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2N3055 and heat

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

  1. John Potter

    John Potter Member

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    Hi spec - how strange, I just checked and he looks through his magnifying glass at 9 min 50 sec. and says "I've a sneaky feeling it's going to be a more normal chip, it's an LM358 - it's an op amp"
    Never mind it's obviously a common chip.

    I bit the bullet and made a complete mess of it but hopefully got there in the end. I ordered a tag strip which should be here on Wednesday. It's a 2 x 36 way Solder Tag Terminal Strip on Paxolin / Bacolite Board (2 strip)
    Item No - Item number 112223776082 - I just tried this as a test run.
    I'll probably end up with a DIY camel hysterectomy kit.

    I think I'll have to decide which type of electronics I'm going to have a go at. I fancy amps but not just the chip ones. I can ask Father Christmas for a few bits of equipment.

    I am going to need knobs and pots and all sorts of mundane bits. It's finding somewhere to keep them so that I can find them again. I think an in depth rationalisation program is called for. What? Don't ask me.

    Dave Allen was perhaps one of the last of his breed. I don't mind Jack Dee - his Siberian solo trip was quite entertaining. So many now think it's funny to be absolutely disgusting. Very bad language seems to be the norm now.
    I'll check those links out.

    I had to look spec
    6 x Rare Vintage Germanium Power Transistors 'Tested'
    OC35 - they don't make them like they used to - probably a good job. My one and only dabble into a transistor amp - a Bailey. It worked.
    Quite why on eBay it's in amongst a pile of chains and sprockets I have no idea.

    2N3055's - 5 for £1.49 0r 1 for £33.69 (free postage mind you - and they sold 4).

    I just forgot that links to video's show as they do. I expect there is a way to stop that.

    Tanks spec
     
  2. spec

    spec Well-Known Member Most Helpful Member

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    Audio amps are where many people start in electronics.

    Yes, storing components is a big problem. You can get plastic cabinets with drawers, that I fancy.


    One of the first transistor power amp I built was the Dinsdale with OC35 or OC28 germanium transistors.

    Be careful when buying power transistors- Farnell is probably a better source

    spec
     
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  3. John Potter

    John Potter Member

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    Hi spec
    To say I am concerned about buying 'stuff' off the Internet is putting it very mildly. Your right of course, if one is going to the trouble of making something then paying a few extra pounds is well worth it. I see that 2N3055's can be used as audio power transistors. I am not fussed about how ancient the design of a component is providing there is nothing better at the same price. I'm pretty ancient myself. My father came home from the RAF, I had a pink bedroom and I was going to be called Charmian Mary. Just one little thing got in the way.

    I see you are the joker of the pack so to speak. Actually I am rather please to see that. It's always good to know someone has a lighter side. 'Is that a gun in your pocket or are you just please to see me ?' Mae West. I would love to have met her. Union Jack flying, Land of Hope and Glory playing in the background, full sized picture of Her Majesty close by - and my feet tied firmly to an anvil. Awesome lady. My favourite American. I am being serious by the way.

    I have been on Ebay for hours. I have a Garrard 301 and a Garrard Lab80 with a Sure M80E cartridge. Both in very good condition. I think it's time they were resurrected. The 301 is boxed and I paid £5 for it a long time ago. I didn't realise how much they are worth. Rubber drive wheels are probably shot now. The 301 is not exactly the most attractive turntable.

    I remember the name Dinsdale. The name was also used in a Monty Python sketch I think.

    I was very pleasantly surprised to find two little RIAA equalisation units on sale on eBay. Nice to know not everything has gone to the wall. Quite a few valve jobs around. I understand the Russians make an equivalent to an EL34. Good chaps.

    JP
     
  4. dave

    Dave New Member

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  5. schmitt trigger

    schmitt trigger Active Member

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    Because that way, they create proprietary devices and they have got you essentially locked to their particular product.
    If you don' like it, a board re-layout may be required.
     
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  6. spec

    spec Well-Known Member Most Helpful Member

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    Hi John,

    As I mentioned before, big/expensive components are often counterfeit. The left picture below shows the guts of two 2N3055s; the 2N3055 on the left is the rip-off- note the small size of the silicon chip, and the smaller heat sink. And the image on the right shows how extreme some of the rip-offs are.

    upload_2016-12-5_6-6-4.png upload_2016-12-5_6-27-51.png
    http://sound.whsites.net/fake/counterfeit-p1.htm

    You can make a perfectly good audio power amplifier with a 2N3055 and an MJ2955, but there are much better complimentary transistors.

