g0ozs

We were there for about an hour plus lunch on the Sunday - sorry we didn't spot you. I'll post some photos to the show report topic in due course. My daughter wants to go back to the control tower again so it was a worthwhile trip. Iain

Hi We will probably drop in after lunch although 35LK88 is a bit modern for the event and will have to go in the visitor's car park! I havent been to Debach in years - I remember working on a HF radio station there with the Ipswich radio club for what was probably a 50th or 60th anniversary many years ago! Regards Iain

GPO was a crown department under the Postmaster General (a minister) until 1969 and telephone vans were dark bronze green. The split into Royal Mail and Post Office Telecommunications resulted in these becoming public corporations and telephone vans turning yellow until after the privatisation of BT from 1984 Iain (who has been with BT altogether too long for his own good

I can only suspect that it was to make the IBHA simpler. The IBHA is needed because the PRC sets lack a separate harness connector found on UK/VRC-321 and UK/VRC-322. The Harness microphone/PTT circuitry works more like the remote than a headset using lower audio levels and changes in the DC resistance across the audio lines for keying (and indeed the RT321 harness audio input and remote terminals are internally connected according to EMER H592 Fig 26). In the case of the RT351/2 using the radio's own remote input saved building the equivalent of a CRL/R box into the IBHA. The CRL/R is needed together with the IBHA when connecting the RT320 which has no remote terminals to a harness. Documentation of the way the harness evolved is most likely lost in the mists of time but I suspect that the origins of Clansman in simultaneous semi-independent projects by BCC (later part of RACAL), Plessey, MEL and Marconi led to a need for the various interface boxes that could have been avoided had the sets all been specified and designed consistently with harness operation as a requirement - the ARFAT box needed to use the UK/VRC-353 with the RACAL(BCC) TUUAM ATU is another case of this. RACAL used pre-existing BCC technology to a considerable extent which led to the need for adapters to "Clansman standard" solutions by Marconi and MEL. Clansman is in any case a considerable advance on Larkspur with the intercom in the harness boxes rather than a radio and an inherent rebroadcast capability independent of harness using the remote terminals of the radios Regards Iain

Andy Figure 1 of http://www.fv432.co.uk/manuals/fv432ClansmanManuals/clansmanfv432installationpart007.PDF shows both audio socket 1 and the remote terminals of the 351/352 connected to the IBHA so I think you are correct. Regards Iain 73 de G0OZS

The only good things I think in NCRS were the Skanti HF radios (I use one as my main HF radio to this day) and the replacement 27' Racal 675 masts (I do miss the trailer I had and sold, but I ended up buying something much bigger than a landrover to tow it .. ) Iain

I have had a similar experience when I was late paying the domain name registrar for one of my websites - it redirected to a "somain parking" service until I paid up Iain

Rich Unfortunately I have lived in East Anglia for the last 27 years and I don't think there are any Shackleton connections down here so I will need to make a special trip to hear and see it again or rely on YouTube ... Good luck with the refurbishment ! Iain

Rich I have subscribed. I used to see and hear them flying over my dad's farm about 20 miles from Kinloss when I was growing up Good luck ! Iain

Welcome here !

Hi I used to have a Plessey NCRS HF Radio trailer which was terribly unbalanced with too much weight forward of the axles (and therefore a tendency to affect front wheel grip of the towing vehicle). This had a label on the towbar saying that the towing vehicle must be ballasted to (from memory) 2200KG to be safe. I understand from someone who was familiar with the NCRS system in service that the ballast physically took the form of metal plates fixed to the floor of the load area. Ballast was fitted and a reduced maximum speed was enforced after a serious road accident early in the life of NCRS and the trailers were disposed of via RAMCO after less than 15 years in service. I believe NCRS was operated by a TA unit within 30 Sigs so if that matches the merlin report it will be a clue ! Regards Iain

Stuart Welcome here ! 73 de G0OZS

I think the best tent I have had to date was a 15 x 15 foot ridge tent - much easier to put up short handed than the frame one but big enough to put up tables for a radio station with room to move around afterwards. I'm going to try a 10 x 10 bell tent this summer and see if it is easier to put up Regards Iain

Hi I dont have one to hand in the house but I can go look for one at the weekend. From memory the PCB is held in by a couple of black plastic rivets which have to be drilled out - I think they could be replaced by self tapping screws afterwards Regards Iain

Bob Usually when servicing equipment with cards slotted into a cage there is an extender card with a pug one end and socket the other end connected pin to pin, which can be inserted to lift the suspect card above the rest so it can be got at - otherwise you are limited to test connectors along the edge. In the absence of this you have to temporarily solder wires to test pins and reinsert the card. The approach of using a bench PSU is sensible - I think it will also be worth checking that the output of the PSU and the input to the DC-DC converter modules is more or less the same in case something has gone high resistance in the input filters - the converters will work from much lower than 20V so the CPU will still run in such a case, even if there isnt enough voltage to run the battery charger proper. Regards Iain

