Work Day 29th May 2021

I picked up on the monitor that that we struggled get the vertical hold stable on last week. It was impossible to adjust the vertical hold with the monitor in situ so the very heavy monitor has been taken off its runners and sits on an old pallet ‘table’ (see below) so I can now get at the variable resistors.

CRU1 and CRU2 can also be seen in the photo, these have now been refitted and the side of the display console is back on. Unfortunately there was still no success in adjusting the vertical hold so does the problem lie with the monitor or its CHARGE channel? (CHARGE being the Ferranti-designed video system – Compact High-Resolution Advanced Raster Graphics Equipment).

I replaced the monitor with our spare which gave a perfect display until it started to show additional horizontal lines.

It was now that other faults with the displays appeared. The Engagement Controller’s display became a white square and the Jamming Assessment display lost it’s vertical hold but I suspect that is the monitor.

Note: The monitors are mounted on their side so what appears to be a loss of horizontal sync is actually vertical sync.

Last week Pete M said ‘first thing to do next week is check the +/- 5V at the CHARGE box’. I actually used a card extender and measured the +5V on a TTL device on a CHARGE card, it was 4.5V! Answer, crank up the +5 power supply but that didn’t make any difference and the +5V power supply is rated at 120 Amps! Is this a problem with the heavy loading of the CHARGE +5V in the LCP? A couple of monitors also need setting up or fixing, e.g. the instructors monitor has low brilliance and looked to have lost a colour (that problem comes and goes) and one CHARGE channel didn’t look to be working – could be the low voltage. The plan now is to give the monitors a refurbish and set up and also check out the suspect CHARGE channel and the spare CHARGE card set.

Here are the CHARGE cards used. There are four sets of cards (one for each display) with each set comprising two Pixel Stores and a Controller. As can be seen these are very complex cards that do not lend themselves to easy fault-finding and repair.

CHARGE Pixel Store
CHARGE PIXEL STORE

CHARGE Controller
CHARGE CONTROLLER

A couple of weeks back all the digital input and output cards were checked for bad AVX decoupling capacitors that were acting as low value resisters and loading their +5V supply (In this case it was preventing the simulator from booting). The CHARGE cards use the same AVX capacitors so these will now be checked as it could explain the power supply loading. Eliminating such ‘known’ problems and refurbishing connectors etc. on PCB’s and monitors in the LCP/simulator will, hopefully, improve reliability.

Last week the LCP roof struts were refitted and this week R clips were fitted to the securing pins as opposed to split pins. The R pins couldn’t be found last week as they had been put somewhere safe!

Pete H

Work Days 22nd & 23rd May 2021

It was good to be able to have company with Pete M joining me for both days this weekend.

This enabled a start to be made on painting the T86 aerials. Time consuming but good progress made. Two photos below show the work being undertaken in applying a top coat, a bit more priming and also the repainting of the inside of the pedestal with ‘red lead’, it might be called that but I doubt if there any lead in it these days. Not much to report on the act of painting only that the difference in appearance is quite marked.

A reminder; this was the state of the T86 when we acquired it.

As there were two of us we also refitted the LCP roof struts. All eight struts refitted, some were easy to fit some not so. We have a complete ‘good’ set of roof struts in that all are adjustable and not seized and all have straight thumb screws for holding the safety sleeves in place. It was only possible to install a complete set of serviceable struts after retrieving some from the derelict LCP (1006) on the North Luffenham airfield to make one good set.

Tested the spare display console relay units CRU1 and CRU2 in the LCP and both declared serviceable after being repaired last week. These two relay units are both ex 1006. The relay units control lamps on the top switch panel, sense switch positions, i.e. the Firing Circuits open and closed as well as sending -50V or 0V to the digital input cards. One puzzle to solve and that is the indicator lamps on CRU1 do not illuminate when relays are energised, they do when bench testing so a possible mod here as it looks like the 0V return is not connected to these lamps in the display console.