    The physical layout of an amplifier and choice of other components, especially capacitors, can make a radical difference to the sound quality.

    As you say, if you are putting in the effort to build a power amplifier, you may as well use the best components, within reason, even if they cost a bit more.

    I do like a good laugh, like many on ETO.:) I have four modes: serious, humorous, angry, nice, like most people. The way that people interact is a good topic for a thread on 'Members Lounge', I think.:D

    It is quite interesting, to me anyway, the different characters you meet, face to face and on the net. It would be fun to meet the other members on ETO for a booze-up/chat.:happy:

    Vinyl has made a big comeback and the prices of vinyl equipment has shot through the roof. I still have a Shure M75EDII cartridge, but the Pioneer PLD12 turntable got written off.

    And valve (tube) equipment has remained popular- with musicians especially. EL84, EL34, KT66, 6V6GT- I remember them well. I started with valves in the 1950s. Valves where what men used- transistors were for girls.:D

    That is right about Monty Python. My favorite is Mr Creosote:


    The Dinsdale audio power amp (Wireless World November 1961) was the archetype for most audio power amplifiers. It was based on a servo amplifier from one of the semiconductor manufacturer's application engineers in the States.

    As I mentioned before, the Dinsdale was the first solid-state audio power amp that I experimented with. I learned a lot about transistor design by building that amplifier. The germanium power transistors used to blow for a pastime and, after a while, I was knee-deep in blown OC28s, like the 2N3055, also in a TO3 can. Although OC28s cost a fortune new, I used to buy salvaged computer boards from the States that were packed with OC28s and lots of other goodies too.

    The Dinsdale amplifier, built with germanium transistors, was very smooth sounding, with no bite whatsoever. With silicon transistors it was much brighter, but edgy.

    spec


     
    Last edited: Dec 5, 2016
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  7. John Potter

    John Potter Member

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    Hi spec - I had seen this :-

    This sort of thing is true of almost everything you buy off the Internet. I have to say though that everything I have had delivered from Banggood has been OK. I just wish their delivery ox cart had a bit more thrutch.


    Hello schmitt trigger- As no doubt you have guessed I'm rather new to this. Even though it's only been a couple of months I have noticed and fallen foul of the 'let's change the name for fun'. I wanted a LM317HV, I could not find any in the UK so I sent off the the US for some. The total cost was not funny. When they arrived they had LM317AHVT on them. LM317HV don't exist at CPC Farnell but LM317AHVT does - 65P. I have had problems locating mounting kits for the TO-3. I was informed by Maplin that 'This 'transistor' ? is old fashioned and is being phased out. They seemed totally unable to grasp that a TO-3 was a case for many different transistors all of which needed a mounting kit. Maplin were good once.
     
  8. John Potter

    John Potter Member

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    Hello again spec
    I have an old school friend of over 60 years. He's a very clever chap who ended up with a company of his one making routers, etc. He virtually insisted I make a linear power supply. I found out later that SMPS to him are death. He's been well into ham radio for years and has often complained about some item that he has to switch off.

    Please forgive the terminology.

    I have been watching :-

    I had more or less understood, I think it was you way back in this thread, that SMPS are small because of the much higher frequency they use. I understand that SMPS are 'dirty' insomuch as they are not as smooth a supply as linear.

    Just one question. PC CPU's are I would imagine are rather sensitive bits of kit. The chap in the above video does say that SMPS can be made 'clean' but it requires a lot of effort to make them so. I have looked at quite a few SMPS and buck conerters and they only have a few 'bits'. However PC power supplies are quite different they are full of 'gubbins'. The SMPS this chap repairs runs an oscilloscope, that too must need a pretty clean supply.

    Am I right in assuming that all this extra gubbins is simply there to emulate a linear supply ?

    Please don't panic.
    That 40V x 80A welding transformer seems OK. I fired it up again yesterday and it's spot on 40.00V. I did not test the load as I don't want a wife and dog wandering around bumping into things with arc eye. If you Google XP welder it's an interesting idea to be able to use a car battery to arc weld with. I am going back many years. This device was almost useless run off a car battery so they brought out this transformer to go with it. The device uses the 'bell' idea to create an arc using a low current. It worked but it was so poorly made that if a rod stuck and you gave it a twist it could easily be damaged. The transformer is quite capable of being used without this device but had a nasty habit of overheating before you even finished 1 welding rod. There is a thermal cut out which earned it's keep. I now have a more professional variable output job - a few large diodes and the odd cap or two ? I jest. 150 Amps. Why it doesn't blow the 13A fuse very often I have no idea.

