Defender power supply resistor boost

saltbreez

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Hey Guys,

What is the resistor we cut on a Defender class power supply to give a small boost to the +5V?

I am seeing +4.8 at the PS under load...

Thanks,
Saltbreez
 
R10.

Have you replaced the small caps on it? Sometimes they will leak enough to bring the voltage down.

Also check the voltages on the voltage regulator pins. The proper voltages are on the schematics. It is often the voltage regulator going out or one of the reference resistors burning up that will cause the voltage to drop.

ken
 
R10.

Have you replaced the small caps on it? Sometimes they will leak enough to bring the voltage down.

Also check the voltages on the voltage regulator pins. The proper voltages are on the schematics. It is often the voltage regulator going out or one of the reference resistors burning up that will cause the voltage to drop.

ken

Brother Ken, R10 on the Defender style ps is in the +12vdc section. R10 is correct for a Robotron style ps.

I don't recall the Defender style having the same setup for increasing or lowering the +5vdc. I am pretty sure that is why it is recommended to install a 5k pot at R2 to make the +5vdc adjustable.
 
DOH! Skipped right over the Defender remark. On Defender power supplies they used 2 resistors rather than a divider network to get the reference voltages. The goal is to get 5.1VDC to pin 5 of the LM723. R1 = 4990 ohm 1% resistor. R2 = 2150 ohm 1% resistor.

I'd pull one end on each of those and check the values to make sure they haven't changed. If they are ok, I'd try socketing and swapping the LM723.

ken
 
Thanks Guys

DOH! Skipped right over the Defender remark. On Defender power supplies they used 2 resistors rather than a divider network to get the reference voltages. The goal is to get 5.1VDC to pin 5 of the LM723. R1 = 4990 ohm 1% resistor. R2 = 2150 ohm 1% resistor.

I'd pull one end on each of those and check the values to make sure they haven't changed. If they are ok, I'd try socketing and swapping the LM723.

ken

The LM723 was already socketed, replacing it did not help. I will scrounge around and see if I can find a 5K pot.

Thanks, Guys

Harnesses: Defender, Stargate?
 
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