Gave the simulator a run and all OK for a while and then the Technical Supervisors monitor lost its Vertical Hold which came and went a couple of
times before failing so possibly a connector or dry joint. No option but to remove the monitor and it now sits in front of the display console on a wooden crate but still connected in readiness for a bit of fault finding on the next visit. The monitors are very heavy so preferred not to remove it off site. If this monitor remains a problem after the next visit then our spare will replace it. Apart from that the simulator is running well and was tested out by our “manufacturer’s representative” running an engagement.

Pete H

Catch-Up – 16th May

Good news!! The ‘Mode Change not Allowed’ problem has been fixed

One fault and one adjustment were the cause, firstly the Bank A Reload/Available switch was U/S and the second, excessive voltage drop on the +5V to the Digital Input box.

Everything looked OK after the switch replacement, the Argus was good, LEDs on the Digital inputs were correct, power supplies were good so what could it be? This morning I had a flashback to the early days and a voltage drop problem between a +5V power supply and the CHARGE box. A quick check showed we now had the same problem with the +5V on the Digital Input box. Briefly, the power supply was set to +5.25V (so you would think that was good enough), the distribution rail was on the computer rack was the same but when I checked the +5V on the Input Box backplane it was +4.1V! Cranked up the power supply even more, restarted everything and bingo, we are now back in business. I suspect the circuit breakers on the back of the I/O boxes may be partly to blame due to their age.

After going around the houses with the ‘Mode Change’ problem I’ll write up some fault finding notes which should help if this happens again. I also spent a couple of hours today checking all the input cards and output cards while I was at it. What I was looking for was reasons for the +5V loading, again experience tells us that the glass encapsulated AVX decoupling capacitors can fail and reduce the resistive load on the +5V, down to a few Ohms in a worst case. I eventually found three Digital input cards and two PeriBus converters with very low resistance between +5 and 0V on the card. I now hope to replace all the AVX capacitors on these cards this week.

A bit more on voltage drops between the computer rack and the I/O boxes. I have a couple of photos of the Swiss computer racks which show the Sense feature on the Farnell’s being used for all the +5V supplies going to the I/O boxes where our power supplies to the I/O rack have no sense wires fitted. Perhaps there’s some history here, I’m all for modifying our LCP by putting sense wires on the power supplies that have none. I have quite a bit of that Ferranti black and white twisted wire somewhere courtesy of recovery from derelict LCP …….

I hope I’m not speaking too soon but while we have had this ‘Mode’ problem it has exposed other vulnerabilities that can be rectified and once rectified there’s no reason why the simulator shouldn’t be a lot more reliable. We even have a complete set of spare Argus boards in the LCP and they include the GX, GL and ME147. After all the hassle it’s time to move forward as  the T86 aerials need painting, if ever it warms up a bit.

Back at “3rd Line” I tested our spare CRU2 (used in the display console). One relay was U/S and has been replaced which was not an easy task as shown in the next two photos.

We now have a spare CRU1 and CRU2, both ex LCP 1006. Both need a final check in situ.

And finally, I set up a scope today just in case I needed to see what was happening on the PeriBus. A contrast to what was used when the LCP was operational.

The setup includes a PicoScope USB oscilloscope connected to a laptop which also holds PDF’s of any AP’s needed. Digital voltmeter, and a can of the wonderful DeOxit gold for rejuvenating the gold plated connectors. Note: the use of erasers in banned. I remember working on the Filter Bank on the T86 and the card edge connectors were copper, the gold plating being removed by regular use of an eraser !

Pete H

PS – That’s me caught up at last so I will be back with our regular Workday blogs – Mike Strange

Catch-Up – 14th May

From this coming Monday (17th) we have approval for up to three ‘bodies’ being present in the hangar at any one time.

Here are some unstaged photos of the LCP being resurrected following it’s sojourn of over a year as a result of lock downs and a repaint of the internal cabin walls when I was allowed in the hangar last summer/autumn.

Note the low level lighting, smart or what!

The simulator is still not booting fully, on pressing the Simulator button nothing happens due to the ‘Mode Change Not Allowed’ message. There is no known reason why this should happen now as we have the correct LED indications on the Digital Input cards. It appears that the Argus is not reading the relevant Input card state across the PeriBus. Trying to work out what’s going on while resisting card swapping is a slow process but with most of our spare cards in an unknown state that’s a risky option and can end up giving us more than one fault. All that said, the Argus is looking ‘solid’ (a technical description for reliable).

