At 2:39 I misspoke and said "2 blue caps." I meant the "2 blue resistors." I had caps on my mind as the resistors are the bleeder resistors for the caps.
Early model 12 tube D+A Phantom 500 dual power linear amplifier on the bench. In the video, I was thinking this was a 10 tube, 4 driving 6, but it is not. It is a 12 tube, 4 driving 8. The small 13th tube is a keyer tube whose sole purpose is to key up the relays. This one someone has gone thru physically and cleaned it up and repainted it very well. Looks very nice. This older (early) model dual stage has a Hi/Lo power switch, no BTL (Bilateral or Preamp). On Hi, it uses all tubes in the 4 driving 8 configuration. On low, the 8 final power tubes are not used and it just uses the 4 driver tubes connected to the outputs. On the later (newer) Phantoms Triple stagers, they use all 10 tubes, 4 driving 6, all the time, but they also have a center tap on the High Voltage, so the B+ or high voltage has 2 voltages. Around 900 Hi and 450 Low. With the combination of 2 power switches, you get 3 power levels. Hi uses 900v (Hi) ti both the driver and final tubes, Medium gives the Low voltage to the driver tubes and Hi to the finals, and Low gives the low voltage to both the final tubes and driver tubes. Since you are not using the drivers for finals in that configuration, the 2nd set of Tune and Load for the drivers is not needed / not there. D&A Phantoms are very nice vintage workhorses, but God help you if you need to retube it. Peace and Happy new year.
