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2N3055 and heat

Discussion in 'General Electronics Chat' started by John Potter, Nov 20, 2016.

  1. spec

    spec Well-Known Member Most Helpful Member

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    Morning John,

    Yes, that is correct.

    But with your power supply there is a slight complication: because of the bridge rectifier the secondary winding of the transformer never goes negative so the two rectifier diodes and two capacitors are needed to get a negative DC voltage for the negative three terminal regulator.

    A negative three terminal regulator (LM337, LM7915) is exactly the same as the normal positive three terminal regulator (LM317, LM7815), except that all the voltages are negative instead of being positive.
    A classic linear power supply with many features similar to your power supply.:)

    spec
     
    Last edited: Dec 9, 2016
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  2. John Potter

    John Potter Member

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    hello spec sorry about the writing but it's a one finger job tonight (as the art mistress said to the gardener)
    the 60a monster had wheels so i managed to get it in the kitchen whilst the hoard were out Christmas shopping. unfortunately after i had stripped it it had no wheels. i managed to slide it on an old mat to the garage door and walk it along the floor to a corner. i will weigh it but i can say it's bl**dy heavy, much heavier than i estimated. i'll post the pics tomorrow. there is an awful lot of really really nice gubbins. i could not find the rectifier. looking at the pics i found them. there are 8 large single diodes 4 on each side mounted through the steel angle frame. they are like nothing i have ever seen. most of the wiring is ok but some of the thinner stuff is in a sad way. all in all though a nice bit of kit if you wanted to jump start a lorry in Siberia.

    will it be ok to post these pics. they are relevant if one wanted to make a linear power supply of unusual thrutch ? Is there a size in MB limit? it's quite complex but I think 4 to 6 pics at about 1MB each should show all. i know it's not exactly relevant but purely from the gubbins point of view it's rather interesting.

    i wonder why it never blew the plug out of the wall? there are several odd bits that i don't understand. i was expecting a very large unit to control the voltage / current ? adjustment but it's quite small. i think it must be done either on the mains side or through some clever gubbins. it's a 60a variable battery charger with a boost facility for starting. i did try it on an old car battery but when white acid vapour started pouring out and the bottom blew out i switched off . The transformer has the look of something that would enjoy being abused. don't we all?

    i got the tv apart. nothing there much these days. it was one of the last CRT types. a few caps, diodes, heatsinks and the odd black thing with legs. very disappointing. there are a few big resistors well off the board that i'll keep.

    last night i decided to look through the volt/ammeters on ebay - all 4397 of them. 90% are repeats. somewhere i found a nice 4 digit dual one quit cheap with trim pots but i can't find it now. might have been on amazon.

    sometimes you see things that 'look right' and they usually are. i have to admit spec that i look at some electronic components, especially switches, and i'm disgusted. planned obsolescence, cheap, cost effective, does the job - and kills people. like these tumble dryers. like car recalls. (I'm vertical) It's what they call progress. No thanks. Give me a great lump of armour plate or a Rolls Royce V12 any day. Those tag strips and heat sinks look nice though

    Changing the subject. I was sitting here watching yet another video on AC sine waves and I suddenly realised half of our AC is below the zero line. Is it really negative or just positive volts in another direction.? It was rather nice I managed to sort it out though. There's hope yet. Are you using those 2 diodes in the reverse action of a bridge rectifier?

    He's not a bad chap, I quite like his videos. He has done one two and a half hour video on an old classic Sony receiver. I didn't understand a word of it. 95% of it anyway.

    If I have 40V DC 3A going through a linear power supply set to a 40V output what watts are going through the power transistors? It's not regulating therefore I assume they would stay cold. The above video is of a 13.5V 16A linear regulator that uses 4 x LN3771 or something similar. That's 276W or 54W per transistor. They do say that you should not use more than 40% of it's advertised rating or even less. A nice row of fans would help.

    I hope this doesn't come out in full on the thread, if it does OOPS! and sorry. It's a good read for me though.

    http://www.repeater-builder.com/astron/astron-intro-stuff.html

    Poor little Lucy, she's only 4 and coughing her heart out in the next bedroom. Her mom Samantha went into the chemist and was advised something that would help. If you drank a gallon of this rubbish it would do nothing. The active ingredient is 'blackcurrant'. That and a preservative. £3.80. Do not exceed the stated dose. Sounds like 'The Green Pineapple' needs an airing.