Starting with the Display Rack:

The Computer Rack

And L Rack showing off the low-level lighting and the FT81

Pete H

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!

Catch-Up – 2nd May

I just fixed the G5 120A PSU that went U/S with no output during the power supply episodes as the simulator was brought back up. Confession time; I was responsible for killing the power supply when measuring the 5V to the Argus. I was measuring the volts on the PS terminals which are very close together and I accidently shorted the +5V. No sparks no nothing other than the O/P disappeared.

What happens on a short, at least for a G5 120A, is the two main power (switching) transistors blow and two protecting fuse links on a PCB (these are only on a G6 120A) also blow, there appears to be no short circuit protection.

The BUY69A transistors to be extracted

The G5 120A has options that can be fitted by Farnell, unfortunately our G5 120A does not have the options which may protect the PS. I have had this fault before and had two BUY69A transistors and fuse links in my stock (always buy extra items if ordering is my motto) so the repair was time consuming but not too difficult.


Transistors and fuse links removed.

One issue is the small gauge wire used in places as it breaks quite easily at the point of the soldered connection, had to re end a few.

Golden rule: Never check the voltage  on the O/P terminals of a G6 120A, it’s too easy to short the O/P!

Catch-Up – 16th to 26th April

16th April
I swapped out the Argus G5 120A (again) which was definitely dead, spare fitted and checked. Configured everything for a memory test and ran that, it takes quite a while with an ME148 but eventually the FT81 came back with ‘Cycle complete, no errors found’ message. Next, all the I/O power supplies checked, no more U/S thank goodness. Finally, fully configure the Argus and switch on the I/O boxes. The result, after a slight struggle to start with (cold and damp probably) is shown in the below

Note the JA display is OK – loss of sync must have been a problem with the green video from CHARGE until things warmed up. I tested by running the Swiss software for a change. Pressed the Simulator button and nothing happened then I noticed a familiar warning on the displays ‘Mode Change not Allowed’.

I let the system have a good run rather than restart again to get  everything warmed up. I also stopped and started the Bloodhound software a few times using the FT81 to check the displays reset etc.

I didn’t have time today to follow up on the Mode Change problem but I recall it was something simple.

17th April
A diversion from resolving the Simulator issue was to complete the low-level lighting which comprises four units of two tubes in series, each tube having it’s own starter. The new LED tubes are driven straight from mains so the wiring wasn’t conducive to an easy conversion. I did  use existing wires for most connections but had to add an extra wire to connect Neutral to both LED tubes.

There was one problem with the LED tubes as the original T5 tubes are thin but LED tubes have a larger diameter, see next photo. No way will an LED tube fit into the original T5 holders.

The original holders were used to control the direction of lighting whereas the LED tubes have that built it. Anyway, the end result is fine as you can see in the attached.

At the end of the day I fired up the simulator using the UK software. The first boot resulted in CHARGE errors as yesterday so this time I powered off and reseated all four sets of CHARGE cards. The End result was a normal boot apart from the Mode Change problem which prevents entering the simulator itself. Time was short so I now need to document what to do to sort this problem. This is a system warning rather than an Argus failure. I do feel the Argus is running well, just need to find out why the Mode Change is appearing.

18th April
After some discussion the topic of -50V missing was raised as possibly relating to the Mode Change error was recalled, lead to an earlier chat. ‘Re, the CRU1 relay unit, when we first applied -50V to the display console one of the 50V fuses in the console blew. One of the four lamps on the relay unit was also ‘on’. The fuse doesn’t blow now but then the lamp doesn’t come on either. Now need to find the short on the -50V after FS8 (1 Amp). Last time the MODE CHANGE problem happened and we couldn’t work out why and it involved us in a fair amount of analysis both hardware and software until we took the covers off the console. Yes the -50V fuse and indicator is hidden away behind the console covers and not visible! Previously the fuse had blown after a long period when the LCP was switched off. Unfortunately I can’t find a ‘this fixed it’ anywhere.

When sorted I’ll get a big notice for the LCP of ‘If this happens check this.’