    Cheers - JP
     
  9. spec

    spec Well-Known Member Most Helpful Member

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    POST Issue 4 of 2016_12_06

    Hello, again John,
    Broadly speaking, there are two types of power supply (PS):
    (1) Linear
    (2) Switch-mode (SM)

    There are two types of linear PSU:
    (1) step-down series
    (2) step-down shunt.
    A step-up PSU is not possible with a linear PSU.

    And there are three kinds of SMPS:
    (1) Step-down (buck)
    (2) Step-up (boost)
    (3) Step-down/step-up (buck/boost)
    The step-down SMPS is the most efficient, and simplest to design.
    The step-up SMPS is less efficient, but also simple to design
    The step-down/step-up SMPS is the least efficient, the most complex, and the hardest to design.

    But, having said that, none of the SMPS are that difficult to design, especially as there are many components, including chips, specifically for SMPS; the National Semiconductor (now Texas Instruments) 'simple switcher' series of SMPS chips epitomizes this. There is also a mountain of literature, including manufacturer's application reports, covering SMPS.

    It is relatively simple to make a quiet linear power supply, but if you have a rectifier in the power supply, that will be switching and, if you are not careful, the rectifier can cause noise problems.

    There is a lot of 'fear and loathing' about SMPS, but while they can be noisy if not well designed and constructed, they can be made as quiet as linear power supplies. Like you say though, it does take some gubbins. A good approach is to have a switch mode power supply feeding a linear power supply.

    The gubbins in a PC SMPS is mainly due to the high power required (350W to 1KW), and the number of supply lines to be provided. The gubbins is also concerned with protection, and power factor correction (PFC). All equipment must meet international electro magnetic compatibility standards (EMC) and some of the gubbins is connected with EMC but, to an extent, a linear power supply would also need some gubbins to meet EMC standards.

    SMPS are used everywhere, from PCs, to mobile (cell) phones to TVs. SMPS are even used in high-end audio amplifiers.

    The best way to describe why a SMPS can be so much smaller than a linear power supply comes from ronsimpson on ETO:
    An electric current is only a flow of electrons in a conductor, just like water in a pipe.
    A reservoir capacitor is just like a tank that stores electrons, instead of water.
    The load on a power supply causes a flow of electrons out the reservoir capacitor, and obviously you have to put as many electrons into the reservoir capacitor as you take out, or the voltage will drop, just like the water level in a tank would drop if you drained more water than you put in.

    So now here is the crunch. The electrons are delivered to the reservoir capacitor in packets. With a linear supply in the UK (50Hz mains supply) and with a bridge rectifier, the packets of electrons are delivered to the reservoir capacitor every 0.01 seconds (10ms). But with a SMPS operating at 100KHz (typical SMPS switching frequency) the packets of electrons are delivered to the reservoir capacitor every 10 millionths of a second (10us). That is one thousand times more often.

    So, straight away, the reservoir capacitor can be one thousand times less in capacitance value; taking the case of your proposed PSU, the 10,000uF reservoir capacitor could be just 10uF- physically a much smaller capacitor.

    But the component size reduction does not stop with the reservoir capacitor. It also affects the transformer, which, because of the higher frequency, can be a thousand times less in volume (to a rough approximation).

    100KHz is a common SMPS switching frequency, but some SMPS switch at an even higher frequency, 4MHz for example, so the scope for size reduction is even greater. Of course, the higher the switching frequency, the more demand is placed on components and on the SMPS, physical layout and design.

    And here is Ron's punch-line, if you liken the packets of electrons to a bucket of water, you could either have a big bucket of water and fill the tank at a slow rate, or you could have a small bucket of water and fill the tank at a rapid rate. In the former case the bucket is huge and in the later case the bucket is minute.

    In practice, the size reduction would not be quite as dramatic as the above figures indicate, because components are not perfect, especially as the frequency increases. But some SMPS are 97% efficient, although the average efficiency would be more like 75%. This high efficiency also affects size: because less heat is generated SMPS need no heatsinks or relatively small heatsinks.

    A SMPS is efficient because it stabilizes the output voltage by adjusting the size of the packets of electrons delivered to the reservoir capacitor. On the other hand, a linear power supply controls the output voltage by wasting energy, that is converting it to heat, hence the large heatsink and fan on your linear PSU. With zero volts output and a 3A load current, you power supply would be dissipating, 3A * 50V = 150W, but a SMPS may only be dissipating a couple of Watts.

    spec
     
    Last edited: Dec 6, 2016
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  10. John Potter

    John Potter Member

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    Thanks spec - that was icing on the cake.
    I have been looking at all 3 types and as you say even the up / down types seem pretty simple. It appears they just have 2 lots of gubbins.
    I don't like the idea of these little trim pots much. I take it one could fit a coarse pot and a fine pot in series(?) instead.

