# Pyramid power supply regulating poorly

D

#### Dan

Jan 1, 1970
0
I've had a 13.8 V, 12 A Pyramid power supply for several years that
I've used with a battery charger to charge flight packs for my RC
aircraft. Part of the operation of the charger is to charge at a
given current for one minute and then drop the current to 0 A to take
a voltage reading on the pack. In the last year, the power supply has
started to shoot the voltage up to > 15 V temporarily when the charger
performs this action. The regulating circuit in the supply seems not
to be able to handle the sudden load change. The charger, which is
designed to operate with a 10-15 V source, gives an error message
regarding the input voltage and ceases to operate.

My first attempt at a fix was to have a constant load on the supply
with a power resistor across it's terminals. These became to warm,
however, and given where I charge (carpet), I don't want to use them.
Is there a simple fix to this? Maybe a capacitor across the supply
terminals to soften the sudden voltage change?

My typical charging currents would draw 2-6 A from the supply.

Thanks,
Dan

J

#### John Fields

Jan 1, 1970
0
I've had a 13.8 V, 12 A Pyramid power supply for several years that
I've used with a battery charger to charge flight packs for my RC
aircraft. Part of the operation of the charger is to charge at a
given current for one minute and then drop the current to 0 A to take
a voltage reading on the pack. In the last year, the power supply has
started to shoot the voltage up to > 15 V temporarily when the charger
performs this action. The regulating circuit in the supply seems not
to be able to handle the sudden load change. The charger, which is
designed to operate with a 10-15 V source, gives an error message
regarding the input voltage and ceases to operate.

My first attempt at a fix was to have a constant load on the supply
with a power resistor across it's terminals. These became to warm,
however, and given where I charge (carpet), I don't want to use them.
Is there a simple fix to this? Maybe a capacitor across the supply
terminals to soften the sudden voltage change?

My typical charging currents would draw 2-6 A from the supply.

D

#### Daniel Nash

Jan 1, 1970
0
Well, as far as a warranty, it was only good for a year. I've had this
supply for about 4. It is only a ~$35 supply, so just looking for a simple fix. ~Dan R #### Rich Grise Jan 1, 1970 0 Daniel Nash said: Well, as far as a warranty, it was only good for a year. I've had this supply for about 4. It is only a ~$35 supply, so just looking for a simple
fix.
For $35.00, it's only worth repairing as a training project, if you want. The thing is broken. Do Not try any work-arounds, you'll just break something else. Spring the$35.00 for a new supply.

Have Fun!
Rich

R

#### Robert C Monsen

Jan 1, 1970
0
Dan said:
I've had a 13.8 V, 12 A Pyramid power supply for several years that
I've used with a battery charger to charge flight packs for my RC
aircraft. Part of the operation of the charger is to charge at a
given current for one minute and then drop the current to 0 A to take
a voltage reading on the pack. In the last year, the power supply has
started to shoot the voltage up to > 15 V temporarily when the charger
performs this action. The regulating circuit in the supply seems not
to be able to handle the sudden load change. The charger, which is
designed to operate with a 10-15 V source, gives an error message
regarding the input voltage and ceases to operate.

My first attempt at a fix was to have a constant load on the supply
with a power resistor across it's terminals. These became to warm,
however, and given where I charge (carpet), I don't want to use them.
Is there a simple fix to this? Maybe a capacitor across the supply
terminals to soften the sudden voltage change?

My typical charging currents would draw 2-6 A from the supply.

Thanks,
Dan

I'm not so sure its your supply. Maybe your charger is getting more
sensitive to this over time? I'm guessing your supply isn't regulated,
and maybe its always done this?

You could get a 14V 1/2W zener diode, and put it across the supply. If
it spikes, the zener will keep it from getting higher than 14V. It
should not put much current across the zener. If it does, and the
zener smokes, I'd get a new supply, or open it up and try to replace
whatever regulator part is in it.

For zeners, try one of these:

http://www.mouser.com/index.cfm?&ha...4V&Dk=1&D=*zener*+*diode*+*14V*&N=0&crc=false

You can also probably get these at RS.

Regards,
Bob Monsen

J

#### John Fields

Jan 1, 1970
0
Well, as far as a warranty, it was only good for a year. I've had this
supply for about 4. It is only a ~\$35 supply, so just looking for a simple
fix.

---
My point wasn't that you should exercise a warranty, it was that the
manufacturer would more likely have the information you needed to fix
it (schematics, troubleshooting advice, etc. or maybe, even, a
pay-for-repair option...) than we would. A simple email or a phone
call would probably get you what you needed. Plus, there are the
repair newsgroups, which would more likely be able to help you better
than we could.

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