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Commodore Plus/4

January 24, 2012 / posted in Commodore Stuff / 3 Comments

Received this Plus/4 today from eBay. Sold as untested with no PSU and fully expected this to be broken.

The power supply connector is a 4 pin affair that looks similar to the C128 and Amiga but it is not. All is not lost however as if you remove the original connector it can be directly replaced with one from a C64, and thats just what I did.


The swap was a very quick operation and to my surprise the system fired up with no issues other than some keys on the keyboard need a little more force than others.

I think the SD2IEC is also compatible but I will need an external power supply for it as mine normally plugs into the cassette port of a C64/128 for its power needs.

Homemade Micro SwinSID

January 15, 2012 / posted in Commodore Stuff / 3 Comments

Today I decided to make my own SwinSID as I had the schematics and also had the parts laying about.
After a short time checking everything was going to the right places I fitted it into my C64 and fired it up.
As expected it works just fine.
The board still needs cut down to size. I didnt add the ground planes on this one due to some through hole issues.

Thanks to Swinkels for making the SwinSID software

VIC20 repair log

January 7, 2012 / posted in Commodore Stuff, Repair Logs / Comments Off

Got Stiggys other VIC20 the other day, it wont load anything via the serial port and just reports back “DEVICE NOT PRESENT”.
According to Ray Carlsen this can be caused by a dodgy 7406 IC and he wasn’t wrong.

I checked all the states of this chip with a logic probe and all seemed to be as it should be so I went through each gate with a logic pulser and checked for its output. The outputs on pins 4 and 6 were stuck.

Removed the chip and eventually found one on a C64c motherboard that was scrap.
Replaced and tested with a demo and a couple of games.

I also took this opportunity to try out the VIC20 JiffyDOS (PAL).
My original test with JiffyDOS on this failed, nothing would load up. Turns out there is an NTSC and a PAL version, the later being significantly harder to find but we got there in the end.

MK-III C64 adapter

December 29, 2011 / posted in Commodore Stuff / 2 Comments

After a few different designs and trials I think Ive finally settled on something I like.
Ive pretty much got double sided boards sorted but making vias are a pain but it works and looks ok.
As you can see this is destined to be fitted in Stiggy’s machine. It still needs cut down to size but im happy with that.

Sorry, I wont be making these for other people so please don’t ask.

C64 – Trilogic 64 Doctor cartridge

December 29, 2011 / posted in Commodore Stuff / 1 Comment

This fancy litle thing arrived today.

It was still sealed so was a little bit of a shame to open it but whats the point in that really?
The box included a cartridge, a user port device and a serial port device

Since I love hardware I couldnt resist opening up the cartridge for a peek. Not sure what I expected to find, maybe something fancy and cool? Not likely.

I tried to open the user port device up but the screws have been deliberately sheared but there is a hole at the top where you can see in and it just looks like a load of the lower contacts are soldered together, terminals B – M according to the allpinouts.org.
One strange quirk about this adapter is it doesnt fully fit into the user port due to the size of the case the edge connector is housed in, you have to kind of mash it in and hope for the best.

The serial port device is also the same but am unable to make out whats connected yet but its very easy to make your own up.
Running the cartridge brings up a nice keyboard test screen where you can press each key on the keyboard and it lights up the relevant key pressed

Pressing the RESTORE key moves on to the Joystick test

And finally onto the computer checks

I didnt have any of the adapter devices plugged in here but they do work, whether they prove anything or not in the event of a real failure remains to be seen.

The manual is pretty informative containing possible problems for each error very similar to the superb info Ray Carlsen has on his site.
There is also a load of order forms for different “Doctor” products for the C64

After a few seconds of google searching I found a ROM dump for this cartridge so it is entirely possible to make up a set of your own should you feel the need to.

Nano SwinSID

December 9, 2011 / posted in Commodore Stuff, Computer Stuff / Comments Off

Got myself a couple of these SID replacements today.

I first saw them around April this year but have not been available to buy until now.
As you can see they are around the same size as the original and my first impressions are very good.

