Burning C64 ROMs ( part 2 ) : Cartridge ROMs and the Versa ZIF 64 cart

<== Read part 1

Ray Carlson's website often refers to the Jupiter Lander Cart being a great tool to identify bad Kernel ROMs.  So I searched around the internet for two things.

1) Why the cartridge was good for this diagnostic and a good reference came from the C64 Preservation website on the Commodore Max and Ultimax carts.

2) How could I make a cart and have a bit of fun at the same time, ultimately I settled on BWACK's VersaZIF64 github project and the original project Versa64Cart for the documentation pdf.

Building this project gave me another great excuse the burn some more roms using my Xgpro TL866II Plus and play with my eraser from Big Moon (or the scary skin cancer box).

VersaZIF64

I built this project pretty quickly by uploading the Gerbers to PCBWay and then ordering all of the BOM items from Digikey.  I thought as I was going to get 5 PCB's anyhow, I might as well build them all.

It was really easy to do everything as it was all documented very nicely in the github repository.

Burning the ROM

In the Versa64Cart git repository there is a great PDF on how to setup your cart after you've built it. It explains how to convert the .crt file to a .bin file for burning, how to get the config from the .crt file and then how to set the switches on your cart to get the rom to run.

The ROM itself is a Ceramic DIP 28 with a little window in it so it can be erased using UV light.  This particular chip is a 27C64 which holds a whopping 8K ( the smallest single image I can use for C64 carts ).  I also have some 27C128's which I can jam 16K images on (or 2 x 8K images).

Diagnostics

So how does this cart compare the my other carts and will it actually be useful. Well it so happens that I have a black screen C64 that generates a PAL signal (not as bad as the last repair I did). So these will be be my new test suite for my next C64 black screen repair.

Ultimate 64 - This works with the c64 only when the menu is entered (otherwise I get a black screen).  The keyboard works but games don't load and the drive resets when the C64 resets.

On the last black screen repair a similar result was seen with a good kernel rom and a bad CIA1, but the text was a bit garbled.  In this case the text is perfect and the keyboard works fine.

Dead Test Cart - This doesn't work. There is no white flashing so the RAM is possibly good?

Jupiter Lander - This starts up fine then gets some corruption after the title screen

Enhancement : Installing Open 64 Saver into my C64's

There are a number of C64 power savers out there, I have a couple of really nice units I bought from Heather at Amibay.  However I really liked the idea of having a power save in my C64 so that it didn't matter if I forgot, it would always be protected.

Trawling through the internet I found this on github which is based on Rays design :
https://github.com/SukkoPera/OpenC64Saver

The build was pretty simple, the repository had all of the resources required ( the BOM and Gerbers ) as well as the references to Ray Carlsens images on how to install the Saver internally.
http://personalpages.tds.net/~rcarlsen/cbm/c64/SAVER/MOBOs/

 You can see from the LED when it's active ( green ) and not active ( red ).  There is a variable resistor on it so you can get it set correctly.  I found with cased board that the heat caused it to trip at a lower voltage ( as per the Git notes ).  So I trimmed it up just a little bit.

The two mother boards I installed mine on were 250469's and required a trace to be cut.  This was a bit of a harrowing experience, but with a stanley knife, a steady hand and lot of patients I eventually got it cut nicely.  I used a multi meter to ensure the break.

 

Initially I was at a complete loss as to how I was going to mount it.  Then it struck me that it was small enough to be mounted behind the keyboard very neatly and more importantly I could mount it without worrying about it shorting out anything.  Take note of the NYLON screw and spacers I used, which fitted perfectly.

 When I first plugged it in I got a bit of a fright.  I am so used to plugging in the live power and nothing happening.  This time the relay kicked into life instantly because it sits before the power switch.  Which is totally awesome, as it will kill the power of a bad power supply even before I turn my c64 on.

C64 Off

C64 On

Enhancement : Upgrading my C128's VRAM from 16K to 64K

I've know for a while that it was possible to upgrade my C128's VRAM from 16K to 64K of RAM.  I'd recently pulled it apart to make sure the caps were all still okay so I took the opportunity to give the upgrade a go.  Also I'd acquired quite a few ram chips for C64C repairs.

Ray Carlson has an article here on it :
http://personalpages.tds.net/%7Ercarlsen/cbm/c128/RGB%20V-RAM/64kvram.txt

I had seen the easy upgrade option using a daughter board.  I wasn't really happy about not being able to put the cover back on the graphics chips properly with that method.  With my new found de-soldering skill I just decided to remove the old chips and put in some sockets.

. . . and well the result . . . I wasn't really expecting any difference for the most part.  My C128 started, I tested it using Ray's test code.  I loaded and ran a demo that used it which for the most part worked however my Commodore Monitor did have some issues with some of the tested resolutions.  I even ran GEOS with the 3.3 Mega patch.  That's pretty much it.  Well if I need my chips back at least I can swap back in the old 8K chips in to the nice new sockets.

Sony Trinitron PVM . . . What a find!

I’ve been looking at Sony CRTs on EBay every now and then, ever since I saw a video with Ms Mad Lemon showing off her Monitors.  I had already bought a Commodore 1084 which works fine, but I wanted a second monitor so I didn’t have to keep swapping my computers about and monitors are hard to come by where I live.

Where I am we have a cyclones ( or hurricane for non Australians ). So once a year before cyclone season we have a clean up where people put everything the don’t want on the nature strip to be disposed of properly before they become flying missiles.

Some one left this magnificent beast out there, I drove past saw it and grabbed it.  I was a bit dubious that I’d just picked up something that would end up outside my house for collection. I brought it in turned it on and . . . Oh my goodness, it is magnificent, a little worn but in perfect operating shape.

So now my Amiga and C64 are hooked up to it.  I’ll leave my c128 on the 1084.

Repair : C64 No signal, black screen fix - part 3 - the final chapter, success!

Well . . . I was totally wrong about the ROM's I replaced both to no effect.

Back to the drawing board.

Looking at diagnostic pictures and my remaining socketed chips I was getting down to a last man standing situation.

I only had 5 chips left, CPU, CIA2, PLA, Color Ram and two identical logic chips.

PLA - ease don't

I guessed the PLA ( I had two spare ) and got to work de-soldering it very, very carefully
WARNING : apparently it is very easy to kill it by removing it.

I eventually got it out very cleanly.  I put in a socket and then inserted a new PLA and got this.

Ugh Oh,  that's not right. I put the original PLA back in the socked and got the same picture. I pulled out the multi-meter and began checking all of the connections, nope everything was fine.  I then checked for shorts.  I already knew that two of the pins short when a cart is attached so I removed it.  I quickly found the short between two pins connected to the Colour RAM.  The solder had joined under the socket.  With a piece of copper solder wick I jammed it against the side of the socket and it cleared the short and I went back to the black screen.

The Final Culprit - CIA2

Time to pull CIA2.  So I got to work and removed it and powered it up without CIA2.

Now we are getting somewhere.  I quickly socketed it and jammed in my two spare good CIA's.

Now it's all working . . . so what was the damage?

I replaced 3 x logic chips ( status unknown, one was probably dead ).

1 x ram chip ( dead ), 2 x CIA chips ( dead ), 1 x SID ( dead ), 1 x 8701 ( dead )

Was it worth the repair.  Cost wise I'd have to say no.  If you wanted to have C64 that works just buy a working one.

Education wise, yes it was a great exercise. On the plus side I now have a test board with almost all of the IC's socketed.  I buy this dead stuff to learn skills and my through hole soldering is so much better now.

I'm also pretty pleased I got the PLA out in one piece.  I've read it's quiet hard to do without killing it.