PDP-11/34 DD11-PK CPU backplane
Error: Pins were found with bad solder.
- GRANT chain was open, despite proper Jumpering.
- Use Ohm-meter and a magnifying glass and lot of light to detect this.
- Error behavior of the same machine may change, if a card is exchanged, or just plugged in and out.
Explanation: Some pins are not soldered in properly, and loose contact to the printed circuit board over time. This is an manufacturing failure.
Repair: No repair possible. Replace backplane.
Contact: Jörg Hoppe