The Pro-197 uses rather large scale integration and almost all surface mount parts. This is not something the inexperienced tech should mess with. In fact it's extremely unlikely if sent in for service they would perform a component level repair. They'd just swap out the board.
Yes, the radio says it requires 13.8V. This is not something the manual will explain. That's a nominal voltage for use in a vehicle. The original power supply is unregulated. It says 13.8 volts at 600mA. The unit almost never draws 600mA and a slightly smaller current supply should work fine. It typically produces 16 volts when operating and 20 volts when in an open circuit. The Pro-197 has two internal voltage regulators, one 8V and one 3.3V. I do not know the maximum voltage input they will withstand and it's likely the exact part used changes by various model revisions and production runs. However, the 3.3V part when set to run at 3.3 will typically withstand 43V and likely is just fine. The 8V part has a common maximum input of 35V and possibly sustained damage but is probably fine. The audio amplifier chip is powered unregulated. It can withstand 30V. If anything died this probably has. There is also a polarity protection diode. This device is intended to “blow up” if the unit is connected with reverse polarity which is my first guess. It does not have any internal fuse. There's a noise filter and a couple of current limiting resistors and other protection diodes. One can troubleshoot the power supply section pretty easily and repair it if handy with a soldering iron. You MUST have a supply in the range of about 10v to 16v, about 600ma, and most importantly the correct polarity, the center is positive.
1) Use an ohm meter (or diode meter) and measure across D41. You should see a high resistance, about 2 or 3M (or the voltage drop) in one direction, with the black probe at the band end. Swap the probes and you should see an open circuit. If you see zero this diode is shorted. Do NOT connect power. This is a typical 1A rectifier such as a 1n4001. If it's good move on.
2) connect power and measure the supply. For these measurements test with the black probe on the chassis, just touch the metal case. The red probe touches our test points. Using the original supply expect about 20V. If the supply voltage is good at that point move on.
3) The supply voltage minus about .6 will appear at the band end of D41. If not this diode is open and needs to be replaced. If the voltage is good at D41, just a little less than the supply, move on
3) turn the unit on, the supply voltage should drop by about 4V when using an unregulated supply. Again about -.6 will be at D41.
4) Measure at D40 and D39. You should see the supply voltage minus about 1.2 at D40 and minus about 1.8 at D39. If these diodes are shorted the voltage will be the same as at D41. This is probably okay but not correct. If good move on.
4) Carefully measure at the center of IC12. One slip and you might cook things. You should see very near 3.3V. Measure IC13 at the pin nearest the speaker hole for 8V. If either of these is wrong they will need replacing.
If the above is all good either the supply you tried is now dead, the scanner has a more serious problem, or maybe it works if you have the proper supply. It's possible one of the related capacitors is bad. Troubleshooting those is probably more complicated than one would like to go into.
The radio says adapter number MKD-48130600. The adapter says it's GPU481380600WD00. I guess 48130600 is the important part.
