View Full Version : Electrical BizHub7228 - Possible to turn on DCPS' Sub Power 24VDC via emulated control signal?

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10-22-2021, 08:17 PM
Hello everyone,


This is my first post so I'll try to provide as much detail as possible so as to respect your time. I'm a hobbyist / tinkerer in my spare time with a background in computer programming. Recently I acquired a confirmed-working BizHub7228 that I've since completely stripped down for part & components.

Steps Taken So Far...

I started off by using a multimeter to probe the DCPS blindly; attempting to map out the voltages and groundings coming off the various leads.
I couldn't find the 24vdc leads so I started researching possible causes.
Tried to lookup the board manufacturer (Matshushita Electronic Components(H.K.) Co., LTD.) and part numbers (27LA84510, ETXKN495ACF, no. 5524V) for any kind of datasheet -- found nothing useful.
Tried checked the physical manuals -- found nothing useful.
Finally searched online for the printer model and found a "Service Manual" that explains why I couldn't find a 24vdc lead...

The SW2 (Sub power switch) is located on the PSW2B (Power SW2 board).

Upon the SW2 on, an ON signal is sent from the SW2 to the SCB (System control board) through the OB (Operation board).

As a result, the SCB sends a control signal to the DCPS (DC power source),

thus causing the DCPS to supply +12VDC, -12VDC (7145 only) and +5VDC to all of the boards and options, including the CB (Main body control board).

The SCB (System control board) then sends to the DCPS (DC power source) a control signal

that causes the DCPS to generate +24VDC.

This 24VDC power is supplied to all of the drive boards and options.
(Quote from manual; Format and emphasis mine)

I looked back at wiring of the DCPS trying to find a path for this "control signal" to be sent through.
My best guess is a bank of leads labeled as such...

3-1 RL CON

3-2 L2 CONT

3-3 L3 CONT

3-4 24V EM

3-5 FM1 EM

My next best guess is that "3-1 RL" pin is the right path to send the signal, as RL might be short for "Relay"

The Problem

I can't find a solid definition of "control signal" within any of the manuals I have. I'm not familiar enough with circuit-board-level engineering to really know how to generate the "control signal". My best guess is that the "signal" is a momentary circuit made from one of the SW1 (offline) voltages (12v or 5v) to that "3-1 RL" pin. At this point I really don't want to just start routing voltages to pins I don't understand.


What is a "control signal" as defined in the service manual?
Is it possible to emulate/reproduce this "control signal" without the SCB, OB, and PSW2B components being involved?
Where should that signal be sent to on the DCPS?
Is there a different solution that I should explore instead? (that does not involve the SCB, OB, and PSW2B components)

Additional Resources

The Service Manual and various images of the components can viewed here on dropbox (https://www.dropbox.com/sh/0t0z2z01pc2pthb/AABEhvnxsxPHFhUsy_ZkvxV6a?dl=0).


Please let me know if there is any other information I can provide that would help solve my problem.

Thanks in advance for any help.

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