So I finally got a chance to wind secondaries in place of the old EHT winding .
I put on two lots of 11 turns worked out at 9.00 volts ac on each ,dropping to around 8.5 ac with a bridge and unloaded regulator after.
Voltage was rock solid on the out of the regulator , with about 85 mV rms noise at 7 volts dc no load ,
Problem was the current draw of the primary alone causes the transformer to hum loudly , and after about a hour switched on the core was roasting hot . Stands to reason I suppose , a microwave tx has a fan blowing cool air on it when its in operation ,which is generally for short periods of time . If it was left energised for hours it would certainly overheat , never mind the roar of the lams which is loud , way way too loud to listen to music in the same room . ;D
I made sure my new windings were well packed with bamboo spacers and nice and tight , there also made from silicone and cloth wrapped wire , the core itself is in good shape ,no rust or loose lams ,
So my primary winding itself is causing the issue , to few turns of too thick wire ,way too much energy in the core .
Looks like I'll have to grind out the welds ,strip the windings and start from scratch , even still its been a worthwhile exercise ,not quite as easy as I anticipated ,but such is life .
So maybe someone would walk me through the elementary maths involved ,
Supply 234 volts , secondary turns count 11 x2 , 9 volts ac exactly per winding ,(nothing connected) ,drops to about 8.5 v ac with bridge ,smoothing cap ,and regulator attached ,no load . I didnt have a clamp meter but I can tell by the noise and the heat the core alone is consuming a large amount of power ,amps of current .So looks like I need to reduce the diameter of the primary wire ,maybe up the turns count 2,3 or 4 times ,and multiply the secondary turns count by the same factor ?
The LT circuit I want to run will consume around 2x 1.6A at 6.3volts from the output of the regulators so 3 amp capacity per winding seems reasonable .
I put on two lots of 11 turns worked out at 9.00 volts ac on each ,dropping to around 8.5 ac with a bridge and unloaded regulator after.
Voltage was rock solid on the out of the regulator , with about 85 mV rms noise at 7 volts dc no load ,
Problem was the current draw of the primary alone causes the transformer to hum loudly , and after about a hour switched on the core was roasting hot . Stands to reason I suppose , a microwave tx has a fan blowing cool air on it when its in operation ,which is generally for short periods of time . If it was left energised for hours it would certainly overheat , never mind the roar of the lams which is loud , way way too loud to listen to music in the same room . ;D
I made sure my new windings were well packed with bamboo spacers and nice and tight , there also made from silicone and cloth wrapped wire , the core itself is in good shape ,no rust or loose lams ,
So my primary winding itself is causing the issue , to few turns of too thick wire ,way too much energy in the core .
Looks like I'll have to grind out the welds ,strip the windings and start from scratch , even still its been a worthwhile exercise ,not quite as easy as I anticipated ,but such is life .
So maybe someone would walk me through the elementary maths involved ,
Supply 234 volts , secondary turns count 11 x2 , 9 volts ac exactly per winding ,(nothing connected) ,drops to about 8.5 v ac with bridge ,smoothing cap ,and regulator attached ,no load . I didnt have a clamp meter but I can tell by the noise and the heat the core alone is consuming a large amount of power ,amps of current .So looks like I need to reduce the diameter of the primary wire ,maybe up the turns count 2,3 or 4 times ,and multiply the secondary turns count by the same factor ?
The LT circuit I want to run will consume around 2x 1.6A at 6.3volts from the output of the regulators so 3 amp capacity per winding seems reasonable .
