Attaching external drive

[ralphb]

Woohoo -- I got it to work! The missing piece was indeed the programmable shunt socket, i.e., the thing posted by Ralf in #24.

 

The crucial thing is to open ALL shunts EXCEPT the single one that selects the drive number. So in my case I bridged pin 2 for selecting DSK1 and nothing else. I guess it was bad luck in #12 that I misplaced the pre-configured shunt from the external drive in my socket so that it ended up responding to both DSK1 and DSK2, thus causing the conflict with the Lotharek. I also learned that using the stock internal drive in a PEB as-is with a second drive won't work because the MX shunt is closed.

 

Once the shunts have been configured the resistor pack needs to be removed. This much has been clear.

 

And finally the Lotharek needs to be configured as DSK2 and DSK3, but termination is not required. And I'm happy to report that the Lotharek works just fine with a twisted floppy cable. The potentially twisted lines correspond exactly to the jumpers in the back of the Lotharek, so you just have to match whatever order your pins have (see the diagram in #6).

 

 

In any case, thanks to all who contributed, and in particular to Ralf for his heroic efforts to help out a hardware noob. (Guess I'll postpone my PEB board prototyping plans just a little bit further. )

 

 

[Opry99er]

Congrats!!!!!!

[+Schmitzi]

Geht doch

 

(worx)

[DPOLARA]

I installed two additional drives to one of my TI 99/4A PEBs today after several hours of trial-n-error.  I finally found the answer here on this post.  Your suggestions and instructions helped tremendously and all three drives, including the original PHP1250, are working great!  I did end up untwisting my edge connector ribbon cable, to get mine to work, however.  Thanks all!

[apersson850]

I have had four drives in my 99/4A for many years. Two are half-height, internal in the box. The other two are full height, mounted in a separate box.

I have straight ribbon cables everywhere. Drives set to DS0, DS1 in the PEB, DS2 and DS3 outside the box. Two termination resistor blocks, in the second and fourth drive.

CorComp controller, as the TI one supports three drives max.