Hello all,
this is my first post and thread here
I made a simple voltage regulator with the common LM338K. Using the datasheet as a reference schematic, i sorted out the circuit (see attachment if does not show):
Behind this circuit there is a transformer with this ratings:
Primary: 0-220-400 V
Secondary: 12-0-12
VA: 100
That's good for a 4 amps at 24V, more than plenty for my uses.
That said, i made the circuit and worked good, at least without load i measured a good 1-30 Vdc range. But that was a prototype.
Then, in the final circuit i made the mistake of using old diodes (1N4007) that were bogus... they burned the set resistor (R2) a couple of times before i figured out that they were duds.
Bought new all the resistors and capacitors and replaced them, everything went fine (no burning resistors!), and i got the 1-30 Vdc without load.
BUT as i apply a load (dc motor, lamp...), Vout voltage drops to zero without having current to move anything, at any voltage setting.
Before the LM (so only rectifier and big capacitor) there is a meaty current to lit the lamp very bright, so it's not the rectifier fault.
I am thinking that with dud protection diodes, a backcurrent did damage to the LM. What do you think about?
Thank you for your replies!
this is my first post and thread here
I made a simple voltage regulator with the common LM338K. Using the datasheet as a reference schematic, i sorted out the circuit (see attachment if does not show):
Behind this circuit there is a transformer with this ratings:
Primary: 0-220-400 V
Secondary: 12-0-12
VA: 100
That's good for a 4 amps at 24V, more than plenty for my uses.
That said, i made the circuit and worked good, at least without load i measured a good 1-30 Vdc range. But that was a prototype.
Then, in the final circuit i made the mistake of using old diodes (1N4007) that were bogus... they burned the set resistor (R2) a couple of times before i figured out that they were duds.
Bought new all the resistors and capacitors and replaced them, everything went fine (no burning resistors!), and i got the 1-30 Vdc without load.
BUT as i apply a load (dc motor, lamp...), Vout voltage drops to zero without having current to move anything, at any voltage setting.
Before the LM (so only rectifier and big capacitor) there is a meaty current to lit the lamp very bright, so it's not the rectifier fault.
I am thinking that with dud protection diodes, a backcurrent did damage to the LM. What do you think about?
Thank you for your replies!
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