David Thanks for the manual. Bob I guess with the unit reporting VLO from a good supply we are at the "backload for repair" stage now. The manual does confirm that it is sampling the input voltage (as it sees it) so it is probably worth tracing that with a voltmeter from the input connector into the unit to see if something has gone high resistance - I imagine the path will be something like socket > filter > fuse > switch or relay > PSU board IBEK inputs. In the past there have been issues with inductors in the input circuit of the 14V DCCU getting hot and going high resistance so that would be worth eliminating here. The test pins are a good match to the 5 and +/-15V outputs of the IBEK units - I imagine when the unit is assembled and powered the PSU outputs can be measured there - I wonder if your source is trying to say "or an external supply can be connected there to replace a faulty PSU card?" The clock and reset pins on the logic board likely allow you to reset the microprocessor (usually by momentarily grounding the reset pin) and determine whether the clock oscillator is running in cases where the display is dead, by checking for a squarewave at a few MHz on the clock pin using an oscilloscope Hope this helps Iain

The IBEK modules are still available btw: http://www.texim-europe.com/power-supplies/dc/dc/search#&&RadViewPageIndexState=0 Type IBEK in the search box for a list - the exact models in the IBMU may not be there but it at least means the vendor is still in business and it explains how to decode the part numbers - 24IPS3-1515 seems to be 24V nominal input 3 Watts 15-0-15V out - from what I can read in the photo the small one is a 15-0-15 supply (probably for the analogue circuits) and the longer one is a 5V logic supply - the discrete component supplies at the end of the board must be the high current 12V and charging supplies. On the soldering topic I used to have a Weller Pyropen portable gas iron that had interchangeable soldering and hot air bits - the soldering version had a side exhaust for the hot gases and you needed to watch where it was pointing, but it was convenient for field repairs. See: http://uk.rs-online.com/web/p/soldering-irons/0660422/

Bob Equivalent electrolytics of similar or slightly higher capacitance and voltage are relatively cheap - pennies not pounds - Tantalum caps were a premium device in their day. I cant quite read the text printed on the PCB in the whole board photo but I expect that there will be test points for each output - the catch may be that a REME workshop or the base repair workshop would have had an extender card to allow a board to be raised out of the chassis for in-operation measurements to be made. You should actually be able to get some signs of life by removing a suspect capacitor - their role is to filter noise and ripple on the supply output - if they fail short circuit they will stop a supply working but if they are removed there will be a noisy output which should at least give signs of life. The capacitors aren't monitored directly - the VLo will be measured by the microprocessor board which will have an analogue to digital converter and some kind of electronic switch able to select various supply inputs and outputs for measurement - the one it is complaining about is likely being dragged down by component failure causing excess load. I suspect on looking at the PSU board that it contains two white converter modules fed from the raw DC input - one will be generating a stable 24V (the longer one with readable text in the zoom photo) - I dont know what the other one is - if 5V it probably supplies the microprocessor if 12V it could be anything. You should be able to measure the output voltages of these converters to check some of the supplies as they have helpful voltage and pinout information printed on top - the challenge will be doing it safely with no extender card. Probably the best way is to tack temporary insulated wires to the pins underneath with solder and bring the ends out to a multimeter. There also looks like being a discrete component voltage converter at the right hand end of the PSU board - this is probably rated for higher currents than the converters and I would guess that it provides the +30-something volts needed for constant current battery charging up to 28V - if you can provide a close up photo I may be able to guess more about how it works and suggest a safe test point. Hope this helps Iain

Strange you should say that - I used to use a small one for the desoldering phase of surface mount repairs (in hot air gun mode). They are Ok for occasional use as a conventional iron as long as you remember to touch something earthed reasonably frequently to ensure that there is no static - I found that the catalyst bits have a relatively short life if used as a main soldering iron (so best to buy a bag of spares at the same time as the iron) and they are of course unregulated as to tip temperature so you need to be quick to avoid cooking things. For field repairs to cables and connectors they are ideal and mine has got me out of trouble loads of times Iain

Bob There is a searchable club database at: https://thersgb.org/services/clubfinder/ - I would have thought Leicester or Grantham or South Kesteven are the next nearest after Melton Mowbray ? Regards Iain

