Rare Diode Threatens Coast Guard’s Arctic Ambitions

The United States Coast Guard heavy icebreaker Polar Star is literally a one-of-a-kind ship. After its sister Polar Sea was deactivated in 2010 it became the most powerful icebreaker in the fleet, and one of only two US icebreakers capable of operating in the treacherous polar regions. The vessel is critical to protecting America’s scientific and economic interests in the Arctic, but according to a recent article in Business Insider, the ship’s age and scarcity of spare parts is making an already difficult mission even harder.

In the article, Captain William Woityra specifically mentions that the ship’s diesel-electric propulsion system is running on borrowed time as the diodes used in its AC/DC rectifier are no longer manufactured. With none remaining in the Coast Guard’s inventory, the crew has had to turn to eBay to source as many spares as possible. But once their hoard runs out, Captain Woityra fears his ship will be dead in the water:

We’ve got a few dozen of these in a box on a shelf, when they’re gone, the ship will not be able to run anymore. It’s really kind of disconcerting … that this ship, and this operation, and the US’s icebreaking presence in the Arctic is reliant on a box of spare parts that … there are no more of.”

The 45 year old ship received a $60 million refit in 2013, but that was only expected to extend the hard-working vessel’s life by 8 to 10 years. There was a proposal for a far more thorough overhaul, one which potentially would have keep the Polar Star in service until nearly 2040; but with an estimated cost of $400 million, Congress decided to go with the more economical stop-gap refit.

Polar Security Cutter

This story comes just days after the Air Force announced it’s looking for a few good hackers to help reverse engineer components on its aging fleet of B-2 bombers. Much like the Polar Star’s vintage rectifier diodes, spare parts for the the stealthy aircraft are getting increasingly difficult to find.

While the Air Force has enough money in the budget to get replacements made, the Coast Guard will just have to hope their stock of diodes holds out a little while longer. Congress has already approved the Polar Security Cutter Program, a fleet of next-generation icebreakers designed to be comparable to newer Russian and Chinese vessels. The first of these ships could set sail by 2024, providing the Polar Star some much-needed backup.

[Thanks to Chuckz for the tip.]

164 thoughts on “Rare Diode Threatens Coast Guard’s Arctic Ambitions

  1. C’mon , “diodes used in its AC/DC rectifier” ……. Some-one need to learn how to find and sort parts in the Digikey web page to find compatible equivalent before doing the “Cry-Baby” in the head line !

          1. That reminds me of the thyristors in a generator excitation unit for a power station, around 1000V and 1000A max. They were similar ceramic disc housings, about 9cm in diameter. Clamped between two huge heatsinks, about 20*20*15cm with two bolts and a “spring”. The spring was a piece of steel about 15cm long and 10*20mm cross section, which had piece of sheet metal as a “clock hand” to indicate the bending. It had to bend about 5 to 10mm to indicate the right clamping force.
            The cooling fan itself had a 3 phase supply.
            So probably the whole rectifier has to be changed to use new diodes, but nothing impossible and probably much cheaper than a few million $.

          1. Actually, the US has been buying its standard liquid-fuel rocket engine from Russia for many years. The diodes should be no problem, especially since the ship is not a combat vessel. which would threaten either country’s “national security.”

      1. Plus the extra capacity from the electrical noise the motor generates… Those motors experience *a lot* of intense periods of intense strain followed by periods of zero (or even negative) load. The ship is designed to essentially beach itself on top of an ice sheet, and betting that the ship’s weight is enough to fracture the ice. It takes a lot of energy to do that, all of which is going to be felt by those three motors and the rectifier bridges that feed them.

          1. Unfortunately not. Diodes have a negative temperature coefficient of the forward voltage. So the hottest wins – most of the current. Until it is not a diode anymore but a blob of molten silicon with very bad rectification characteristics.

          2. Since all high-current silicon rectifiers are made by connecting a number of dice in parallel, you kind of have to be wrong. Where you are wrong is that if devices in parallel are mounted on a substrate with high thermal conductivity, this issue is mitigated. You still have to derate them because the sharing isn’t going to be perfect, but this is standard practice.

