God dammit! I was watching your video on my TV in a dark room, and everything started to go completely dark for split seconds. At first I thought maybe it is just me closing my eyes, but then I realized that it is not the case; and was afraid that I have retinal detachment or even a brain tumor which is pressing against my nerve causing my vision to disappear for a moment... God dammit...you scared the shit out of me:)
The lowband switch shows a pair of back to back diodes to clamp the input voltage... maybe one of those are blown ? At least they should protect the switch assembly. UPDATE: called it :-) Very nice repair by the way.
Perhaps this has been asked a million times before and I just failed to find the answer, but you could tell me the origin of your introduction music? It's quite good! Is there a longer version somewhere?
So my comment is that you seem to be given this diode protected instrument. I never realized they would give you this component as you seem very happy to receive and use this costly instrument someone burned by accidentally either running an amplifier through it or equally probably lightning backfeed stricken while testing feed lines. Either way the instrument was not usable and you could not fix it without a wire bonding unit. Not sure of the value of the component you purchased from ebay, but I would think if you repaired these machines as hobby time you could quickly cover the cost of purchase unless thousands of dollars and maybe this company has one they might want to sell you that is sub-optimal to them but perfect for you. One failed component will not ruin your business scheme as your comprehensive microwave knowledge is wonderful and every attempt cannot be successful. Those are the laws of probability.
No, I don't but the PSU regulation should be easily enough to trace down. I suggest you start with the FETs for short (if fuses are out), if OK then test the gate resistors are in spec. Often there is a darlington pair transistor that controls the oscillator driver that is triggered from the PCM. You might like to test the zener diodes too. If the zeners are gone, then replace with larger wattage zeners. Check that the large smoothing capacitors are not leaking and might have expanded making the cross at the top expand and the bottom seal loses electrolyte. The capacitors become resistors and pass AC, they get hot and can explode. I hope the pointers help. Oh
This is really an impressive repair, I don't know how many hours has been spent for to work on this! I would be very interrested about die level repairs.
So did you notice that the diode arrays look like Greek Architecture? At 24:00 there are four small stubs surrounding the RF input . Are these to adjust the impedance balance across the input?
