Internal HD20 emulator for Plus/512ke using Tashtwenty

[cheesestraws]

I've built an internal HD20 emulator for the Plus and (presumably) the 512ke (but I don't have a spare logic board to socket the IWM on, so...). It sits between the IWM and the logic board, which allows it to be internal while still letting the floppy port on the back of the machine works. It also makes an attempt to look pseudo-period - although nothing with an SD card slot will ever look really period. The things we do for ease of use.

This does mean you need to socket the IWM, which can be a painful thing to attempt - attempt at your own risk! - but the board itself is fairly easy to build.

Here it is working.


View attachment IMG_2936.MOV

Board files and details are at https://github.com/lampmerchant/tashtwenty/tree/main/pcb/Internal

 

[mg.man]

This does mean you need to socket the IWM, which can be a painful thing to attempt

Ah ha... hence the need for a couple of Plus logic boards? Don't worry, haven't forgotten - just Mac-time-poor atm!

Neat design - well done!!

 

[Iesca]

Wonderful!

 

[JAG]

Late to the show but this is fascinating. I haven’t been able to get the clip on internal SCSI interface to work on Mac Plus so this might be a nice alternative.

As an aside how did you make that analog board to logic board extension cable? I’ve been wanting something like this forever but couldn’t figure out what connectors to use.

 

[cheesestraws]

I haven’t been able to get the clip on internal SCSI interface to work on Mac Plus

Yeah, I managed to the clip-on SCSI approach working originally but the clip has been quite unreliable in the long term. I'm not sure it's a good way to go if you want reliability, unfortunately - either that or my build of it was incompetent, which is also possible.

I’ve been wanting something like this forever but couldn’t figure out what connectors to use.

It's not an extension exactly, it's just a longer cable with the same connectors on the end.

The original connectors are Molex KK396 connectors. Personally I usually use cheapish clones but some people are more fastidious. If you haven't got one already you'll need a suitable crimping tool but you can get relatively cheap ones of those for hobbyist prices too - for heaven's sake don't buy an official Molex one - and I've personally found mine extremely useful.

 

[JAG]

The original connectors are Molex KK396 connectors. Personally I usually use cheapish clones but some people are more fastidious. If you haven't got one already you'll need a suitable crimping tool but you can get relatively cheap ones of those for hobbyist prices too - for heaven's sake don't buy an official Molex one - and I've personally found mine extremely useful.

Excellent. Thank you for that info-nugget.