    I really do appreciate your dropping down to my caveman level and using that (for me) highly technical term 'gubbins'. In future like you I will use it with relish (or pickle).
    I have a noticed an 'odd lump' (simple bit of gubbins) on the mains input to a couple of the power supplies I stripped.
    I assume these units are some sort of mains voltage spike suppression ?

    PCPSInput.jpg

    A bit of wood between this and the table top will be fine. I have about 60 feet of shelving in my garage and a mountain of bits collected over 40 odd years. This was the first item top shelf. I think perhaps my Guardian ARC Angel was at work. Standing in a cold garage sawing off 3mm screws, dropping them, finding them and cleaning the ends up does not turn me on.
    Record Junior No 51 - Made In England. Mines even better than the one in the photo. A left over from my model aircraft days.

    Record Vice.jpg

    Starting up this electronics lark is beginning to feel like going back in time. Quite a nice feeling.

    Many years ago I had some scented multicore type solder, do you know if they still make it?
    It does make the house smell a bit like a lady of ill reputes boudoir - I think I had better add 'I imagine'.
    Everybody thought it had a lovely smell. One girlfriend even thought it was a rather feminine after shave.
    It made a really clean joint, rather smokey though.

    I still have not found my 100W? soldering iron, wooden handle, bit about 20mm thick or a big variac about 100mm dia.
    I don't need them but................

    Is a 50mm (roughly) choke of any use or does it need to be a specific value?
    It came from an older PC power supply. Looks quite well made.

    My order from eBay should arrive tomorrow, those tag strips. They may not be exactly what you had in mind but the looked similar to the ones I used.

    JP
     
  11. spec

    spec Well-Known Member Most Helpful Member

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    Morning John,

    No problem- it is always nice to talk to someone who is proactive and interested in learning about electronics.:cool: By the way, I have just added a bit more to post #109
    That is true.

    Trim-pots are for calibration, while potentiometers with knobs are for user control. There is no reason why you cannot replace any resistor with any combination of trimpots and control pots (in principal that is).

    Yes. The reason why the parts are mounted on a separate printed circuit board (PCB) directly to the input/output is to minimize wire length- wires not only have an impedance, which could compromise the performance of the suppressor, but also wires act as antennas and radiate noise all over the place.

    :)

    Rosin multi-core solder is the stuff- it is still available (but get proper lead/tin solder).

    If your solder gets tarnished with age you can clean it quite easily with kitchen metal scouring pads (not plumber's wire wool, which is too sharp).

    In addition to the flux in the solder, it is also useful to have a separate tin of flux paste and, later, get a container of modern surface-mount liquid flux.

    :D

    A Variac is extremely useful.:cool:

    Generally, there are two types of inductors (chokes, coils) in SMPS: energy storage and suppression, each designed for their specific purpose.The inductor you describe sounds like a suppression type. All the same, it may be suitable, with limited performance, as the energy storage inductor in a SMPS.

    The energy storage inductor in a PC SMPS looks like a transformer with multiple windings. It will also be much larger than the inductor you describe.

    The energy storage inductor in a particular SMPS certainly needs to be a certain minimum inductance value, and must be able to conduct a minimum value of current before saturating, but, practically, any inductor would be suitable for SMPS experiments.

    Any tag-strip that you like will be fine.:cool:

    spec
     
    Last edited: Dec 6, 2016
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  12. John Potter

    John Potter Member

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    Good afternoon master.

    It was passed 0500 when I finally finished here, my email and a Skype from Australia and America. It was 1330 when I woke up. OOPS!
    All seems to be well re PayPal and eBay so far. I think I will do a mini survey of eBay / Amazon. I didn't use Amazon but found Banggood through them. I'll keep a log of those companies that are value for money and deliver - eventually.

    I did notice on eBay they have this click and collect from Argus. Do you know what that's all about spec?

    After we have finished this power supply or at least got a MK 1 running well I'll start looking at other gubbins. I am finding this power supply fascinating though as it has lead to so so many areas I know nothing about. There seems to be enough complexity in one to form a good background knowledge.

