green winding is 60 Ohms and the Yellow/Blue winding is 34.5 Ohms
The White wire appears to be tapped into the Yellow/Blue winding with 14.5 Ohms between Yellow and White and 20 Ohms between White and Blue.

I've a few questions about it ...
1) What can these transformers be used for?

2) What's the purpose of the White wire?

3) If they're 1:1 transformers, how is it that the windings have different resistances? Is it because they're on concentric windings?

4) Which is the Primary and which is the Secondary winding?

5) What sort of impedance would work in and out of them?

Many thanks.

I found some notes:

600:600
1:1
Primary is center tapped.
mum core?

I think its a general purpose isolation transformer.

Sounds like the white wires the primary center tap.

yel-white-blu is the center tapped pri (from dcr specs)

red- green is the sec

sometimes a primary center tap is used for noise issues, you can experiment with grounding it to the chassis, or not, listen for least hum,

you still need to phase the thing, which wire will have positive  peak when pri is positive,

do this with a scope or run a signal thru it and connect the sec wires to the pri wires and see which way cancels out the signal or makes the signal generator explode,

if it cancels, then it is wired out pf phase,

switch the wires just to make sure and test for in phase,

can be used for pultec input of mixing board, maybe a transistor line amp input like RCA,

Yellow, Red +

Blue, Green -

Thanks guys for your helpful input on this.

I'm wondering how the white wire is a centre-tap on the Yellow / Blue winding when the resistance between the White - Yellow (14.5 Ohms) and White - Blue (20 Ohms) is not the same.

> how the white wire is a centre-tap...when the resistance ... is not the same.

"Centre" is number of turns.

Resistance is turns times length of turn.

If half the winding is close to the core, and half is on the outer edge of the bobbin, there is easily a 1:1.5 difference in length-of-turn.

The _audio_ impedance is always much-much higher than the resistance. Probably 600 ohms. Probably meant to work "un-loaded", 10K or more. A 5.5 ohm difference compared to a 10K load is "nothing".

Can Someone tell me if the LL/88 ASC can used as Output transformer for RFZ V781ay?

Data of RFZ V781ay:

Betriebsspannung: 20 - 24V Gleichspannung, Pluspol geerdet (!)
Stromaufnahme: < 90mA (Typ. 45mA)
Frequenzbereich: 40 Hz .. 15 kHz
Eingang: symmetrisch, erdfrei (Übertrager), 2,5kOhm, +12dBm
Ausgang: unsymmetrisch, 3-15 Ohm, +12dBm

Thanks and CHEERS!

I don't see why it shouldn't work - try it?

Jakob E.

sorry for bumping this antique thread. but does anyone know what kind of zobel network would be appropriate for them? i want to use them as outputs for a compex compressor. cheers