I want to see if the replaced lamps all work and I will want to measure the Beomaster power supplies.
It turned out that I had the LED replacement lamp installed with reverse polarity. I switched it around and then it too worked.
Looking at the previous project I now see that this indicator lamp panel has differences more than just the two board connectors.
Here is the Beomaster 2400 Type 2902 indicator board from my previous restoration project. The FM3 lamp (between the two board connectors) does not have the jumper that the current Beomaster 2400 does. The same is true for the Beomaster 1900 Type 2903. The wiring path for that lamp is indeed different...as I found out.
On to the power supply and no-load current adjustments.