    I'll post a little photo of this choke. It only has 2 wires and looks like a normal transformer.
    There was a YouTube video of a chap converting his rather small arc welder to DC as he had problems with a continuous arc and getting started. With just the bare bridge rectifier the rods were sticking as normal and some quite large capacitors made little difference. However when he put a choke inline the difference was quite noticeable. I have a very rough idea of what chokes do and I remember valve amps always had one.

    Is it worth using or keeping those mains input gubbins ?

    I have been trying to locate a supply of copper that I can use to make soldering iron bits from. I have a rather nice temp. controlled Weller that Weller no longer stock the tips for. They have sub contracted them out to various other American firms. I also have 2 other irons. One is a cheap horrible thing from Toolstation with a cable like a towing rope and just came with 1 tip and there are no spares. The other is an old favourite that needs a new tip. It came with just a plain copper tip and I find it works well. I have turned it back as far as I can now though and if I can't get a new tip it's days are numbered. I got some tips through Banggood that I'm pretty sure I can adapt but their outside dia. and mass is much less. The iron will heat up quicker but it may have problems with larger joints. I had a brainwave and remembered that grounding rods where solid copper - wrong. They are now either hollow or plated. I have a lathe with 3 jaw and 4 jaw chucks. I can turn some tips from almost anything copper if it's thick enough. I have even considered melting some odd copper wire and bits down to get what I need. I will if I have to. I made a 100W fan assisted charcoal barbecue. It melted.

    Any ideas ?

    I find this nonsense about lead amazing. After quite a short time lead develops a coating that prevents any migration into water. I'm sure though that if one is soldering all day there might over a long period be problems although I have never heard of any. When they were clearing the site where the old Smith's Industries dials, pressure gauges, clocks, etc. were made they found the ground in one area was dangerously radioactive. It's where they had dumped the empty tins of luminous paint. The site was treated as a serious threat and given the full treatment. Everything tinned and dumped in the North Sea no doubt. Retired workers from the plant were checked and no problems were found and they had been using this luminous paint for years. Humbrol did little tins for the hobbyist. Mine sits gently glowing on the shelf at the back of my shed. Mind you there are spiders in there with 14 legs.

    JP
     
  13. spec

    spec Well-Known Member Most Helpful Member

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    Afternoon John,

    'Click and collect' is where you order an item on the net and then collect it from a local location, typically Argos.
    As you say a power supply is a good project to start with as a power supply uses so many circuit techniques.

    OK

    Yes

    I would be inclined to get a new soldering iron suitable for miniature work.

    Bits have a special plating to stop them oxidizing. Your best bet would be to make an adapter so that your old iron can take the new range of bits.

    spec
     
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  14. John Potter

    John Potter Member

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    The old 30W iron was meant for printed circuits, that sort of fine work. The original bit is about 7mm OD stepped down to 3/4mm for the last 20mm. Very much like the Weller irons.
    I have tried these new plated bits but I guess I'm just used to the old copper ones. If they get a bit rough a quick polish on some emery and off you go again. These new plated ones don't seem to tin so easily as pure copper.
    I like a small angled flat on the end, that's what I have always used. This Toolstation thing has a knitting needle type modern plated bit and a lead like a tow rope - no thanks. Maybe it's my ancient solder. The Weller is the same, a beautiful adjustable temp. iron, must have cost a fortune, but again it would knit a lovely jersey. It's such a shame it's hardly been used.

    I think if I tried to make an adaptor the small heating and sensing gubbins would be rather far back from the tip on the Weller and it would end up a bit long. I could make a new tip or 6 in almost the same time and the adaptor would have to be copper which is the problem. The 30W is very similar to the one below with a silicone lead.

    antex-soldering-iron-cs18-with-silicone-cable.jpg

    It seems a shame to bin both Weller and my old 30W just because I can't get a bit for them. Many of the newer irons do have replaceable bits. They come in a pack of all shapes and sizes most of which I would never use. The tips I got from Banggood are quite nice but rather small but now fit. I'll have to slot them to stop them binding and locking solid on the iron. Being copper I can make them into any shape I like. I'll sort one with a junior hacksaw and see how I get on. It'll probably fall off and burn a hole in the new carpet. The old spring clip is too big - so more far*ing about. All good fun.
    http://www.banggood.com/10Pcs-Solde...eries-Solder-Tips-p-1067613.html?rmmds=search

    I have put the one below on my next order to Banggood but I'm waiting for the first order to be completed first.
    At that price it's got to be worth a try.
    http://www.banggood.com/Mustool-MT2...-p-1077119.html?rmmds=detail-left-hotproducts
    If it's as good as they advert says it is how on earth can they make it and deliver it for that price is beyond me.

