Re: T912 storage oscilloscope - No 2.7 KV high Voltage


Roger Evans
 

Attilio,

You say 'CR468 diode continues to boil', which implies that something is drawing too much current from the -120V supply. Which capacitor did you change? Can you measure the voltage across R469 and maybe check that the value of R469 is reasonably close to 1.2k? If this excess current is going to the storage board (rather than a leaking C469) then something will probably be very hot. It is not safe to touch components while the board is powered since there is 220V (and +335V!) in places but you can check that the -120V and -220V (and also +335V) have decayed a few seconds after the scope is turned off and then try touching a few components. I would start with Q942, Q944, Q946 and Q948.

Be very, very careful about not touching the parts which have high voltages (ie more than 50V) on them!

Regards,

Roger

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