DC686 Fuser Setup

The DC1A686 is a DisplayPort compositor: it takes the picture from your main PC and your second PC and combines them into one image on a single monitor, so the overlay your second PC draws sits on top of the game. This guide covers the connections, the five buttons, the status lights, the on-screen parameters, firmware updates, EDID injection, and how to push a monitor to a high refresh rate.

The source manual is dated 15 October 2026. Specifications and model names follow it.

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Downloads

What	Link	Password
Common tools (serial driver, utilities)	wwqt.lanzoum.com/b04wf3l0b	6666

Open the link, enter the password in the box it asks for, and the file list appears. It holds the vendor's tools: the Serial Port Management Tool (firmware and EDID), the serial driver, and miscellaneous utilities.

Firmware is not a separate download for this unit — the configuration tool checks the vendor's server and updates the device over USB-C. See Firmware upgrade.

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1. Connections

Left to right: DC 12 V power, capture USB-C, data USB-C, secondary PC DP, main PC DP, monitor DP. The silkscreen under each port is in Chinese — the table below gives the same order in English.

Port	Purpose
DC 12V	12 V, 3 A power supply
Data USB-C	Debugging and firmware upgrades. Can stay disconnected in normal use
Capture USB-C	Video capture output; requires USB 3.0 or later. Can stay disconnected if you do not capture
Main PC DP	Main PC graphics card
Secondary PC DP	Second PC graphics card
Monitor DP	The monitor you look at

All three video connections are DisplayPort 1.4, so there is no HDMI/DP mixing to worry about — unlike the HDMI-based fusers.

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2. Buttons

Left to right: K1, K2, K3, K4, K5, then the three indicator pairs, then the red power button. The silkscreen under each button reads 按键K1–K5, so they identify themselves.

Each button does one thing on a short press and another on a long press.

Button	Short press	Long press
K1	Show the parameters in the top-left corner	5 s — switch between EDID injection mode and automatic adaptation
K2	Increase chroma-key strength (5–255)	5 s — regenerate the monitor ID, serial number and other monitor information. The device restarts and the power light flashes rapidly 5 times
K3	Decrease chroma-key strength (5–255)	3 s — reserved
K4	Switch compositing modes	5 s — restore factory settings: native EDID back, chroma key to 20, capture to DP0, injected parameters cleared. The power light flashes rapidly 5 times
K5	Show only the main PC or only the second PC, disabling compositing and chroma keying	3 s — reserved

Power switch: press in to power on, release to cut power.

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3. Status lights

The indicators sit between K5 and the power button. Upper row: power, secondary PC, compositing. Lower row: display, main PC, capture.

Indicator	Meaning
Power	Steady when powered normally
Display	Steady when the monitor is connected. Slow flash while connecting; off if the monitor is off or unplugged
Secondary PC (upper layer)	Steady when connected. Off means the compositor and the second PC are not talking — check both ends of the cable, restart the second PC
Main PC (lower layer)	Steady when connected, slow flash while connecting. Off means check both ends, restart the main PC
Compositing	On when compositing is enabled, off when disabled
Capture	On while capture is in use

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4. On-screen parameters

Short-press K1 to show these.

Parameter	Meaning
DP0	Main PC (lower layer) resolution and refresh rate. [Y] means only this image is displayed
DP1	Second PC (upper layer) resolution and refresh rate. [Y] means only this image is displayed
EDID mode	AUTO — automatic adaptation (default). EDID — injection mode
ALPHA	Chroma-key strength. Default 20, range 5–255
RH	ON compositing enabled, OFF disabled
CJ	Capture mode. DP0 captures only the main PC, DP1 captures the composited image
SN	Monitor serial number currently presented
ID	Monitor ID currently presented
FW	Firmware date
TEMP	Device temperature, live
DNA	Unique chip identifier

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5. Firmware upgrade

Connect the Data USB-C port to the PC and open the Dichen Technology Serial Port Management Tool (v1.3.0 or newer, from the tools download).

1. Select the detected COM port and connect to the device.
2. Open the Firmware Upgrade tab. The tool checks the vendor's server automatically, or click Check Firmware.
3. If a newer version is listed, select it and click Download and Upgrade.

What to expect: if the compositor is in use, the screen goes black during the transfer. It takes up to about four minutes, after which the device restarts by itself.

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6. EDID injection

Use this to make the compositor present a specific monitor identity, usually to unlock a refresh rate the panel does not advertise, or to fix a display that will not sync.

Connect Data USB-C, open the same tool, go to EDID Management, then:

1. Click Select File and choose an EDID .bin. Click Check File to validate it — the tool reports the size, block count and CRC32.
2. Click Inject EDID. The tool uploads the file and reads it back to verify.
3. Press K1 to confirm the mode. Injection leaves the device in EDID mode; Switch to AUTO returns it to automatic adaptation.

Screen behaviour: in EDID mode the screen goes black for a few seconds while the sink re-handshakes. In the default AUTO mode it does not go black.

