Repair : C64 Black screen with signal : bare board

So I've been looking for a challenging board on Ebay as it's pretty much the only place available for me to find dead C64's.  They are expensive and in general not difficult to fix.  The board I fixed first up was a really dead Gumtree purchase.

Anyhow on with this new board.

1) The Power on flicker

When I first turned the board on I got the "power on" flicker.  This was a really good sign.
The SID on this board is soldered on the board so I'm pretty hopeful it's working at this point.

2)  Dead Test Cart.

Plugging in the Dead test cart I got the black then white flashing screen.  This is a sure sign that one of the RAM chips is dead.

I felt each chip on the board and one of the RAM chips was boiling so I pulled it and put a known good one in.

On turning the machine back on it was still flashing, this was a sure sign that both RAM chips were dead.

I replaced the second one and straight away I got the Basic screen.

3) Jiffy Dos Dead?

The Jiffy DOS screen only stayed up for 5 seconds, then the cursor stopped flashing and then the screen cleared.  I had a spare kernal on hand ( that I had burnt in a previous project ) so I swapped it in and ever since it has been rock solid.

Finale!

Well that was easy, two ram chips, one kernal rom and everything is working, even the SID.

So I'm thinking I am done with C64's . . .

I'm thinking about trying to pickup some dead Amiga 500's as I'm getting a little bored of easy to fix projects.

C64 : Another Black screen with signal . . . Complete

A few months ago I went out on Ebay looking for more dead c64's.

This time I got two, one looked like a really simple fix with a logic chip the other was a black screen. Fortunately ( or in my case Unfortunately ) I was sent the wrong for the logic chip issue and instead got a working c64 with one key missing, as a bonus the missing key was really easily replaced with one from https://www.retroleum.co.uk/.

The second c64 proved to be another black screen, however unlike the last one I was getting a PAL signal. The first thing I did was pull the SID and tried it in my newly created test board.  The SID was dead and only with the volume turned up to maximum could any sounds be heard, even then one of the voices was static.

Pulling the SID however didn't fix the black screen.

Putting in my trusty 1541 ultimate, I got a really clear normal menu with the Kernel overlay in place.  So I de-soldered the kernel and tested it in my test board.  The Kernel proved to be just fine so I put it back in place.

The next thing I did was de-solder CIA 1.  This also proved to not help as the CIA worked fine and I still had a black screen.

I had previously tried the put the memory chip over another memory chip to look for bad RAM so I tried it again on one of the two RAM chips.  I pushed the pins in so the made a good connection and nothing happened.  After mucking about pushing the RAM onto each of the RAM modules, the C64 sprang back into life.

So at this point in time I am thinking that I need to socket the left most RAM module as there maybe a dodgey solder connection there.

. . . Update . . .

After much playing about I simply can't reproduce the problem at all.  I've put in an ARMSID to replace the broken SID.  I've also put in brand new capacitors and installed a 5V powersaver.

Another unit working.

Repair : Bad C64 Colour RAM

One of my first C64C Ebay purchases was a complete "working" C64C with a 1541II and a number of games.

When I got it, it was great but it just looked washed out.  It wasn't until I tried a few more games that I realized that something was actually wrong.

. . .

To the Internet

. . .

Everything we need these days is a quick search on Google.  I found two fantastic site right away.

Ray Carlsen's amazing website : http://personalpages.tds.net/~rcarlsen/

Pictorial C64 Fault Guide website : https://derbian.webs.com/c64diag/

The first thing I did was order a C64 power supply from Ray.  I really did not want to damage my C64 any further.

The second thing I did was buy a cheap desoldering gun and some DIP sockets.  Get the right tools and do it right the first time.

The last thing I did was get a couple of colour RAM chips.

. . .

So the process was pretty simple.

Add a little solder and use the desoldering gun to free all of the pins
Use some solder wick to remove the remaining solder with your soldering iron.
Solder on a DIP socket ( always put in a socket . . . always ).
Push the chip in.

Behold . . . real colour . . .