astrohoof

 The Dell p/n Y1224 - Control Panel, with power button, for Dell 8400 Computers, can be purchased from HERE

The power switch and circuit board is one unit. Dell has not published a guide to remove the front bezel of the Dimension 8400, you can use this GUIDE,

<ADMIN NOTE: Broken link has been removed / replaced from this post by Dell>

it's for an Optiplex GX50 Small Mini Tower, the procedures are the same.

 A hint: The Dimension 8400 also, has a Hex headed screw on inside right side of front bezel/panel, just below the front USB ports, holding the front panel to the metal chassis, this MUST be removed and is not mentioned in the guide.

Bev.

Bev:  Wow, What marvelous help!  I've already ordered the control panel via your provided link!

I also really appreciate the pointers on getting the front bezel off!  You are a life saver.

Thanks a bunch,

Dennis

Dennis

Happy to have helped.

Bev.

I've a dead power switch on my Dimension 8400 too...

Do you happen to know the pin-out configuration of the front panel connector?

Such that I might be able to power up the Dimension by shorting the power switch pins?

The front panel is not Pins.  The power button goes to a 16 pin ribbon cable to a U1456 Board

 There is a 20 pin ribbon connector that goes to a front panel board W3300.

Pinouts are not available not posted for any dell.

Helps to know What Model Case.   The Dells have a Naming Convention.  Most 8400 used the Skydive Tower Chassis.

Dimension 8400 Front I/O USB Audio Panel Board M5989

Dell Optiplex GX280 Sm MiniTower Front I/O Control Panel, Dell W3300

Dell™ OptiPlex™ GX280 Systems User's Guide

 

Sorry, I meant the pin configuration for the ribbon connector on the motherboard. My simplistic plan was to just remove the ribbon to expose the pins and then short the power pins with a screwdriver to boot up the dimension... :) Thereafter, go into the bios and configure it such that it will power on when electricity is restored. Not sure if this is a futile idea?

Thanks, realised that that was the case... But I guess it is still possible that someone here might have mapped out the pin configuration on their own accord?

Thanks, realised that that was the case...

But I guess it is still possible that someone here might have mapped out the pin configuration on their own accord?

U1456 Via 16 Pin Ribbon plugs into > M5989 Board then Via 20 pin Ribbon Plugs into >motherboard.

You would have to reverse engineer the 2 boards and ribbon cable to figure out which goes where.

Seeing as the Pins are VERY VERY TINY for the Front Panel Ribbon I do not believe that anyone ever tried this.

If I Did do such a thing it would be to the Pins on the 16 pin header which are inside on the back face of the machine

ITEM #1

With a meter it should be possible to trace the push button pins on the Front Control Panel Board.

HOWEVER Given the AGE of this system its much more likely that the power supply is bad.

Not sure if this link actually holds the key?

scarvell.net/.../index.php

Which pins do I short to simulate a power button press?  Pin 20 and... ?

That Link is a good Guess.   OM686:Dell 0M686 GX260 TOWER Front USB Audio Panel is the same on the GX280 and Dimension 8400 etc with SKYDIVE Mini Tower.  I don't see an exact correlation between this and the power switch however.  If you guess wrong you may damage things. 

Looks Very Similar to

http://www.lnmdesign.com/400sc/front_pnl.html

Front Panel

Located halfway up under the front bezel section with the ventilation holes.

Photo available of the backside and a super-duper overlay and a bigger size front.

Connector List:

• CTRL_PNL: Control Panel connector, 16-pin, two-row, jumper-spaced, Pin 1 is missing, blocked on the connector.
• FNT_PNL: Front Panel (connects to motherboard). 34-pin, two-row, tight-spaced, Pin 21 is missing.
• AUDIO_CABLE: Connects to motherboard. Single-row, 10-pin, tightly-spaced; Pin 7 is missing.
• INTRUDER: Connects to the chassis intrusion detector switch. Single-row, 5-pin, jumper-spaced. 5-pin version of the 4-pin CD-AUDIO connectors.
• EXT_SPK: Optionally connects to external speaker.
• HP_OUT: Headphone out. Stereo 3.5mm jack.
• USB_FNT: Front USB connectors. Double USB connector.

CTRL_PNL

See Control Panel documentation.

From the pin-side:

Pin	Description	Connects to FNT_PNL Pin
1	Removed and blocked on the connector	—
2	PWR SWITCH LEFT SIDE (Both)	20
3	GND	GND
4	HDD LED NEG	22
5	PWR LED GREEN POS	23
6	HDD LED POS	5 thru R19
7	GND	GND
8	ESUP SWITCH RIGHT SIDE (Both)	28
9	PWR LED YELLOW POS	27
10	N/C	—
11	GND	GND
12	N/C	—
13	ESUP LED NEG	24
14	ESUP LED POS	5 Thru R20
15	GND	GND
16	GND	GND

FNT_PNL

From the pin-side:

Pin	Description	Connects to
1	INTRUDER 3	INTRUDER 3, FNT 32
2	VCC ??	FNT 3, FNT 4
3	VCC ??	FNT 2, FNT 4
4	VCC ??	FNT 2, FNT 3
5	LED VCC	CTRL 6 thru R19, CTRL14 thru R20
6	?
7	?
8	INTRUDER 5	INTRUDER 5
9	GND	GND
10	GND?	GND?
11	GND	GND
12	?
13	?
14	GND	GND
15	?
16	GND	GND
17	?
18	?
19	GND	GND
20	PWR SWITCH LEFT SIDE (Both)	CTRL 2
21	Pin removed	—
22	HDD LED NEG	CTRL 4
23	PWR LED GREEN POS	CTRL 5
24	ESUP LED NEG	CTRL 13
25	GND	GND
26	?
27	PWR LED YELLOW POS	CTRL 9
28	ESUP SWITCH RIGHT SIDE (Both)	CTRL 8
29	GND	GND
30	INTRUDER 1	INTRUDER 1
31	EXT_SPK 2	EXT_SPK 2
32	INTRUDER 3	INTRUDER 3
33	EXT_SPK 4	EXT_SPK 4
34	EXT_SPK 1	EXT_SPK 1

AUDIO_CABLE

From pin-side:

Pin	Description	Connects to
1	GND	GND
2	OUT LEFT	3.5 jack tip
3	GND	GND
4	OUT RIGHT	3.5 middle ring
5	GND	GND
6	?
7	Pin removed	—
8	?
9	?
10	GND	GND

INTRUDER

From pin-side:

Pin	Description	Connects to
1		FNT 30
2	GND	GND
3		FNT 1, FNT 30
4	GND	GND
5		FNT 8

EXT_SPK

From pin-side:

Pin	Description	Connects to
1		FNT 34
2		FNT 31
3	GND	GND
4		FNT 33

HP_OUT

From solder-side:

When unconnected to a 3.5 jack:

When connected to a jack:

Pin	Description	Connects to
1	SENSE	GND if connected, otherwise Base Ring (floats)
2	GND	GND
3	SENSE	GND if unconnected, otherwise floats
4	SENSE	GND if connected, otherwise Base Ring (floats)
5	GND	GND
6	SENSE	GND if unconnected, otherwise floats
7	Left channel	Tip
8	GND if connected, otherwise floats	Base Ring
9	Right channel	Middle Ring

USB_FNT

This I cannot be bothered with, way too many surface mounted components. You are welcome to drop me an email (@ 400sc-at-peterlada-dot-com) if you draw a circuit diagram, or have any info.