I use my radio in Guatemala with a 12V adapter and it has worked great for years. Now, I get nothing. I have tried it with the 120 cord as well. When I push the power button, nothing happens. Is there a fuse anywhere?
I replaced the protection diode, a 10v zener, with a 9v from my junk box. This did not fix the problem, but as least I have 6vdc going into the radio now. Looking further ... maybe an onboard regulator got fried. Still no source for a schematic.
I have one that I am repairing that has the same problem ... putting 12v on the 6v input shorts the protection diode to ground. I pulled the diode and found it to be shorted and currently sourcing a replacement.
Since I don't have a schematic, I am guessing at the part number ... it is a 1N4xxx something, I think ... hard to read it. I'm pretty sure this is the only problem.
If you are not an electronics tech, I don't recommend trying to replace the diode yourself. It requires a major disassembly of the radio.
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Check your cord first, make sure it's in good shape. Sometimes the main transformer goes out, and you can use a DC adapter to bypass the 120 V source. Could be a fuse, or something else in the power supply inside the unit.
Or you can just type in 12v 2.5A LCD Adapter in an Ebay search. You can usually find a bunch of buy now power supplies that come with cords for a decent price. I've been using one of these for a year or so on my monitor.
A transformer type (Linear Mode Power Supply) AC to DC power adapter with a 9.V nominal output, measures about 12.V without load when tested with a multimeter. A power adapter with a nominal output of 7.5 V, measures a little over 9.V. Considering a number of people across different forums reported the adapter's measured power output as 12.V, I think the nominal rating of the AC to DC adapter should be 9.V. However, keep away from Switch Mode Power Supplies.
DO NOT use the HP power adapter that is 19V / 3.95A. That is too much power for the Scanjet, which is expecting 12V DC (and a much lower amperage). It's possible that hooking up this power adapter may further damage the electronics inside the scanner. If the second adapter has stopped working then it is possible that the internal circuit board has damage already and another adapter may not work. If you have access to a multimeter / voltmeter you could check for the 12V coming from the adapter. If you're getting the 12V, then the internal circuit board to the Scanjet is probably defective.