    I am a bit concerned about the last bit to be delivered from Banggood. 2 days after I got confirmation of the whole order I received an email saying the 'tracking documentation' had been lost for one bit. It's the most expensive item (only £14) and has still not arrived. It's not much overdue so hopefully it will turn up. It's one of these SMPS gubbins with V & A adjust. I thought that at 65V and 400W it might not burn out after 10 minutes.

    .http://www.banggood.com/DKP6008-400...age-Current-Meter-p-1082317.html?rmmds=search

    I've got to have something to play with over Christmas - hopefully.

    Thanks for the help and advice yet again spec.

    JP
     
  15. John Potter

    John Potter Member

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    Hi spec - an update
    I added the 3rd power supply case today. This power supply doesn't exactly look like one off the shelf. More like something out of Buck Rogers - without the buck.

    I would have my work cut out to put the fan below the heatsinks as the main rails that the cases are mounted on are too close together and will obstruct the fan. So it's back to plan A but I am going to cut out the floor below the heatsinks and fit legs.

    If I remember correctly you mentioned that there would be a transistor (or possibly gubbins) that would need about 10W of cooling. The No3 case which is for the technical gubbins (I assume) will have this 10W unit in it.

    Is it critical where this 10W transistor is mounted?
    I have a rather nice heatsink for it.

    Being a heat freak and a little concerned as to where the heat from the 2N3055's is going to circulate I will fit No 3 fan.

    The 1.6A fan power supply needs a LM317 as it is 17V. It seems though from the many YouTube videos where it seems the' in thing' to destroy perfectly good PC fans that all of them will run easily at 17V and some over 40V before they burn out.
    The main heatsink fan is designed to run between 13.2V and 14.4V, I'm sure the other two 12V fans won't mind 14V. I have about 10 spare 100mm 12V ones.

    I notice that on your latest circuit it states the output as 0 to 40V and 0 to 3A.
    Like an idiot I have not kept your previous circuits and therefore I can't see what changes you have made. I think we mentioned regulating amps but without going back through this thread I'm not sure where we are. Needless to say I would be more than happy to be able to regulate the amps.

    I am making a shopping list for items from Farnell, transistors, etc. Basic items like knobs, fuses, fuse holders I'll bulk buy from eBay.

    The tag strips arrived and are rather well made. It was another going back in time moment, they looked just as I remembered them. I nearly had an organism.

    Incidentally my lathe is pre war. That's world War 1. It's American and the best theory so far is that it was for turning rifle barrels or that sort of light work. When I got it 30 odd years ago it took me over 3 months to get the bed true. It was worn badly under the chuck area - over 0.030" (nearly 1mm). The whole bed had to be lowered by this amount. I did it by hand and used a tool room straight edge, etc. It is very unique in that it has a 4 'V' shaped bed. 2 for the headstock and saddle and 2 separate ones for the tail stock. Why it is made this way nobody knows. Quite mad. We get on well together.

    JP
     
  16. spec

    spec Well-Known Member Most Helpful Member

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    Hi John,

    Just to clarify, the latest circuit is shown in post #92. It would be best to simply ignore the other circuits as they are now obsolete.

    Q5 (TIP41C) in the post #92 circuit will dissipate around 7W worst case and, as you say, will require a heat sink.

    From a frequency stability point of view, all of the electronics should be connected with as short a leads as possible. But don't worry. You just do what you think best from the cooling point of view and we will sort the frequency stability later.

    But the wiring lay-out is important, again from a frequency stability point of view, but we can also sort that later.

    14V will be fine for the fans. The LM317 will be dissipating (17V-14V) * 1.6A = 4.8W, so that will require a heatsink too.:)

    If you remember, we decided, initially, to have a single current limit of 3A.

    The post #92 power supply output voltage will be adjustable from 0V to 40V and the power supply will meet any current demand up to 3A. Any more current demand than 3A and the output voltage will drop. For example with a 1 Ohm load the output current would be 3A and the output voltage would thus be 1 Ohm * 3A = 3V, even if the power supply voltage setting were 40V. If the output of the power supply were shorted, the output current would still be 3A, but the output voltage would be, zero Ohms * 3A = zero Volts.

    spec
     
    Last edited: Dec 7, 2016
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  17. John Potter

    John Potter Member

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    Hi spec, that's all fine by me.

    It was nice to see the circuit develop spec. I didn't understand very much but after looking up what the various gubbins does the clouds thinned a little bit.

    Apart from the power from the DC 52V supply I can try and keep all the leads to a few inches.

