Working on an old Harman Kardon 75+ and the 30V supply is flaking out.
This "regulator board" is fed from a rectified power source of aprox 46 volts. It's sole responsibility is:
1) Provide regulated 12vdc
2) Provide regulated 30vdc
3) Control the "stereo tuned" indicator bulb (12v) via a simple transistor (base controlled from the tuner).
I am basically deleting the board and replacing it with my own. I have no need to keep the functionality of #3 because I have replaced the old indicator bulb with an LED. Ahh technology.
Now... for #2... I need 30 volts DC. I understand (correct me if I am wrong) that there is (theoretically) no voltage limit of an LM317.. just a differential limit. So, am I correct to say that using an LM317 in this application is safe?
Regarding #1, I plan to feed a SECOND lm317 from the 30vdc out of the first in order to keep a safer margin of error. Again, am I on the right track here?
The total current requirements of the 30vdc is less than .05ma. The 12 volt is even less and only used for the AM tuner. (it was originally ALSO for the stereo indicator, but adios to that!).
This board originally used 3 bjt's, a couple zeners and a handful of other passive components. I mainly want to completely refresh this using parts I already have on-hand and simplify the design in the process.
- Dean
This "regulator board" is fed from a rectified power source of aprox 46 volts. It's sole responsibility is:
1) Provide regulated 12vdc
2) Provide regulated 30vdc
3) Control the "stereo tuned" indicator bulb (12v) via a simple transistor (base controlled from the tuner).
I am basically deleting the board and replacing it with my own. I have no need to keep the functionality of #3 because I have replaced the old indicator bulb with an LED. Ahh technology.
Now... for #2... I need 30 volts DC. I understand (correct me if I am wrong) that there is (theoretically) no voltage limit of an LM317.. just a differential limit. So, am I correct to say that using an LM317 in this application is safe?
Regarding #1, I plan to feed a SECOND lm317 from the 30vdc out of the first in order to keep a safer margin of error. Again, am I on the right track here?
The total current requirements of the 30vdc is less than .05ma. The 12 volt is even less and only used for the AM tuner. (it was originally ALSO for the stereo indicator, but adios to that!).
This board originally used 3 bjt's, a couple zeners and a handful of other passive components. I mainly want to completely refresh this using parts I already have on-hand and simplify the design in the process.
- Dean