Catch-Up – 9th May

The first job was to replace the Bank A Reload/Available switch on the top switch panel. Not a difficult task just a bit awkward replacing the top panel as a one-man job.


Replacing the Bank A Reload/Available Switch

After replacing the switch the I/O rack was switched on to check the operation of the replaced Bank A switch was reflected in the operation of LED 22 on the digital input card in slot 12. Operating both Bank A/B switches now switching LED’s on and off on the input box. Powered up the simulator and the Mode Change Not Allowed message was still present!!!

I know what you are thinking but the BANK A switch was definitely U/S. I had a document with me giving the input box LED state for the switches on the top switch panel and a quick check showed the Firing Circuits LED was indicating it was closed but it was definitely set to open. Operated the switch a few times (hoping that I didn’t have to take the top switch panel off again) and LED 22 on slot 16 now showing the switch is operating correctly. Unfortunately the Mode Change Not Allowed message still appears on the displays! I have documented the mode control LED state and have left a copy in the LCP. See below the photo of input LEDs for correct indications; ignore LED 24 on slot 8, I need to check what it indicates.

Input Box LED State for Mode Switching

Is there a problem with processing the digital input cards? The initial boot of the simulator is OK and the Argus ‘looks’ to be running well. Boot banner on FT81 OK, no 0044 errors, CHARGE OK and displaying the correct screens but some strange things happened. On one reboot the Mode Change message did not appear. Pressing the Simulator button caused all sorts of random displays as though someone was operating the system and random indicators flashing. This has now stopped and we are back to the Mode Change Not Allowed message. There was also a problem indicated by the digital output box as the 1 second switching indicated in the first group of cards happened now and then if at all. Current suspicion, or possibility, is the PeriBus cable. I reseated it on the I/O boxes and the IDC connectors do not feel that positive when being plugged in.

A question: Do the display lamps flash if you get if you have the ‘Mode Change Not Allowed’ message? I do not think they do. Again they did ‘come on’ randomly, now and then with the random operation of digital output cards! I intend to swap out the  PeriBus cable but our spare is installed on the test rig at home, this is job number one for my next Cosford visit.

During the day I removed the ME186 (PeriBus Converter), a spare is in the LCP. Made no difference to the fault but I need to replace the Xtal on the removed card. Usual corrosion problem with the original cards that have an Xtal, the rubber pad, or chemicals in it, will eventually corrode through the Xtal pins. Replace before it fails is the policy and it looks like this Xtal is not far off failing.

There is now a full compliment of spare power supplies in the LCP for PSU’s 1 to 14. I need to check PSU15 and out -50V supply  (need to take the cover in L Rack off).

At “3rd Line”

I need a new can of DeOxit Gold spray for cleaning and lubricating the backplane connectors. Will sort that for my next Cosford visit.
(NOTE: Donations of this kind of item always gratefully received!)

I’ve occupied myself with checking out our spare CRU1, a relay from the console. Some years ago I made a test lead for the CRU1 so testing is not a problem. Our spare CRU1 was salvaged from LCP 1006. LP1 should be ‘on’. LP4 is not used. Fault being a U/S RLA. These metal can 48V relays are ‘very’ obsolete so our source of spare relays is from cannibalising a unit (Amplifier Launcher) salvaged from 1006’s M Rack.

Below is Mike Strange acquiring spares from derelict LCP1006 May 2013

Salvaged 48V Relays; a good stock!

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