Vic 20 color strangeness

[macc]

I only noticed it when I tried Gorf on cart, the characters are all wrong, no color! Any ideas people?

[macc]

Plug my working Vic in using the exact same setup and cables, everythings fine!

[macc]

And while im here, I may as well talk about another Vic thats got odd colors, this more apparent from the off. No amount of adjusting the oscillator cures this, and strangely, two games Ive tried (Starship Escape being one of them), when you die, the death sound keeps looping and the game freezes like that)

[Mike]

Which mainboard type do those two VIC-20s have?

#1 looks like the VIC chip 'lost' the capability to display multicolour. That should also be apparent in other programs/games. In the READY prompt you can try whether changing foreground colour with POKE646,8..15 exposes the same fault - normally the cursor should turn to black[1], and READY should appear multicoloured. Another possibility might be a defect of the colour RAM or the 4066 analogue switch.

#2 could also be a wrong initialisation by the KERNAL (purple border instead of cyan). What value do you read with PEEK(36879)?

If possible, try to swap the suspected VICs into a functioning VIC-20 to see whether the fault goes with them.

Michael

[1] as long as there is a 0 in the upper 4 bits of the aux. colour/volume register in 36878.

[macc]

Hi Mike, just tried those tests, POKE646,8 makes the READY prompt and cursor turn black, 15 turns both yellow. The PEEK command returns in a Syntax error however

[Mike]

Hi Mike, just tried those tests, POKE646,8 makes the READY prompt and cursor turn black, 15 turns both yellow.

Actually I meant to test the whole range of 8 to 15. Nonetheless, when 15 gives a yellow cursor, multicolour doesn't work anymore. Please check the result of the following program - it checks whether the colour RAM works, as seen by the CPU:

Code: Select all

1 FORAD=37888TO38911:FORT=0TO15
2 POKEAD,T:IF(PEEK(AD)AND15)<>TTHENPRINT"ERROR AT"AD"!":END
3 NEXT:NEXT:PRINT"OK!"

If it comes out with "OK!" then most probably the fault is inside the VIC chip. Otherwise the colour RAM and/or 4066 are suspect.

The PEEK command returns in a Syntax error however

That's what you get when you write the PEEK() function on its own, without a preceding PRINT. Did I really need to explicitly point that out?

[macc]

Sorry Mike, my basic knowledge of BASIC escaped me! I tried PEEKing and its 27 on both, 27 also on my working vic so that seems to be checking out. The pokes to display mutlicolor just give straight color, the whole range, apart from one (forgot which) which froze the machine (Run/Stop Restore got it back) Ill try that program now and report back

[macc]

Ok, just typed that in to the dodgy multicolor machine, after some wait all the text was changed to yellow and Ok message displayed, just because i could i tried it on the other one, still OK but text now pink/brown combo

[Mike]

So then that looks like two dodgy VIC chips.

When they are all socketed in the three VIC-20's, try putting the suspected ones into the functioning VIC-20. When the error goes with the VIC chip, all you can do it buying replacements (fortunately there seem to have appeared new old stock of them recently).

[macc]

Cheers Mike, I suspected as much sadly. Both machines are soldered in. Just had a quick browse for 6561's and of the two I found on ebay, they are commanding quite a price! £34.99!!

[Spirantho]

Hi Macc,

(apologies for the spam )

The £34.99 price tag I'm asking for is because I'm trying to find out how much they're worth. As there are so few of them around it's very difficult to work out a good price.

I've got them on my shop here (as I've just posted in this forum in case it's of any help to others):
http://www.mutant-caterpillar.co.uk/sho ... p?cPath=65

If you want I'll do you two working VIC 6561-101 chips for £40 though - just let me know. I'm trying to build up the ultimate spares webshop for 8-bit computers, but right now I'm trying to recoup some of my costs!

Thanks,

[macc]

Its no problem Ian, still a bit out of my league price wise, I can understand it from a persons perspective that wants to keep and use the machine but Im repairing, refurbing and then reselling, theres not much in it after initial costs, parts and labour are incurred. Thanks for the offer though!

[Spirantho]

For what it's worth, I just lowered the price on eBay to £20, so I can do two now for £30.

Still trying to find the right price for these babies.

[Groovydrifter]

How cool is this, I've just bought from ebay two "untested due to lack of power supply" VIC-20s with this exact same problems on both. What a marvelous coincidence. So then both VIC's are dead? I will do the test anyway to confirm but the symptoms are exactly the same and guess what... I also tested the first one with GORF and looks just the same (did that because it does not recognice drives, so say it's a VIC+VIA failure) . The second also has a purple border instead of the normal cyan one.

[Spirantho]

Sounds like a dead VIC chip to me. Good thing I stocked up... going to need them at this rate.

Are you in the UK? If you want to send me your VIC chips I can check them in my known-good VIC-20 - but to be honest it does sound like they're kaput.

If you do need two VIC chips, the offer of £30 is still available, of course - and if you find it doesn't fix it I'm happy to take them back as long as you pay postage costs (and, of course, as long as they come back in the same condition they leave me in).

(There was me thinking I had enough VIC chips to last about 10 years...!)