Work Day 26th November 2022

T86

New stainless bolts were fitted to brackets supporting the flexible waveguide at the join to the rotating joint at the head of the pedestal.

LCP

The 5V power supply for the Argus 700 failed last week and has now been replaced. Due to age a common fault is a bad Tantalum capacitor on the power supplies’ control board so that is the first check in the repair.

The simulator is now serviceable after finding a loose 0V connecting stud on the digital input box causing the resistance between the 0V on the Digital Input box and 0V on the bus bar to be It’s the 2.7ohms; this reduced the +5V across the TTL on input cards preventing the LED state (controlled by console switches) being read by the Argus 700. For safety reasons the Argus computer software checks that the console control switches are not in their correct position when they are. The LEDs showing the staus of the Digital Input and Output Cards (1 second after switch-on) are shown below.

Digotal Input Cards

Digital Output Cards

Unfortunately to tighten the nuts and bolts that make up the terminal it is a two man job, one at the front of the box, another at the rear. Anyway. It’s working. I expect the Swiss don’t get these problems as their kit wasn’t left in the open for twenty years. I have a spare Digital Input chassis (ex 1006) at home so if I get time I’ll do some checks on it.

Cheers
Pete H

Work Day 19th November 2022

T86

No work was carried out on the T86 this week but new UNF machine screws to replace those used for brackets and clamps on the aerial assembly have been ordered; stainless of course.

LCP

The software developed a ‘Mode Change’ notification recently and covered in a previous blog. This is a notification that inhibits the simulator software running. One check required to identify the cause is to check the resistance across the 5 volts on the digital input and output cards. Why do this? A simple Ohms check across the 5 Volts will reveal a known problem, that the original glass encapsulated decoupling capacitors fail regularly. The resistance check should give around 270R but three input cards were well below this value, one card being just a couple of Ohms. The three digital input cards have been removed and will be repaired soonest. This photo shows stacks of digital input cards awaiting their Ohms check.

Occasionally lamp lenses in the LCP are removed for rejuvenating as they deteriorate with age. Lenses are cleaned and treated with Polytrol surface restorer.

The lamp lenses on the left have not been treated but those on the right hand unit have been – if you look carefully as the camera lies!

SALVAGE

We did manage to salvage a few subassembliesfrom LCP 1006, as seen here, before its final destruction

The main reason for recovering these was to salvage parts. Some have already been used especially 50 volt relays used in repairing units CR1 and CR2, relay control units in the console. Both CRU1 and CRU2 recovered from 1006 have had relays replaced and are now part of our spares stock. We are thinking about keeping one reasonably good sub assembly for display somewhere or by someone else if approached with an appropriate contribution to our funds.

Pete H

Work Day 12th November 2022

T86

A start has been made on checking various items previously removed from the T86 cabin. Some are already refurbished including the anchor pillars for the aerial pedestal.

The storage drawers and their case have also been refurbished. They await reassembling once the telescopic guide rails for the drawers have been cleaned to remove the old congealed grease.

One item that needs cleaning, and perhaps a repaint of its lid, is the Simulator Switching unit, see accompanying photo. This unit is part of a later modification to the radar and its purpose is not fully understood apart from connecting in the LCP simulator.

LCP

The frame for the computer rack that houses the original disk and tape unit has been refitted. A task that turned out not to be straight forward but was eventually completed and now houses an original disk and tape controller. The appearance of the computer rack is now back to its ‘in service’ state.

The simulator was run up but still has the ‘Mode Change Not Allowed’ message on the screen which prevents the simulator from being initiated. Always a bit tricky to resolve this problem when there’s no obvious switch in the wrong position. The basics such as power supplies and input box LEDs are as they should be so everything points to the Argus not seeing the input LED state.

Cheers
Pete H

Work Day 5th November 2022

T86

Lesson learnt but a bit late – when dismantling always record and photograph everything, this was done but not for the Transmitter waveguide fittings. Reassembling the waveguide on the rear of the aerial assembly has been completed but the brackets used were a puzzle.

What added to the challenge is that the T86 was modified to take a dummy load so several fittings are there for that purpose and not used.

Access covers refitted to the RF Rx cover.

New seals had been made for the covers which meant replacing the DZUS fasteners.

LCP

A start has been made of rebuilding the 19” frame that holds the original disc, tape and disk/tape controller. Refitting this frame with its front panel will return the computer rack to its original appearance even though it plays no part in currently running the Ferranti Argus 700.

The Argus 700 was updated to use a SCSI interface as opposed to the original FINCH interface for which there are no spares, especially for the original Winchester disk.

The simulator was run up but displayed a message indicating a switch on the console switch panel is in the wrong position e.g. the Firing Lines are closed. All switches on the switch panels are correct for starting the simulator e.g., the Firing Lines being open. The start-up problem was resolved by restarting the software but it needs investigating.

Cheers
Pete H