21st April
After spending a few hours today on the Mode fault I had documented the checking so far.

Checked the Console switches:

  • A Reload Available ‘UP’
  • B Reload Available ‘UP’
  • Firing Circuits at OPEN ‘UP’
  • Off/Check/Select switches OFF ‘UP’
  • Keyboard supplies On ‘DOWN’

Check the -50V

  • FS8 on Power Supply Shelf OK
  • FS9 on Power Supply Shelf OK
  • Metered both fuse holders -50V OK
  • -50V is on the PSMI Switch B to position 8 and should be 5V but it was 0V.
    NEED TO FOLLOW UP
  • Checked -50V at JC4 on the Power Supply Shelf OK
  • Checked -50V at PLCRU1 Pin A OK
  • Checked -50V at PLCRU1 Pin B OK

Attention turned to Digital Output box

  • Checked -50V at OB3 Pin A OK
  • Checked -50V at OB3 Pin B OK
  • Swapped relevant Digital Output cards with spares, slots 7, 8 and 10.
    NO CHANGE
  • Only Digital Output cards in slots 2 to 5 have red LEDs flashing at 1 sec, no LEDS on other Output cards.
    NEED TO FOLLOW UP

Attention turned to Digital Input box
FOLLOW UP ON ALL

  • Slot 8 LED 24 out
  • Slot 12 LEDs 23 and 24 out
  • Slot 15 only LED 10 ON
  • Slot 16 only LED 1, 2, 11, 17, 18, and 22 ON

Attention turned to CRU1

  • Disconnected CRU1 and it made no difference to the MODE fault
  • Removed CRU1 to see if I can check it at home.

I couldn’t do any more without working out how to check that CRU1 is working correctly (it’s fairly basic after conversion for the MK2A LCP) and I need to trace more of the -50V cabling and switched -50V. I think the 0V shown by the PSMI is misleading as I have -50V everywhere except I need to check the -50V switching by the top switch panel without dismantling the complete console. I’m assuming the -50V is sent to Digital Input cards from the Available/Reload switches and others. There’s a card extender in the LCP so once I’ve worked out the wiring I can check the -50V on individual input cards.



CRU1 Schematic

23rd April
I’ve created a diagram for the switch states following power on and before the Simulator button is pressed to energise Relay STS on the Lower Switch Panel.

Mode Chage Logic

We need to ensure the inputs and outputs are correct at this stage before moving on. Feel free to check what I’ve done as I’m known for the odd mistake.

What I’ve noticed is that Slot 12 LED 24 should be OFF. Check my diagram as the LED 23 and 24 state should be the same

Please refer to the attached. The input box photo below was taken on Wednesday while the MODE CHANGE NOT ALLOWED message was on the displays.

With the MODE CHANGE fault I’m always dreading that Relay STS on the lower switch panel is U/S. Not that we haven’t got a spare but it’ll be a right S.O.D to change as it’s buried in the wiring and hidden behind a bracket holding two big multi connection sockets. The relay itself looks to be the standard type of 50V relay used everywhere in the LCP of which we have many spares. Our spare relays are salvaged from LCP 1006 so will need testing before using!

25th April
Today was all about fault finding the ‘Mode Change Not Allowed’ problem; the cause has been identified but not rectified.

Using my ‘new’ fault finding diagram I set about tracing the -50V switched by the Bank A Reload switch. I checked the -50V at various plugs and sockets as it wound its way from the bottom switch panel to the top switch panels to the Input box. All the time thinking ‘will I find the problem without taking a switch panel out’! Long story short the -50V was going into the top switch panel but wasn’t coming out again when the Bank A switch was toggled up and down. Top switch panel taken out! It was actually suspended on ropes so I could measure the -50V on the rear of the bank A switch – see below

Suspended Top Panel

Bingo, -50V at the switch but not being switched out. I double checked with the action of the Bank B switch. The Bank A switch is definitely U/S. Has this switch been our Mode Change problem over the years, who knows. The body of the faulty switch does not appear to be secure, could be an indicator.

Next problem, replace the switch. Not having a spare switch let alone with me it was time to call it a day with the fault as I went on to PolyTrol some more plastic switches and knobs. By gum everything is starting to look very smart now.

