Diagnosing and Fixing TVs That Reject Line-Multiplied Signals from Retro Scalers

A TV that rejects a line multiplied signal is a specific HDMI sync failure caused by non-standard video timings. The OSSC at 5x 320×240 optimized mode outputs at 60.08 Hz with a pixel clock of approximately 162 MHz and a horizontal total of 1952 pixels, not the CEA-861 timing of 1920×1080 at 60 Hz with 148.5 MHz. Some TV HDMI ports, particularly on Samsung TU-series models around 2020, reject this off-spec refresh rate because the EDID reports a maximum TMDS clock of 300 MHz but the actual rejection threshold for non-standard timings sits closer to 225 MHz. The screen stays black, shows "no signal", or flickers in and out of sync. The problem is documented across the Shmups Forum, the OSSC wiki, and RetroTINK support documentation. The community has developed several fixes that do not require changing your scaler or your TV.

Line multiplication is not framebuffer scaling. The OSSC reads each scanline from the console and outputs it immediately, multiplying the lines to a higher resolution with no frame of storage. This produces pixel clock rates and blanking intervals that do not match any standard CEA or CVT-RB timing. At 5x 320×240 optimized mode, the OSSC outputs 1600 active pixels horizontally with 1952 total pixels, 1200 active lines with 1275 total lines, and a vertical refresh of 60.08 Hz. That 0.08 Hz difference from 60.00 Hz is enough for some TV scalers to reject the signal entirely. The HDMI sync fails because the TV expects a timing descriptor in the EDID that matches its internal lookup table. When the scaler sends a timing the TV does not recognise, the TV refuses to lock onto the signal and reports no input.

The rejection is not universal. LG C-series OLEDs from the CX (2020) through C4 (2024) all report a 600 MHz maximum TMDS clock and accept the OSSC's non-standard timings without issue. Sony Bravia X90-series sets from the X90J (2021) onward also handle them. Samsung TU-series and some TCL 6-series models (R635, 2020) are the common offenders. The community-maintained TV compatibility list for the OSSC, hosted by the Video Game Perfection wiki, tracks specific model behaviour. The RetroTINK compatibility list is maintained through the RetroTINK community Discord and a Google Sheet. Check your TV model against these lists before buying any hardware fix.

Which Samsung Models Fail

The search "OSSC no signal on Samsung TV" returns consistent reports across Shmups Forum threads from 2019 through 2023. Samsung TU7000, TU8000, and Q60T series from 2020 are the most frequently named. The symptom is a black screen on HDMI input 1 or 2 when the OSSC is set to 5x 320×240 optimized mode. Switching to 5x generic 4:3 mode, which runs at 60.00 Hz with a pixel clock of 148.5 MHz, restores the image. The Samsung TU7000 EDID reports a native resolution of 3840×2160 at 60 Hz and a maximum TMDS clock of 600 MHz for HDMI 2.0, but community testing shows the actual maximum for non-standard timings is closer to 225-250 MHz. The TV's HDMI port can handle 600 MHz for a standard CEA timing but rejects the off-spec blanking of the OSSC's 5x optimized mode.

What To Try First

If you own one of these Samsung models, try every HDMI port. Some Samsung TVs accept the signal on HDMI port 3 or 4 but not on port 1. Disable HDCP on the OSSC if you have not already. HDCP negotiation adds another layer of sync that can fail on top of the timing rejection. Set the OSSC to TX mode 0 or 1, which adjusts the HDMI transmitter's output swing and pre-emphasis. The ITE IT6613 transmitter on the OSSC has a datasheet-rated maximum TMDS clock of 225 MHz, but community testing finds stable operation only up to approximately 165-170 MHz without additional cooling. If none of these steps work, move to an EDID emulator or an intermediary HDMI splitter.

TV Model	EDID Max TMDS Clock	Actual Rejection Threshold	OSSC 5x Optimised Mode Result
Samsung TU7000 (2020)	600 MHz (HDMI 2.0)	~225-250 MHz	Black screen or no signal
LG CX (2020)	600 MHz	600 MHz	Image displayed correctly
Sony X90J (2021)	600 MHz	600 MHz	Image displayed correctly
TCL 6-Series R635 (2020)	300 MHz (HDMI 1.4)	~225 MHz	Black screen or sync drop
TCL 6-Series R646 (2021)	600 MHz	600 MHz	Image displayed correctly

The RetroTINK 5X Pro uses an Analog Devices ADV7513 HDMI transmitter with a 300 MHz maximum TMDS clock. Its 1440p mode runs at 60.00 Hz with a pixel clock of 237.6 MHz, which is within the transmitter's capability and within the CEA-861 timing for horizontal and vertical parameters. Some TVs still report "no signal" or drop sync intermittently. The cause is not the pixel clock but the EDID negotiation. The RetroTINK 5X reads the TV's EDID and selects an output mode based on what the TV reports. If the TV reports a maximum TMDS clock of 300 MHz but cannot sustain that clock for a non-standard blanking interval, the sync fails. This is the same mechanism as the OSSC rejection, but the symptom is more intermittent: the screen may work for minutes or hours then go black, or it may flicker on and off during resolution switches.