          3. Martin is probably right, due to the temperature coefficients.
            Paralleling diodes is certainly possible, but they usually need to be fairly tightly coupled thermally to not overheat and kill them one at a time.

          1. I know.. so those things aren’t specified.. there must be more to the story.
            Wouldn’t think salt would be an issue though, they’re not going to be outside.

          2. Once it passes the electrical specs, it is a matter of mechanical to handle the environmental. Yes, even if you have to build some insulation for cold or shock mount or enclosed box for the humidity and salt spray.

            The Russians just use pencils while the American spent money to invent a space pen.

          3. You do not want any salt (or other conductive liquids) near HV DC equipment. Otherwise you can literally watch your conductors getting dissolved by electrolysis.

        1. I am 71 now, a retired electrical power engineer at 62, and obviously behind on who carries parts. I was surprised to see that Digikey now has power diodes of this size. They didn’t used to. I would not have even guessed. I am glad to see you spending the time to guide the person that requested the help. Networking amongst all of us really helps. Hopefully, your information will get back to the Coast Guard and they will go forward with what you provided. Thank you.

      2. Recently worked for na Aluminum factory where they put 12 pulse three phase 64kA rectifier at 1100Volts, so theses specs are not unoptanium, maybe size restrictions are more of a issue.
        Man that was amazing place! Near DC busbars you could put screwdriver in open palm and it would stay vertical due massive magnetic field

        1. @Tom I don’t suppose it was the smelter in Kitimat?

          I don’t know about the busbars, but stacking paperclips vertically in your palm is a great party trick when you’re in the Cell room.

        2. At ABB in Turgi, Switzerland we made Alum Smelting Rectifiers up to 500,000 Amps and around 2000 Volts, using the big Ceramic Press-pak type Diodes & SCR’s.

      3. Soooo… I put in those numbers (min 1000V withstand voltage and min 1000A) into the digikey search and there are 328 hits, the cheapest one costs €54 (but only 2 in stock) for €65 you get one where they have 24 in stock.

        So you might have to make some converter to make them physically fit. And if you cecide you don’t like the ones that are in stock then you may have to wait for 8-12 weeks.

        I’m (going to be) involved in a multimillion dollar overhaul where manufacturers are complaining they can’t keep producing spare modules because components are no longer being manufactured.

      4. This is a likely “hockey puck” diode commonly used on older (BIG) motor controllers especially noting the torque specs (special hold down clamps are used). wouldn’t be surprised they could find all they need polling big city water departments paper mills etc in the US…. Had a stack of 1200A ones around here somewhere cant remember voltage at the moment…

        1. Or a diesel electric train with a few MVA traction power. But in a train you normally use thyristors to control power/volatge/current nut just “dumb” uncontrolled didoe rectifiers. That brings the question: How do they control the drive power on this ship. Do they really use only didoes in the rectifier?

          1. Without looking at the article, I would suspect the diodes are used in a cycloconverter ( https://en.wikipedia.org/wiki/Cycloconverter ). Cycloconverters take megawatts of AC input and turn it into megawatts of AC output at a lower frequency. Build enough stages of it and you have a crude, harmonic-rich variable frequency drive that can nonetheless scale up into the fractional gigawatt class. They were common in the Pleistocene era but obsolete now. They’re still used on ships, though – Carnival Cruises blew one up a few years ago and was dead in the water. I hope their Sea-Tow membership was paid up…

            These widgets are still COTS from ABB. I don’t know if they ship from stock.

      5. My first thought is how poorly designed is that power supply that the diodes in the rectifier are considered consumables?

        My second thought is that that is really not a huge amount of power. If we’re talking about a $400 million project, how hard is it to simply replace the power supply with something designed better and using easily-sourced parts?

        Anyway, 1kv diodes aren’t that hard to find, and you can connect diodes in pararell to share current. And those numbers just don’t seem that high that the part should be so obscure. The power available in house is 230VAC 200 AMPs. Surely that diode is unimpressive to an industriual electrician.

