Built the extender board, spliced the replacement cable for magnetic pickup

CONSTRUCTED THE EXTENDER BOARD

I dug out some hardware, drilled holes and anchored the wire wrap style connectors onto the end of the extender PCB. The mounting aligned the wirewrap tails of one side up against the PCB traces, so I soldered that side down. The other side needed jumper wires from the tails to the PCB holes further down the board.

Mounting brackets and direct solder of one side to wire wrap tails

The design of the extender PCB didn't directly connect the contacts on the card cage side with the contacts on the new connector that will hold the extended reader PCB. There are pairs of holes for each signal, thus the signal can be passed between the holes, blocked, or a new signal substituted, depending on the debugging requirement at the time. While it is a flexible approach, I didn't need that functionality.

It did leave me with the requirement to bridge the pairs of holes even for the side of the connector that I had soldered right to the PCB traces, because the traces were interrupted at the hole pairs. I put in small yellow jumpers which established an end to end connection for all signals on that side of the extender board.

Yellow jumpers for other side's direct soldered pins

 

The other side needed jumper wires soldered to each of the connector wire wrap tails and the other end soldered into the hole in a pair that was connected to the other side, the card cage end. I used blue wires for this purpose. With those wires all in place, the extender was put into the cage and is ready to accept the Clock card for when I restart my debugging.

Wire wrap tails jumpered to far side holes

SPLICED NEW CABLE ONTO THE MAGNETIC PICKUP

I put the new cable onto the short ends of the existing cable coming out of the magnetic pickup. I wrapped as much shielding around it as I could and then taped it up securely before loosely fitting the pickup into its bracket under the machine near the many-toothed timing wheel. 

Black wrapped replacement cable to pickup

The other end had its two signal leads already soldered to the leaf contacts that fit into the Amphenol connector. The shield should be attached to a third leaf contact but it had broken during the repair operation previously. I put the two signal contacts into the connector but have to wait for a new contact before I can finish the insertion. 

Black and white wire contacts inserted already

I did verify good connectivity of the magnetic pickup and its approximately 630 ohm DC resistance, same as the working pickup on the M600 reader nearby. When the cable shield is soldered to a contact and inserted, the pickup itself must be positioned to .007" distance from the timing wheel teeth before I can turn on the reader. 

ORDERED REPLACEMENT CONTACT FOR PICKUP CABLE

After twenty minutes of internet detective work, I found the proper contact part at Digikey and ordered it. I should have it by midweek and wrap up the pickup repair. 

WORKING OUT WIRING FOR SECOND EXTENDER BOARD AS ANALYZER CONNECTION

I received two boards from Datamuseum, one of which was outfitted with the connectors for use as an extender. The other will serve as an easier method of connecting a logic analyzer to the motherboard (backplane) signals. The card cage has a connector in place at row 4 but no card sits there. I can plug this special extender card into that slot and it can give me access to all the backplane signals. 

If the holes in the PCB were the right size for standard 2.54mm (.1") header pins, I could have used female-female jumpers to connect those pins to the logic analyzer cables. Instead, the holes are much larger diameter so I have to sort out the easiest way to reliably make connections between my logic analyzer cables and the board. The solution is yet to be determined.