    May I ask why the connection to the centre tap of TR1, it's AC?

    The LM317 for the fans will be on the same heatsink as the 2 diodes. One is the 52V 10A and the other the 17V 6A.
    The photo No4 on #71 sh0ws the heatsink and diodes. It's the old 25V AC configuration but not much will change apart from the the 10,000uF capacitor and the wiring of course..
    I think they should be OK with the fan almost touching it.
    The total load of the fans (at the moment) is 0.95A - say 3W. The LM317 might just about handle the 1.6A, it's rated at 1.5A but I can swap it for an LM338 which is 5A.

    I'm going to buy one of those tapered sheet metal hole cutters. The eldest granddaughter Ella who is a well built lass of 12 can help me bring the drill press in from the garage. It can sit as head of the dining table.

    That crude system I have on the battery charger I would think does the same job as your current limiting. #71 again. About 1V managed to get through. I was quite surprised that the fan and shielding stopped a meltdown. I had bought the wrong thermal switch which cut in at high temp and not out so I left it off. The transformer was quite hot but touchable, no doubt the fan 'up it' helped.

    We have the grandchildren this weekend from tomorrow night. I have cleared the decks ready for action. Whilst at this grandmas and granddads they can have whatever the shouldn't have. There's several large bottle of coke and things go downhill from there. I caught our lurcher Elli licking out an empty glass of advocaat which gives you some idea of this madhouse.

    I should be back online each night and morning but I doubt I'll get much else done.

    Thanks spec.

    JP
     
  18. spec

    spec Well-Known Member Most Helpful Member

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    Evening John,

    I will post an explanation of the of the power supply functions and all will be clear.

    The leads from the 52V rectified voltage do not matter- they are not in the power supply feedback loop, but another capacitor, say [correction 2016_12_09] 1,000uF will probably be needed locally where the other electronics is.

    The two wires carrying the 52V should be at least 18SWG and should connect directly to the terminals of the reservoir capacitor.

    Yes, it is AC.

    The center- tap is only used to reduce the negative voltage to the negative voltage regulator.

    The two diodes, and two capacitors, convert the AC voltage from the transformer center-tap to a negative DC voltage to power the negative voltage regulator

    Yes, the LM338 will be required.

    I too, have been involved in domestic things today: ferrying my missus around to the various places that women go too. At one stage I escaped to a hardware store and bought some handy plastic stackable cabinets with drawers, which will be ideal for components when my new workshop is commissioned. They may be handy for you too, as you mentioned that you were not sure how to store your components. http://www.properjob.biz/HOMEWARES_STORAGE_DRAWER_UNITS_and_CHESTS-C102020

    You missus must be very understanding to allow electronics on the dinning room table.:D

    spec
     
    Last edited: Dec 8, 2016
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  19. John Potter

    John Potter Member

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    I'll answer the last line first spec. I have always been very active but I guess I kept my foot on the throttle for a bit too long at times. A few minor garage accidents catch up with one as the years go by. It is thanks to you and the others that I have found an alternative hobby that I can manage - albeit rather slowly. My wife is the best, I do not say that lightly after 43 years. Mind you she doesn't like my cottage pie but fortunately the dog does. The dining table is a great big pine affair that would support a small car easily. When I use it I put cork floor tiles where I work or under anything like this drill press. Right at this moment it is bare. Normally I try to keep the gubbins to the first couple of feet.

    The main problem is this 'gubbins'. Poundland do some nice little toolboxes which are fine for small electronic tools and odds and ends, I have 2 of those. I also have 4 of their little organisers that have spacers to change the little containers inside. The hinges are rather weak though. I got 3 large plastic boxes with lids about 500mm x 300mm x 300mm which hold larger stuff. At the moment the day to day kit is in an old sink bowl. When my wife is out one day ( hair do soon) I am going to 'steal' one of the 2 large chests of drawers that are in the dining room. I should be able to keep everything in there, even this power supply. There is a nice little gap for the 3 large boxes though.

    Working downstairs though does mean I can talk to the old dragon and watch the very rare TV program. It also means I can drop hints about coffee, sandwiches and a get a quick fix from the defibrillator every now and then.

    I have a garage and 2 sheds with power but that's OK for the summer but not this time of year. As I think I have mentioned we do have a spare small bedroom that will be ideal when I get around to finishing this PC lark. Most of my friends now have gone over to laptops, Windows 10 - LOL, which means I do not even try and mend them. They gave me their PC's. I had 8. 4 have gone, hence the power supply cases. I do keep a couple as spares for friends who are not so well off. My eldest daughter can kill a PC by looking at it. I bought her an Acer laptop about a year ago and it's still alive, so I bought one for myself. I kept getting email from Microsoft offering help until I asked them how to make Windows 10 look like XP (which of course it is underneath) - for some strange reason the email stopped.