        1. Soc Rat,

          You and I are in agreement. However, it must be remembered that one is interacting with a division of the US government and they have a limited point of reason. It is difficult, if not impossible ,for them to deviate from a predetermined line of thinking. Usually, when there is a requirement for part “X”, then only that specific part will work. It is very difficult for them to deviate from the proscribed methods set down in their rules and allow for a reasonable and acceptable alternative in the face of a component shortage.

    1. If you can’t find exact parts, somebody will have to qualify replacements that work the same or better, fit the same, etc. Or reengineer the whole thing. If they blow out a lot, maybe that’s the way to go.

    2. The comedic part of this outcry is exposing two contrasts : $400 millions and Diodes, I careless about the size of such diodes nor their amprage capability , somewhere down the line is laying the grounds to stiff US ..and it is not the Chinese no way in the world to put such a high tag on something so abundant in the semi conductor market, additionally it is so deplorable to make believe that American technology and know how diminished so low to seek diodes from ebay. Unless the author has manufactured his claims about a silly diodes shortages , it’s a colossal disaster, pouring $millions on a bogus problem.

    3. I’m pretty sure diesel electric freight train engines offer a source of alternative diodes capable of handling the amperage. Whatever they’re using now is under sized for the job. You shouldn’t be frying diodes except rarely as oxidation and heat take a toll over time. A 20 to 30 year life for a diode engineered to do the required job is a normal expectation.
      As spring and summer come to the Arctic they should already have the freight train replacement parts ready and waiting to install before fall of 2021.

    4. These diodes are not just the run of the mill diodes. These diodes must provide 5000 amps at 900 volts and are packaged with a large case and leads. I suspect they are banked in a parallel fashion. My suggestion would be to contact manufacturers that make high voltage AC to DC converters in substations for transmission of power across country. These converters use triacs; however, your inquiry might give you a lead for high current diodes. Another lead to try are companies that use diodes in exciter systems for large electric utility generators. These generators require the voltage and current ranges as the diode ratings you are looking for. I would also suggest the peak reverse voltage rating be at least 1000 volts PRV.

        1. Those old DC locomotives are gone or going now. One of the problems they had was the armature windings had a tendency to fly out of the cores and that rendered them scrap iron. They started fires on a regular basis out in service, the motors weren’t the only causes of fires though. The engines had other components that went up in flames on those old units. Exhaust valve pieces, carbon chunks, and course there were the those pieces of the carbon and metal resistive shunts that were used for dynamic braking that would melt down and fly out of the cooling towers which are still used in AC traction systems today. Older locos weren’t always equipped with spark arrestors years ago. New Locos are equipped with arrestors and some emission controls now. Then there is as in the past as in the present that all DRAMATIC engine explosion that will send people on the engines running for cover sometimes. I have heard about these engine blowups from friends that worked around the maint. shop in my home town. There is a Dynomometer that the engines would be rolled onto after major repair work for testing at the yard in my home town which is the larges locomotive facility and yard between Chicago and Seattle, from time to time an engine didn’t pass the test. I always got goose bumps when I was in the area and a test was in progress, those engines would really be cranked up and the noise was just awesome, sort of like standing near an airport when a huge jet was leaving only more rattling and other mechanical sounds that let you know something was making a shit load of power, I’ve always be a gearhead and that kind of stuff gets me fired up. The RR’s used to run DC motors a long time ago but most of that tech as far as I know has either been scrapped or sold off to other countries. Almost everything now is 3 phase AC. If there are still any DC units running here, they are or should be restricted to local yard usage for switching. That’s just what I know from being around an area that has the nations largest coal train concentration coming out of Wyo.. My grandfather was a conductor for the BN which became the BNSF for 43 years and I lived with him during my high school years, a lot of my family was with the BNSF till they all retired. I had friends that worked there also. Those old BN DC units were always breaking down, smoking, starting fires and just costing the RR too much to keep running. They were too wasteful, inefficient, under powered and poorly maintained back then. The EPA and Gov. demanded newer better designs and the RR was happy to comply. If you think about it, it makes little to no sense to stick with a high power DC drive system because there is simply TOO much power loss in them, they have components that an AC can be made without so there is a wear issue also. A 3 ph AC motor of higher HP would require smaller conductors for the windings, no rectifiers, however it would still require components to regulate motor speed and reversing functions, that only requires switching 2 of the 3 leads that supply current out that make it 3 ph.. A 3 ph motor can have current which it can generate on its own fed right back into itself and be converted into a partial load that can assist in slowing the train down also. General Electric and GM, along with a couple of other firms stepped up for the task of supplying better locomotives and I am very sure that these same Corps. would gladly step up to the task of refitting such a ship as one of these old Ice breakers aside from the fact that as with any vessel in use in and around a salty environment has the same issue as a car or truck exposed to salt. There comes a time when it is simply better and in the end cheaper to scrap it and replace it with something already improved in design and more suited for the job! The Gov simply needs to accept it and figure out how it is going to include it in the defense budget. Of course we all know what the result of that will lead to. More Taxes ! DC motors have their place and always will but this is not one of those places anymore.