Bob You need to find a radio club offering a course and exam for the Amateur Radio license and armed with the pass certificate you can apply to OFCOM for the license. There are now 3 levels - Foundation, Intermediate and Full - for Clansman kit the power and frequency coverage are such as to require an intermediate license which is the 2nd level. The Radio Society of Great Britain website http://www.rsgb.org.uk has details of local clubs and their courses - I help with the ones at the Felixstowe club and I know our exam secretary would respond in a few days to any inquiry as we are always trying to get enough candidates to make the combined foundation course and exam viable so it's disappointing that you didn't hear back ! Best Regards Iain 73 de G0OZS

Bob An ESD safe low voltage iron is best around CMOS chips so certainly for the logic board - most anything else is OK with any old iron as long as it is not too big and too hot (I would say 0.1" point and 360 deg C are the upper limits) - a file and a piece of brass rod will result in a suitable tip for most cheap irons so it is really the temperature that needs checking. If it isnt earthed for ESD (be very suspicious if it has a 2 wire power lead) touching the tip to something that is earthed will clear any static charge. If the iron has a direct mains supply rather than DC from a control unit it's worth also checking with a multimeter on a low AC volts range between earth and the iron tip that there isnt a AC voltage on the tip due to capacitive coupling from the element (which some irons meant for non-electronic use do suffer from and which is at least as dangerous to integrated circuits as static) The landrover is really nice - my GS 35LK88 is also ex Ghurka but a bit more recent (1994 in service) - I intend to fit it out with a 320 and 352/TUUAM clip in installation once I get over the house move Welcome to VMARS ! Regards Iain 73 de G0OZS

Bob I always use the Weller temperature controlled static protected irons - got issued with one on my first day at work and they have always been reliable and never destroyed anything (they have an earthed tip so are static safe if correctly installed). The WES series are I think the current ones and are between £50 and £100 on e-Bay - I still love my old EC4100M controller with EC1301 iron that I bought from stores at work about 20 years ago. The cable tie is probably not a repair - if the chip is the EPROM holding the IBMU firmware it needs to be socketed for upgrades and then needs to be secured so the chip stays in despite the rigours of military use. These days there are good low ESR electrolytics in similar sizes to the tants that dont have the same failure modes so you should probably consider replacing with 10uF rated at least 30 volts - something like: http://www.rapidonline.com/electronic-components/10uf-35v-5mm-micromin-electro-capacitor-11-1512 Best Regards Iain

Bob I havent been inside an IBMU - mine never gave any trouble when I had it - and don't have the EMER to hand - I agree with you that the cords are likely to be for card removal - if so they should come out without too much force. Hopefully someone here has done it before or has the EMER to hand but it should be ok to pull gently and see! The things with the corrosion generally look cadmium plated yellowish/copper - it's probably worth handling them with gloves to keep the H&S people happy in case and standing upwind when brushing off the white powdery corrosion outdoors. I think the pin looks more like a mechanical than an electrical function. Gold plated things shouldnt be affected by damp - if damp has done harm it will be to plain copper contacts that have tarnished, or steel components that have rusted. The IBMS is too recent to have paper capacitors or resin bonded paper boards that can hold damp in truly vintage radios - probably only transformers are likely to suffer from damp affecting the insulation breakdown voltage until dried out. The more worrying possibility is that if it was ever powered up damp the conductivity of moisture in transformers or on the surface of the PCBs may have affected circuit operation and done some collateral damage that will still be there when it is cleaned and dried out. I agree with Andy that the NSN method is usually ok for identifying cards - as to solder it would surely have been the original 60/40 Tin/Lead version when the IBMS was made. If forced to use ROHS solder it's best to desolder and clean the joint with a suction tool or solder wick braid and start over I think. Regards Iain

Bob Thanks for the photos. The corrosion is indeed a concern. I would be inclined to suspect it was opened previously and not closed in a hot dry environment or the seals weren't fitted properly. This may have been compounded by outdoor or semi-outdoor storage in a stillage while waiting to be sold. If the dessicator is the usual kind based on silica gel the dessicator can be restored by heating in an oven to expel the water from the silica gel crystals - I believe it needs to be 120 degrees C for a couple of hours. I note that there are a number of flexible PCBs used in place of a wiring loom - the IBMS is probably too new but I have had issues with those becoming brittle with age in other older products and being nearly impossible to reconnect reliably if solderless connectors are used to clamp the ends of the flexible ribbon in preference to soldered connections. The soldered connections are prime candidates for dry joints or tracks lifting off the flexible substrate if they are under stress all the time due to curvature of the ribbon. The blue connector with end levers is fairly typical of mid-1980s practice and are relatively reliable. Certainly I used them in things I designed in my day job at the time and had no trouble. Another cause of bad joints is where gold plated leads are soldered with ordinary solder. This results in a brittle alloy at the junction of gold and solder and fails relatively quickly - I had to resolder the offending boards after 6 months once dry joints started to appear the one time I made that mistake at work in 1988 or 89 ! Regards Iain