I have been working to maximize Ramixx500 V2’s analogue RGB video output and interestingly I have found few improvement points that are essential:
- Pin 15 of CN9 so-called _CCK requires 47Ω termination (normally provided by genlock if plugged)
- Alternatively, the following pin can be lifted (disconnected / desoldered) from the motherboard to disable the buffered _CCK line:
- Ramixx500 V2 pin 6 of U41
- A500 Rev. 6, 8A1 (PAL) pin 6 of U41
- A600 Rev. 1.5, 2 (PAL) pin 11 of U32
- A1200 Rev. 1D.1, 2B (PAL) pin 4 of U32
- Each colour line benefits of a L-R bead insertion as bead cuts high-frequency noise.
- A high standard VGA cable increase the noise immunity.
- A decent grounding of the motherboard.
In the Amiga environment the jail bars are probably generated by peak noise induced by a floating _CCK (clock out for the genlock) and empathised by bad quality shielding/grounding at cable ends, regardless the resolution or de-/interlaced PAL/NTSC video modes.
- Amiga Test Kit v1.18
- EA Deluxe Paint III and 4.5 AGA
- BenQ LCD Monitor G2420HD (ET-0027-B) October 2009 Rev. 00-132-BA [VGA]
- UGREEN 11614 VGA Extension Cable [length 6 ft / 183 cm]
- Sony Trinitron CRT Monitor PVM-9045Q [RGB + SYNC]
- RS 790-2805 Straight 75Ω RF Adapter BNC Plug to RCA Sockets [250MHz]
- Mediabridge 70-040-06B Component Video Cable [length 6 ft / 183 cm]
(schematic from amigawiki)