Back to the switch. Not a problem I thought as we have two spare top switch panels and one has already been cannibalised so I’ll remove a switch from that panel. Unfortunately the switches on both the spare panels are not the same make or style! Our LCP sports snazzy chrome switches while the other panels have the basic black toggle switch as used elsewhere in the LCP.

26th April

It struck me that the ‘normal’ black toggle switches are OK for none critical stuff as the quality isn’t up to that of the Bulgin chrome switches. I need to check the other serial number on our spares (and in the LCP) but the cannibalised panel, with cheap black toggle switches is BR8001, this first of the spares being a ‘BR’, I suspect this panel is ex 1006 from Luffenham.

It’s fortunate I’ve found replacement chrome Bulgin toggle switches … on order!
Pete H

Catch-Up – 9th to 14th April

9th April

I installed the dead GX Processor from the Argus 700 computer in the test rig at home and it was still ‘dead’. Dismantled the GX, brushed out the dust and cleaned the edge connectors. I re seated the various plug in DIL devices (ROM’s and 2901’s) and noticed one ROM had lifted slightly at one end, re seated it. Reassembled the GX and back in the test rig,  it ran – Yipeee! Been running it on a memory test for a few hours so I’ll take it back to the LCP with the spare boards that I removed for the winter.

12th April – Back at the LCP

  • I tried to adjust the vertical sync on the jamming monitor and after an hour gave up. The Vert Sync control is accessible on the underside of the monitor and not easy to get at and trying to hold a light and engage an adjusting tool proved too difficult, it’s a two man job! Easier to remove the monitor but again it takes two to lift it out.
  • Fired up the Argus and run a memory test. At least that gives some confidence that most of the boards are working save the ME172 FP board and the two ME153 GL Processors. I now use the updated test utilities, at least the whole of the memory bank is tested now! See the screen shot below from the FT81, note the memory size (in Octal), this was also an ME148.

  • Refitted the FT81 back in to its position in L Rack. The original FT81 was playing up by losing it’s Vert Sync now and then so it’s been replaced with a spare, a couple of weeks back. The original FT81 has been checked out and the Vert Sync adjusted and is now OK and held as a spare.
  • Next task was to fire up the rest of the simulator. Before attempting a boot I had noticed that one CHARGE channel wasn’t initiating or resetting but it does if I use the little bit of wire to reset manually, I also had a fiddle with the WEETABIX cards.  Booting up took a couple of resets on the GX before the familiar banner appeared on the FT81 followed by a number of the infamous 0044 errors. Fiddled about a bit more and changed a GL processor and  the simulator booted but gave a couple of CHARGE errors but the boot displays appeared OK – you can’t see four as the other monitor was pulled out, beside it wasn’t syncing. Pressed the ‘Simulator’ button and nothing happened which I discovered was for a good reason, possibly as the MP140 Serial I/O card wasn’t plugged in (idiot).

Things went a bit downhill from here. Trying to reboot gave some strange half messages on the FT81. Trying to work out what was going on I checked the +5V to the Argus which was 6.5V and I couldn’t adjust it (Tantalum capacitors on the controller board perhaps?). Changed for the spare. I tried booting again but the following the usual start up the boot stopped after a ‘System Recovery Complete’ message. I suspected I may have screwed up the files on the Compact Flash card somehow. I did have a second emulator to run the memory test (SD card!) so refitted that and ran a memory test again which ran OK.
Returned to checking the +5v on the replacement power supply and adjust. Accidently shorted with the Voltmeter probe, no sparks but it killed the output for good!

I felt I was starting to screw things up so I called it a day and the weather didn’t help! I’m hoping to get back during the week as well as next Saturday, got to catch up.

I’ll check the UK Software SD card in the next couple of days and check over the 6.5V power supply adjustment problem. Must learn how to test GL processors on the test rig!

POST SCRIPT – Back in the workshop … I must be losing it. The Argus +5V PS that was not adjustable has been fired up and it’s OK now!!!!! Giving it a good soak test.

