Power tranny specifications - need help

[slidincharlie (Carlo P)]

Thanks Juan!
Just a couple more questions about two of your points:
1) in your post I can see a current rating of 3A mentioned for the heater winding instead of 3.5A cited in above posts. Should I tell the guy to use a 1.3 mm wire (or 1.5? or 1.6?) or should I rather tell him to respect the 3A (or 3.5?) rating?
2) should I tell the guy to ensure a 120 mA rating for the HV winding as per Chuck H's advice above, or should I just tell him to use the same wire as the current one because the current rating of the HV winding is not so important?

[Chuck H]

My approach was from a purely "functional" perspective. The only criteria for the determination of a 3.5A rating was "over rate = good".
Pretty much the same on the 120mA HV rating. No doubt the winder will be able to match what's already there, which will no doubt be a little different.
Juan's approach is much more considered (though probably unnecessarily so ). You would probably do well enough just printing this thread and delivering it with the transformer to the rewinder so that they understand your concerns, criteria and considerations.

[J M Fahey]

Thanks Juan!
Just a couple more questions about two of your points:
1) in your post I can see a current rating of 3A mentioned for the heater winding instead of 3.5A cited in above posts.

Get your glasses and read again
I mentioned 3A/mm^2 which is a general purpose copper wire rating meaning 3A per square millimeter
It's not current but current density .
If necessary, google both terms .

Should I tell the guy to use a 1.3 mm wire (or 1.5? or 1.6?) or should I rather tell him to respect the 3A (or 3.5?) rating?

Current rating depends on how cheap you are or how much space is available.
3A/mm^2 is a quite tight one; 2A/mm^2 is more generous, voltage will be more stable, will overheat less, etc; problem is sometimes it does not fit in the window.
I gave you 2 suggestions:
a) a tight cheap one would be to use 1.30 mm wire , his Math will be the same as mine.
b) but the older rewinder already used 2 x 1.1 mm diameter wire and , by definition, it fit; so I know , 10500 km away,

that then 1.55mm diameter wire will also fit
Since that's not a Metric size, pick 1.5 or 1.6 .
To be safe, pick 1.5 mm diameter which means it will fit and still be above minimum diameter.
Anyway, let the new rewinder check thses suggestions, shit happens and we may have overlooked some detail or misunderstood your needs or whatever.
Just play it safe, and as Carpenters say:" measure twice and cut once".

2) should I tell the guy to ensure a 120 mA rating for the HV winding as per Chuck H's advice above, or should I just tell him to use the same wire as the current one because the current rating of the HV winding is not so important?

Well, ALL ratings are important.
Tell the winder that you expect 120 to 150mA`consumption, but that the wire already used works, so if it's slightly above minimum, use that size.

What he should not do is use thinner wire.

As I said before, you already have a functioning transformer, just want to correct some errors.

The main one is filament voltage because it is very critical, much more than HV voltage.

I guess I've earnt a Caponatta and Pasta alla Norma dinner for my next visit to Sicily

FWIW my ex Father in Law's surname is Messina ... I guess it may ring a bell

[Chuck H]

FWIW my ex Father in Law's surname is Messina ... I guess it may ring a bell

Ahhh, a Sicilian! I'm told my family hails from there before immigrating, though my mothers maiden name originates in Tuscany. We can all be Italian