Beomaster 4400 Type 2419: Getting the FM tuner working

Power is good on this Beomaster 4400 now.  I have tested the Tape 1 and Tape 2 source inputs.  Now I can work on reinstalling the FM boards.

The first thing I will do is check if the FM boards have any power to ground short circuits. There were two traces burned up on the main board (PCB5) that involve ground and the +15VDC regulator. I am concerned those are related to the FM boards so I will test them by applying DC power to them via a bench power supply that I can regulate the current to. That way I won't let anything burn up.

First is the Stereo - Decoder board (PCB3).

No problem there.
I will move on to the IF and Tuner boards (PCB2 and PCB1 respectively).
PCB2 has both +15 VDC and +35 VDC.  I am testing with a dual 30 VDC bench supply so I will only do 30 VDC in place of the +35 VDC.

Great! No apparent power problems on the FM boards. I can reinstall them and give them a try.

The result...No FM at all from the Beomaster 4400.
Like most of the other issues with this Beomaster the problem came down to another broken wire.
Actually two wire issues with the FM tuner.
A ground wire from the main board - PCB5 to PCB6, a board on the switch rail, came loose.
Unfortunately the reattachment point on PCB5 is underneath the overhang of PCB6.  I am in no mood to disassemble the front panel to reconnect this wire.

Instead...I rewired the ground wire from the bottom side of the Beomaster.

Restoring that ground got all six of the FM preset tuning pots working again. The large, main tuning dial however was still not working.

The low side of the FM tuning pots for the six presets and the large tuning dial are supposed to tie together and connect to a leg of the 6R1 2.5KΩ trimmer. In addition there is an FM tuning voltage adjustment in the service manual to use 6R1 to set that common node to 4.6V.

I discovered that the connection of the six preset tuning pots and their connection to the 6R1 trimmer resistor did not include the main FM dial tuning pot. That trace must have a break in it but I could not see it.

As with the ground wire issue this problem would require another disassembly of the front panel. I did not want to do that so I used a jumper wire to fix the broken connection.

Now that the missing wires were fixed I could make the FM tuner upper and lower voltage adjustments per the service manual.

First the upper tuning voltage.  It is made with the main tuning dial all the way to the right.

That is followed by the lower tuning voltage adjustment. It is performed with the main tuning dial all the way to the left.

Finally, all of the FM tuning dials work....as do the signal strength and stereo indicator lamps.