Alternative parts : Replacing SID with a SwinSID ( and building one )

I've been fascinated for years with the original attempt to replicate the SID, the SwinSID.  I've always wanted to build one but I found my lack of knowledge of electronics and lack of detailed step by step instructions on Swinkels website was quite a stumbling block for me.

Years later and with quite a few electronics projects under my belt, this little gem from Tolaemon appeared in my search while trolling around the myriad of shared projects at PCBWAY.

Tolaemon's nano SwinSIDb tutorial . . .

And so before I even went to website I ordered the PCB from PCBWAY

I must admit I was a little worried that this wouldn't work but hey I'm giving everything interesting a go that I can and here is what I ended up with.  After soldering MiSTer I/O boards and SDRAM boards this project proved to be a very easy build.

The version of the Microchip software I used was a little newer than that used in the tutorial and it was here that I became unstuck.

I burnt the firmware fine and the lockbits but when it came to the fuses all of the options had been renamed.  I left everything default and selected the correct external clock setting (EXTCLK_6CK_14CK_65MS) and burnt it to the chip.

Putting the SwinSID in the c64 I got a horrible horrible tone that didn't change.  The good thing is when you go to re-program the chip you can re-read the settings and for some reason the external clock hadn't changed from the default.

So I changed it and burnt it again and this time there was silence when the power went on.  On loading a game I found it would make a little noise then silence then some more noise but was nothing close to the music I expected.

Again I put the chip back on the programmer and one of the fuses that was default on needed to be turned off ( the CKDIV8 ).

This time I got success!!!

So what do I think about the SwinSID . . . well it's actually pretty good, the project was a lot of fun and I learnt quite a bit doing it.  For my C64's however I think I'll stick to the ARMSID as my SID replacement of choice.

I found the SwinSID did pretty well on the games I tried, but it just sounded a little off in some places also for ShadowFire it just didn't work at all.

Alternative parts: Replacing 6526 with 8520 cia

I found it hard to find 6526 CIAs to replace the dead ones in my C64s.  Scouring the the Internet hoping for an alternate I found this Forum discussion about using an Amiga 8520 CIA instead and what was different between the two chips. As 8520 chips are abundant on AliExpress I thought I'd give it a crack.

For the most part they work pretty well. Ive found some weirdness with my Ultimate 64 cart where the auto run doesn’t work, but mounting and loading normally is fine.  I wonder if it’s the clock?

Overall they seem like a good substitute until someone builds a better one.

Alternative parts : Replacing SID with ARMSID

The biggest problem with retro computers is sourcing parts, which haven’t been manufactured since the 1980s.  SIDs and CIAs are pretty expensive to replace these days so the new awesome alternative parts are fantastic.

I’ve got two c64s both with broken SIDs, so I thought I’d give the ARMSID a red hot go. I’m pleased to say everything I’ve read about them is true. I’m not an audio aficionado but they sound great to me.

You can read about them here and you can buy them from here.

It took about 3 weeks to get to me from the Czech Republic, most of that was probably spent in customs in Australia.

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.

Indulging myself with a C128D

A while ago I bought a pretty cheap C128D keyboard on Ebay.  I have been using it a lot with my MiSTer using an Arduino as a USB HID interface.  The recently I got an Amiga 2000 keyboard to build a new interface for my MiSTer ** so the C128D keyboard was about to become surplus to requirements.

There is something about the C128D that I really liked so I picked up a working one all the way from Germany.  I'm really happy to say that it arrived safely and it works beautifully.  I am going to set this up with my 1084 monitor as my center piece for my Commodore retro collection.

It's so pretty!

** If you haven't seen the MiSTer project, you are missing out.  It is an Open Source project with a FPGA the runs a huge amount of retro computers, console and arcades.  I've been using it since it was first released, having been a Mist user previously.
MiSTer on Atari-Forum
MiSTer on GITHUB

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.

Burning C64 ROMs ( part 1 ) : Kernel ROMs

I've always wanted to try to burn new EPROMS for my C64.  I remember as a kid pulling apart my carts and pretending I could mod all sorts of stuff into them.  Well now I can . . . sort of.

As part of my trouble shooting it looked like the Kernel/Basic ROM was shot so I thought I'd have a go at burning one.  Turns out it's actually pretty easy with the right equipment (It also turned out the Kernel ROM on the board was fine after all).

I bought myself a "TL866 II plus" and some 27128 EPROMS from Ebay.

This site has the C64 ROM images and which EPROMS are compatible:
https://ist.uwaterloo.ca/~schepers/roms.html

The UV Erasable ROMs I got were actually ST27c128 which the software didn't have an entry for, but I read on the internet that if you just use the AMD AM27C128 and turn off the "Check ID" it works fine, and it does.

Read part 2 ==>

Desoldering DIPs

I've had a bit of practice now desoldering DIPs, so here are some of my desoldering DIPs tips.

