Commodore 64 loading devices

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May 292011
 

Ive recently got a couple of devices for loading games onto the Commodore 64.
The first is an SD2IEC which allows ROMs to be loaded from an SD card. This is a homemade version (thanks go to SirMorris) but works very well. If you install JiffyDOS then loading time is as fast as it gonna get on the 64. I loaded up Last Ninja 2 in about 4 seconds!


Second device is something called a Cassadapt. This allows me to load .WAV files straight into the C64 from a PC or other sound source.
Its not something many people would want as it brings back the long loading times that plagued the 64 but being a bit of a purist I happen to like some of the loading screens and music you get with some games, plus its that whole nostalgia thing too.
Its a very nice device which has the ability to copy .WAVs onto cassette using the original Commodore data cassette unit and vice versa. It even has a built in program that helps you calibrate the trigger level to obtain optimum sound levels.



I came across a small problem with JiffyDOS installed as it doesn’t support tape drives or similar, only disk based devices so I removed the 27c128 EPROM that JiffyDOS was on and fitted a 27c256 with both the C64 kernel and JiffyDOS programmed onto it and fitted a switch at the back to switch between the 2 as needed. Its a simple case of toggling pin 27 (A14) high an low to select kernels.

Commodore 64c repair log

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May 282011
 

The data cassette player would not power up and there was no sound outputted.
There is a big 1.5A fuse inside labelled F1. This supplies the +9v to pin 28 of the SID chip and is also used in powering the cassette unit.
Replacing this fuse brought everything back to life.

The C64c boots up fine without this fuse. I have been using an SD2IEC adapter to load games and didn’t realise at the time that the cassette unit was not working either.

Amiga Apollo 1230 expansion card repair log

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May 272011
 

My good mate Andy over at RCM gave me his 1230 MK2 expansion card to have a look at last time I was there. The problem was the PLCC socket on the FPU was cracked at one corner.


I did manage to confirm this was the problem by holding the socket together so I ordered some socket from China and removed the old socket
The old one came off easy enough with a hot air gun.

The sockets came and I set about fitting it. I decided to use solder paste as it makes the job quite a bit easier when soldering surface mount things with many pins.
5 or so minutes later the new socket was on and after a quick check under the magnifying glass it was time for a test run.

Workbench reported the extra RAM and my 1200 was now a flying machine so im happy its working. Tried Scorched Tanks to make sure, its the only game that was on the compact flash drive!

Rastan repair log #1

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May 022011
 

Very nearly gave up with this one thinking it was a custom IC fault, glad I never.

Was sold this board as a non worker, the guy said it boots to a white screen and the CPU needed to be looked at.
He was right on both counts.

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Before I did anything that CPU needed socketed. Once I had done that I fired the board up again but got the same white screen. I checked the data lines of the CPU and they were dead. I initially tried a known good 68000 CPU but this resulted in the same screen.
There are 6 ROMs next to the CPU which are the program ROMs. I pulled all these and checked them against MAME. The first 3 checked were fine the last 3 were actually from an Operation Wolf board and 2 of those were dead anyway. Burned 3 replacement 27c512 EPROMs and tested again.
This time I got a white screen with some garbage on.
After this I plugged in the Fluke 9010 and ran some ROM and RAM tests. The ROMs passed fine but one of the RAMs had failed. The TMM2063 @ IC10 was shot, I used a D4364 as replacement as its the first one I found compatible on a scrap board.
Board still booted with garbage.

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All lines on the CPU had frozen.
Checking the game running in MAME I could see that when you first boot the game the whole screen flashes white for a second then the game boots.
I checked the 3 Interrupt line, IP0, 1 and 2, and found that IPL1 was dead, this came from a nearby PAL @ IC36. The PAL was giving an output so I ran a jumper wire to the CPU and booted again.
This time I got a full white screen with the Hi Score at the top and the game ran but only showing the sprite data.

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I checked all the ROMs that hold the background data and they all checked out fine. These are MASKROMs and can be read as either 27c301 or a couple of reads as 27c512 with a small modification.
Following the data route from these ROMs I eventually came to a 74LS157 @ IC72. It had dead pins at #3 and #11. Pin 3 should go straight to +5v and pin 11 should come from address bus A10. Ran a couple of jumpers for these and got something a little different, the screen was still mainly white but I could see text underneath it and the sprite colours were now messed up.

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Looking underneath the board I found a discoloured track, when I ran the screwdriver over it, it came away from the board looking a little charred.

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Only a short jumper required but it was underneath the palette RAM. I started checking the palette RAM and found pin 16 was dead. I removed this 2018 RAM @ IC73 and it tested faulty, replacing this with a 6116 brought the graphics back fully.