There are 2 jumpers on these.
The top one needs to be removed for older C64′s. It has something to do with resistor R3 and bring the volume level up.
The lower one is to switch between 6581 and 8580 emulation. A switch could also be added here to switch between then on-the-fly.

To test these against an original 6581 I used the SIDPlay program running from SD2IEC and fed both the samples into a PC to record them.
The most noticeable difference for me is the volume level on the original is far higher and I also think its a better, cleaner sound BUT as the SID chips are now going for stupid money by opportunists on eBay then this is a really nice alternative and one that will come in very handy in the future for many people.
Here are the .WAV files. Ive not converted these in any way, they were taken using Sound Recorder app that comes with Windows XP. The samples were taken directly after each other and no settings were altered at all.

Real SID
Nano SID

Amiga 4000 repair log

December 1, 2011 / posted in Commodore Stuff, Repair Logs / Comments Off

Its been a good week for repairs this week. Got Jimbob’s Amiga 4000 here which would constantly reset with any RAM in bank 0 and would not detect any RAM at all with bank 0 empty.

The board has had some repair work done before but its been done to an excellent standard. The new SIMM sockets looked flawless so that was my first suspicion down the pan. I checked the on board battery which was showing the first signs of “furring” on the contact. The battery was completely dead so I replaced this while I had the board out. There doesn’t look like there has been any battery leakage but I cleaned up the area anyway just in case.

With a bit of internet searching and a bit of probing I found a knackered 74F245 transceiver at location U891. I ordered some up and replaced it.

Fired up the unit and checked the free RAM

Played a game of Blood Money for good measure.

Commodore 128 repair log

November 28, 2011 / posted in Commodore Stuff, Repair Logs / 2 Comments

Got Stiggys C128 here that showed the same problem as I encountered with mine. The system was in monitor mode all the time and printed DSAVE over and over.
Fault fixed by replacing the CIA at location U1

PLS100 chips

November 23, 2011 / posted in Commodore Stuff, General Info / Comments Off

Today I received a job lot of 20 x PLS100 chips that I got from ebay recently.
For those that aren’t aware, these are what was used as a PLA in the older breadbin Commodore 64′s and are probably the most common failure in the machine as they tend to run hot.
Ive got the JEDEC fuse map from a genuine C64 PLA and have tested with no problems. These should keep mine and RCM’s Commodore’s going for a while longer now

C64 breadbin JiffyDOS dual boot

November 12, 2011 / posted in Commodore Stuff, Computer Stuff / 2 Comments

Today I finished my adapter to make a breadbin 64 accept a 27C128 EPROM.
The standard kernel ROM is a 2364 pinout and is 64Kb. To fit both the original kernel and the JiffyDOS kernel on obviously we need a ROM twice the size.
The problem is the 2364 is not compatible with any EPROM pinout unlike the C64c so this adapter is necessary.

I used 2 turned pin sockets, a 24 pin and a 28 pin one.

On the 28 pin socket cut pins 20, 23 & 26 short,not completely off but short enough not to make contact with the pins on the 24 pin socket when pushed together.
Connect pin 1 to pins 27 and 28
Connect pin 14 to pin 20

Get the 24 pin socket
Connect pin 28(VCC) of the 28 pin socket to pin 24 of the 24 pin socket
Connect pin 2 of the 28 pin socket to pin 21 of the 24 pin socket
Connect with 23 of the 28 pin socket to pin 18 of the 24 pin socket

Attach flying leads from pins 14, 26 and 28 of the 28 pin socket, these will go to your switch.
You can also fit a 4.7k resistor between pins 26 and 28 which means you don’t need that extra flying lead from pin 28 to the switch, just makes it that little bit easier.

Mash the two sockets together lining pin 14 of the 28 pin socket to pin 12 of the 14 pin socket, fit your 27C128 eprom and you should be good to go.
My first attempt works well but isnt the neatest. If I make another and I almost definitely will, it will be neater (sorry Stiggy)

UPDATE: Thanks to Eric for pointing out I forgot to add connecting the VCC (pin 28) line up

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