PDP 11/24 - A Step Backwards

On-Topic OK, so I disconnected ACLO only. It was quite a struggle to separate those nylon connectors, is there a trick to it? In doing so I spotted two backplane wire wrap pins touching and a couple of others that were quite close too, so I separated them and inspected all the backplane pins. I didn't see any other ones touching. When I powered on, the CPU LEDs did not light up. Some random characters appeared on the console, but probably just a bit of noise maybe? However, I did notice that the CLK LED flickered on briefly when I powered it off. I put a scope probe on TP1 (p152 of the PDF), there was no activity, the pin remained high. The problem now is that I expect I will need to probe various pins to find out what is going on. But I don't have a Unibus extender and I am reluctant to remove the backplane. From what I can tell in the Technical Manual you can't install the CPU in other slots to make room for attaching probes either. I am forced to tack solder probe wires to the chips, which works but is time consuming. Any other ways? Using tack soldered wires, I have traced back and I *think* I have found something. There could be a fault in E52 (sheet K6, p157 of the PDF). While K6 BUS DCLO L is +5V, I am measuring K6 BUF DCLO H at an average 1.64V with 50us spikes at 2.08V. According to a NatSemi datasheet for the DS8641 (http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005806.PD F) the logical 0 output should be 0.4V max and the logical 1 output should be 2.4V min. I also measured K6 BUF DCLO L to be always low, suggesting it thinks the K6 BUF DCLO H is a logical 1. This seems to suggest that E52 may be faulty. Trace here: https://rjarratt.files.wordpress.com/2022/04/e52-dclo-signal.jpg. Regards Rob