    I'll definitely look at your link.

    Gubbins
    When you feel reasonably confident about the components for this power supply I'll post a shopping list here. I'll get spares of course. The cost of these components is so cheap now that any additions or changes is fine. More fun to be honest. I will need at some time though what voltages for the capacitors, etc.

    I think that almost all the wire from these PC power supplies I salvaged is probably 18SWG but I'll check. I suppose a nice couple of polished copper bus bars would be OTT? Pity. I do have a couple of reels of wire but I thought I would try and use different colours for different sub circuits, something like that.

    One day spec, perhaps not yet, could you please explain negative voltage ? I did guess that you had used the centre tap as it had less volts but from then on everything went rather grey. Negative voltage regulator eh - lovely gubbins.

    I have LM338's, LM317's and those 60V LM317AHVT's.

    It's going to take me a week or more to get the case ready. It's no fun cutting square holes or any hole in thin sheet metal. I have some lovely plated light sheet steel in my garage with no way to cut it or bend it. One day in the old coppersmiths and I could make a lovely case. I'll think of something. I have a cunning plan.

    Regards - JP
     
  20. spec

    spec Well-Known Member Most Helpful Member

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    Very interesting set-up John

    Yes, your wife must be one of the best.:cool:

    I will explain about negative voltage- it is nothing difficult.

    spec
     
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  21. John Potter

    John Potter Member

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    Hi spec
    Would negative voltage be where the negative wave of AC is rectified to produce a negative DC voltage. Pure guesswork which I had to stop as my brain started to hurt.

    I found the below and thought it worth a watch. Repairing a large linearr fixed output power supply. It basically reinforced what I have read. He seems to always do a thorough job.



    I stripped that XP welder transformer down today. I managed to get it done and basically cleaned up before the hoards arrived. I thought that it looked like there was a tapping from the primary to the output. There wasn't of course, all it was was the output wire from the secondary hard up against the primary.

    There was no point in keeping it in it's original case which was pretty dusty and dirty inside and the mains lead and output leads were well passed their use by date. It's worth keeping though as the windings look bright and I have checked for continuity and V, all seems OK. I can't measure the resistance through the secondary as it well below 1Ohm. The primary winding is 1 Ohm (ish).

    Input 245V at 13A (13 A fuse does blow)
    Wire dia is 1.3mm / 0.051"

    Output stated as 40.0VAC at 80A (3200W)
    Wire dia is 2.8mm / 0.109"

    The 40.0VAC is spot on.
    However the 80A is overloading the rating for the wire. The dia of the wire seems non standard. It's not SWG and the nearest is the American AWG 11
    10AWG is 70A at 125C
    12AWG is 50A at 125C
    The wire is roughly rated at 60A at 125C. No doubt 80A is possible for short periods and judging by the thermal trip going after only a few minutes they rely on that.
    Continuous rating using pure guesswork 20A.
    Weight 6Kg.
    Use - door stop or burglar deterrent until further notice.

    Next will be the 60A continuously rated 12V (I'm expecting a lot more than that say 16V at No 10 setting) battery - starter - booster - boiler. I bet that's a 'big un'. Say 30W / 2N3055. That's 30 2N's. Lot's and lot's of gubbins.
    You know that circuit your doing for me, well spec would it ...................................... I'm joking.

    It's 3.04am and the house is quiet at last. I'm too exhausted to sleep and feel like I have been run over by a bullock cart on it's way to the UK from China that's very late with a broken SMPS under the drivers arse.
    11 more days spec and the days start to get longer. Just +3 seconds longer on the 22nd. Can't wait to see that can you spec, Oh you can - fine.

    'Interesting set-up' Your being very kind and generous. When a lurcher with muddy feet comes through our patio door at 30mph 3 feet off the ground and almost cannons off the bureau at the far wall 'Interesting set-up' is most kind.
    She just loves to run, but the poor lawn - ah well, it'll grow back. Why don't dogs need toilet paper ? I suppose natural selection made sure that the dogs that didn't need it survived. I wonder if Darwin noticed that.

    JP

    PS Maybe that 'big un' tomorrow. Oh forgot, and an old TV. I'll short the caps but it's not been used for years. The girls love 'helping' granddad.
     

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