          1. Ok [Bret],
            I worked for BN (fot 2 weeks in 1976). Where was this test depot?
            Do you have some model numbers of the old locomotives?
            (I’m just curious, I’m not trying to set you up or anything)

          2. I was told by a usually reliable source that diesel-electric locomotives were more or less mandated because they could function as mobile power generators for the Civil Defense system. It doesn’t answer the question why they’d be DC rather than 3 phase AC but the rules were probably made during the Cold War for different technology.

          3. At the Railway Museum at Bulawayo they have some old diesel electric locos and you can crawl all over them and look at how they were made.

            None of this look at it from 3m away!

            What surprised me was the massive V12 diesel engine which was driving a surprisingly small alternator.

        2. Long ago, yes. These days, inverter drives are the rule, both for efficiency and better control. Alternators with rectifiers (simple rectifiers, usually) do the energy conversion from rotational to electric.

          Marine has a pretty good variety, including every option locomotives have used, as well as others.

        3. DC generators get hot from the commutator, they’re very inefficient, and you can’t make the brush and commutator large enough for a really big dynamo. Your best bet is an AC alternator and a DC rectifier if you need thousands of amps of DC. The rectifier can be solid state and some massive and pricey diodes, or even mercury-arc tube rectifiers if you live in an era that didn’t reliably produce big diodes. Theoretically substitutions for hard to find diodes is easier than replacing a mercury-arc tube.

          1. The short wave transmitters like the Marconi BD272 were originally supplied with mercury arc rectifiers in 1963 and these all converted to silicon rectifiers since then.

            But their power was primarily derived from a high voltage of about 11kV rather than a high current so 30-40 amps was adequate.

    1. If it burns enough diodes in a year, could this be used as a new fuel source? Anybody know the energy density (MJ/kg) of those diodes? Anything North of 55 and we have a deal.

      You know sillier things have been proposed.
      De Lackner HZ-1 Aerocycle

      Or as I like to refer to it:
      Army HZ-1 Mince-O-Matic

    1. It’s hard to imagine any kind of electronics costing more than a few million, unless it’s too classified to even mention or something.

      Like, maybe it’s mega of gigawatts, but so are lots of things. People know how to do this stuff, they still do it, it’s not a lost art, and we’re even better at it now.

      I’m guessing this probably has to do with regulations and it being super expensive to properly test the new configuration, more than any issue of being unable to do it.

      1. Paper work doesn’t do itself..

        If the engineers who sleep on the boat at 85 degrees north are comfortable with it, it ought to be good enough. But probably the fleet managers figure the boat is worth more to them than the engineers’ own hides are to themselves, so probably Much Paper will have to get properly un-blanked first.

      2. They would rather have a piece of junk ready for scrap not sea worthy than to spend money to keep it running? Money spent now means it’ll be easier to replace parts later. Pork barrel accounting is not real math.

        1. The government hasn’t been known to spend our money wisely.

          Like the space pen comment above. But a space pen doesn’t have little conductive pieces that break off and float around like a pencil does.

  2. I find it difficult to believe that no modern components can be pressed into service to do the job. I suspect what we have is a lack of imagination and determination. Apparently we have lost our ” American Exceptionaliam”.

    1. I would imagine a modern functional (does the job on the bench) replacement is too big a deal, but an operational one (suitable for operational use in the field) might be problematic.

