17-03-2018, 03:26 PM
I have finally got to the end of this project. Some pictures of the finished converter are posted below.
On the back of the converter is RF out, power, audio and video in.
On the front is from left to right
Pattern switch which selects test card or grey scale
Tone switch which selects 400Hz or 1kHz audio tone.
Aperture switch which selects soft, medium or sharp interpolater apertures.
Equalising pulses on off
Pedestal on off
Aspect ratio 4:3 / 5:4.
Chanel selection covering channels 1 to 13
Power LED
405 Video out.
The aperture switch came about as I liked the 6 line interpolater, it gives a nice sharp picture, but I wasn't sure if the artifacts that it produces would be intrusive. So I decided to make the aperture switchable with the original two line as medium the 6 line as sharp and I adjusted the coefficients of the 3 line to give a softer aperture.
It would have been nice to have a full size (1/4" shaft) switch for Chanel selection but I couldn't find one that would fit in the space I had and anyways any of the PCB mounting types were expensive.
I have used two sections of the DIP switch (A and B) as a means of turning off the video and audio modulators to aid setting up. The other two sections (C and D) were left just in case they were needed, for now they just provide a means to carry out some basic tests on the converter.
Depending on there setting they will flash the front panel LED
if the 50MHz FPGA board clock is present,
if 27MHz video decoder clock is present and
if the Field ID pulse is present this proves that a valid PAL signal coming from the video decoder.
Presets provide adjustment of audio gain and carrier level for the audio modulator.
The front and back panel legends were just printed on colored paper and then laminated, they fit into the groves in the case provided for the front and back panels. I decided to call it "Hedghog" with just one "e"
I have made a change to the circuit posted in the last post. C38 and C39 have been reduced to 1pF. and the 15K resistors from pin 4 of IC4 and IC5 have been dispensed with.
A big thanks to all on this forum for all the support I got throughout this project and especially to Jeffrey for all his help.
Frank
On the back of the converter is RF out, power, audio and video in.
On the front is from left to right
Pattern switch which selects test card or grey scale
Tone switch which selects 400Hz or 1kHz audio tone.
Aperture switch which selects soft, medium or sharp interpolater apertures.
Equalising pulses on off
Pedestal on off
Aspect ratio 4:3 / 5:4.
Chanel selection covering channels 1 to 13
Power LED
405 Video out.
The aperture switch came about as I liked the 6 line interpolater, it gives a nice sharp picture, but I wasn't sure if the artifacts that it produces would be intrusive. So I decided to make the aperture switchable with the original two line as medium the 6 line as sharp and I adjusted the coefficients of the 3 line to give a softer aperture.
It would have been nice to have a full size (1/4" shaft) switch for Chanel selection but I couldn't find one that would fit in the space I had and anyways any of the PCB mounting types were expensive.
I have used two sections of the DIP switch (A and B) as a means of turning off the video and audio modulators to aid setting up. The other two sections (C and D) were left just in case they were needed, for now they just provide a means to carry out some basic tests on the converter.
Depending on there setting they will flash the front panel LED
if the 50MHz FPGA board clock is present,
if 27MHz video decoder clock is present and
if the Field ID pulse is present this proves that a valid PAL signal coming from the video decoder.
Presets provide adjustment of audio gain and carrier level for the audio modulator.
The front and back panel legends were just printed on colored paper and then laminated, they fit into the groves in the case provided for the front and back panels. I decided to call it "Hedghog" with just one "e"
I have made a change to the circuit posted in the last post. C38 and C39 have been reduced to 1pF. and the 15K resistors from pin 4 of IC4 and IC5 have been dispensed with.
A big thanks to all on this forum for all the support I got throughout this project and especially to Jeffrey for all his help.
Frank
