Commodore 128D 100% NOT tested, does it work?

I present to you my “new” 100% NOT tested Commodore 128D, which I purchased on eBay. Shall we try it? In your opinion, will it work?

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Purchase of the Commodore 128D 100% NOT tested

I occasionally buy some vintage computers for my collection. Unfortunately, sometimes it happens to receive computers that do not work, despite being declared as perfectly fine. Or, it happens to receive computers ruined due to inadequate packaging.

This time, the premises are even worse: will this 100% UNTESTED Commodore 128D, purchased on eBay, work?

Lot Commodore 128D, CBM 128D, C128D, German keyboard, power supply and external drive bought on eBay

In addition to the Commodore 128D and the keyboard with German layout, there are also a number of accessories that have little to do with the Commodore 128. There are two power supplies of the Commodore 64, an external drive power supply (which can be the 1581, for example), and an external Commodore 1541 drive (which does not require an external power supply, though...).

Here is the "new" Commodore 128D 100% NOT tested!

A few days after purchase, I received the 100% UNTESTED Commodore 128D. Here it is, in all its splendor. Work? Won't it work? We'll find out shortly. All the tools present near the computer are used precisely to find out.

Commodore 128D, German keyboard, dual monitor connection, 40 columns, 80 columns, test and trial

The keyboard has a German layout, in fact the Commodore 128D comes from Austria. The case is plastic, with side handle. The keyboard can be housed at the bottom of the case, which has a special compartment.

Commodore 128D, CBM 128D, C128D, German keyboard, plastic case, side handle, bottom keyboard housing

Check supply voltages of the Commodore 128D

Unlike the Commodore 64, Commodore 128 and other home computer models, the Commodore 128D has an internal power supply. Before connecting it to the mains and turning it on, it is advisable to check the supply voltages. They must be corrected! I had written this article To learn more: I invite you to read it.

To check the power supply voltages of the vintage computer, you have to open it. There are four screws to unscrew, at the bottom.

Commodore 128D, German keyboard, internal, floppy disk drive controller card, power supply

Before giving voltage to the power supply, we detach the two connectors that bring power to the internal floppy disk drive controller and to the motherboard of the computer.

Commodore 128D, internal power supply voltage test, motherboard connector, floppy disk drive connector

The goal is to be able to power the computer, test the voltages with the tester, but without any incorrect voltages reaching the computer cards.

The voltages to be verified are:

  • 5V direct current, for computer logic;
  • 12V direct current, for floppy disk drive;
  • 9V in alternating for the SID (on this voltage there is a lot of tolerance).

Thankfully, in this 100% UNTESTED Commodore 128D, the voltages are correct.

Commodore 128D, internal power supply voltage test test, 5V 12V 9V, connectors, testers, multimeter

First power on of the Commodore 128D

After reconnecting the two connectors that we disconnected to test the supply voltages, we can try to power the computer. To my surprise, Commodore 128D 100% NOT tested… works!

Power on and Test Commodore 128D, CBM 128D, C128D, works, green boot screen, Microsoft Basic V7, 122365 bytes free

On closer inspection, it was found that the computer's internal floppy disk drive cannot read the floppy disks.

The Commodore 128D allows you to use two monitors

This is a speech that I had already deepened in this article: the Commodore 128 (as well as the Commodore 128D) allows you to use two monitors, one with 40 columns of text, one with 80 columns.

To connect a VGA monitor to the RGBI output (the 80-column output of the Commodore 128), you need a specific adapter, as well as a monitor that supports a horizontal synchronism of 15 kHz. Typically, however, monitors support synchronisms starting at 31 kHz. So, most likely, a randomly chosen monitor will not fit.

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Commodore 128D, dual monitor connection, 40 composite video columns, 80 RGBI columns

Although you only see one monitor used at a time, the C128 actually allows you to use both monitors so that they display different text (or images).

More in-depth test: the diagnostic test 586220

To carry out a more thorough test of the peripherals and circuits of the Commodore 128D, we can use the diagnostic test 586220, which I had already reviewed in this article. It works for the Commodore 64 and the Commodore 128.

The 586220 diagnostic test consists of an interface to be inserted into the expansion port, as well as other interfaces to be inserted into the various ports on the computer. In the image below, you can see the red diagnostic cards.

Power on and Test Commodore 128D, diagnostic cartridge 586220, diagnostic test Commodore 128 64

When you turn it on, the computer starts with the diagnostic screen of the Commodore 64 version 586220. The computer performs several tests (ROM, RAM, SID, computer ports, etc.).

C64 C128 C128D diagnostic cartridge rev 586220, harness, test connector circuits

My Commodore 128D 100% NOT tested may have some problems with the user port. I don't think it's a difficult problem to solve: either there is an interrupted track on the printed circuit board, or there is an integrated fault (diagnostics already indicate which integrated ones may be responsible).

What do you say, I'm happy with this Commodore 128D 100% NOT tested?

Would you be satisfied with such a purchase, bought as 100% untested and finding it in these conditions, still working?

I consider myself quite satisfied, also given the previous experiences, in which I bought things that worked, which then did not work. While we're at it, I remind you to subscribe to the YouTube channel and activate the notification bell.

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2 Comments

  1. Hello

    I have recently gotten my hands on a C128D (the European version with plastic case and handle, not the CR one).

    It was running fine, until I heard a sound like a steak being grilled on coal, followed by the smell of burned electronic components! 🙁

    I looked at the monitor and the computer seemed to be working fine, but I turned it off immediately and disconnected it from the 230V socket.

    Everything looked ok inside, except the IEC filter was REALLY hot, I could not even touch it. It melted the white glue used to fix the wires that go to the PSU too. Some of it fell on the RF shield, so good thing it had one! 🙂

    I disconnected the PSU from the rest of the system, and plugged it into the 230V socket using the IEC filter and now it works ok. No sizzling sounds, IEC running cold.

    The only thing strange are the output voltages (no load):

    11.70VAC which I think it should be 9VAC.
    11.79VDC which I think it is the 12VDC rail.
    5.45VDC which I think it is for the 5VDC rail. I am particularly concerned about this one, because for the C64 when the 5VDC rail is above 5.2VDC it can damage the internal components (according to the C64 wiki).

    With the computer on (ready prompt), I got the following voltages:
    9Vac: 11.3V
    5Vdc: 5.13V

    So I am trying to find out if those output voltages are fine. The wiki only have the safe voltages for the C64. 🙁

    Anyone can help?

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