krs
Member
I have 3 PRO197s that have worked fine but last night one of them that's only about 3 months old mostly died. The only thing alive is the lighted front panel, no text on the display, no audio, no nothing else.
Opened it up to look for anything obvious like burned resistor, etc but didn't see anything. Doing some checking I find the output of the LM317 is only about 1.4 volts...I am guessing since I have no schematic this is supposed to be the 5V supply and that something downstream is kaput. The 7808 fixed regulator next to it is working properly, that might be what powers the display and button backlights? I kinda doubt there's any circuitry in this scanner that uses 1.4 volts.
I suspected C195, the first component on the 317s output line so I took it out and it's fine. There aren't any shorted diodes or resistors in this area of the power section...the (presumed) 5V line runs off in several directions and disappears inside some shielded compartments, but I'm not about to start dismantling those things. I guess I'll scare up a new LM317, that's one gadget I don't seem to have, but I don't have a lot of faith that is the problem, it isn't dead shorted to ground and those things are usually pretty bulletproof.
Just thought I'd ask in case anybody has run into a similar problem and might have any ideas...thanks
Opened it up to look for anything obvious like burned resistor, etc but didn't see anything. Doing some checking I find the output of the LM317 is only about 1.4 volts...I am guessing since I have no schematic this is supposed to be the 5V supply and that something downstream is kaput. The 7808 fixed regulator next to it is working properly, that might be what powers the display and button backlights? I kinda doubt there's any circuitry in this scanner that uses 1.4 volts.
I suspected C195, the first component on the 317s output line so I took it out and it's fine. There aren't any shorted diodes or resistors in this area of the power section...the (presumed) 5V line runs off in several directions and disappears inside some shielded compartments, but I'm not about to start dismantling those things. I guess I'll scare up a new LM317, that's one gadget I don't seem to have, but I don't have a lot of faith that is the problem, it isn't dead shorted to ground and those things are usually pretty bulletproof.
Just thought I'd ask in case anybody has run into a similar problem and might have any ideas...thanks