rewinding secondary on toroid

[guitar_joe]

have seen the recent posts
i have plenty of 160va 25+25's

i want to rewind a ht for tube amp and a filament suppy

theres no problems doing that is there?

 

[AndrewT]

Voltage is the problem.
Then there are the logistics of controlling all that wire for the high number of turns required for a B+ supply.
The heater supplies are easy in comparison.

Keep in mind the turn to turn voltage if you start to multi-layer the toroid. Slight damage to the enamel insulation could create a fire hazard.

 

[guitar_joe]

well im planning to make the secondary 180 volts and use a voltage doubler rectifier for the HT.

Does this sound like a good idea?

 

[AndrewT]

I think I should order the flowers now.

 

[guitar_joe]

care to elaborate?

 

[peranders]

= It's not a good idea

 

[guitar_joe]

i do understand the issues, i would like to know how to do it safely though.

I do know that winding a toroid with 10 metres of ecw could lead to cracks in the enamel and that very tough dielectric materials should be used to insulate these layers.

 

[AndrewT]

I do know that winding a toroid with 10 metres of ecw could lead to

and scratches and production flaws. 10m is never going to get anywhere close to 180Vac. More like 100m for a B+ supply.

How do you intend testing the insulation quality after you have rewound it?

BTW,
the flowers were for the funeral.

 

[SheldonD]

[I f you have plenty of toroids why not stack them to get your voltage. You do not have to rewind anything 3 x 50V = !50V
or 4x 50 gets you 200. Filament transformers unles you use 25 V tubes.

 

[guitar_joe]

alright so the idea is crazy... unless i have a proper winding machine it's not going to be safe. damn...

btw i could connect two toroidals back to back and get 230vac if i really wanted too. A guy i know in australia makes valve amps by doing that.

anyhoo dun worry bout the flowers... at the rehearsal studio there was a guy using a variac inplace of a transformer in the amp and there were bare live wires hanging out everywhere... give him the flowers.

 

[AndrewT]

Hi,
back to back will work.
Isolation is just as good.
If there were some taps to adjust voltage you would be in clover.
But, you could easily add these on.
Two sets of 5V and 10V windings on the second transformer gives lots of options.


Adding 5V & 10V secondary to the first transformer would allow a large increase in final voltage (choice of feeding 50V/55V/60V/65V to the next secondary). I see 330Vac coming from 240Vac, if 15V (5V+10V) were added to No1 and 15V(5V+10V) added to no2. 65/50 * 255/240 * 240 = 331.5Vac (plus regulation)