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Hantarex MTC 9000 image squashed vertically
grantspain:
well something is pulling the b+ down thats for sure
be77amyX:
So update! I wanted to test for faults so I rebuilt the circuit in multisim so I could put faults on every component to see what happens. So I used 145V because that was the no load voltage from my PSU and I got exactly the same voltages in the simulation so I don't think there's a problem on the chassis!
So I took the PSU apart and noticed a resistor and a diode soldered to the back of the PCB which aren't on the schematic. I desoldered the resistor and tested.. no change. I desoldered the diode and shorted something out with a flash :-[ now PSU doesnt power up at all! soldered the diode back on.. still nothing. Tested all the fuses and all good but R2 getting super hot. Started testing some diodes and shorted something and blew F2!! Gonna replace F2 tomorrow but any idea what the likely victim of my first short that'd stop it powering up?
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be77amyX:
Replaced the fuse and instantly blew again. found TP3 shorted. Seems to be a BUV48 rather than a BUS48P as the drawing suggests. Can't seem to find anywhere to buy either? Is there a more readily available alternative anyone is aware of?
be77amyX:
Further update! Managed to get my hands on an isolated transformer power supply out of a scrap cab with a Hantarex 9000 in (with no chassis). hooked it up b+ solid at 135v with everything connected!! great! picture still the same (half the screen height with the bottom folded over) then slipped with the probe and shorted pins 2+3 together on the yoke plug cause that's the kind of week I'm having! magic smoke from around the TR18 area! Replaced TR18, R119 and R94, Powers on for a second then shuts down.. Lift a leg of D10 chassis stays powered up, neck glows but no picture on the screen. Just keeps going from bad to worse!!
grantspain:
i think you should consider sending these items to an experienced tech