I recently acquired a Commodore 1084S-D2 monitor, along with a C64 - both were not working when I received them (C64 is now up and running - see here for worklog). The D2 variant was manufactured by Daewoo for Commodore in the early 90's. I thought initially that the 1084S was showing some signs of life (de-gauss sounds when switching on) but shortly after setting it up for testing it died completely, and then the power switch failed also - it won't stay locked in anymore, so will have to be repaired/replaced as well (apparently a common issue). So the unit was taken apart for some initial diagnostics. Fortunately I was able to find a schematic on-line which has been very helpful so far. I started tracing out the power supply section, which consists of a switch-mode power supply to generate 2 main voltages - B+ which is around 108V, and a 22V output that supplies the audio amp (1084S has stereo speakers inbuilt). I started by isolating the B+ at the output of the switch mode supply, so as I could attach a load for test and measurement - in this case a 40W light bulb. The switch-mode supply was dead - no output voltage on the secondary side, though I could measure 330V at the main filter cap (C109) on the primary side (after the rectifier), so there had to be a fault somewhere in the switching power supply section. After a quick poke around with the multimeter, I found an open resistor (R111 - which should be 100k and measured open circuit both in and out of the board). After replacing that, the supply was back to life and I was able to measure the B+ output at 108V : So I've put it back together (removed the light bulb and reconnected B+ to where it should be) and retested. Nothing - nothing on the screen at all - brightness control has no effect (even without a video input the screen should "bloom" when the brightness and contrast controls are cranked up). Using my home made high voltage probe (worklog here) I was able to measure approx 23.8kV at the high voltage output on the flyback transformer though, which is in spec : The horizontal output transistor (HOT) and control circuitry must be doing its job, switching the HOT on and off to produce the high voltage output at the flyback, however, there should also be a secondary high voltage output from the flyback which goes off to the board on the neck of the monitor for the focus (around 8kV I think), and it seems that this is missing altogether - I'm measuring 0 volts. This is the flyback transformer - the large red wire is the high voltage output (24kV), and the white wire is the focus output that goes off to the board on the neck of the monitor. So at this stage it's looking like either the flyback has an internal fault with the voltage divider for the focus output, else the connector on the neck board (if that's what you call it!) is faulty. This is where the focus wire runs into the neck connector that plugs into the rear of the picture tube : I think I'll see if I can take that connector apart so as I can see if there is wiring fault inside - it is possible that the focus output voltage is present, but with a poor (no) connection to the board. It could also be a fault with the pots on the flyback, so I'll have a look at them as well.