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Looking for help - HP Netser LC wants to be live again

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First post, by mita

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Hi,

I got a HP Netserver LC motherboard with DX4 CPU board and control panel. I tried to switch it on but it was not sucessfull and I need help to figure out how the switch on is working on this MB.

I mean unsuccessfull start on switch on:
- No picture
- No post code on the PCI post analyser panel
- Reset button on control panel can not provide reset on the PCI bus

Unfortunately I found only one document describing the LC model in 10 pages: https://theretroweb.com/motherboard/manual/hp … 75452824081.pdf
This is just basic info, more than nothing but quite less to be more useful. A user manual would be quite handful to describe the front control panel, especially the led's functions.
The server PSU part number: 5063-5689. I was not able to find any usable info about this PSU on the net.

The MB has 4+1 power related connectors:
- P1 and P2 seems to be a normal AT power supply P8-P9 connector according to the pinout printed on the silkscreen. Of course it is possible HP changed the operation of these pins especially PWGOOD. The PWGOOD signal maybe inverted who knows.
- P3 connector for 3.3V only. All the 3.3V input pins are wired together. P4 is GND all. P3-P4 are not P8,P9,P14 style because the notches on the connectors are different otherwise it is identical. I used a P14 connector, cut the notches and rearranged the pins to have 2x3.3V and GND on the connector.
- J3: "Power Supply On". Pin1 is GND, Pin2 is ?, Pin3 is a signal output. This three pin connector probably connected to the PSU and my problems start here. I assume - maybe I am wrong - the MB signals the PSU via J3 - Pin3 to switch on when the control panel's power on switch is switched on. Switching on "MY PSU" provides power to the P1,P2, P3. J3-Pin3 has a 5V level with control panel's power switch switched off. J3-Pin3 goes low when control panel's power switch switched on. This level change should start the server's PSU. The only problem that it seem to me there should be a standby voltage present in order to work the power on sequence correctly. Power standby should provide power to the control panel's power switch and circuit to be able to signal the PSU to switch on via J3-Pin3. But I was not able to identfy where the standby voltage provided to the MB if any. My candidate would be J3-Pin2. It has megaohm resistance to GND.

Checked all power rails, voltage leves are OK on P1-P3 when I manually switched on "MY PSU", a standard 200W AT PSU.

Unfortunately I was not able to trace J3-Pin2. Difficulties just growing: it seems there is NO standard super IO chip on board, HP decided to use this custom gate array chip instead of: https://theretroweb.com/chips/11090. Reset circuit is handled by a PAL22V1O as well just to "ease" the debugg process.

So I am a bit stucked in the revival process right now.
I would appreciate any help:
- info about the servers's PSU, especially the pinout of J3
- user, service manual of the server, especially the functional description of the front control panel
- if anybody has this type of server by any canche at home working than a voltage measurement on J3-Pin2 at plugged in but switched off state to check the possible standby voltage presence.
- any other ideas how to proceed forward with the debugg process.

Reply 1 of 3, by eisapc

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I need to check my local archives.
Got several Netservers from this generation at home, including LM, LH, LH+ and LHpro.
They probably share the same PS?

Reply 2 of 3, by mita

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eisapc wrote on 2026-01-22, 09:34:

I need to check my local archives.
Got several Netservers from this generation at home, including LM, LH, LH+ and LHpro.
They probably share the same PS?

Sorry for the late reply, waiting for copper bushes for helping the trace discovering.

Some basic info can be found in the following document: https://theretroweb.com/motherboard/manual/hp … 53889106387.pdf

On the page 130 the LM servers mother board layout show different power connector placement (3 PSU connectors) with no designation. One notable difference is the PSU enable connector. Based on these I suspect this product line use a modified PSU, with different power connectors.

What I am curious to know is where the standby voltage goes to the MB? On the front IO panel a standby voltage should be present to sense the PW on button. This standby source should power the SIO custom logic chip. If this trace can be found than the power connectors' standby pin could be identified. Based on this I can modify my custom ATX PSU connector.
Next step would be to trace the PS_ON-PS_GOOD signals between the SIO chip and the power connectors. Measuring these lines could help to figure out the right levels and sequence of handshaking and my custom PSU should be modified based on this. I am sure HP made some trick like inverted levels of handshaking signals comparing to the standard AT,ATX just for fun.

One important step before crawling deeper in this hole: check the cpu and the bios status. Maybe the processor board got all the power and signals but there are other problems.

Time is a scarse resource but I will try.

Reply 3 of 3, by mita

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OK, some progress regarding standby voltage.

Sending high regards for the HP engineer designing this PCB. All the power connectors' pins are designated except for the last two pins of P4. Nothing on the silkscreen just empty spaces. How difficult would be to put the +5VSTBY label next to the GND label.

Anyway. I backtraced the power on switch on the control panel's switch to GND signal to the U21 Altera EP224. Datasheet: https://www.artisantg.com/info/Intel_Altera_E … 19225151830.pdf
This chip is powered by 5V and it was easy to find the last two pins of P4 connected to the EP224 28 pin as VCC.

The possible power on sequence:
- 5V standby on P4 last two pins
- P2 pin1 PWR_OK is High by the PSU signaling the rails are ready
-J3 Power Supply ON Pin3 goes Hi to Low switching the power switch On on the control panel. It seems as standard ATX switch on process.

I am going to modify my custom ATX PSU:
- adding one more trimmed P14 connector with GND and 5V STDBY
- adding a 3 pin connector (fan connector) with GND on Pin1 and PS_ON on Pin3

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