High Voltage Forum

General electronics => Electronic Circuits => Topic started by: v.coelho on September 23, 2020, 01:11:50 PM

Title: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: v.coelho on September 23, 2020, 01:11:50 PM

Hello,
I start by saying that I am new to this theme of Server PSU. But I bought a Server PSU to use as a power supply for my CB radio, to use with 13.8V, the PSU I bought was Fujitsu DPS-800GB-5 A (as you can see in the pictures).
I managed to turn on the PSU by connecting pins 31-34 and 26-GND. However, the problems started when I tried to increase the output voltage using a potentiometer between the 32-GND pins, just above 13.3v the overvoltage protection circuit disconnects the PSU output.
After some research I found out that a possible solution would be to disconnect one of the pins from the OVP chip, but I can't find the OVP chip on this PSU.
Can someone help me?

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: Zipdox on September 23, 2020, 01:34:42 PM

Can you make some internal photos? Preferably high quality so we can read ICs.

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: petespaco on September 23, 2020, 04:26:34 PM

I haven't used a CB radio in a car since about 1980, but I don't understand why NEED 13.8 volts.  The thing should run off a car battery with the engine off, shouldn't it?  I'd think that anything over about 12.0 volts should be fine.

Pete Stanaitis
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Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: v.coelho on September 24, 2020, 01:11:27 PM

Here is a picture of the chips in the PSU I marked the references

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: klugesmith on September 24, 2020, 03:02:00 PM

I agree with Pete.  Set the PSU to 13 V and start using the radio.

At 13.0 you are most of the way to nominal voltage of the radio set. Probably within the radio's rating.
You retain the benefit of OVP, so a random component failure in PSU won't destroy the radio.

Disabling OVP can be more excusable than bypassing a fuse so you can get a little more current out of something.
Am reminded of getting 120 volts directly from car engine alternators, by changing the rectifier diodes and modifying the voltage regulation (field current control).

At least one 4-channel amplifier IC for OEM car audio equipment needs 14.4 V DC to reach its nominal power output.
What's the nominal DC voltage for great big car amplifiers and associated ultracapacitors? 

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: Bjoe10 on September 02, 2021, 09:12:12 PM

Hi! I got the same power supply and i want to remove the ovp because i need 14v to power my project

Does somebody has any idea?

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: stefunk on February 11, 2023, 05:10:52 PM

Hi,

I bought this PSU, and can't find information about bypassing OVP, or disabling it, did anyone succeed with doing so, or found instructions somewhere?

Title: Re: Server PSU OPV Hack - Fujitsu DPS-800GB-5 A
Post by: Mikixyz123 on August 15, 2023, 05:00:04 PM

Hello, I think of buying that power supply too. Can someone tell me how noisy it is? (On idle/no current draw)