24 euro VIC-20

mrr19121970 · Post by **mrr19121970** » Wed Feb 17, 2016 12:08 pm

I needed a VIC-20 badge and PSU, so bought a clearly dead one on eBay. 28.45 euros including postage. I've never been so shocked, hoe can someone have treated it so badly. I had to drill open the case, the screws had rusted and there was no "+" to even scrape away to try to unscrew. Inside dead bugs, dirt and more rust (mainly around the power entry and on-off switch). The user-port and cassette connectors were so fouled up - I scraped them free with a screwdriver and finished off with petrol. (now i just bought a glassfibre pen for next time)

I pluged it in, and it didn't explode. Turned on the TV and picture. Clear and sharp. Even 10 chips socketed (MPU, 2xCIA, VIC, Char, UB4/UF8/UE8/UD8 - whatever these are ??? and Kernal).

This is a lucky find? I ordered the missing INST/DEL key from Phil@retroleum and come case screws too.

Post by **joshuadenmark** » Wed Feb 17, 2016 2:32 pm

Nifty find

congratulations.

vicist · Post by **vicist** » Wed Feb 17, 2016 5:02 pm

Also a decent picture on the screen too. Great find.

I wonder what makes some cr vics produce such a rubbish composite output (like the two that I have) compared to others - such as this one?

pixel · Post by **pixel** » Wed Feb 17, 2016 10:18 pm

Congratulations! Good to have a stack of VICs when the pension is gone the minute you try to collect it.

One of my 1541 actually did explode when I plugged it in. Then I found out that the fuse box is in the apartment of my neighbor who wasn't at home. So I went to the local pub. "What are YOU doing here? Did they turn off the mains?" "**** ***!" "Ah! Must be that."

mrr19121970 · Post by **mrr19121970** » Wed Feb 17, 2016 11:27 pm

vicist wrote:Also a decent picture on the screen too. Great find.

I wonder what makes some cr vics produce such a rubbish composite output (like the two that I have) compared to others - such as this one?

I think it is the vic-i chip. At the weekend I swapped a 1983 from a cr to test in a 1982 9v. The 9v had rich and vivid colours and the 1983 chip made it checkerboard.

eslapion · Post by **eslapion** » Wed Feb 17, 2016 11:47 pm

mrr19121970 wrote:
vicist wrote:I wonder what makes some cr vics produce such a rubbish composite output ...
I think it is the vic-i chip.

I would tend to disagree.

In my own VIC-20 with PSK, I put a 1983 6560 with S-Video mod and the image is top-notch. The secret to little to no luma noise seems to be on the mainboard.

The older mainboard has a small coil filter which the VIC cr doesn't have. On NTSC machines this makes a huge difference. Dunno about PAL ones since I only have a VICcr on the PAL side with nothing to compare.

orion70 · Post by **orion70** » Thu Feb 18, 2016 12:20 am

Don't forget the trimmers! Tweaking with them can make a big difference in quality of video signal. It's always the first thing I try when a new VIC hits my mailbox

.

mrr19121970 · Post by **mrr19121970** » Thu Feb 18, 2016 2:04 am

As I mentioned, by experience is this:

9v VIC-20 with 1982 6561 - has crisp edges and rich colours (no s-video mod). I pulled this out and replaced with a 1983 6561 which I took from a VIC-20cr. The edges were blurred, reds where more pink and and the dreaded checkerboard came. When I replaced the 1982 6561 the image and colours were perfect again.

vicist · Post by **vicist** » Thu Feb 18, 2016 4:55 am

There should be no confusion here. I'm not talking about the different output from different era/region machines, but like for like machines.
The question I asked arose after seeing the pretty good image output from mrr19121970's cleaned up vic compared to mine (pal), which are (were) rubbish. My psk vic has a good composite picture compared to my cr vics when connected to the same tv which seems to coincide with most peoples observations that the older vic had a better composite output. This is probably why most s-video mods are carried out on cr vics.

orion70:
Playing about with the r10 adjuster only changed the contrast and saturation on my vics, it did nothing to improve the clarity of the image. This is why I decided to do the modification to them.

mrr19121970:
The picture of the board in the first post is of an unmodified cr vic, yes?
Are you using anything between the vic and the display to help improve the output?
I also notice there's no shielding around the display components. Could this make a difference?

How about the chip revisions?
My vic 1 = 2083
My vic 2 = 2383
Yours = 4883

mrr19121970 · Post by **mrr19121970** » Thu Feb 18, 2016 6:16 am

vicist wrote:mrr19121970:
The picture of the board in the first post is of an unmodified cr vic, yes?
Are you using anything between the vic and the display to help improve the output?
I also notice there's no shielding around the display components. Could this make a difference?

How about the chip revisions?
My vic 1 = 2083
My vic 2 = 2383
Yours = 4883

I am not currently at home, but from the pic I posted : the date code on the PAL 6561 is week 48 in 1983 (I'd have to lift out the chip to check the country of manufacture).

The VIC-20cr is totally unmodified, I have 2 units without the shielding box. I don't recall the serial number of the one that arrived yesterday (I have a spreadsheet with all details, I will update and upload tonight).

I used a composite video cable that I bought from eBay.fr for 8 euros incl postage. There is nothing I've done to improve the display, other than drill open the case, remove the rusty power panel to soak in WD40 and scrub the user-port and cassette connectors as I was afraid the 'junk' was a conductor and would give me a short circuit.

fuzzybad · Post by **fuzzybad** » Thu Feb 18, 2016 9:59 am

Always nice when you buy a computer advertised as "not working" only to discover that it works perfectly.

I've had this happen twice recently; I picked up a VIC-20 from eBay advertised as non-working for $6 because I needed a spare keyboard; and I picked up a 64C in 'unknown' condition, extremely dirty and missing keys for about $20. Both of them turned out to be in perfect working order..

mrr19121970 · Post by **mrr19121970** » Thu Feb 18, 2016 10:37 am

Actually when I sell, I always state not working + spares and repairs. I don't want to get caught out having to offer a guarantee as a private person. I also assumed this was standard practice in germany for this very reason.

I found out the hard way when paying top dollar for a c128 that not working really means chickens were living in and on it and no chance in the world to revive it.

mrr19121970 · Post by **mrr19121970** » Fri Feb 19, 2016 2:05 am

I had a closer look at the board yesterday to update this thread and observed the 2 CIA chips had different date codes. One was late 1984 which was substantially older than all other chips on the board. This indicates to me a (professional) repair either under or out of guarantee - maybe also why so many chips are socketed too (the soldering is 'factory quality')

eslapion · Post by **eslapion** » Fri Feb 19, 2016 6:23 am

There is no such thing as a CIA in a VIC-20.

Just like the 1541 drive, the VIC uses a pair of 6522 VIAs for communication.

The 6526/8520/8521 CIAs are used in the C64, C128, Amiga computers and 1571, 1581 disk drives.

mrr19121970 · Post by **mrr19121970** » Fri Feb 19, 2016 6:30 am

I stand corrected, the 'big black chip thingy' top left of the mainboard is newer than the other chips. Or now as I found from Wikipedia:

6522 Versatile Interface Adapter (VIA)

not

6526/8521 Complex Interface Adapter (CIA)

Denial

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