emmetgilgunn Posted June 12, 2011 Share Posted June 12, 2011 preferably in ireland or the uk? any helpfull hints before i start pulling it out ir for putting new ones in (apart from that great resource the all charged up series) thanks in advance. Emmet Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 12, 2011 Share Posted June 12, 2011 I can probably give you equivalents if only I could access my frozen PC. In the meantime are you absolutely certain that the diodes have failed by direct testing? Rather than just my suspicion that they have failed, you need to ensure the associated connectors & wiring are satisfactory before. Major generator surgery:-) Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 12, 2011 Author Share Posted June 12, 2011 so far running all the checks i could it seems to suggest your diogionas was correct. further investigation is needed to confirm that they need replacing but as i use this landie reguraly i am trying to get it back on the road asap so gathering all details i can so i can order and recieve as soon as i know what i need. Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 13, 2011 Author Share Posted June 13, 2011 si there any trick to getting them out? i dont have a socket that fits around the diodes and also fits in the holes they are set in. if you understand my meaning? do i need to take the cover off the outside of the alternator? Quote Link to comment Share on other sites More sharing options...
Tony B Posted June 14, 2011 Share Posted June 14, 2011 PM sent. Quote Link to comment Share on other sites More sharing options...
sirhc Posted June 14, 2011 Share Posted June 14, 2011 http://cgi.ebay.co.uk/Land-Rover-Military-Generator-24-volt-fit-Series-3-2A-/170654303426?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item27bbca04c2 Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 15, 2011 Share Posted June 15, 2011 You don't need a diode pack, you just need to replace the 3 small relatively low power diodes, which are actually rather insignificant in size. I see I have mislabelled the pic in ACU. When you look at the 3 diode packs each has 3 studs. The studs at each end of the trio are the high power diodes. They are functionally identical to each other although one in each trio is the reverse polarity of its partner. This is because they share a common heat sink so one has the cathode (-ve) on the stud & the other partner diode has the anode (+ve) on the stud. But the central stud of the 3 studs is not a diode it is the stud attached to the stator winding. So my picture is misleading & I need to correct it. The low power diodes have the cathode to the stud connecting each directly to the heat sink & each stator. The original low power diodes were Lucas DD3026A = CV8871, these are obsolete & were replaced by 5961-99-833-9958 = FV636048 which are used by a number of vehicle manufacturers. No doubt if I gave a list of part numbers one could spend a lot of time chasing distributors reluctant to deal with an individual customer & wanting to charge hefty prices, fancy handling charges to cover all the invoices a paper work. So I would forget that. There is nothing special about these diodes, the DD3026A is just a silicon diode rated at 1.5 amps able to withstand a PIV (Peak Inverse Voltage) of 400 volts. In order to dissipate heat in these early diodes they had to be bolted to a heatsink. Modern diodes are more robust looking in the Maplin catalogue there are diodes which look man enough AND THEY ARE ONLY 29p As long as they don't get hotter than 150 deg C they don't have a heatsink stud & can just be wired in. They are rated at 3A & 1000 PIV. http://www.maplin.co.uk/3a-glass-passivated-rectifiers-46407 http://www.maplin.co.uk/media/pdfs/Module%2046407.pdf Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 16, 2011 Author Share Posted June 16, 2011 that is incredably helpfull. thank you Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 16, 2011 Author Share Posted June 16, 2011 you dont by any chance know if the thread on the pully wheel castle nut tightens to the right or left? i know these pulley nuts can be unusuall. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 16, 2011 Share Posted June 16, 2011 The ISPL makes no reference to it being special with a left hand thread. So once the cotter pin is removed it should undo turning anti-clockwise. Quote Link to comment Share on other sites More sharing options...
Paul Drake Posted June 16, 2011 Share Posted June 16, 2011 I am watching this thread with a great deal of interest, as when my Series 2A comes back, with it's new genny fitted, I will need to look at the old one which does not charge. I did send two emails to a company which seems to do a lot of military stuff, but got no reply, even to say No! Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 16, 2011 Author Share Posted June 16, 2011 well i have had a similar expierence trying to find parts. no luck i am afriad. i got serveral replies saying no Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 22, 2011 Share Posted June 22, 2011 I'm updating ACU, went to the Maplin site to check on the diodes to find "This product has been discontinued" Not very helpful so I'll start looking again. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 22, 2011 Share Posted June 22, 2011 Well the obsolete Maplin diode was 1N5408G, which was a glass version of 1N5408. This is still available at 29p however the maximum working voltage has dropped from 150 deg C to 125 deg C. Although it can withstand short term high temperature soldering, given the heat in the vicinity of engine, it would be best to have as high a temperature rating as possible. Moving to 6A diodes, the P600J is rated at a PIV of 600v & a maximum operating temperature of 150 deg C. The price rises to 99p but that is still good value. http://www.maplin.co.uk/6a-silicon-rectifiers-46413 Click on "Specifications" Although this is Hobson's choice having a diode rated to withstand a much higher current means it will not be struggling & overheat. These 6A diodes are rated at 600PIV whereas the original Lucas diodes were rated at 400PIV so there is an additional safety margin. It may seem curious that diodes with such a high PIV are used, but it has to be remembered that inductive loads (coils, motors, alternators etc) can produce high voltage transients & can destroy diodes if their PIV is too low. Quote Link to comment Share on other sites More sharing options...
