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			December 2, 1976

HP-1144							Bulletin

No:

Power Supply						HP-1144-1



	 Precautions necessary when using as a 12VDC Bench Supply



If HP-1144 is used for test power supply, the 20A output fuse should be

replaced with a low amp fuse when repairing HW-8, HW-7 or other low

current units.  Failure to do this may result in foil burns in the event

of solder or foil bridges, the foil will not withstand 20A at 12VDC.

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			July 24, 1978

HP-1144A						Bulletin No:

Power Supply						HP-1144-2



	              New Product Information for the HP-1144A



An updated and improved version of the HP-1144 Power Supply is about to

be shipped.



The "A" version is identical in size and specifications, but has one

outstanding feature: a "crowbar" protection circuit.



Unlike its predecessor, the Hp-1144A will "shut down" when the DC output

voltage at the connector execeeds 15.5 volts.  By opening the DC line

fuse, F2, the current flow to the unit under load is interrupted.



The over-voltage protection will be of great advantage.  Many units will

be saved from the 28-volt surge which happened when various components

malfunctioned in the original supply.



A modification kit [PN 830-33] will be available at the end of August for

customers wishing to update their present HP-1144 Power Supplies.  The

"mod" kit consists of a new circuitboard with all components, plus

new-type pass transistors.  The board is to be installed and wired in

place of the existing circuit board.  Selling price will be approximately

$9.00.

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			November 20, 1978

HP-1144A						Bulletin No:

Power Supply						HP-1144-3



	Fuse Blows When Switchng From Tune to Receive Mode Or

	                      On Voice Peaks At High Power Output



High RF power or high voice peaks can cause the SCR to trigger in the

HP-1144A and blow the fuse.



To prevent this, install a .1 uf capacitor [PN 21-195] from the anode

lead to the gate of the SCR.  Remove the brown wire from the gate lead to

hole G on the circuit board.  After you pass the one capacitor lead

through the gate lead, slip a piece of sleeving [PN 346-1] over the lead

and insert the free end of the lead into hold G and solder.  Then

resolder the anode connection [large lug] with the new capacitor lead and

heavy brown wire attached.



This change will appear in new production.

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			March 7, 1980

HP-1144							Bulletin

No:

Power Supply						HP-1144-4



		         Crowbar Circuit Blows Fuse



+ + + + Information not yet available + + + +

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