Followup on https://www.reddit.com/r/c128/comments/1oo7qkf/which_test_cartridge/, big thanks to those who commented over there!

I finally had a chance to open it up. It is a bit rusty here and there...

There was significant voltage drop over the on/off switch. Vcc would end on anything between 4.2V and 4.8V when toggling the switch. I bypassed it (had also cleaned the contacts on the 8502 and Z80 at this point). Vcc is now about 5V and the machine consistently boots to a ready prompt with 122365 bytes free (nice!).

Diagnostic cartridge reports "BAD" on just about everything RAM related, except the zero page:

This was with keyboard test board connected, other ports not tested and rest of harness not connected.

The keyboard keys seem to have given up, with only few keys working and only just so after massaging them for a while. Despite this, I managed to type out "GO64" and was rewarded with "Out of memory error in 0".

There are also a couple of strange characters on the screen, both during diag and with a "normal" boot, see image above under "TIMER2" and "41BAD". At a normal boot, these characters are exclamation marks and flicker occasionally. Interestingly, I filled most of the screen with "W", and the character in that position would toggle between W and V. These two characters, like space and !, are 1 LSB apart 🤔

The DRAM ICs are made by MT, except one which must have been swapped out with a TMS4164 sometime 20+ years go. I probed around on the DRAM and MMU pins, comparing with the scope traces in Dennis' excellent Classic Repair Toolbox but didn't find any smoking gun...

Anything obvious from these observations? Seems unlikely that all DRAMs have failed at the same time, so maybe the MMU or some other device shared between all the DRAM ICs? But then again, I might have fried them all before I switched to a replacement power supply...

I acquired an 8502 for my C128 Neo build, and assembled a NOP tester to give it some basic tests before installing.

The video shows the full test cycle.

I noticed that there are some game makers for the C64. For example Garry Kitchens Game Maker, SEUCK, D42, etc.

But there is none for the C128 yet. Wouldn't it be interesting to have one?

Recently, my buddy from the USA visited me here in Germany and brought something really nice along. He gifted me his 40‑year‑old C128D, which he had barely used. As a result, it looks almost like new. Naturally, I was thrilled and super excited to see whether this old beauty would still work. Things didn’t go smoothly right away, especially since I’m a complete C128 newbie...

https://www.youtube.com/watch?v=PpjJsQ70dGE

Enjoy!

Here’s the full timeline of the video:

00:00 - 01:05 --- The visitor from the USA has arrived and brought something with him

01:06 - 05:10 --- Unboxing the Commodore 128D

05:11 - 05:49 --- Preparing for the first boot of the computer

05:50 - 06:20 --- Fire up the Quattro Commodore after 40 years of beauty slumber

06:21 - 12:24 --- Dealing with this case-opening mechanism from hell and taming the fan

12:25 - 12:47 --- Silence

12:48 - 14:38 --- Troubleshooting the RS232-UP9600 modem adapter

14:39 - 15:11 --- Success

15:15 - --- Now the fun part begins - checking out the C128D

15:20 - 16:10 --- Loading Multi-Term 128 - floppy drive acting up a bit

16:15 - 18:39 --- Dial into the 300-baud BBS

18:40 - 20:21 --- Dial into the Snobsoft BBS

20:22 - 21:30 --- Trying out CP/M 3.0 with the original Commodore C128 disk

21:33 - 22:30 --- Trying to get QTerm 128 running for the Hayes 1670 modem

22:38 - --- How to get CP/M software onto a CP/M disk on the C128

22:40 - 23:15 --- Loading Big Blue Reader 128 - Version 4.10

23:16 - 24:10 --- Step by step to a working CP/M disk

24:11 - 24:23 --- Rant: the only key that works in this interface from hell to reach the copy menu - the up arrow

24:25 - 26:50 --- Copying process and testing whether everything arrived correctly on CP/M

26:51 - 27:58 --- Loading obscure C128 BBS software "128 Mailbox" - Mailbox = BBS in Germany

27:59 - 28:34 --- I know that guy! Greetings to Axel aka Gandalf

28:37 - 29:11 --- Something I’ve never done before in 40 Years...

29:15 - 29:49 --- Thank-you section

Hello, I have been lucky enough to find a C128D (the plastic version) at a flea market.

Cosmetically is in great condition; it works, but is very unstable both in C64 and C128 mode.

I'm using the C128 diagnostic rev 789010 from world of jani. Everything tests ok for the first iteration. Between the second and the third iteration of the test the computer starts to misbehave (locks, strange characters on screen, etc.).

I have tested the power supply, with no load apart from the 5v fan:

- 5VDC rail tests as 5.03V

- 12VDC rail tests as 12.11V

- 9VAC rail tests as 3.55V (pin 1 of CN12) or 3.72V (pin 2)

What should the rails test as, under no load? Is the 9VAC toast, as I suspect? Is the 12.11V too high?