Things worth knowing from the manual's own notes:

• EDID V2 is shared by the main and second PC — one file, applied to both paths — and is stored in the device's flash, so it survives a power cycle.
• The status panel shows whether the file was saved, what mode is currently applied, and whether a switch is still pending. Wait for a pending switch to finish before injecting again.
• If an upload is interrupted, End Stale Session clears the half-finished state before you retry.
• Export Injected Source File and Export Current Working Copy let you download what the device is actually using, which is the fastest way to check what is really applied.
• AUTO stays in AUTO after an injection on supported devices: it replaces the EDID in place and restarts the handshake on both paths.

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7. Refresh-rate setup

Start in Windows Display settings. Rates up to 1K 600 Hz / 2K 360 Hz / 4K 160 Hz can usually be selected directly.

For anything above that, and anything missing from the monitor's EDID presets, create a custom resolution in the graphics card control panel:

1. If the pixel clock stays under 1430 MHz, you can simply raise the refresh rate and save.
2. Above that, choose CVT-RB (Coordinated Video Timings – Reduced Blanking, called "CVT – Reduced Blanking" in older panels), then reduce the horizontal and vertical total pixel counts.
3. In some cases, set the colour format to YCbCr 4:2:2 before creating the custom resolution — and remember the chroma-key strength should be 20 for 4:2:2.

Limits that catch people out:

• AMD integrated graphics generally cannot create custom resolutions. Use the default rates.
• Windows 10 caps at 500 Hz. Above that, Windows 11 is required.
• Some monitors need DSC disabled in their own on-screen menu before high rates can be set (the manual cites the MPG341CQR X36).
• Some monitors need the input mode changed from DP 1.2 to DP 1.4, or from AV to PC mode (the manual cites the Samsung LS27FG602SCXXF).

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8. What each card can reach

With default settings and only the refresh rate changed:

Graphics card	720p	1080p	1440p	2160p
RTX 50 series	1000 Hz+	639 Hz	364 Hz	164 Hz
RTX 30 / RTX 40	1000 Hz+	550 Hz+	339 Hz	150 Hz+
GTX 10 / GTX 20	1000 Hz+	480 Hz+	271 Hz	144 Hz+
AMD RX 6000 / RX 7000	1000 Hz+	639 Hz	364 Hz	164 Hz
AMD RX 500 / RX 5000	1000 Hz+	480 Hz+	320 Hz	144 Hz

720p = 1280 × 720; 1080p = 1920 × 1080; 1440p = 2560 × 1440; 2160p = 3840 × 2160.

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9. Recommended custom timings

These are the vendor's figures for pushing a panel beyond its native presets. Test your own monitor's limits carefully — the section after this one is what to do when a timing is too aggressive.

1920 × 1080

With only the refresh rate changed: 50-series cards reach 600–639 Hz, 40-series 540–600 Hz.

Timing totals	Horizontal	Vertical
Minimum	2040	1117
Common	2080	1215

Example manual timing: active 1920 × 1080, front porch 88 / 4, sync width 44 / 5, totals 2080 × 1215.

2560 × 1440

50-series reach 350–364 Hz, 40-series 320–339 Hz.

Timing totals	Horizontal	Vertical
Minimum	2680	1481
Common option 1	2720	1481
Common option 2	2720	1525

Example manual timing: active 2560 × 1440, front porch 48 / 3, sync width 32 / 5, totals 2680 × 1481, polarity positive horizontal / negative vertical.

3840 × 2160

50-series reach 144–164 Hz, 40-series 120–144 Hz.

Timing totals	Horizontal	Vertical
Minimum	4000	2200
Common option 1	4000	2250
Common option 2	4000	2332

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10. No picture after a restart

If a custom refresh rate leaves the compositor frozen with no picture after a restart, there are three fixes. They apply to either PC.

Solution 1 — regenerate the monitor information (recommended). Hold K2 for 5 seconds. The device regenerates its monitor ID and serial, and the PC sees it as a brand-new monitor. In NVIDIA Control Panel, delete every previously created custom resolution, set the colour format to YCbCr 4:2:2, and recreate the resolution.

Solution 2 — connect the monitor directly. Unplug the compositor and connect the monitor straight to the PC, using the same DisplayPort connector on the card — NVIDIA's settings differ per connector. Delete the custom resolutions, reconnect through the compositor on that same connector, set YCbCr 4:2:2, and recreate the resolution.

Solution 3 — use another DisplayPort connector. Move to a different DP output on the card and recreate the custom resolutions there. NVIDIA does not synchronise these settings between connectors, so the old ones do not carry over.

This problem only affects custom resolutions — stock refresh rates are unaffected.

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Quick reference

Symptom	First thing to try
No picture, display light off	Check the monitor cable and power; the Display light should be steady
One PC missing from the picture	Check the Main PC / Secondary PC indicator; restart that PC
Compositing stopped working	Check the Compositing light, press K4 to cycle modes, K5 to switch sources
Nothing responds after a firmware update	Hold K4 for 5 seconds to restore factory settings
High refresh rate not offered	Section 7: YCbCr 4:2:2, CVT-RB, then custom timings from section 9
Frozen after a custom resolution	Section 10 — and delete the old resolutions first