Is my common cathode diode assembly broken?

[scsi]

Hello all,

I am testing ultrafast rectifier diode with DMM (internal schematic attached)

pins 1 - 2 reads diode drop (0.6V) reverse (infinity)
pins 2 - 3 reads diode drop (0.6V) reverse (infinity)

pins 1 - 3 reads short

Is this a normal behavior?

[daqq]

Should not be. Are you sure you have the right diode?

[scsi]

original part in question is U1640G in TO-220 package and it is from SMPS so it must be ultrafast rectifier 

desoldered one pin and it still reads short accros 1 - 3 pins.

[ogden]

original part in question is U1640G in TO-220 package and it is from SMPS so it must be ultrafast rectifier 

desoldered one pin and it still reads short accros 1 - 3 pins.

Oh, you are measuring in-circuit. Then your initial measurement was OK because often those diodes are used in parallel, pins 1-3 tied together. Why you still measure short between anodes - dunno. Perhaps you think you desoldered one pin but actually did not?

[scsi]

Perhaps you think you desoldered one pin but actually did not?

Might be, these double sided commercial pcbs are pain to desolder without damaging the pads.

Thanks for the info!

[exe]

I propose title "is my common cathode diode assembly broken?".

[David Hess]

Oh, you are measuring in-circuit. Then your initial measurement was OK because often those diodes are used in parallel, pins 1-3 tied together.

Or the two diodes are connected to different points on the same transformer winding producing the same result.