Three simple questions: Answer the damn questions!

Which of the two trannys in the photo is used to make the ~300V?

Which one is the one that gets hot?

Are there any holes or perforations in the cover that was removed to take the pictures?

 

Three simple questions: Answer the damn questions!

Which of the two trannys in the photo is used to make the ~300V?

Which one is the one that gets hot?

Are there any holes or perforations in the cover that was removed to take the pictures?

the one on the left is the one that gets hot and the one on the right is the one with 300v..yes the covers have holes .

 

the one on the left is the one that gets hot and the one on the right is the one with 300v..yes the covers have holes .

also the spare windings of the left transformer are taped together unused.

 

Any idea who made the left tranny? Any data on it?

 

Any idea who made the left tranny? Any data on it?

yeah i remember i got it from a roland chorus .the vintage one with the reel tape echo..

 

also the spare windings of the left transformer are taped together unused.

I hope you don't mean that they are electrically connected together and then taped?

 

yeah i remember i got it from a roland chorus .the vintage one with the reel tape echo..

the other is probably from an old crt tv circuit board.

 

I hope you don't mean that they are electrically connected together and then taped?

no just bunched together not connected.

 

no just bunched together not connected.

once i am happy with everything will tape them up correctly.sorry if it does look crazy..terrible i am...:-(

 

Try measuring a 40 watt fluorescent ballast. I phoned the MFG and they said it produces about 400 volts. Subtract the loss in the rectifier tube or find out he meant, "RMS" and the rectified voltage is going to be way too high. Anyway, worth a measure if it doesn't cost you a penny.

I doubt the ballast output is isolated from the input and thus would not be something you would want to use for a supply.

just rectifiers havent drawn the entire bit..i read that heaters could use 12v dc as well........

DC is sometimes used on audio tube heaters to minimize hum, but your circuit is just a half-wave rectifier which will reduce the voltage on the heaters to 1/2 the value (6V). You could use a full-wave bridge and a filter cap to get smooth DC but that would give a DC output of over 15V which would mean a short life for the filaments.

 

I doubt the ballast output is isolated from the input and thus would not be something you would want to use for a supply.

DC is sometimes used on audio tube heaters to minimize hum, but your circuit is just a half-wave rectifier which will reduce the voltage on the heaters to 1/2 the value (6V). You could use a full-wave bridge and a filter cap to get smooth DC but that would give a DC output of over 15V which would mean a short life for the filaments.

if i use another transformer just for the heater volts would that be a better option and use a full wave rectifier and better dc filtering caps would be a better option i guess.....

 

I doubt the ballast output is isolated from the input and thus would not be something you would want to use for a supply.

I checked. You're right. Even in the most primitive, low wattage ballasts, a capacitor carries what could be dangerous current to the secondary.

 

if i use another transformer just for the heater volts would that be a better option and use a full wave rectifier and better dc filtering caps would be a better option i guess.....

Yes you could. But you would need an AC voltage of 10V from the transformer to get a DC voltage of about 12V after filtering the output of a full-wave bridge consisting of standard silicon rectifiers.

 

Yes you could. But you would need an AC voltage of 10V from the transformer to get a DC voltage of about 12V after filtering the output of a full-wave bridge consisting of standard silicon rectifiers.

cool...will give that a shot. thanks mate.will purchase a 230: 15-0-15 tranny. probably that would also prevent the 1st transformer to heat up.

 

You could buy an isolation transformer with a 240VAC output.
If you need a little more voltage you can add a 12VAC filament transformer of the same current output rating in series with the output of the isolation transformer.

 

You could buy an isolation transformer with a 240VAC output.
If you need a little more voltage you can add a 12VAC filament transformer of the same current output rating in series with the output of the isolation transformer.

thanks mate i have a put a fan and it has done wonders thank you for all your input appreciate it.

 

I checked. You're right. Even in the most primitive, low wattage ballasts, a capacitor carries what could be dangerous current to the secondary.

thank you for your input appreciate it lots.

 

I hope you don't mean that they are electrically connected together and then taped?

thanks Mike..i put in a fan and the transformer stays luke warm ..so thats awesome ..thanks for your input i appreciate it a lots cheers.

 

If you have 240v RMS at the output of the reversed transformer,you should get around 337v dc out of a bridge rectifier (allowing for the voltage drop in the two series diodes on each half cycle).

If,however,you have 300v RMS out of the reversed transformer,you probably have different low voltage secondary voltages.
If the first transformer has a 15v winding & it is feeding a 12v winding,you will get the higher output from the reversed transformer.
This is a major "no-no",as you will be overloading both of the low voltage windings,so that one,or both will get hot.

 

If you have 240v RMS at the output of the reversed transformer,you should get around 337v dc out of a bridge rectifier (allowing for the voltage drop in the two series diodes on each half cycle).

If,however,you have 300v RMS out of the reversed transformer,you probably have different low voltage secondary voltages.
If the first transformer has a 15v winding & it is feeding a 12v winding,you will get the higher output from the reversed transformer.
This is a major "no-no",as you will be overloading both of the low voltage windings,so that one,or both will get hot.

Depends entirely on current being drawn from the second tranny's secondary winding.