      These are pretty tightly designed systems, with requirements for certification for safety and suitability for service. This makes things interesting (I have had material and parts certified for use on naval vessels. It is interesting, even when it is NOT a change of engineering)

    2. I’m sorry but “American Exceptionaliam”, like “Philco”, “RCA” and the like was broken up, the pieces liquidate and the rights to the names sold to companies in China.

    3. Some of the links on here seem to show diodes that might be inside spinning components so they interact with brushes. If nothing’s the same shape anymore (all built for static installation in a switching station or something) then they’re looking for a drop-in replacement instead of an electrical replacement, or else they’d need to re-engineer that part of the system.

      1. Think you’re onto it. It’s not the electrical characteristics that are the problem, if it were, a modern diode would work. It’s the physical factors: size, mounting arrangement, cooling…that sort of stuff can be hard to rework (especially on a ship where space may be tight).

        These things don’t just solder into a PCB :-)

  3. This is just a BS article. Doesn’t make any sense to any Electrical Engineers out there. Quote: “We had a diode on our AC-to-DC rectifier that blew out, and we had to replace it. And this is a part that is no longer available. It’s not made anymore.” AC to DC rectifier?! Come on, you can replace that even with power mosfets, or jury rig several replacement high current diodes together.

    1. This isn’t some hack you throw together in your basement with the garbage you’ve got on hand, this has to actually work with people’s lives in danger if it explodes while it’s being used.

      1. I make electronics for the marine industry. It really isn’t that difficult to design the electronics. It’s the ridiculous charges for the insurance companies to read the paperwork. Imagine.. $100000 just for a first pass read of the design. Then it needs to be tested to certain standards, which are pay walled, and so can only be performed by notified bodies, who charge a fortune. It becomes more expensive than it’s worth.

        1. Plus its a government ship meaning someone has to answer to the taxpayers. The reason Space X can have SN9 and 10 blow up and still carry on is because they are a private company and don’t have to answer as much as the government does.

          1. Haaaaaa, no one EVER answers to the tax payer for government decisions. The government has sovern immunity. And when they do seldom if ever is anyone held held accountable.

      2. They’re using some ancient rectifiers someone dug out of his basement and sold on ebay, it can’t be that critical. Seriously, they could just hit up ABB or IXYS and get a functionally superior replacement.

    2. If you had infinite but time and money, sure you could come up with some solution. But this is a ship that’s on active deployment and has no replacement.

      They can’t afford to sit around waiting for somebody to hack the propulsion system, people’s lives are at stake.

      1. Which is a exactly why something and someone should be and probably is already working on a solution. These ships have shops on board and people that know how to get things done when needed. Then there are places that have people even smarter on solid ground with access to planes and helicopters that can move parts quickly when needed. This stuff isn’t being done without forethought. There are contingency plans for all of whatever could or would happen. Since the Gov. already decided a replacement ship is not an option at least for now, I’m pretty sure a solution is already been arrived at. I’m also sure the defense forces are always looking for a few good men and women and even smarter men and women.

    3. My usual bet: it boils down to liabilities.

      I assume that most repair “shops” won’t touch such a job because, if they use a replacement part and something goes wrong, they will have a shitload of lawyer going after them (because the shop has to explain why and how they did the replacement in such a way and experts might all have opinions), never get a job from government again and be royally screwed.

      So the middle chain of command (here “Captain”) has to paint the situation in such dire straits that the repair contract will cover this aspect. Therefore he needs some publicity to get the message heard. On the plus side, his ass is covered, “because he said it early”.

    4. I’d say mercury arc rectifier octopus tube, but ships wobble around.
      If they can call a few million a cheap retrofit, a box or diodes can be soldered into an appropriate network to meet the voltage and current requirements. For that money, someone could do some research and get the original remanufactured if they are that worried about keeping things authentic.

      1. With Hg vapor tubes you can never get the 99% plus efficiency. The question is for drop in replacement diodes which have the same form factor and “bolt hole distance”. Otherwise there are plenty of silicon or SiC diodes available which could do the job electrically.

