You didn't mention whether the 2 examples you have are the same model suffix or not. They might be different which could explain PS differences. The orange wire is the least of the differences. Look at the picture below and you can see some very substantial circuit design differences. It is not uncommon for a manufacture to produce a board with several optional configurations. Missing components or extra unexpected jumpers do not necessarily mean modification. Might be perfectly normal. The Photo showing the PS with the tape over the transformer appears to be correct for models VZ-2000, VZ-2000X and VZ-2000XA. I do not know which model the other picture is for. Also, parts are not necessarily interchangeable. For example, the transformer and the voltage selector switch would be different and if someone swapped the wrong ones, it might be problematic.
Also, the VZ-2000 is a very complicated boombox, with very complicated designs, even in the power supply section. It is not always easy for understand the circuit design or reasons for them.
I suggest you start with the proper service manual or at least the schematic and do voltage tests at the appropriate locations to get a better picture of where the problem might be for your low voltage issue. Unfortunately, you are showing 2 different versions in your pictures and the circuits are different so you'll need to find the right one.
One thing for certain I would recommend is to clean thoroughly the AC/DC switch, and the DC-in switch. Both are located within the jacks themselves, and either one could account for poor connection and low voltage (tension). Also, if you have access to a variable lab power supply, you can inject 15v to ground (or pin 8/9 to connector 403 - tape deck) and + to pin 1 of connector 701 - power switch. If it works normally now, then you have poor connections at either AC/DC switch, DC-in switch or power switch. If still not working properly, then you'll need to then move on to voltage checks at other locations. Again (see previous paragraph), you will need the proper schematic for your board, and do a thorough voltage check.