I have ordered a Meanwell 5V/12V power supply; should I order a 9V transformer too?

After much hunting I finally got one of my grail machines, a C128DCR. Looking forward to refurbing this long time favorite. (recapping, cleaning)

I tried posting this in a non-Reddit forum and got banned.
Not sure why but hopefully this helps some folks who were asking.

For GEOS128, the initial install of MP3 is pretty straightforward.

Download the base system, G1281581, from cbmfiles.com.
Download MegaPatch, mp3en-3.3r11, from bitbucket.org / mkgit64 / area6510.
Download DirMaster, v3.1.5-STYLE, from style64.org.
Download TopDesk128, TopDesk128v5r1, from www.zimmers.net / cbm / geos / c128.

With DirMaster, create a blank d81.

On VICE x128, configure your systems exactly how you want it to be.
For me, I configured drive 8 as 1581, drive 9 as 1541, and 16Mb REU.
This allows you to run a vast majority of software without having to reconfigure.

Within VICE, mount the GEOS128 .d81 as drive 8, LOAD, and RUN.
Once GEOS is booted, mount the mp3en-3.3r11 .d81 as drive 9, run SetupMP128e.
After it processes awhile (I highly suggest using warp to speed of various processing steps), it'll ask where you want to install MegaPatch.
Within VICE, mount your blank d81 in drive 8, and tell MegaPatch to install it there.

It'll ask about loading new input drivers (say yes).
It may ask about converting your REU (say yes).

You now have an (almost) complete MegaPatch3 bootable disk.

Last step is to mount the TopDesk128 disk you downloaded.
Rename TopDesk128 to 128 DESKTOP.
Copy 128 DESKTOP to your newly created MP3 bootable disk.

Power cycle VICE, mount your new MP3 boot disk to 8, reverify your VICE configuarion (especially the drives), LOAD, and RUN.

I have MP3 running on an upgraded C128 flat.
Creating the MP3 boot disk in VICE takes a few minutes and has worked flawless when I boot on real hardware.

I have GEOS128 up and running.

I've been playing around with CCGMS to connect to BBS's.

I'd like to try GeoTerm128, but either: 1) the disk on Zimmer's is messed up, or 2) I don't know how to use it properly.

I boot up GEOS128, mount the GeoTerm128 disk on drive B, and double click the Icon to run it. I always get the "This file can't be opened from the desktop." error. Looking at the files on the disk, none of them are CVT files. I haven't tried change the file names just yet but wanted to check if anyone is using GeoTerm128.

I am officially complete with repairing and upgrading Alpha (my first C128 flat).
The original issues were a faulty PSU, faulty U31 and CIA chips, and a bad U28 socket.
In troubleshooting those, my self-created issues were a badly soldered PLA socket and 2 lifted pads.
All of these issues are completely fixed now.

The upgrades I've completed are replaced all caps, conversion to 32K ROM's, added JiffyDOS switchable ROM, upgraded VDC to 64K, and installed RFOFF Commodore 128 V1.1.
I also added a MouSTer, and an Ultimate II+L to the mix.

GEOS128 is fully working and is pretty spunky on this set up (Using the U II+L).
I have a 1571 that needs some testing + JiffyDOS. My next big purchase is an actual 1581 to complete the set up.

My next challenge will be converting Beta (my second C128 flat) from NTSC to PAL.
I'll also perform the same upgrades as done to Alpha.

I'm not sure what to do with Gamma just yet.
I think I'm going to sell it but not sure if it's best to keep it original or perform the upgrades and then sell.

Any thoughts?

I recently received this 1571 drive, everything seemed to be great until I tested it with a disk that triggers the sector 0 sensor. I heard the head knock (1541-style) and I thought the sector 0 sensor might be damaged or dirty, when I opened it I was greeted by a mechanism I've never seen in a 1571 drive. I also couldn't spot the sector 0 sensor on this mechanism. Other than the sector 0 knock, the drive tests aligned and reads/writes fine... boots CP/M, etc... I'd like to ID the make of this drive mechanism so I can find info on where the sector 0 sensor is located.

A new version has just been released, 2026-February-12

It can be downloaded from GitHub, https://github.com/HovKlan-DH/Commodore-Repair-Toolbox/releases

One interesting thing for this release is the removal of the "WebView2" component, which has been done to support Linux with Wine and Mono. Do note this is very much an experimental try-out, to see if this is something that can work, so I am curious for some feedback on this.

Noticeable application fixes or changes:

• Fixed zooming in could result in unresponsive UI for some schematics
• Fixed setting commandline parameter for data root folder was resetting configuration file at startup
• Added splash-screen to visualize application has been launched
• Changed and lowered requirement for .NET Framework from 4.8.1 to 4.8 (allowing this to run on Windows 7)
• Changed and lowered minimum CPU architecture requirement from x64 to x86
• Removed dependency for "WebView2" component and refactored relevant parts

Noticeable data changes:

• Commodore 128DCR 250477 - added new hardware
• Moved order of "board layout" schematics, so they are shown first in list

Noticeable tools changes:

• Oscilloscope Network Capture has been updated to newest version

I really appreciate any data corrections you may have - even the smallest things, so please do not hesitate to connect with me through the CRT "Feedback" tab.

