Disco Volante
Well-known member
Got this donut for 7 euro at surplus. 2x18V 2.2A. I need 2x24V, and a small 6,5V winding, (to replace a underrated, cheap, humming PT in a Beomaster 900).
So why not just add some copper?
Secondary is two windings jumbled in one layer. By the look of it, they've used a double feed.
I added a length of 0.8mm copper to each end and wound another layer about half way back around, then adjusted by backing off and measuring until I got 27V unloaded on each winding.
Now, the trouble started when I added a small extra sec (tertiary?) to get my measly 6.5V.
I added the third winding about 3/4 way round with 0.5mm wire and generous spacing, about 100 turns.
Made sure to wind the same direction as the other windings.
This blew the 1A fuse with a blue flash.
All the layers are insulated with clear tape. The two joints are heatshrink insulated.
The Primary measures 9.4H 69DCR with the two extended sec's. With the third winding, it's 9.2H 22DCR.
The secondaries are 2x115mH 0.7DCR, 16mH 0.5R. Measured with a relatively cheap component tester @ 1kHz.
I'm new to transformer hacking, but I've done a good amount of speaker coils and voice coils...
Did the third winding somehow short the transformer?
Should the secondaries not be layered on top of each other but be next to each other maybe?
What happened?
And, dear magnetics gurus, how is this done correctly?
Thanks,
Viggo
So why not just add some copper?
Secondary is two windings jumbled in one layer. By the look of it, they've used a double feed.
I added a length of 0.8mm copper to each end and wound another layer about half way back around, then adjusted by backing off and measuring until I got 27V unloaded on each winding.
Now, the trouble started when I added a small extra sec (tertiary?) to get my measly 6.5V.
I added the third winding about 3/4 way round with 0.5mm wire and generous spacing, about 100 turns.
Made sure to wind the same direction as the other windings.
This blew the 1A fuse with a blue flash.
All the layers are insulated with clear tape. The two joints are heatshrink insulated.
The Primary measures 9.4H 69DCR with the two extended sec's. With the third winding, it's 9.2H 22DCR.
The secondaries are 2x115mH 0.7DCR, 16mH 0.5R. Measured with a relatively cheap component tester @ 1kHz.
I'm new to transformer hacking, but I've done a good amount of speaker coils and voice coils...
Did the third winding somehow short the transformer?
Should the secondaries not be layered on top of each other but be next to each other maybe?
What happened?
And, dear magnetics gurus, how is this done correctly?
Thanks,
Viggo