The documented fix is to force the RetroTINK 5X into a specific output mode rather than letting it auto-negotiate. Set the output to 1080p-over mode, which uses a horizontal total of 2200 pixels, 1125 vertical lines, and a pixel clock of 148.5 MHz exactly matching CEA-861. This mode is accepted by every TV that supports 1080p. The trade-off is that 1080p-over mode does not give you integer scaling from 240p, so you will have uneven pixel sizes. If you need integer scaling, use 1200p mode instead, which runs at 154 MHz with a horizontal total of 2080 and vertical total of 1235 lines. This timing is still within the CEA-861 specification and most TVs accept it. Enable triple buffer mode in the menu if you experience sync dropouts. Triple buffer mode masks sync failures by holding the last good frame until the TV re-locks.

No single manufacturer publishes a list of TVs that accept line multiplied signals. The community maintains the only reliable data. The OSSC TV compatibility list is hosted by the Video Game Perfection community wiki and has been updated since 2016. It lists specific model numbers, firmware versions, HDMI port numbers, and which OSSC output modes work or fail. The RetroTINK compatibility list lives on the RetroTINK community Discord and a Google Sheet, updated annually. Both lists rely on user reports, so entries carry a verification date. A report from 2021 for a Samsung TU7000 may no longer apply after a TV firmware update changed the EDID behaviour. Check the most recent entry for your model.

If your TV is not on either list, run the 240p Test Suite from Artemio Urbina (2011) or the built-in OSSC test pattern to test each output mode. Record which modes produce a stable image. Then contribute your findings to the wiki or Discord. This is how the list stays useful for the next person searching for a line multiplied signal TV compatibility list. Without community reports, every new buyer of an OSSC or RetroTINK repeats the same troubleshooting cycle.

An EDID emulator is the most reliable fix for a TV that rejects a line multiplied signal. The device sits between the scaler and the TV on the HDMI cable. It stores a copy of the TV's EDID and presents it to the scaler continuously, even when the TV is off or in a sync loop. The scaler sees a stable EDID, selects its output mode based on that stored data, and sends the signal. The TV then receives the signal and must accept it or reject it, but the sync loop is broken because the EDID does not change. The Dr HDMI is the most commonly used EDID emulator in the retro scaler community. It allows you to force a specific EDID timing or remove HDCP flags. The cheaper alternative is an HDMI splitter that strips HDCP. A splitter that does not pass HDCP will force the scaler to send an unprotected signal, which some TVs handle more reliably than a protected one.

To use an EDID emulator, connect it to the TV's HDMI port first, let it read the EDID, then connect the scaler to the emulator. If the emulator has dip switches, set them to mimic a 1080p display with 148.5 MHz pixel clock. This forces the scaler to output standard CEA-861 timing regardless of what the scaler's own menu says. The result is that the TV receives a signal it recognises, and the image appears. The trade-off is that the scaler may output a lower resolution than its maximum capability, but a stable 1080p image beats a black screen at 1440p. The EDID emulator retro scaler fix is documented on the OSSC wiki and in RetroTINK support documentation as the last resort before replacing the TV.

An intermediary HDMI splitter can resolve the sync failure by re-clocking the signal and stripping HDCP. Not all splitters work. The splitter must be powered by an external USB or barrel jack, not by the HDMI port alone. A passive splitter that draws power from the HDMI port may under-power the signal and cause the same rejection. The splitter must also support the TMDS clock rate your scaler outputs. For the OSSC at 5x 320×240 optimized mode, that is approximately 162 MHz. Most HDMI 1.4 splitters support up to 340 MHz, so the clock rate is not the limiting factor. The limiting factor is whether the splitter re-negotiates the EDID with the TV or simply passes the scaler's EDID through. A splitter that passes EDID through does not fix the sync. A splitter that generates its own EDID and presents it to the scaler does fix it.

The community recommendation is a powered HDMI splitter that explicitly strips HDCP. Connect the scaler to the splitter input, then connect the splitter output to the TV. The splitter's own HDMI transmitter uses a different driver chip than the scaler's, which changes the signal's voltage swing and pre-emphasis. This can be enough to push the signal within the TV's acceptance window even if the timing is still non-standard. The fix is not guaranteed, but it works often enough that it is the second thing to try after switching to a standard output mode. If the splitter does not work, move to an EDID emulator.

