The trimmer capacitor is used to fine-tune the crystal oscillator circuit; it is best not to touch it unless your colour is way off. Twiddling it will shift the colour hue around a bit. The potentiometer near the VIC chip adjusts the overall brightness of the image. The way I adjust these two is to start by getting the brightness "about right" and then tweak the colour if it still needs it. At low brightness, that colour will be wrong. The little PCB is almost certainly a mod they added to change the US NTSC video into Japanese NTSC-J video, as someone else mentioned. Unfortunately, there are a few MOS TTL chips on that board; if it doesn't work when you power it on, they may well be the cause of the problem. I've heard reports that they are horribly unreliable. That is a really cool find - I'm a bit jealous.
yes this motherboard is also in the VIC 1001, amazingly I posted a video about this just today, but I uploaded it on January 3rd and only made it public today. Dave is a mind reader!
That modulator pod port board might do the level-shift of N America " NTSC" to "NTSC-J" Japan analog TV wikipedia The black and blanking levels of the NTSC-J signal are identical to each other[10] (both at 0 IRE, similar to the PAL video standard), while in American NTSC the black level is slightly higher (7.5 IRE) than blanking level - because of the way this appears in the waveform, the higher black level is also called pedestal.
I opened up another Vic-20 today and found a short version of the board...once again, that I have never seen...looks like it has one RAM chip for the memory for the computer...sort of like the 64 short board that brought to life the superPLA chip...and needed a special adapter so it could be secured in the case...I do not think this was is very rare, I just have never seen it before...
Very cool and different! Thanks for sharing and this is now noted 😊
@@RudysRetroIntel Noted indeed!
The trimmer capacitor is used to fine-tune the crystal oscillator circuit; it is best not to touch it unless your colour is way off. Twiddling it will shift the colour hue around a bit. The potentiometer near the VIC chip adjusts the overall brightness of the image. The way I adjust these two is to start by getting the brightness "about right" and then tweak the colour if it still needs it. At low brightness, that colour will be wrong.
The little PCB is almost certainly a mod they added to change the US NTSC video into Japanese NTSC-J video, as someone else mentioned.
Unfortunately, there are a few MOS TTL chips on that board; if it doesn't work when you power it on, they may well be the cause of the problem. I've heard reports that they are horribly unreliable.
That is a really cool find - I'm a bit jealous.
I had no clue it was such a rare bird...I was intrigued by the early keyboard and stunned when I looked inside...now I have to get it working!
I don't know if the ROM checksums would tell you if this was the Dec 1979 model VIC-1001 (JAPAN)
yes this motherboard is also in the VIC 1001, amazingly I posted a video about this just today, but I uploaded it on January 3rd and only made it public today. Dave is a mind reader!
Just a coincidence...thanks for you input and help on all of this!
That modulator pod port board might do the level-shift of N America " NTSC" to "NTSC-J" Japan analog TV
wikipedia The black and blanking levels of the NTSC-J signal are identical to each other[10] (both at 0 IRE, similar to the PAL video standard), while in American NTSC the black level is slightly higher (7.5 IRE) than blanking level - because of the way this appears in the waveform, the higher black level is also called pedestal.
Thanks...I had no idea...but am always fascinated by the depth of the knowledge of others on so many diverse obscure subjects...thanks so much!!!
Hi Dave! I posted a video similar to this just today! Amazing!
Excellent...long live the Vic-20 in all of the various variations!
@@DRBradleyPhotography 😃
I opened up another Vic-20 today and found a short version of the board...once again, that I have never seen...looks like it has one RAM chip for the memory for the computer...sort of like the 64 short board that brought to life the superPLA chip...and needed a special adapter so it could be secured in the case...I do not think this was is very rare, I just have never seen it before...