  4. How many amps are the unobtanium diodes, and what is their maximum forward voltage ?
    Surely a few thousand or tens of thousands of available diodes could be jury rigged into a replacement part.

  5. I could believe the BART thyristor problem from a few years ago, where it probably had to fit a confined space and have particular turn on/off times, but a diode? Seriously ? They’re just not trying.

  6. I’d be very curious to know the required ratings for that diode. Power rectifiers are common parts, and they can be easily manufactured upon request; it’s not rocket science. Also, sometimes it’s much better to think about function blocks and replace the entire circuitry performing them, I mean, is the diode used in a generator? If so, then the wind turbines industry probably has something that could be adapted with minor effort to do the job, and that would also mean one less block to replace in the future.

  7. “…comparable to newer Russian…”
    The Russkies have nuclear powered icebreakers. Several of them. How does a conventionally fueled ship match a nuclear powered one??

    1. In principle it does not make that much difference, if your generator is powered by a diesel engine or a steam turbine. Of course the power level may be higher in the nuclear powered vessel.

  8. An ASME engineering outline of the propulsion system is here (sorry about the link, it’d be 20 lines long without the shortener) https://bit.ly/3eAl91B

    From what I can gather, the ship has diesels (18,000 HP) and gas turbines (60,000 HP). The turbines can drive the props directly for ice breaking in thick ice, and the diesels are used for cruising and thinner ice in diesel/electric mode. Lots of redundancy it appears.

    1. Great link and great read! From the document it shows each generator produces up to 1400A at 560V at 130% overload or 1074A at 900V; plenty easy for a Puck rectifier to handle

  9. “Rare diode” isn’t very descriptive, likely because of the non-technical source. I was expecting a tunnel diode from the title. But it could be more than a power diode.

  10. Sounds like the ship may not be in service before its replacement is plying the water. That’s not an acceptable outcome, and instead of reading of wringing of hands over some diodes we should be reading about a lifeline being given to the one remaining ship, thus capability being preserved with prudency. USCG and Pols, stop dallying.

    1. Yeah something doesn’t add up. I bet its more along the lines of no one is interested in future proofing the ship. No one cares to put the work in to replace this particular tried and tested diode of which there are limited supplies.

      i.e. once they run out of these diodes they will look into replacing it and I suspect they will find many suitable replacements.

      If they care to that is.

      1. So, here’s why it doesn’t add up: a guy says they have a box of scrounged replacement parts. Another guy says, if they run out of diodes, the ship will not be able to operate. Okay, so, a) how long do these diodes last, on average, and b) how many of these scrounged parts do you have? It’s a pretty simple calculation, and if you have a comfortable margin, there is no problem. My guess is, there are much bigger problems than a few hundred, or even thousand dollar parts.

  11. A bunch of armchair engineers that know jack about what is going on trying to match electrical specs in a commercial catalog for mil spec parts, LMAO! The basic electrical specs are one thing. But more important is package, MTBF, 2.5 MEGSWATTS power dissipation, and mil spec reliability. The control systems were 2 sets of a one off system and the required spares. A very high power semiconductor manufacturing company built x number for the contract for a specific system and I’m sure a one off package. Does not mean they will build more if they are even still in business? No. I faced this problem as an ET in the Guard for a surface search radar power supply that blew transistor in the power supply 10 at a time. We eventually retired the Radar as junk when we could no longer get the special Mosfet transistors. Many comments here seem to believe the U.S. Coast Guard has no ability to find parts, LOL! Wrong, but if they are no longer made and you have exhausted the surplus market it is over, people on here also seem to not be aware there are numerous parts location companies that also have little known sources. We (USCG) used them often when I was in.

    1. > 2.5 MEGSWATTS power dissipation

      No it isn’t. You make the basic error of calculating amps x volts at the generator, while in reality the power dissipation is amps x forward loss, which for a high efficiency rectifier diode is about 1.5 Volts nominal.

      After all, you’re supposed to be turning a motor, not using the rectifier as a heater to melt the ice.

        1. We usually et that slide, because while the diodes do not dissipate 2.5 MW, they do have to pass that much power. The key is that they have to withstand ~1 kV reverse voltage and ~1 kA of forward current. Just not both at the same time!

