Re: Tektronix 532 LV rail shorted


randolphbeebe@...
 

I have been away from my computer for a few days and finally have been able to try Rajesh's diagnostic suggestions. All the tubes were previously checked but I re-checked all the rectifier tubes and they were all good with no shorts. With all the tubes in place C640 and R110 were getting hot when the scope is powered up with a current limiter.

-I removed V605 and V606 from the sockets and powered it up. C640 no longer gets hot but R110 still does. R110 gets hot so quickly that if I left the power switch on for more than 90 seconds I am certain it would burn in half . This is without a plug-in installed

-Voltage across C640 measures 0V DC and around 80V AC which is about the same whether or not V605-V606 are installed. (Measured when C110 was disconnected to remove ground and short on R110, C110 is a new cap and still tests good)

-Filament voltage measures 2.3V AC across Pins 2 and 8 of 606

Once again This is through a Variac with 90V selected. When the scope is turned on this value reduces to 50V.

It was suggested that perhaps C110 was installed backwards, the schematic indicates the (-) lead to ground. I tested it when C110 was installed in both directions and the results are the same either way.

The pertinent schematic photos are under the Tek 532 folder

Thanks Again Guys

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