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2011-07-24 22:05

Talon
Account closed

Registered: May 2007
Posts: 11

Replacing sid/vic, version question

Aloha!

I currently have four C64 (of which one is a C64c) in my home. Yesterday, the last functional one broke (only shows a reset-y screen with no characters on it on startup).

The C64c's keyboard is broken, but I connected one of the other keyboards to it so that works. But the 6581 in it seems to be dead too!

Do you guys know if it would work stealing a 6581 from one of the older machines? I remember one of them sounding especially nice - it has a 6581 from mid 1983 in it (the so called "6581, revision 3"). The C64c has an 6581 revision 5 in it (8580R5). If it's an OK operation it will just have made the C64c sound better :)

Apart from that, have anyone of you experienced the failure I described at the top (unresponsive screen without text, looks like 38 columns or so)?
Maybe I could just as well steal a working vic chip instead, and fix that machine? Or does it seem more of a CPU thing? Crappy error description from me I suppose - maybe you can ask me some good questions about it if you care to help.

I haven't been much of a hardware guy till now, but since I now have 4 malfunctioning vintage computers it might be time to get a soldering gun and have a go :)

Best
/T

... 15 posts hidden. Click here to view all posts....

2011-07-25 07:52

taper

Registered: Dec 2001
Posts: 119

I agree with Devia. At LCP (www.lcp.c64.org) in a few days, Mogwai will attempt to repair broken hardware, just as he has done prvious years with great result.

Bring your machines there, or give them to someone from Stockholm who will attend.

That is, unless it was the fuse that needed to be replaced afterall! :)

2011-07-25 07:54

taper

Registered: Dec 2001
Posts: 119

Devia: By the way, I ofcourse knew that the 6581 and 8580 is not interchangable because of voltage differences.

But, could you elaborate about VIC chips not being interchangeable aswell? This is news to me. How come this is the case? Do you mean the really old cheramic VIC's, or also the plastic ones?

2011-07-25 10:21

Devia

Registered: Oct 2004
Posts: 401

ARRGH!!! I wrote a shitlong post and it got lost on submission :(

shorter version:

Old VIC-II (6569/6567) needs +12 VDD on pin 13.
New VIC-II (8565/8562) needs +5V VDD on pin 13.

Old VIC will work perfectly in new C64, but without video output, which I presume most people would want ;-)

New VIC in old C64 will work perfectly too, but you'd be supplying it with 7V more than it was designed for. There is a chance that C= thought about this and actually implemented some sort of voltage regulation or whatever, but until someone with the right skillset takes a closer look at the hires die photos of the new VIC-II and can say that this is the case, I would not risk it on other peoples behalf.

Personally I have had an 8565 running in an old C64 for a couple of days without any issues.

2011-07-25 10:40

Devia

Registered: Oct 2004
Posts: 401

same thing goes for SID, btw.. New SID in old C64 will work, but sound really awful due to the 3V overvoltage ;-)

haven't tried old sid in new machine, they are too precious ,-) ..but I suspect that they would either be silent or sound like crap.

2011-07-25 14:20

Talon
Account closed

Registered: May 2007
Posts: 11

Quoting ready.

about display problem, if you get the usual light blue & blue colors at start up, VIC is 99% ok, the problem might be one of the CIA chips or both (6526), or even a damaged RAM chip.

Yeah the blue/lt. blue screen, blank, and in what looks like 38 column mode.

Thanks for the pointer here.

/T

2011-07-25 14:24

Talon
Account closed

Registered: May 2007
Posts: 11

Quoting Devia

uhm.. just read your post again...

So you have a functioning C64c with no sound?
Check the fuse in the machine!
Check the fuses in the powersupply, if it's the old model powersupply with fuses in them. Alternatively, try a different powersupply.

Yep, the C64c has a broken fuse. So sound might be an easy fix then. To bad it's the 64c though ;) And it needs some keyboard surgery too, but that should be reasonably simple to work around.

Thanks for all your responses!

/T

2011-07-25 14:30

Talon
Account closed

Registered: May 2007
Posts: 11

Oh, and the two remaining breadbins "power up" as they use to say in ebay ads, but the TV screen is just black.

One of then went from fully working to this condition just overnight (switched off) a couple of weeks ago. Do you experienced ppl know of anything like a typical diagnosis of this?

Answers and suggetsions have been great so far - I am impressed with this forum!

/T

2011-07-25 16:58

Devia

Registered: Oct 2004
Posts: 401

Quoting Talon

Oh, and the two remaining breadbins "power up" as they use to say in ebay ads, but the TV screen is just black.

If you have a monitor with a horizontal centering/position potmeter, like 1084, then adjust the picture all the way to the right. On the far left of the screen, you should then see a vertical white line of approximately 4 pixels in width, just before the light blue border. Test this with one of the C64s showing a picture. If you have a regular TV or LCD, you cannot see this.

On the "black screen" ones, if this vertical line is present, it means the VIC-II is getting power and clock and is actually generating a video signal. Troubleshooting from here on gets sort of tricky, without knowledge of the c64 electronics.
If there is NO vertical line, it's most likely one of the internal voltage regulators which has given up, meaning an easy verification and fix. However, it may also be something in the clock generation (I have rarely seen this).
So, hope for NO vertical line ;-)

There are two voltage regulators: A 7812 and a 7805 marked VR1 and VR2 respectively in the lower right corner of the PCB. On pin 2 of these (rightmost pin. Numbers should be printed on the PCB) you should be able to measure the output voltage. It should be +12V on the 7812 and +5V on the 7805. If these voltages are not present or are off by more than 0.5V, check pin 1, which is the input voltage. It should be around 19-20V for 7812 and 10-11V for 7805.

2011-07-25 19:08

taper

Registered: Dec 2001
Posts: 119

Thanks for your answer regarding the VIC, Devia. I will keep it in mind!

Talon:The most common thing that makes a c64's go bust is a bad powersupply. The old c64 powersupplies (ALL versions of them, with the only exception being the heavy duty PSU that was shipped with some REU's, as they are in reality C128 PSU's with a c64 connector).

Don't be fooled, a PSU can seem to work for hours, but suddenly decides to put through more voltage than it should when it gets warm. Or it can kill the machine right away, or anything inbetween.

Solution? DO NOT USE C64 PSU's! Instead, buy or build yourself a heavyduty PSU, or modify a C128 PSU and add a c64 connector (the C128 PSU can die, but it switched and will not take the computer with it if it acts up).

I learned this the hard way. A c64 broke, I threw in another one and used the same PSU, and it took that one with it too. This was 15 years ago, and I haven't forgiven the old brick PSU's yet... ;)

2011-07-25 19:21

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: Thanks for your answer regarding the VIC, Devia. I will keep it in mind!

Talon:The most common thing that makes a c64's go bust is a bad powersupply. The old c64 powersupplies (ALL versions of them, with the only exception being the heavy duty PSU that was shipped with some REU's, as they are in reality C128 PSU's with a c64 connector).

Don't be fooled, a PSU can seem to work for hours, but suddenly decides to put through more voltage than it should when it gets warm. Or it can kill the machine right away, or anything inbetween.

Solution? DO NOT USE C64 PSU's! Instead, buy or build yourself a heavyduty PSU, or modify a C128 PSU and add a c64 connector (the C128 PSU can die, but it switched and will not take the computer with it if it acts up).

I learned this the hard way. A c64 broke, I threw in another one and used the same PSU, and it took that one with it too. This was 15 years ago, and I haven't forgiven the old brick PSU's yet... ;)

And I've flamed 3 SID-chips with a broken PSU... Grrr!

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