Thursday, October 5, 2017

HP 1000 updated to 7970E drive, work on new terminals


As expected, I had a burned out light bulb in the Reset button, as well as one in the begin/end of tape (BOT/EOT) sensor. Replacements ordered but temporarily swapped a bulb from the working Unit 3 button to the Reset position. I also hooked in a 5V mini bulb I had from the IBM 1130 project, temporarily, to restore the BOT/EOT sensor to operation.

I still have the fault where the Load button engages the relay but does not attempt to tension the tapes. There are a number of components involved in this, beginning with a chain of four microswitches that detect the limit of travel of the two tension arms. 

Unexpectedly, however, Al Kossow gave me a 7970E drive (the 1600 BPI type that matches my controller cards) and I spent a good hour wrestling the very heavy B drive out of the rack and replacing it with the equally heavy E drive. Each drive weights 130 pounds and is a cumbersome 24x19x16 in size.
System with 7970E tape drive in place
The transport portion of the new drive is working well, although the rollers over which tape will pass are sticky with hardened lubricants and therefore barely rolling. This makes the tape motion sluggish but once I deal with that, I can test the remaining portions of the control circuitry for read and write. Using the fwd and rev CE switches on the back proved out most of the motion control logic.

Al also gave me plenty of parts to complete a 2645A and a 2622A terminal, with keyboards. These will fit the two serial IO cards installed in the processor cage and give me the last of the items I would need to have a running RTE on the system.

HP 2645A terminal

Terminal keyboard

Box full of terminal parts
The tape rollers were first up on the repair list, then having received more kimwipes and 99% isopropyl alcohol, I could clean up the 7906 disk drive heads and platters. I had quite a bit of trouble getting the circlip back on the first roller that I freed up, enough that I decided to wait until I was fresh to try again.

I cleaned the disk platters, which looked great, but I had difficulty trying to clean the edge of the heads with Kimwipes alone. I will have to come up with a safe support for the wipe allowing me to gently rub the head to clean it. The flextip foam swabs that should work for this purpose will arrive Sunday.

I assembled the motherboard onto the 2622A terminal and powered it up. It has a great crisp display, only a small amount of burn-in along the bottom, and seemed to pass its self test okay. I will have to make up a cable between the keyboard, which was missing the bottom casing and cable, and the rear of the terminal. The keyboard itself looks okay, it is just a matter of building a cable.

I am currently inventorying and studying the 2645A terminal to understand what other boards must be installed and any configuration settings I must make on the cards. It does appear I have a sufficient set of boards to complete the terminal, but there are so many permutations and configuration settings that this is far from clear. 

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