im_in_asia_now
New Member
I've pulled apart some of my old 220 V Power Supplies used for home electronics (I moved here from Korea) and the larger transformers I've desoldered are kind of confusing not to mention intimidating.
What I've noticed in general is the use of smaller 4-pin transformers near the AC in, and larger, 7, 10, various different numbers of pinned transformers after the rectifier and closer to the DC out.
Ok, so the 4-pin transformers weren't too complicated to figure out. There's a short between the input and output pins, one for the signal, and the other for ground. When I used them in a circuit I built though, it seemed that there wasn't a noticeable step-up or step-down (like you would expect when going from 220VAC to 12 VDC).
So I've got how the 4-pin transformers at the top of the circuit work, but if they aren't step down, what is their purpose? Just for coupling? On the original circuit board they're labeled as "LF1" while the larger transformer is labeled as would be expected as T1. What does "LF" mean?
Then this is really something that's been bothering me because I haven't been able to find a lot of practical information on the internet about this. How in the world do you use a 7 or 10 pin transformer?
When I tested for shorts between the different pins, it just got more confusing. Could I get some help sorting through what I've observed so far:
10 pin transformer:
original circuitry takes output from transformer LF01. Output from LF01 connected to a GBP 206 bridge rectifier. Positive and negative outputs from GBP 206 rectifier are then connected to side 1 of the 10-pin step down transformer through additional resistors, conductors, and some are connected through more complicated circuits.
Side 1
pin #....shorts to pin# ....originally connected to
1.........2......................first a diode then an IC circuit fed from neg output of rectifier
2.........1......................neg output of rectifier
3.........4......................pos output of rectifier
4.........3......................connected to the IC circuit
Side 2
(continuing counter-clockwise)
5.........7,8
6.........9,10
7.................................goes through some components to -VDC output
8
9.................................goes through some components to +VDC output
10
There are no shorts in the transformer from side one to side two. The two sides are connected through additional circuitry.
On the side of pin 1 and pin 2 theres a circuit involving a few capacitors and a resistor going to a circuit on the side of pins 8-10. On the side of pin 3 and pin 4 is the IC circuit with input from neg side of the bridge rectifier, connected to a circuit on the side of pins 5-7 through a resistor, capacitor, Q01, U01 and U02.
Ok, no schematics and a lot of information to look through, no useful numbers on the large transformers... Are there any datasheets I could look at for reference for general 7, 10 or however many pin transformers? Are these large transformers even reusable or are there too many unknowns? Then the big question. Can step-down transformers such as these be used as step up transformers? Thanks for your time
What I've noticed in general is the use of smaller 4-pin transformers near the AC in, and larger, 7, 10, various different numbers of pinned transformers after the rectifier and closer to the DC out.
Ok, so the 4-pin transformers weren't too complicated to figure out. There's a short between the input and output pins, one for the signal, and the other for ground. When I used them in a circuit I built though, it seemed that there wasn't a noticeable step-up or step-down (like you would expect when going from 220VAC to 12 VDC).
So I've got how the 4-pin transformers at the top of the circuit work, but if they aren't step down, what is their purpose? Just for coupling? On the original circuit board they're labeled as "LF1" while the larger transformer is labeled as would be expected as T1. What does "LF" mean?
Then this is really something that's been bothering me because I haven't been able to find a lot of practical information on the internet about this. How in the world do you use a 7 or 10 pin transformer?
When I tested for shorts between the different pins, it just got more confusing. Could I get some help sorting through what I've observed so far:
10 pin transformer:
original circuitry takes output from transformer LF01. Output from LF01 connected to a GBP 206 bridge rectifier. Positive and negative outputs from GBP 206 rectifier are then connected to side 1 of the 10-pin step down transformer through additional resistors, conductors, and some are connected through more complicated circuits.
Side 1
pin #....shorts to pin# ....originally connected to
1.........2......................first a diode then an IC circuit fed from neg output of rectifier
2.........1......................neg output of rectifier
3.........4......................pos output of rectifier
4.........3......................connected to the IC circuit
Side 2
(continuing counter-clockwise)
5.........7,8
6.........9,10
7.................................goes through some components to -VDC output
8
9.................................goes through some components to +VDC output
10
There are no shorts in the transformer from side one to side two. The two sides are connected through additional circuitry.
On the side of pin 1 and pin 2 theres a circuit involving a few capacitors and a resistor going to a circuit on the side of pins 8-10. On the side of pin 3 and pin 4 is the IC circuit with input from neg side of the bridge rectifier, connected to a circuit on the side of pins 5-7 through a resistor, capacitor, Q01, U01 and U02.
Ok, no schematics and a lot of information to look through, no useful numbers on the large transformers... Are there any datasheets I could look at for reference for general 7, 10 or however many pin transformers? Are these large transformers even reusable or are there too many unknowns? Then the big question. Can step-down transformers such as these be used as step up transformers? Thanks for your time
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