Apple II

Hello Friends:

So here is a bit of a mystery issue I am trying to solve.

I am using an Apple II+, standard board, no mods.

In the machine are the following

Slot 0: Saturn memory card

Slot 1: Grapler

Slot 2: A2DVI 

Slot 3: Videx 80 col card (A2DVI configuration Videx is enabled)

Slot 4: Microsoft Z80 Soft Card clone

Slot 6: Disk Controller Card - Disk 1 is a Floppy EMU Disk 2 is a physcial floppy drive

Slot 7: Sider Interface Card - no Sider connected at this time

My Apple IIe has two Disk II drive cables, each secured to the back panel with a U-shaped clamp and a single screw. The clamp has two screw holes with captive nuts, but only one screw was installed (on the open end of the U I believe, didn't quite look). Figuring the second screw was just missing, I added one to the closed end, and the computer wouldn't power up at all. Removed it, powers up fine. Repeatable.

I must have shorted something with the 2nd screw. Has anyone else run into this? Is a single screw actually the intended installation, despite the clamp having two holes?

I've read that this is a common problem when the 74LS125 goes, and mine was so fried it blew a hole in the case such that you could see the die. I replaced it with a brand-new part, and the behavior has not changed.  

C4 is not visually damaged and is not a dead short. None of the legs on Q2 are shorted. The drive reads okay until it tries to read a track it has already passed over (and thus erased).

All the pins on the head connector are a dead DC short; is this normal? 

Hi,

While browsing various forums, I've noticed that people are having trouble connecting a DuoDisk to a Disk ][ card with two IDC20 connectors. Below is a diagram of such a cable (without the DB19 connectors). It's a direct connection from the DB25 to the two IDC20 connectors. Everything works and has been tested. The DB25 pinout is as described on the connector, but pay particular attention to the correct IDC20 pin assignment.