A team discussion decided the sense wires in the LCP need checking especially as the crimped terminals on the +5V sense wires do not look good and being at the top of the computer rack where the damp from the LCP’s days in the open was a significant cause of corrosion. To confirm the theory, the lack of sense wires on a G15 16A on test were not fitted and the voltage could not be adjusted.

14th April

Nine T5 LED (12”) LED tubes for the low level lighting arrived today, eight to use and one spare, thanks to one of the Team. They are the same type as the roof tubes so the chokes and starters need taking out of circuit to fit the LEDs. A job which I may do this week.

The G15 16A and the G5 120A that gave problems are OK are ready to go back as spares in the LCP. Both have had a good run at home. A replacement PCB plus components fitted has arrived to replace the burnt out PCB on the G6 60A that smoked out the hangar, courtesy of APS in Harrogate.

I’ve carried out some fault locating on two dead GX’s we have. Two different faults so I’ve done some board swapping to try and make one good from two bad. Problem – they both have the same faulty PCB, the Arithmetic Mother board. Everything has been swapped around including daughter boards so it’s definitely the Arithmetic Mother as the faults follow them around. Faults are:

  • Processor does not run and Processor data on the monitor shows ‘77000000’. Completely dead, the monitor panel doesn’t even recognise it’s connected to a processor.
  • Processor runs ‘normally’ until it has an interrupt then it hangs in a loop, I think at the moment. Try to Fill (load) the Disk Utilities which fails and the ME1461 SCSI controller has its Yellow LED permanently ‘On’.

I’ll have a look at the second of these as the Yellow LED is indicating an interrupt has been sent to the GX but whatever the GX is then supposed to do it isn’t. Trying to work out how the hell things work first to get an idea of where to look. I can get +5V on boards but testing may be checking ‘all’ logic levels as once the board sandwich is split out how can they run?

Pete H

Catch-Up – 8th April

The power supplies have now had a good run and they look to have settled down. We had three out of the eleven power supplies in the computer rack where the RIFA’s blew. The G6 60A that ended up with a destroyed PCB last week can be repaired as a replacement PCB is on its way to me courtesy of APS in Harrogate. I did find another power supply problem at the start of the day after powering up all supplies off load. I found a G15 16A had an output of 16.5V and not adjustable. I suspect the Tants on the controller card. I swapped this PS out for a spare.

Next, I switched on the I/O and displays to check CHARGE and the four displays. The four CHARGE channels are OK but the Jamming display has lost its vertical sync. Will need to determine if it’s a fault or just an adjustment.

Next, I/O and displays were off and I configured the Argus with a basic set of cards to run the Disk Test Utilities. Powered on and the GX was ‘dead’, no register LEDs showing on the front panel. Removed GX and brought it home for testing, this GX was the working GX last time we ran the simulator.

The FT81 is OK (I installed a spare to give it a run a few weeks back) and the Argus fan tray is back in and all six fans are running so the main issue is the dead GX.

In between times I did a bit of cleaning and tried out some Polytrol restorer on some knobs and switches to good effect.

Before and after

Before and after

I’ve not made any further progress with the tape drives at home after double checking everything and it confirmed that both PCB’s are U/S. The photo below shows the test setup for tape drives. Not a problem as we have three serviceable tape drives now put to one side.

Archive 2150L Test Bench

The simulator has been off for over a year and it’s feeling the effects of it. I’ll give the Argus another go AFTER I’ve checked all the boards out on my home test rig.

Pete H

Catch Up – 5th April

I’ve opened up the G6 5V 60A power supply that smoked out the hangar let alone the LCP. Unfortunately the Filter PCB has been destroyed as in these two photos.

Looking at the amount of damage the RIFA capacitor had a good time to brew up and effectively became a mini electric fire.

The power supply was one of the originals but had its RIFAs changed in the past as all original power supplies had. The sooner we eliminate all RIFA’s the better. We have plenty of spare G6 60A power supplies so that’s not a problem. Interesting that the fuse didn’t blow!

The Argus fan tray is OK again after the ‘dead’ fan was re oiled, I use sewing machine oil. The fans get dry and stiff, stop rotating and the coil will go O/C if not re-oiled quickly.

Pete H

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