    JP
     
  3. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    In case you are still looking for methods to insulate a transistor from the heat sink, another method that is used for both transistors and high power diodes is to NOT use any insulator but instead to mount it directly to the heat sink using regular heat sink paste and then insulate the WHOLE heatsink from the chassis using insulating stand offs and nylon shoulder washers. The stand offs keep the heat sink metal from touching the chassis, and the washers keep the metal screws that are used to mount the heat sink from touching the heat sink. It is a very effective method. For high power diode rectifiers, the two types of stud diodes are employed: the anode stud and the cathode stud. Two diodes with anode stud are mounted to one heat sink and two diodes with cathode stud are mounted to a different heat sink, thus making up a full wave rectifier. Example diodes are the 1N1188 series stud mount but a diode with a tab could be used instead of course.
     
  4. dave

    Dave New Member

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  5. John Potter

    John Potter Member

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    Hello MrA1
    Thanks for the input.

    I have suggested that myself. If you go back to the video's on page 1 - second video there is a chap who does various tests on different mounting methods for the TO-3 case. I was going to use the direct method as it is a lot more efficient but it does have a drawback. The heat sink is an awfully big lump not to short to the case with a wandering screwdriver. I have to agree with spec there.

    I don't think I will have any trouble running at 30W per 2N3055 with insulators. If I do then mounting the 2N3055's directly is a an easy option as the heat sinks are not directly mounted to the case. There are 4 separate heatsinks connected together under a fan hanging from brackets. I fancy some rubber grommets as insulators.

    JP
     
  6. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Well the insulated heat sink method was used on converters that go up in power to maybe 30Kwatts and cost thousands of dollars so it is certainly a viable method, so it is not "just an idea". The case protects everything inside.
    It's always your choice though.
     
  7. John Potter

    John Potter Member

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    Your perfectly correct, I'm just a bit wary of shorting things out whilst I'm making this thing. When the design and construction is finished it's a different matter. It won't take long to remove the insulation.
    Have a good look at the photographs that follow. It's an XP Metalworker transformer of 40V and 80A (total overload)
    The main ones are of a car battery charger / starter circa 1969. There's no insulation on those diodes on the frame. 4 each side. The frame is insulated.
    XPtran.jpg

    View attachment 103043
     

    Attached Files:

  8. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Yes, when you are building something for yourself you want to feel comfortable with the design and construction. If you dont you wont feel like working on it :)

    We've also used sil pads for very expensive equipment. They used to sell it in a roll too but not sure anymore if they sell that or not, that was back in the 1980's.
     
  9. John Potter

    John Potter Member

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    Hi MrA1 - I take it one is a mature gentleman of the old school? When chips were cooked in beef dripping and not nasty little black things with legs.

    I have to say that spec has been wonderful in his patience. One thing I have found with many replies is that those who are knowledgable forget to come down to the level of the moron asking the question (like me). If you are intimate with a piece of equipment you are the last person who should write the instructions on it's use. Unless you can go from moron to expert and back, very rare.

    An example (don't take offence, it's half joke) What's a 'sil pad' ? If you mean the insulation in sheet form for CPU's etc. I'm with you.

    Hello Master spec
    My new soldering iron came today. It's a bit chunky but seems well made. I got 2 chisel and 2 screwdriver type blades as well as the knitting needle it came with. They are quite heavy tips and should be quite good heat reservoirs. Whether it is quite right for the job only time will tell but for £5 and 99P a tip I am very surprised. People moan about the quality of Chinese kit but I honestly can't fault it. Even the lead is acceptably pliant. Mind you I haven't plugged it in yet.

    I have never used a 60W, 30W is my usual but I have fount it a bit slow, mind you it was old. The only thing I don't like is the 2 screws that hold the tip in. Pity the screw heads are a slightly different size, I expect the little Chinese girl that assembled mine ran out and found an odd one on the floor.

    They are going to be replaced with a couple of stainless socket headed flush grub screws or a couple of slotted ones for now. They have to go as they will get in the way and catch on other gubbins. I bought an £8 iron from Toolstation. It is nowhere near the value and they don't do tips. Same with Screwfix. I'm not sure about this new tip material but I'll get used to it no doubt. I'm still going to keep my eye open for a bit of copper - just in case.

