Lab Series L9 Transformer

[Kenny Moja]

Hi, I have a lab Series L9 which has an open circuit winding on the feed to the preamp and reverb board. The power amp winding is fine. Does anyone know if there is a suitable replacement transformer available in the UK? If not then an option may be to install a second transformer to feed just that circuit, any thoughts?
Cheers

Kenny

[52 Bill]

Hi, I have a lab Series L9 which has an open circuit winding on the feed to the preamp and reverb board.

Welcome. Single open windings can sometimes be caused by bad connections at the point where the lead wire connects to the winding wire. Have you considered opening the end bell and checking for bad connections or having the transformer checked by a winder?

[Kenny Moja]

Thanks for the swift reply. I can check the connections, the transformer will need to be demounted anyway. Will post my findings in a couple of weeks when I get back off contract.
Kenny

Welcome. Single open windings can sometimes be caused by bad connections at the point where the lead wire connects to the winding wire. Have you considered opening the end bell and checking for bad connections or having the transformer checked by a winder?

[J M Fahey]

And yes, worst case you can install a small low voltage transformer somewhere convenient.
If the "big" winding were bad, that would be different.
And I *guess* (just a hunch) that sometime the low voltage winding shorted and the mains fuse didn't blow because of the low power involved.
In that case the thin wire itself works as a (non replaceable) fuse.
Same as in wall warts, they almost never have a fuse, for the same reason.

[Kenny Moja]

Two of the 1N4004 rectifier diodes were shorted, no further damage is apparent. I suspect a second transformer is the way to go.
Kenny

And yes, worst case you can install a small low voltage transformer somewhere convenient.
If the "big" winding were bad, that would be different.
And I *guess* (just a hunch) that sometime the low voltage winding shorted and the mains fuse didn't blow because of the low power involved.
In that case the thin wire itself works as a (non replaceable) fuse.
Same as in wall warts, they almost never have a fuse, for the same reason.

[mozwell]

The low current secondary is 23 - 0 - 23VAC, i guess a 1A winding will do you fine if you use a second transformer.

enjoy

does anyone need schematics for L3, L5, L7, L9, L11 ?

[J M Fahey]

Dear Mozwell.
If at all possible, please post at least the L9 schematic, which we'll need now.
Thanks.

[mozwell]

Dear All, apologies for the delay in posting.... overseas for work & not always able to log in here....
enjoy the files, hope they are of use for repair....
Lab Series, L3, L5, L7, L9