Rover8FFR Posted June 22, 2011 Share Posted June 22, 2011 I am watching this thread with a great deal of interest, as when my Series 2A comes back, with it's new genny fitted, I will need to look at the old one which does not charge. I did send two emails to a company which seems to do a lot of military stuff, but got no reply, even to say No! Is uour S2a Gen 40 amp or 90???? I believed that the diodes are in the 90amp and replace the selenium rectifier??? Clive can you clarify??? Regards Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 22, 2011 Share Posted June 22, 2011 I believed that the diodes are in the 90amp and replace the selenium rectifier??? Clive can you clarify??? Yes Wayne you are correct. The 40-amp alternator AC724/1 has no internal rectifier of any type & relies on the external selenium full wave rectifier. In the event of the selenium rectifier failing it would of course be possible to cook up an equivalent bridge rectifier using silicon diodes. They could be discretely mounted into the fins of the old rectifier preserving the look of a toastie. I feel a toastie with no rectifier behind the grill is a bit of a let down. The 90-amp alternators of course have integral silicon rectifiers. Quote Link to comment Share on other sites More sharing options...
Rover8FFR Posted June 22, 2011 Share Posted June 22, 2011 Yes Wayne you are correct. The 40-amp alternator AC724/1 has no internal rectifier of any type & relies on the external selenium full wave rectifier. In the event of the selenium rectifier failing it would of course be possible to cook up an equivalent bridge rectifier using silicon diodes. They could be discretely mounted into the fins of the old rectifier preserving the look of a toastie. I feel a toastie with no rectifier behind the grill is a bit of a let down. The 90-amp alternators of course have integral silicon rectifiers. I thought so....Just wanted to flag as a S2a Gen is not the same as a S3 due to amperage and the good old Toastie Selenium rectifier. Couldn't agree more about a Toastie without a working rectifier on show.....Hence why we are precious about genuine Toasties in the Warburtons camp Quote Link to comment Share on other sites More sharing options...
fv1609 Posted June 22, 2011 Share Posted June 22, 2011 I thought so....Just wanted to flag as a S2a Gen is not the same as a S3 due to amperage and the good old Toastie Selenium rectifier. Ah but a late 2A will have a 90-amp system. Pleased that you will be keeping the real thing behind your toast rack. Quote Link to comment Share on other sites More sharing options...
Rover8FFR Posted June 22, 2011 Share Posted June 22, 2011 Ah but a late 2A will have a 90-amp system. Very correct, but they are even rarer I believe as short life before S3??? Pleased that you will be keeping the real thing behind your toast rack. I couldn't and you wouldn't approve of me doing anything else. Hence why I have sensibly aquired a few 40amp Grade1 working Gens and NOS Selenium Rectifiers Quote Link to comment Share on other sites More sharing options...
Paul Drake Posted June 22, 2011 Share Posted June 22, 2011 Is uour S2a Gen 40 amp or 90???? I believed that the diodes are in the 90amp and replace the selenium rectifier??? Clive can you clarify??? Regards Both my 2A and 3 are 90 amp. Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 23, 2011 Author Share Posted June 23, 2011 sorry another question re diodes i am doing the tests given in all charged up part 4 and getting the following results first multimeter giving resistance across probes as 25 across the terminals on a new alternator (out of truck) i am getting the usuall very high readings but when reversed i am getting nothing as in the two probes are not connected. this is happening across all diodes on a newly refurbished alternator. am i missing somthing or is there somthing worng with my multimeter or am i just making a schoolboy error Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted June 23, 2011 Share Posted June 23, 2011 am i missing somthing or is there somthing worng with my multimeter or am i just making a schoolboy error Current only flows one way through a diode ! Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 23, 2011 Author Share Posted June 23, 2011 yea i figured that but why would i be getting a reading of 130 on the 200K oam setting on my mutimeter. is that not high Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted June 23, 2011 Share Posted June 23, 2011 yea i figured that but why would i be getting a reading of 130 on the 200K oam setting on my mutimeter. is that not high Think that one is a question best answered by Clive ! Quote Link to comment Share on other sites More sharing options...
emmetgilgunn Posted June 23, 2011 Author Share Posted June 23, 2011 i think ill post this in a new topic. thanks Quote Link to comment Share on other sites More sharing options...
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