          However, the power they DO dissipate is still considerable. In the document supplied by a commenter, there is about 11 kW dissipated in each “diode”. Now, this is a block-level diagram, so it is very likely that these “diodes” are actually more complex than a single device, but in any case, SOMETHING is required to remove that 11 kW of heat, which may be at the root of why only a particular device will work.

    2. You miss an important fact: they HAVE managed to buy replacement parts on eBay. This means these were NOT parts that were made only for this specific system, nor was the package unique.

      The other part of the story, though, is that it would seem from the article, that the U.S. Coast Guard has no ability to contract out engineering. When you have a one-of-a-kind ship, you had BETTER have engineering resources. But I ran into this a lot in the Air Force: on the front lines we would submit suggestions to improve the reliability and maintainability of our Radar systems, only to have these rejected because the Air Force did not have sufficient long-term plans for our systems to justify doing engineering evaluations on our proposals. Never mind that they knew we had these solutions already in place and running for years “off the books”.

    3. Those “parts location companies” can be great resources…or sleazy scammers. A company I once worked for bought some parts (DRAM, I believe) from one of them…they turned out to be fakes. There’s a lot of risk buying from parts brokers, and, if you don’t know those risks (like, for example a senior manager might not), you can end up spending premium prices for junk.

      In my case, I always warn in no uncertain terms, that buying from these guys carries a very high risk of getting fake or out of spec parts. Where there’s lots of money to be made (e.g.: selling to the government), you’ll find all sorts of nasties.

  12. After spending a decade in the military I can tell you that it does not allow ingenuity. If it’s not in the reg it is not allowed and does not exist. There could be a thousand different diodes that could work but since they are not authorized they will not ne used. Once the supply of authorized parts are exhausted the ship will be mothballed without a second thought by the powers to be. It’s mission will be contracted out until such time as the new ships come on line.

    1. There is also the matter of these replacement parts they’ve scrounged from eBay sources. Once the top brass hears about this unauthorized cache of questionable parts, it could result in the immediate destruction of these. Probably not, though. Mid-level officers usually have the authority, and sometimes the even the initiative, to keep their systems running by whatever means they can find. That’s what my military experience taught me. There were a number of times when what I needed to get done was specifically prohibited at the squadron level, but I pressed the issues, asking, “what do we have to lose? What is the worst that can happen if I screw up a job I haven’t been certified to do?” This was usually sufficient to get something running on a temporary basis, and at least a couple times for the remainder of the life of the equipment in question.

        1. The actual answer, in a couple cases I remember, was, “well, you could destroy the core part that we would otherwise have been able to rebuild at the depot level.” But then they weighed this against the fact that a radar site in active use in defending American airspace would be out of commission for a month or more, and authorized me to make the repairs.

          One of these was a memory drum for a 1960s Philco computer. One of the heads had shorted, and they were going to have to power up a computer that had been removed from service years ago, test to ensure the drum was still usable, and ship it to us. Which is when I said, “what are these two ‘spare’ tracks shown in the schematic?” After a couple more rounds of “why not .. because regulations”, they talked me through swapping the heads and going through the head alignment procedure. Procedure was successful and system ran for two more years before the whole site was shut down.

          No loss of dessert. This was at my first duty assignment, and was my first experience with “getting to yes” in the Air Force; the people with the ability to say “yes” were the same ones who really didn’t like how THEIR performance numbers could be affected by doing everything by the book.

  13. Even before reading the comments I found it hard to believe they don’t make better diodes now compared to some 40 years ago.

    So what else could be going on?

    I suspect a ploy to drill into the consciousness of people how “poor and under budgeted ” they are in an attempt to create more ground for more funding.

    1. When a part is designed and built for a specific device and only 2 units in the world nobody designs a “better” part for it to hope to sell a few to the Coast Guard, LOL. Why do people think there are plenty of diodes to replace it. Can they not read there are NONE being made for this specific application? I’m sure there are literally thousands of diodes available on the commercial market. But none like these, that is what the purpose of this article is, not to get people to search the internet for diodes at their favorite commercial distributor. They seldom handle mil spec parts and half the readers probably don’t even know what a diode is much less a 2,500,000 WATT diode. This is nothing new in older military equipment.

