625 TO 405 LINE


Hedghog II is a homebrew 625 to 405 line standards converter which is based on the Hedghog converter.

On this page you will find the files required to build it.

 All material including Downloads on these pages are provided 'as is' without warranty of any kind, either expressed or implied.


A Hedghog II has all the features of Hedghog with the following differences.

All the components are mounted on a single PCB.

The FPGA is changed to a more modern Cyclone IV EP4CE6E22C8N.

The DAC is changed from 9 bit to a 10 bit.

It can be used as a System A modulator.

The video out socket is moved to the back panel to make room for an additional toggle switch on the front.



All Resistors, Capacitors and Inductors are 0805 size.

All Capacitors are ceramic multilayer types.

Where given manufacturers part numbers are given as examples alternative parts may also suit.

The PCB is double sided and measures 100 mm X 89.5 mm.

Link to uploaded Gerber files on PCBWay.



A: video modulator off.
B: audio modulator off.
C: Video clock check. LED flashes if OK.
D: 50 MHz clock check. LED flashes if OK.
E: Checks that a valid PAL signal is being received from the video decoder. LED flashes if OK.

F: When on the 4:3 test card can be displayed even if the decoder is not present or not working.

Also when F is on the video port from the video decoder can be checked one bit at a time.
The bit being checked is selected by the HEX switch. 0 = bit0, 1 = bit1,......7 = bit7.
A flashing LED is good. LED continuously on is fail.
It checks if the bit is stuck high or low. or if the pin it is not connected.
It wont reliably show up if two adjacent pin are shorted together.

If DIP switch F is on video coming through the converter can be corrupted and rolling horizontally/vertically. This is normal.

As they all use the LED to display the result only one of the switches C to F can be on at a time. Otherwise the result will be unpredictable.



Circuit diagram (.pdf)

Component list (.pdf)

Component layout top (.jpg)

Component layout bottom (.jpg)

Front and rear panel legends (.pdf)

FPGA program file (.jic)





Hedghog II PCB top

Hedghog II PCB bottom