Display Failure

Problem: ND8L wrote: The display on my 1995 vintage 'MP went dark tonight. The rig still seems to function (I can computer control it)...and the front panel indicator lights are working. I tried resetting the CPU...no luck.

Solution: If the problem is what I had, it's on the inverter board that provides some rather high voltage - a few kV? - to the display. The inverter board is not manufactured by Yaesu, so there's no schematic for it in the manuals and they do not repair it (at least based on my phone call to them a few months back) and so have no components for it. They will sell you an entire board (I don't recall the price).

The inverter is behind the front panel. You need to remove at least the top cover (and I believe the bottom as well) in order to get access to the screws that hold the front panel on the main chassis. (No need to take the front panel itself apart - just disconnect it physically from the MP's main chassis.) You *can* get it to kind of hinge down on two screws though not enough, if I recall, to get full access to the inverter.

The inverter is a board about 25mm x 75mm (under a metal shield) mounted on the far right as you are looking at the MP from the front. It's not on the front panel assembly, but on the front surface of the main chassis. If I recall correctly, a couple of screws hold the cover on - remove these and then you can get to the screws that hold the board to the chassis.

There's not much to the board - just a few components. There are two fuses - a leaded over-current type (looks like a resistor) in series with a thermal fuse (mine looked like a square-package capacitor - about 5mm x 5mm x 2mm thick with radial leads). The thermal fuse proper is mounted between and thermally coupled to two transistor (or FET) devices. My fuse was open circuited - I simply bypassed it and the display started working. I am still looking (albeit less enthusiastically) for a suitable replacement. It says 2A 102°C.

In addition, apparently lots of folks have seen this happen (and I have as well): You turn the radio on, and the display takes an inordinate amount of time to come up (many seconds) but it does light up. Next time you power it up, it may come up much faster. No solution has been offered for this problem as far as I can tell. Mike N2MG