VIC-1001 Repair

Schema · Post by **Schema** » Mon Dec 01, 2008 10:45 am

I finally got a chance to try out my "cheap" VIC-1001 on a TV that can handle the Japanese NTSC video output, and a North American 9VAC VIC power supply whose output matches that of the original power supply.

It doesn't appear to work

I do get a black screen (not static) with a subtle pattern on it, so at least there is some video signal coming out.

I'm assuming I can follow Ray Carlsen's VIC repair article, but before I get too deep into that, I want to understand the differences between the 1001 and a "normal" VIC20. Is it just the VIC chip, Kernal, and Character ROM that are different?

i.e. I'm wondering if I can move the Kernal and Character ROM onto another VIC motherboard, or move the VIC onto this motherboard, and get a Frankensten 1001 with NTSC output? (Which would be more useful, actually).

yoyodyne · Post by **yoyodyne** » Mon Dec 01, 2008 5:53 pm

Schema,
I have a motherboard from a very early vic that works.
I posted about it here this summer, as it is quite different than
other boards I have seen. Eslapion ( I think) told me it
was basically identical to a 1001 board. Here is a picture
of it :

http://good-times.webshots.com/photo/27 ... 8028hoPZhv

It had a bad 6560, which I replaced after the photo was taken.

All the other chips have 81 dates, except the new 6560.

If you can't repair your original board, you can have this
one for the cost of shipping.

Take your time, this one isn't going anywhere.

Brian

eslapion · Post by **eslapion** » Tue Dec 02, 2008 7:22 am

yoyodyne wrote:... Eslapion ( I think) told me it
was basically identical to a 1001 board.

AFAIK, VIC-1001s have exactly the same board (same part no.) as early VIC-20s that use a 2 prong PSU and are "Made in Japan".

Distinctive sign: (as on your pic) the 6522s are placed laterally instead of vertically on the board.

On the VIC-1001, many chips have ceramic casings with gold square on top. VIC-20s don't have that.

Pretty much all VIC-20s with PET style keyboard also originally came with the same PSU as the VIC-1001.

ral-clan · Post by **ral-clan** » Tue Dec 02, 2008 8:18 am

I know the part number printed on the motherboard of my 2-prong VIC-20 ends with 1001.

gklinger · Post by **gklinger** » Tue Dec 02, 2008 10:32 am

I'm pretty sure I gave Centallica such a board at the WoC last year (maybe the year before?) You should ask him if he still has it as it might be just what you need.

Centallica · Post by **Centallica** » Tue Dec 02, 2008 12:22 pm

gklinger wrote:I'm pretty sure I gave Centallica such a board at the WoC last year (maybe the year before?) You should ask him if he still has it as it might be just what you need.

Yup, sure do man!

It's the one with the botched power supply rig on the side, so you'll have to fix that if you want it?

I hear things people get for free at WOC, some people later sell for a profit? So that'll be $29.95 if you're interested Leif

But, that Chardonay Bloomquist from Sat night in a trade is acceptable, let me know if you want it by Wed 4:30? (As it's in Barrie and I'll be there that night before WOC)

Schema · Post by **Schema** » Wed Dec 03, 2008 8:44 am

If the board and video chip are identical, what is it exactly that makes the VIC-1001 generate an NTSC-J signal instead of standard NTSC?

gklinger · Post by **gklinger** » Wed Dec 03, 2008 10:14 am

Schema wrote:If the board and video chip are identical, what is it exactly that makes the VIC-1001 generate an NTSC-J signal instead of standard NTSC?

Nattō.

Schema · Post by **Schema** » Fri Dec 05, 2008 8:56 am

I didn't get to try Nattō when I was in Japan, yet another reason to go back.

Any serious replies?

6502dude · Post by **6502dude** » Fri Dec 05, 2008 10:12 am

Standard NTSC has black level at .339vdc while black level for NTSC-J is at .285vdc for composite video.

Check for different bias resistor values around Q7 and compare with standard NTSC pcb.

Apparently you should just be able to turn up brightness pot R7 as an alternative to swapping out resistor values for Q7

Otherwise NTSC and NTSC-J should be same signal format.

Leeeeee · Post by **Leeeeee** » Fri Dec 05, 2008 10:17 am

Any serious replies?

The black levels are slightly different, the J variant being slightly lower, so you may have to alter the brightness to get the same image but not by much.

The other thing is that the channel frequencies also differ but you should be able to use your NTSC modulator with your NTSC-J VIC without any problems. Otherwise you could either retune the NTSC-J modulator, or your TV or bypass the modulator and just use the video out.

Lee.

Schema · Post by **Schema** » Sat Dec 06, 2008 6:02 am

Interesting. I seem to remember needing a special TV for my MAX to get a picture, even with direct video-out. The MAX and the 1001 should put out the same video signal, right?

Leeeeee · Post by **Leeeeee** » Sat Dec 06, 2008 7:02 am

The 1001 video signal timing should be the same as that of the MAX so any TV that you can use with the MAX should work with the 1001 using direct video. The only change you may have to make is to the brightness.

Lee.

Schema · Post by **Schema** » Sun Dec 07, 2008 9:19 am

Ah, I had forgotten an important detail. The MAX doesn't have a composite output, which is why I had to use a multi-standard TV to see the output (RF only). That's the big difference.

It's encouraging to hear that I should (in theory) be able to see the 1001's video on any NTSC monitor.

Schema · Post by **Schema** » Tue Dec 09, 2008 10:17 am

Next question. Does anyone know what the differences are in the kernal ROMs? 901486-02 (VIC-1001) vs. 901486-06 (NTSC VIC-20). I found the thread about it in cbm-hackers but there isn't a lot of detail. Just curious what functional differences there might be.