August 15, 1979

HP-13 Series						Bulletin No:

DC Power Supplies						HP-13-1



		         Using HP-1144A as Bench Supply



When using the HP-1144A as a bench supply to check the  HP-13 series of

DC power supplies, the crowbar circuit in the  HP-1144A may cause the 20A

fuse to blow at turn-on.  This is due to high turn-on current of the 

HP-13 causing the  HP-1144A regulator circuit to compensate for sudden

output voltage drop.  This, in turn, causes an instantaneous voltage

increase to the crowbar circuit and causes the  20A fuse to blow.



So, when using the HP-1144A to test the HP-13's, disconnect the cathode

of the SCR Q4 to disable the crowbar circuit.



Be sure to reconnect the cathode lead to Q4 after servicing the HP-13.

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