    What I will ever use this XP transformer for I have no idea. The only snag is I am enjoying making this power supply rather too much perhaps and I keep getting an urge for POWER. Can you imagine a 3Kw linear power supply with 100 2N3055's. No? Neither can I. Pity though. As for the monster, one can dream - Rows of power transistors glinting in the sunset LOL

    JP
     
  10. spec

    spec Well-Known Member Most Helpful Member

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    Hi John,

    I can imagine rows of power transistors glinting in the sun.:cool: Some test equipments, like active loads for example, have just that. With a holistic design approach, there is no reason why you could not make a 100A linear power supply with your man-sized transformer. But the reservoir capacitors would be huge and cost a load of money.

    spec
     
  11. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    A "sil pad" is a piece of thin material that goes between the transistor case and heat sink that insulates the transistor from the heat sink electrically but allows the heat so conduct decently from transistor to heat sink.

    Here's a link but i am not sure if that is the only product like this anymore:
    http://www.bergquistcompany.com/thermal_materials/sil-pad.htm

    Also be aware that there are devices made with internal ceramic insulation so that you dont even need a mica or sil pad or anything else. Just bolt the device to the heat sink and you have electrical insulation already. There are several triacs that came out with this feature as well as voltage regulators like the LM317, but i dont know what transistors might have this feature these days (you'll have to try to find that if you want to use one) as the ones we used were 100 amp transistors from the 1980's.
    So with some devices you dont need to add any electrical insulation as it is built right into the device.
     
  12. John Potter

    John Potter Member

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    Good morning again Master.
    I have noticed that as one matures ones dreams tend to the more 'useful' side. I'm sure one could make a 'burglar deterrent' device. Just a few bits of old copper pipe close together with this thing across them. It would not help your night vision that's for sure. The odd bit of molten copper running down your leg or burning through your sneekers might might even want you to become a Jehovah Witness. Keep the cats from pooing in your garden.

    I shall fire up this soldering iron later. I have some separate paste flux. If I remember correctly it was hydrochloric acid with dissolved zinc chips that made Baker's. They always sold it in a tin whose bottom fell out and the contents did everything it touched a world of good. Good on tinplate though.

    We are off to Poundland later. I need a few USB power supplies. Poundworld just got fined £150,000 for selling crap ones. Bigclivedotcom stripped the Poundland ones and found them quite good. My original vaping batteries are only lasting an hour or two and we pass a shop that does them. They have one that takes a removable 18650 battery. It's such a shame to throw these old ones away with all the lovely gubbins in them. I think it's time for brute force and gardening gloves. I suppose I could try charging them with that.............maybe not.

    JP
     
  13. John Potter

    John Potter Member

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    Hi MrA1
    The stuff you mention is what CPC Farnell suggested I think so I was near enough. I noticed that there are devices with 3 pins and the case is dead. That sounds a better idea. I expect it's all to do with heat transfer. I found a list of power transistors starting with the 2N3055 and how the power has slowly progressed - and the price of course. There isn't much surface area to transfer heat and that hasn't changed.

    JP
     
  14. spec

    spec Well-Known Member Most Helpful Member

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    Hi John,

    They will lock you up for doing that- you must not hurt criminals in the UK.

    Zinc Chloride is the normal flux for tinsmith work.
    Some of the surface-mount liquid and paste fluxes are excellent.

    The Asda twin USB socket wall warts are also pretty good at £5UK

    You have to be careful with Liion batteries, but on the protected types you can remove the plastic sleeve and salvage the protection board.

    If you need batteries, as I and others have said many times, it is essential to buy a mainline manufacturers batteries and only buy from a reliable source. Many batteries, including some famous high-street named types are not too good. The mainline manufacturers for retail sale are, Panasonic (Sanyo), Samsung, LG, and Sony. And here is a good source, http://batteriesplus.co.uk/acatalog/copy_of_Lithium_Ion__Li-Ion___3.7V_Batteries-1.html
    Some battery chargers badly over-stress LiIon batteries, so it is important to get a good battery charger.

    End of today's lesson... amen:)

    spec
     
    Last edited: Dec 14, 2016
  15. John Potter

    John Potter Member

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    Hi spec, it used to be called 'killed spirits'. Sounds a bit ghostly. I was in the coppersmiths (tin bashers) for a year as an apprentice. I had burned myself lighting the furnaces in the foundry so I ended up doing a double stint belting two buckets of whatsit out of sheet steel. I didn't. I even managed to learn how to bend 3" pipe full of sand and oxy weld quite well. I got 100% at college, you cannot imagine the fuss that caused at work because 'nobody is that good'. I just kept my head down and let 'them' sort it out. I then did 6 months in the blacksmiths, 6 months in the gearbox bay, 6 months in the engine bay, a year in the engine test house, a year............... 5 years 9 months I was an apprentice. These days it's 4 weeks and all they do is change bits and not mend anything. LOL. A neighbour of mine was repairing his Landrover starter, just new brushes, when a young chap doing a vehicle apprenticeship came over to have a look. He said to George you don't do that it'll never work, why don't you get a new starter. George just said 2 words. The second one was 'off'. The starter was fine of course.

