|
|
Post by robheaton on Apr 20, 2019 14:42:03 GMT
Hello,
I have a C128, on initial power on, the colours look bright and vivid, after a few seconds the colours look washed out.
I'm using the video socket (Not RGBI) connected to a scart cable.
Using the same screen and cable with a C64, the colours stay bright and vivid.
Does anyone have any suggestions?
(The C128 has already been recapped)
Many Thanks,
Rob.
|
|
|
|
Post by hydrophilic on Apr 21, 2019 12:55:36 GMT
I have some video hardware experience, but I must admit I am stumped... If the same monitor and cable give good results with C64, I don't know why C128 would fade away (especially after replacing capacitors).
The only thing I can imagine is that C128 has a bad power supply, and/or your cable/monitor is drawing too much power...
Imagine: C64 has "superb" power supply and your monitor/cable is "defective". The defective monitor/cable is trying to "drain" your computer, but your C64 has a "superb" power supply so it "wins" the battle.
Imagine: C128 has "average" power supply and your monitor/cable is "defective". The defective monitor/cable is trying to "drain" your computer, and eventually (after a few seconds) your C128 "looses" the battle (picture fades).
--- OR ---
Imagine: C128 has "defective" power supply and your monitor/cable is "normal". Your C128 starts with "fresh" colors, but after it "warms up" (a few seconds) the drain from internal C128 parts increases, which reduces output power (because power supply is defective).
I have no way to prove any of this, but it is the only logical thing I can imagine based on your description and my engineering experience.
In summary, try another power-brick for C128 (my best advice). I hope you find a solution (any solution, not just mine) and tell us all about it ...
|
|
|
|
Post by robheaton on Apr 21, 2019 15:09:48 GMT
I'll dig out another power supply and give that a try.
Ray Carlson has recommended I swap out the VIC chip, I've ordered another, but it'll be a few days before it arrives.
I'll keep you posted!
|
|
|
|
Post by robheaton on Apr 27, 2019 16:05:08 GMT
I changed the VIC chip but this made no difference, however I fitted a Lumafix and this has stopped it happening.
(I did try a new PSU too)
Been a couple of days, but so far, so good!
|
|
|
|
Post by hydrophilic on May 16, 2019 8:11:31 GMT
I understand new VIC chip.
I understand new PSU.
None of that helped (if I understand you correctly).
For you, only Lumafix helped... Can you explain Lumafix for me? (I've never heard of it)
|
|
|
|
Post by bjonte on May 17, 2019 10:00:02 GMT
For you, only Lumafix helped... Can you explain Lumafix for me? (I've never heard of it) The unintentional vertical stripes in the video output is caused by other signals leaking into the video output. Lumafix is a small board that is placed under the VIC chip to add a negated version of those signals to get a more clear picture without stripes. |
|
|
|
Post by robheaton on May 17, 2019 16:32:58 GMT
|
|
|
|
Post by hydrophilic on Jun 13, 2019 7:09:34 GMT
The unintentional vertical stripes in the video output is caused by other signals leaking into the video output. Lumafix is a small board that is placed under the VIC chip to add a negated version of those signals to get a more clear picture without stripes. Thanks bjonte , I've heard about that VIC-correction issue, I just didn't know it by the name of Lumafix. It seems to be more an issue with C128 than C64. Also the problem (my experience) is usually not noticeable when using composite connection, but becomes obvious with S-Video (separated luma/chroma) -- and things derived from S-Video (like component [YCbCr] and HDMI). |
|