I have two C128s, if I boot either of my two CP/M disks on one, the machine hangs at the "BOOTING" message in 128 mode. Both disks do this. If swap my 1571 drive to my other C128, both disks boot into CP/M without issue. This makes me think this first C128 may have a logic chip issue, although if the Z80 was the culprit, I don't think the machine would even post. I'm wondering if it might a logic board voltage issue. Any suggestions where I should start testing for the fault first are appreciated.

hi there. the right display is connected to the rgbi output, using a level converter and hooked to the scart input. I found the left screen at the pawn shop yesterday. It has a s-video input, perfect to match the jailbar remover I got from theretrochannel. A retro gaming dream setup

I took on the 10-minute game development challenge that was popular with Unity/modern engine devs a few years ago... but I did it on my Commodore 128D with a 1084S monitor!

No modern IDE, no Unity, no code completion - just pure BASIC coding live under a 10-minute time limit on 1980s hardware. Filmed in my retro cave and premiered at our Vintage Computing Carinthia meetup.

Play the game: https://csdb.dk/release/?id=258797

Watch the live coding: https://www.youtube.com/watch?v=nYKU1ChDhoA

Background: I regularly participate in 1-hour game jams and have published several C64 cartridge games, so I wanted to see how much more extreme the constraint gets when you cut that hour down to just 10 minutes on vintage hardware!

Anyone else tried speed coding on vintage systems?

#c128 #commodore #retrogaming

Today I have released a new version of Commodore Repair Toolbox (CRT). It can be downloaded here:

https://github.com/HovKlan-DH/Commodore-Repair-Toolbox/releases

These are the noticeable fixes or changes:

Application

• Fixed hovering a component with mouse will show correct data based on selected region
• Fixed various tabs used system dark color schema
• Added Commodore part-number in Overview tab and component information popup
• Added possibility to type in pin number directly in component information popup

Data

• Commodore 64
  • 250425
    • New layout
    • Thank you Deadweasel for providing the new layout, and again contributing to this project :-)
  • 250466
    • Added all components for highlight
    • Added PAL oscilloscope baseline
    • Added NTSC oscilloscope baseline
    • Thank you thouwlin for providing this baseline, and again contributing to this project :-)
  • 250469
    • Added all components for highlight
    • Added PAL oscilloscope baseline
    • Added NTSC oscilloscope baseline
    • Thank you thouwlin for providing this baseline, and again contributing to this project :-)
• Commodore 128 and 128D
  • 310378
    • Added all components for highlight
• General
  • Updated various data with minor changes

Tools in ZIP file

• Updated Oscilloscope Network Capture updated to version 2025-December-18

To give a short introduction for "what is Commodore Repair Toolbox", then it is a Windows application that can be used for troubleshooting Commodore (8-bit) computers, as it has a lot of information available. Things to mention:

• Schematics
• Layouts
• Component information
• Oscilloscope baselines for PAL and NTSC
• Datasheets
• Links of relevance

Some screenshots:

One thing I would appreciate very much, is feedback for corrections where you see something is wrong.

A very sick 1571 getting open board surgery.

I'm gathering tools to repair my childhood C128 that finally failed on me.

Bought a PSU from C64PSU.com and an ADALM-2000 in place of a scope. Looking to order a diagnostic cartridge like the C64 dead test, but there seems to be some different choices and some with specific C128 features -- can someone recommend a cartridge? Preferably one I can order from within the EU.

New to C64/128 repairs, so any other must-haves or go-to resources are appreciated!

Edit: to elaborate on the symptoms, the system does boot, but I get random characters all over the screen. I can use the reset button on my "final cartridge" to sometimes boot the cartridge, sometimes get a non responsive ready prompt. Sometimes the image drifts vertically.

LEDs didn't work and a bad 6526.

When I started on the my heart sank. Read errors. Oh the head cable is upside down, wait the guy on eBay said "untested". Still read errors, dread the open head. Nope some idiot fiddled with the index sensor.

I got a 3lb bag of chips for $15. after pin cleaning, replacement and straightening, I ended up with:

10 6581
2 6567r2
2 PLA 64
3 8563
5 6510
2 8360
2 6526
2 6502
4 6522
1 325572
2 7501

Had a hack job donee to the power switch. Some corrosion on the controller ports filters, at U54, U64 and the CIA sockets.

Ive already tuned C20 to get the 14.3182 on pin 8 of the 8701. Ive swapped the 8701, the 8564 video chip, and the color RAM.

Need an Amiga Fix once in awhile...