I use a cheap desoldering station, you can heat the work quickly then pull the trigger.  I've used manual solder suckers in the past and man I suck at using them, but the desoldering station, bang done. https://www.youtube.com/watch?v=Ft50m8UU5WQ

After inspection, if there is a lot of solder on some pins still (where it went right through the via normally) add some new solder and repeat the process again.  Putting fresh solder on initially helps as well.  I use a microscope and some ESD tweezers to have a good look.

Don't pull the IC's initially.  If you give them a little side ways twisting motion you can usually see which pins are not free.  Big dips are quite hard to remove and need more patience as the leg count increases.

For troublesome pins you'll need some flux and some desoldering braid.  While running the braid down the pins with the soldering iron, just push the pins into the body of the dip.  This helps get the pin off of the via and gets all the solder off of it.

Once you can give it a twist and see that all pins are moving freely you can pull it, with care.

Repair : Amiga 600 Keyboard Troubleshooting and Fix

Having never owned an Amiga before and definitely never opening one I did something silly.  I pulled the keyboard membrane right out of the socket without unlocking it.  Only once I had fixed the board and got it back to a bootable state did I realise that a whole row of keys ( the caps lock row ) was dead.

So off to the internet I went. I read a lot about people inadvertently stripping the material off of the end of the membrane or just doing it from taking their Amiga's apart a lot.  I though darn it I just broke it.  However when I looked at the end of the membrane there was heaps of material left on it, nothing like the photos I had seen.

The people were talking about bad sockets as well.  I had a second Amiga 600 so I carefully unlocked the socket and swapped it into the other Amiga.  It worked, so there was nothing wrong with the socket.

The last thing I read was about carefully checking the membrane looking for breaks.  All in all it looked fine until I got to where the tail went into the keyboard.  I had already noticed rust on the RF shield above a corroded trace.  When I looked at the keyboard tray it was rusty in the same position.
Obviously the previous owner had spilt some water in the keyboard and it leaked.  And right at the join two of the traces had completely oxidized.

 It may be a bit hard to see in this photo but under the microscope it was easy to see lines 3 and 5 (from the left) have turned to mush.  I confirmed it with a multi-meter as well.  There was no fixing this bad boy.

I headed off to EBay and after carefully checking the membrane type ( there are different A600 keyboards requiring different membranes ), I got a membrane from retrocloud-store.
https://www.ebay.com.au/usr/retrocloud-store?_trksid=p2047675.l2559

The membrane came nicely sandwiched in two thick pieces of cardboard. Now it was time to clean up the keyboard.  The keyboard was dirty, however a good going over with a blower, a damp cloth and some q-tips fixed that. The tray was another issue.  Water had gotten into the edges and had rusted the inside of the tray.  I gave it a good sanding and washed and dried it.  Then I gave it a coat of Zinc Gal (used to protect welds) over the tray.

Now I've got nice clean working keyboard to go with my Amiga 600.

Alternative parts : Replacing the 8701 with TOLB

As part of the Black Screen repair I had discovered that the 8701 timer was bad.  There was not video signal coming out of the c64 at all.  With a swap of a good 8701 it was confirmed, but in the end I needed a new 8701.

So I bought a couple of TOLB (pal) from Eslapion and they've just arrived from Canada so in they go!!
https://www.ebay.com.au/usr/eslapion

They work really well.  He sells two versions one for PAL and one for NTSC and he sells a PLA replacement as well for older c64's ( not my c64c's which have a much bigger PLA with more integrated logic ).

Repair : C64 No signal, black screen fix - part 2

Who's the suspect?

So at this point I was stuck.  I scoured and read every bit of Ray Carlsons C64C chip notes.
http://personalpages.tds.net/~rcarlsen/cbm.html

I'd looked at every single picture of the C64 pictorial fault guide.
https://derbian.webs.com/c64diag/

The only cart I had that sort of worked was my dead test cart.

But then I had a flash of inspiration.

Ultimate II 1541

Now I mentioned Gideon's Ultimate 64 in part 1 of this article.  However I also had an Ultimate II 1541.  Initially I wanted to use it to make sure the disk test I had done with the 1571 was okay.

When I plugged the cart in and turned it on . . . nothing.  The disk light flashed but the screen was black, but then something great happened.  When I brought the menu up with the middle button on the cart I got this!

Looking at it I could make out where the menu text was meant to be.  There was a lot of junk on the screen but I could definitely see the menu.

 

The Kernel is a bit iffy

Looking back at the Ray's site and the Fault guide, everything started pointing to a Kernel Fault.  This also made sense as the Kernel and Basic ROM are on the same chip.  So when I returned back to Basic I'd get a black screen, but then when I went back to the Cart menu, it didn't use basic.

So it's definitely the Kernel Basic Rom and probably the Character Rom too.

I didn't have anything that could replace the Kernel Rom, OR DID I!!!  One of the great things you can do with the Ultimate II is to use a replacement Kernel Rom and VOILA!!  When I return back to basic I get nothing, but that's to be expected as the Cart can not replace the Basic or the Character Roms.

Slow boat from China . . .

At this point I'm waiting for some EPROMs and a Burner to come from AliExpress and for some replacement parts from Ebay . . . so stay tuned.