    When I was in the electricians I had to rewire the battery leads on a big crane called an 1119. I wired from the batteries up to a big master switch in the cab with a 'T' handle - and promptly got the wires mixed up and took them back to the battery. You cannot imagine what happened to that switch when I threw it. I was left holding the handle with molten brass, copper and zinc alloy all over me and the cab. I think they were a pair of TN12 batteries, bigger than milk crates. They threw them away as they might have been damaged. I was told to try and not let it happen again. Strange sense of humour they had in those days. I still have a scar on my wrist - ah the good old days.

    These 'built in' vaping batteries have everything on board. You can't overcharge, run flat or short them out. All can be switched off by 5 presses of the on / off button. Some you can adjust as in SMPS up and down. Some display W, A, V, coil Ohms, battery state, temp. (and the BBC news and weather). Mine goes from 0W to 41.3W , 1.4V to 9V. The coil I use is not a sub ohm as they can go to 80W. It detects which coil is fitted and adjust the max output to suit. In other words it's a full bench power supply half the size of a fag packet including the battery with a very high quality illuminated LCD display. Only black and white on mine.

    There are those that take the 18650 or 18630 batteries that you write about which should have a safety circuit / charger built in, not all do of course. Not a good idea to carry one in your pocket along with you car keys and money - idiots. They then blame the battery of course. I have 9 of the built in variety and have been charging maybe 2 or 3 a night for over 2 years. They never get warm and behave perfectly. They charge in a steel tin on a really nice piece of thin asbestos - painted with emulsion. I am beginning to wonder why I bothered.

    They are specifically designed so that you cannot get into the steel casing without destroying the gubbins. I had one where the top had come off when I sat on it and a wire to the tank coil connection was broken. Nothing would budge.

    Today I am going to get a 'battery' with a replaceable battery with built in gubbins. 'Batteries' in vaping cover all sorts of set ups. They even use rechargeable Liion in one use throw away vaping units and E-Cigs in Poundland.

    I have seen a video on YouTube where someone used 3 x AA 2200mAh NiMh batteries. I am going to have a go using a Poundland aluminium torch. I set my vaping battery to 7W which comes out at 3.6V. Got to be worth a play. You only use them for 2 or 3 seconds a puff. That's the vaping puff not the other sort.

    So endeth the second lesson.

    JP
     
  16. John Potter

    John Potter Member

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    What a beast. At it's lowest setting it's spot on what I usually use - 7W. It's a 'kangertech KBOX MINI C' . I chose the 3500 mAh battery. I'm not so sure of the tank and coil assembly though. Sucking on the end of a short piece of plain 10mm steel tube does nothing for me. I've fitted one of my other tanks as it's obvious the one supplied is meant for the more 'adventurous vaper', or as those that want to use these things as a replacement for cigarettes call them ' Dick Heads'. It's not as aesthetically pleasing to look at as my 'Cuboid Mini' but has the same features. The battery cover is held in place by 4 small neodymium magnets. It comes as quarter charged and took several hours to fully charge from a 1A USB adaptor via the mini USB port and built in charger / safety / control circuit. Jump leads are an option. LOL

    JP
     
  17. John Potter

    John Potter Member

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    I just want to thank all those that are doing their best to update a 50 year gap in electronics - all I can say is thank you and -
    The Best Of British Luck
    Your going to need it.
    Happy Christmas.

    Apart from the linear supply your enthusiasm is catching - these old Tannoy's have been quiet for far too long so I dug out the old Sansui AU-317 and connected the laptop.
    They are Tannoy Red - the last Tannoy before they went to 8 Ohm and stopped using magnets the size of dustbins. 1958 vintage. In case you are wondering, it's those big black things.
    I made them nearly 40 years ago.

    I took the Jaguar mascot on the fire off the last Jag MkII I had before it was scrapped 40 odd years ago.

    Tannoy1.jpg
     

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