Not everyone shares my preference for SMD. And I promised some time ago to make a version of the TriMod CBM adapter without SMD. And I would like to introduce this to you in this article. One could also say, the fasting time is over, it may be again something more...

 In the article TriMod CBM Adapter - One Commodore Floppy for two worlds I had already introduced the following adapter for the Commodore VC1541 Floppy:

TriMod CBM Adapter Beitragsbild



If you own a CBM or PET computer and want to buy a floppy disk drive with IEEE-488 today, you will be surprised about the prices, which have partly been increased on the different platforms. Fortunately, there is an alternative, and that's the 1541. This drive is cheap to get and the market is flooded with these drives.

Of course the VC1541 is a drive for the VC20, C64 or Commodore 128. But Commodore had brought the drive 2031 on the market at that time. It was basically a 1541, which was only minimally modified. Thus this drive had, instead of the IEC interface, an IEEE-488 interface.

If you look at the original schematics, the differences are really marginal, and it only takes a handful of components to build an adapter that turns a 1541 into a 2031.

After the conversion, this floppy would of course no longer be operable on the C64 and Co., at least not with the IEC interface.

And there is the special thing about this adapter, because it is switchable at the push of a button. So you can use this floppy alternately for both worlds. 


Please no SMD project

This adapter has been available for some time in an SMD version. But I know that not everyone likes SMD soldering. That's why I announced at that time that I will make this adapter in a version that does without SMD components and is completely built in "THT" (Through Hole Technology). Of course this adapter is a bit bigger. I took this as an opportunity and integrated a kernel adapter. So you save an external adapter.

TriMod CBM Adapter Platine


The circuit board is designed in such a way that it is simply attached at the top. The MOS 6522 VIA chip and the kernel ROM have to be removed. The VIA chip is plugged onto the adapter board. Additionally an EPROM of type 27C128 or EEPROM of type 28C128 is required. There the kernel for the IEC mode is burned first, as the original kernel of the 1541 (or JiffyDOS and similar) and in second place the IEEE-488 kernel of the 2031.

The construction and also the parts are analog to the SMD board, only with the difference that instead of the SMD version now the normal "THT" components are used. The finished board looks like this when installed:

TriMod CBM Adapter Platine eingebaut


And again from above:

TriMod CBM Adapter Beitragsbild


Rebuild adapter

Who would like to copy this adapter, can have gladly from me a circuit board. I still have some left. You can get it here: PCBs

The exact component list and IEEE-488 firmware will be sent to you by eMail afterwards.


Translated with


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RuudBaltissen's Avatar
RuudBaltissen replied the topic: #60 1 week 13 hours ago
I möchte gern eine Platine bestellen aber das funktioniert nicht.
MfG, Ruud
diwou's Avatar
diwou replied the topic: #61 1 week 12 hours ago
Hallo Ruud,

Precies waar gaat het niet verder? Is er een foutmelding?

Ik had het net getest, en het werkte. Misschien een of andere Script Blocking Tool actief in de browser?

VG Dirk
RuudBaltissen's Avatar
RuudBaltissen replied the topic: #62 6 days 22 hours ago
Hallo Dirk,
Maf, zojuist werkte het wel. Ben ik blij :)
Maar gisteravond belandde ik tot drie keer toe op op de eerste pagina om te bestellen nadat ik mijn adresgegevens had ingevuld en op "Weiter" had gedrukt.
Vraag: is het ook mogelijk het schema te krijgen?
Ik wil de print gebruiken om een IEEE variant van mijn 1541IDE project te maken:
Alvast bedankt!
Groetjes, Ruud
diwou's Avatar
diwou replied the topic: #63 6 days 18 hours ago
Hallo, Ruud,

Ik heb je een keer een e-mail gestuurd met meer informatie.

VG Dirk

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