No color on some programs (when there should be) ???
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I've tried my hand wired Hydra system on a couple different TV's with the composite input with slightly different results. Overall the system works fine running the games that came pre-loaded on an SD MAX cartridge. However, some of the games and demos which should be in color just show up in black/white on the screen. One in particular "Alien Invaders" shows up in color on one set and black/white on the other.
Has anyone run into this before? If so what may cause this?
I've been searching online for possible solutions and one mentioned that the clock speed may be off slightly. Since I didn't have a new 10Mhz crystal on hand I had used one that had been in my spare parts drawer. If the crystal was a bit off would that affect the color?
From the board to the connector is a short jumper (unshielded) with a 2-pin header to connect to the board. I wonder if this may be part of the problem. If so I have some small lengths of RG-174 coax I can use to replace that jumper.
At the moment I have a few things to try:
- Try to connect the Hydra to the VCR instead of directly to the input on the TV
- Try connecting it to a regular color composite monitor
- Swap out the short jumper cable from the board to the the connector
- Swap out the 10Mhz crystal
Any other suggestions?
Has anyone run into this before? If so what may cause this?
I've been searching online for possible solutions and one mentioned that the clock speed may be off slightly. Since I didn't have a new 10Mhz crystal on hand I had used one that had been in my spare parts drawer. If the crystal was a bit off would that affect the color?
From the board to the connector is a short jumper (unshielded) with a 2-pin header to connect to the board. I wonder if this may be part of the problem. If so I have some small lengths of RG-174 coax I can use to replace that jumper.
At the moment I have a few things to try:
- Try to connect the Hydra to the VCR instead of directly to the input on the TV
- Try connecting it to a regular color composite monitor
- Swap out the short jumper cable from the board to the the connector
- Swap out the 10Mhz crystal
Any other suggestions?
Comments
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I am 1010, so be surprised!
1. The actual crystal frequency. The drivers normally use a frequency divider/PLL loop based on the crystal, and not everything divides evenly into 10 million.
2. The video driver -- some push it a little, like HEL's slightly longer HSYNC cycle.
The signal outputted by the Hydra is not exactly a 100% in-spec signal at all times, due partially to crystals and partially due to coding practices. Both of these affect the output, and depending on how picky your screen is (I've heard that PAL-based TV's are sometimes especially bad with not-quite-perfect NTSC signals as well as LCD screens.)
Any thoughts?
Anyway here is what I have to put in my programs to get color
_xinfreq = 10_000_000 + 5000
If that is the case the I can try swapping out the crystal with a couple different styles to see if I can get it working with the standard setting. I'd rather do that and get the board working exactly as it should instead of having to tweak and recompile code to get it working perfect on my board. Swapping it isn't a problem since it's just two pins to unsolder! The crystals are fairly cheap and I'm going to order some the next time I need some parts.
Have you thought about swapping your crystal to see if you can drop that extra setting on your board?
Robert
Also once you find the right tweak number, then it should work on all TVs. I have tested my racing·game on 2 CRT TVs, 1 Digital DLP TV, and a PC with a video capture card and they were all in color.
Post Edited (JT Cook) : 4/15/2008 10:54:08 PM GMT
Robert