Geetings.I have a transformer that I would like to rewind.I unwound it a few years ago out of curiosity and it looked a little bit burnt(outside layers).It is a 25 cycle unit that I may as well convert to 60 now.It says .08 amps on the label.Uses 2 6X4 rectifiers,2 6AQ5'S,1 12AX7 and a couple 6BE6,6BA6ETC,6AT6.So how would one mathematically determine the number of primary turns using the heavier wire of course.Then the high volage and filament windings could be determined from this.Does the .08 amps mean that the transformer "chokes" the current only letting this amount through ?? or something else?Also what amp fuse should be installed for safe operation? Any information on this topic would be appreciated.Books I have don't seem to really explain this.

:Geetings.I have a transformer that I would like to rewind.I unwound it a few years ago out of curiosity and it looked a little bit burnt(outside layers).It is a 25 cycle unit that I may as well convert to 60 now.It says .08 amps on the label.Uses 2 6X4 rectifiers,2 6AQ5'S,1 12AX7 and a couple 6BE6,6BA6ETC,6AT6.So how would one mathematically determine the number of primary turns using the heavier wire of course.Then the high volage and filament windings could be determined from this.Does the .08 amps mean that the transformer "chokes" the current only letting this amount through ?? or something else?Also what amp fuse should be installed for safe operation? Any information on this topic would be appreciated.Books I have don't seem to really explain this.

There are too many variables to give an answer from the information given. Transformer voltage to turns is a ratio; i.e., 12 volts out would be 1/10 the number of turns for 120 volts in. Wire size is dependent mostly on current. However the number of turns is dependent on the size of the iron core, the quality / type of steel used, and the way the core is laminated. Transformers typically use laminated cores to cut down on core losses. A 25 cycle (hertz) transformer might have thicker laminations than a 60 hertz transformer, and core losses would be great at 60 hertz. On the other hand, the transformer manufacturer might have used the same laminations, in which case you have a lot of iron to make a really conservative transformer at 60 hertz.

If you have the time and patience, and want to determine windings experimentally, I would start with a primary winding of 300 turns of about # 30 to # 33 wire. Place on the re-assembled core. Measure excitation current at 120 VAC 60 Hz in; should be less than 50 ma. If excitation current is higher, you need more turns (or the core is unuseable at 60 Hz.) If excitation current is low, Then let the unit 'cook' a while. If the thing gets hot, you have a core that probably cannot be used at 60 Hz. If you have made it this far, and want more help, let me know.

Another option: 25 Hz. transformers tend to be HUGE. If you want the unit to look original, I have cut out the inside of the core, and dropped new 60 Hz. units inside the core and case. Just make sure there is a lot of metal to metal contact internally so the heat can get out.

I would recommend a 3 amp fuse, or 2 amp slo-bl0.

Ed M

::Geetings.I have a transformer that I would like to rewind.I unwound it a few years ago out of curiosity and it looked a little bit burnt(outside layers).It is a 25 cycle unit that I may as well convert to 60 now.It says .08 amps on the label.Uses 2 6X4 rectifiers,2 6AQ5'S,1 12AX7 and a couple 6BE6,6BA6ETC,6AT6.So how would one mathematically determine the number of primary turns using the heavier wire of course.Then the high volage and filament windings could be determined from this.Does the .08 amps mean that the transformer "chokes" the current only letting this amount through ?? or something else?Also what amp fuse should be installed for safe operation? Any information on this topic would be appreciated.Books I have don't seem to really explain this.
:
:There are too many variables to give an answer from the information given. Transformer voltage to turns is a ratio; i.e., 12 volts out would be 1/10 the number of turns for 120 volts in. Wire size is dependent mostly on current. However the number of turns is dependent on the size of the iron core, the quality / type of steel used, and the way the core is laminated. Transformers typically use laminated cores to cut down on core losses. A 25 cycle (hertz) transformer might have thicker laminations than a 60 hertz transformer, and core losses would be great at 60 hertz. On the other hand, the transformer manufacturer might have used the same laminations, in which case you have a lot of iron to make a really conservative transformer at 60 hertz.
:
:If you have the time and patience, and want to determine windings experimentally, I would start with a primary winding of 300 turns of about # 30 to # 33 wire. Place on the re-assembled core. Measure excitation current at 120 VAC 60 Hz in; should be less than 50 ma. If excitation current is higher, you need more turns (or the core is unuseable at 60 Hz.) If excitation current is low, Then let the unit 'cook' a while. If the thing gets hot, you have a core that probably cannot be used at 60 Hz. If you have made it this far, and want more help, let me know.
:
:Another option: 25 Hz. transformers tend to be HUGE. If you want the unit to look original, I have cut out the inside of the core, and dropped new 60 Hz. units inside the core and case. Just make sure there is a lot of metal to metal contact internally so the heat can get out.
:
:I would recommend a 3 amp fuse, or 2 amp slo-bl0.
:Ed,I will try this and then I can determine the high voltage and filament winding turns if all works out.It is handy having a motor rewinding shop just up the street to get spools of wire from!By the way you were right in your response to my other posting about the unknown radio with star shaped tube socket punch outs.It is Philco model 62 or 65 (can't remember)but there are 2 versions one with 2 45's and one with 2 71A's output!
:Ed M
: