QL-VGA manual

QL-VGA is an FPGA based RGB to VGA converter specifically developed for the Sinclair QL and ZX Spectrum 128/+2. The input signal is buffered in a RAM chip and output as a standard VESA 1024×768 60Hz video signal. This signal is so common that it can be further converted to HDMI using any cheap Chinese converter (available for as little as 4€).

For the QL the 512×256 50Hz signal is doubled in X direction and tripled in Y direction, giving an exact 1024×768 screen.

Warning: do not connect QL-VGA to the QL while the QL is switched on. The ULA is extremely allergic against hot-plugging and can die quickly.

For the Spectrum 128 there are two modes: “normal” where the border colour is visible (X*3, Y*3) and “zoomed” where the screen contents takes over the whole screen (X*4, Y*4).

The device is supposed to be “connect and work”. Connect your computer (while powered down!) using the supplied RGB cable (straight 8-pin Mini-DIN to DIN) and your monitor using any suitable VGA cable. Connect the supplied power cable to any USB power supply, amperage doesn’t matter. Then power up the computer.

QL-VGA outputs a “screen saver” with the QL-VGA logo whenever it is working and no input signal has been detected. The logo should change position every few seconds.

There is only one button and a few LEDs:

D3The board has power
D2/D4D2 off, D4 off: Auto detect mode, waiting for valid signal
D2 on, D4 off: QL mode
D2 off, D4 on: Spectrum 128, normal mode
D2 on, D4 on: Spectrum 128, zoomed mode
D5This mirrors the CSYNC signal. It should dim (be about the same brightness as D3) when there is a valid CSYNC signal present

By default QL-VGA starts in “auto detection” mode and waits for a valid QL or Spectrum 128 signal. Once a signal is detected the mode is displayed using the LEDs.

The button next to D5 can be used to explicitly change through the modes. It is usually just needed to switch between normal and zoomed Spectrum 128 mode. Once a mode has explicitly been set no auto detection is done from this point on until the power is removed.


The monitor does not show anything

Check the power LED D3. If that is dark check the USB cable and power supply. If it’s on, check your VGA cable and monitor input selection.

The monitor only outputs the QL-VGA logo

Check LED D5. If it’s brighter than D3 then no CSYNC signal is detected. In this case check the RGB cable. If the cable is okay there might be a problem with your computer. If you can, check using a different connection like SCART. If you don’t get any picture there either chances are you connected QL-VGA while the QL was powered on and your ULA died. Only connect the QL when it is not powered on.

A few lines/columns are missing

The VGA signal is analog and subject to interpretation of the monitor. Adjust the picture in the monitor settings. QL-VGAs picture is always complete!

The colours are weird

Switch off the computer and check if the QL-VGA logo is white. If not, your VGA cable is probably the problem. If yes, remove the DIN connector mantle on the QL side of the RGB cable and check for loose wires.