Help! HP 6434b DC Power Supply problem

[itsmerandy]

Hello I am trying to get my Power supply working and apparently don't have the knowledge to figure it out. Anyways its an HP 6434b DC Power supply and the problem is that it won't adjust to the settings I need. For example - if I set Voltage to 15 vdc I can't get amperage above 10 amps or vice versa. its like it wants to keep the meters similar in voltage and amperage. If I need 25 amps I have to crank the voltage up to 40 vdc. This is using a dummy load 1.6 ohm's. If I use a 10 ohm load I can't get amperage over 10 amps and voltage is around 10 vdc as well. I have gone over this circuit board many times testing components and everything test like its should. I have downloaded the service manual as it is readily available online for download and followed diagnostics with no luck.   PLEASE HELP!!!!  I have spent hours trying to resolve this! Just need a circuit guru to help me.
Thanks!

[VK5RC]

Remember the current is related to the voltage divided by the resistance, 40v/1.6ohms is about 25A. The 40A will require a load less than 1ohm at 25V.

The current knob sets the limit to which the current will go, not the actual current. The voltage is the main parameter set, the current can, if the load is low enough resistance, go up to the limit set, then the supply will drop the voltage to keep the current under the set current limit.

[itsmerandy]

Remember the current is related to the voltage divided by the resistance, 40v/1.6ohms is about 25A. The 40A will require a load less than 1ohm at 25V.

The current knob sets the limit to which the current will go, not the actual current. The voltage is the main parameter set, the current can, if the load is low enough resistance, go up to the limit set, then the supply will drop the voltage to keep the current under the set current limit.

   I think I'm just use to the digital  power supplies I have and  you just set them for what you want. No wonder I couldn't find any bad components. 

Thank you!

[Monkeh]

Remember the current is related to the voltage divided by the resistance, 40v/1.6ohms is about 25A. The 40A will require a load less than 1ohm at 25V.

The current knob sets the limit to which the current will go, not the actual current. The voltage is the main parameter set, the current can, if the load is low enough resistance, go up to the limit set, then the supply will drop the voltage to keep the current under the set current limit.

   I think I'm just use to the digital  power supplies I have and  you just set them for what you want. No wonder I couldn't find any bad components. 

Thank you!

I think you just need to learn and understand Ohm's law.