      1. If his was the case – that these diodes and the complement of spares made for the boat were unique – then they couldn’t very well be finding suitable replacement parts on eBay, could they? If these diodes are no longer made, it is almost certainly because they were made obsolete by far superior newer devices. It’s not like high-power solid state devices have gone out of style.

  14. this sounds like a bureaucracy problem. parts exist, its possible to build a new rectifier. but i have the feeling the government has limits to what companies it can source parts from in the military industrial complex. lobbyists payed a lot for those exclusive parts deals even though they are incapable of doing the job. the crewmen are going to run whatever kludge they can come up with in the mean time while they wait for the 300 step multimillion dollar approval process for a new part.

  15. Has anyone looked to the AF’s large radars? We worked with 3 foot tall diodes in the AN/FPS 27 radar power supply . Don’t remember the spec’s but damn fine rectifier for a radar that pumped out 3 phase 480.

    1. Not. Even. Close. I was a 303×2 myself. Never worked on the ’27, but on other “high power” radars (FPS-93A, -26A) These all had impressive peak power specs, but even the mighty FPS-27 only put out about 30 kW average. So we’re talking several orders of magnitude below the megawatts it takes to drive an icebreaker.

      I remember thinking we were hot stuff in the search radar tower, but then I discovered that the transmitters used for the UHF tropospheric scatter system (White Alice) that linked our data to NORAD produced about four times the average power of our transmitters!

  16. Should completely strip both ships down to the bare hull, decks, and bulkheads. Then install all new mechanicals, electrics, and electronics. *Make both ships identical*.

    How could building a new ship from the keel up cost less when these two hulls are already built? Be rough as needed when doing the removal, hack and cut what’s being taken out, don’t care about saving anything being removed, it’ll all go in the recycle bin or trash, don’t damage what’s being left.

    1. Well…
      Ships are built through a variety of techniques. (You’ve probably seen the YT vids of cruise ships being built by welding huge prefab modules together). But, for some, the key drive components go in/on just after the keel is laid. Then the decks, bulkheads and hull are built. Your idea might work, but the hulls themselves may be suffering from metal fatique (and corrosion).

  17. I am concerned, by what I don’t see in the schematics. No provision has been made to drop power to the motors ONLY AT THE ZERO CURRENT CROSSING, So it is Russian roulette..where in the current cycle does shutting down take place. A collapsing magnetic field from the motor will generate extremely high voltage/current, counter EMF, KICKBACK and sooner than later the the kick back will destroy the rectifiers…….

  18. You seen the lines at legal dispensaries lately. Dock the ship, use the revenue from 30 days of legal pot sales and buy 6 modern ice breakers. Create a new bud strain and call it Semper Paratus.

    1. I believe the agency in charge of decisions to fund and deploy adequate Ice Breakers over the past 50 years has the catchy motto;

      Semper Paralyticus

      Too bad Adm H. Rickover didn’t have a “thing” about creating a squadron of nuclear powered, Dreadnought Class, Ice Breakers. Might be needed when a USN Submarine gets stuck in the ice. Seawolf

  19. Supposedly this is what did in Hubble.
    The (extremely) expensive space rated 80486’s aren’t made any more and if NASA had some there’s no guarantee that even if they could be replaced they’d run for the full 10 years anyway due to electromigration etc.
    That its lasted this long in the first place is impressive.

  20. Reminds me of the build-out of the internet in the way back when… Around 1999 the company that was putting in undersea internet cable needed (for their own reasons) a very specific bipolar power transistor that was no longer manufactured here in the Valley of the Sun. When their engineers came to talk with us, they explained what and why they wanted them so one of our older engineers who had designed a ton of bipolars over the years said, “No problem!” and within a silicon cycle time we had the parts back to Tyco Boat for their undersea cable amplifiers – probably still down there…

  21. What components are used to build DC interconnects between AC power grids? Surely there must be some really hefty rectifiers involved and they must still be manufactured somewhere.

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