The OSSC's TX mode setting adjusts the HDMI transmitter's output characteristics. TX mode 0 is the default, with standard voltage swing and pre-emphasis. TX mode 1 increases the swing, which can help a TV detect the signal on a marginal sync. TX mode 2 and 3 adjust pre-emphasis for longer cables. If your TV shows no signal at TX mode 0, cycle through all four modes while the scaler is connected to the TV and the console is outputting a 240p test pattern. The change takes effect immediately; you do not need to reboot the scaler. This fix costs nothing and takes 30 seconds.

DVI mode on the OSSC disables HDMI-specific features like audio embedding and HDCP. When DVI mode is active, the OSSC outputs a DVI-compatible TMDS signal that lacks the HDMI metadata some TVs use to validate the input. Some TVs that reject an HDMI signal accept the same timing as a DVI signal. To enable DVI mode, go to the OSSC menu, select Output Options, and set Output Type to DVI. The scaler will no longer output audio over HDMI, so you will need a separate audio connection from your console or an audio extractor. The trade-off is worth it if DVI mode produces a stable image. This fix is documented in the OSSC firmware changelog and is tested against the same Samsung TU-series models that reject HDMI mode.

HDMI ITC (Infoframe Timing Change) is a metadata packet the scaler sends to the TV to describe the video timing. Some TVs require a valid ITC packet to accept a non-standard timing. The OSSC does not send ITC packets in all output modes. The RetroTINK 5X does send them, but the TV may still reject the timing if the ITC packet describes a refresh rate that falls outside the TV's accepted range. The off-spec refresh rate of 60.08 Hz from the OSSC 5x optimized mode is the key factor. The TV's scaler expects 60.00 Hz or 59.94 Hz (the NTSC rate). 60.08 Hz is close enough to 60.00 Hz that the TV should accept it, but the HDMI specification requires the timing to match a CEA-861 descriptor exactly. If the TV's EDID does not list a descriptor for 60.08 Hz at that resolution, the TV treats the signal as unsupported.

The community has tested the 59.94 Hz output from the OSSC, which is the standard NTSC refresh rate for 480i and 240p content. The OSSC at 5x generic 4:3 mode outputs at 60.00 Hz, which matches CEA-861. The 5x 320×240 optimized mode outputs at 60.08 Hz because the timing generator uses different blanking values to achieve integer scaling from the 240p source. The 60.08 Hz is a consequence of the math, not a deliberate feature. If your TV rejects 60.08 Hz, use the 5x generic 4:3 mode instead. You lose the optimised blanking that produces perfectly centred integer-scaled pixels, but you gain a stable image. The 60.08 Hz rejection is the single most common cause of the "TV rejects line multiplied signal" problem across all scaler brands.

Sync dropout during gameplay, where the screen goes black for 2-3 seconds and then returns, is caused by a momentary sync failure. This is different from the initial no-signal problem. The sync fails during a resolution switch, such as when a PlayStation 1 game switches from a 240p menu to 480i gameplay, or during a white flash on a Super Nintendo that drops the sync voltage below the scaler's threshold. The OSSC's sync tolerance is adjustable. Set the sync threshold to low in the OSSC menu to prevent the scaler from losing lock on a weak sync signal. The RetroTINK 5X's triple buffer mode holds the last good frame in memory during a sync failure and displays it until the signal returns. This eliminates the black screen but adds one frame of lag during the dropout period.

If you experience sync dropout on a TV that initially showed the image, the cause is the TV's own processing. Samsung game mode reduces input lag but can also reduce the TV's tolerance for timing jitter. LG OLEDs in game mode handle off-spec signals better than Samsung sets. Disable HDMI-CEC passthrough on the scaler and the TV, because a CEC command from another device can trigger a sync re-negotiation. The fix for persistent dropout is the same as for the initial rejection: use a standard output mode, enable DVI mode, or insert an EDID emulator.

Buying Before Checking

The most common mistake is buying a scaler before checking your TV model against the community compatibility list. A Samsung TU7000 owner who buys an OSSC and expects it to work at 5x optimized mode on the first try will spend hours troubleshooting a problem that is documented and predictable. Check the list before purchase, or buy from a retailer with a return policy.

Blaming The Cable

The second most common mistake is assuming a newer, more expensive HDMI cable will fix the sync. Cable quality does not cause a 60.08 Hz rejection; the TV's EDID and timing tolerance cause it. A certified HDMI 2.0 cable costs the same as a generic one and will not change the sync outcome. Spend the money on an EDID emulator instead.

Updating The TV Firmware

The third mistake is updating the TV's firmware hoping for a fix. TV firmware updates from Samsung, LG, and Sony do not include changelogs for EDID behaviour changes. A firmware update that breaks a working sync is as likely as one that fixes it. If your current setup works, do not update the TV firmware. If it does not work, the fix is on the scaler side, not the TV side. The EDID emulator is the only reliable hardware fix that does not depend on your TV model or firmware version. It saves hours of trial and error with TX modes, DVI modes, and output resolutions.