2N3055 and heat

[spec]

The 2SC5200 (npn) & 2SC1943(PNP) are nice linear gain power transistors and as such are popular with audio amplifier builders. I expect they could be useful in power supply circuits too. I have read elsewhere that good amplifiers and good power supplies have a lot in common.

Nice transistors. They are members of the audiophile power transistor families that the Japanese companies pioneered in the 1980s. ON Semiconductor (was Motorola Semiconductor Division) now makes similar devices since the Japanese have pulled out of the market, to an extent.

Spec: this thread is an absolute treasure trove on practical power supply building, have you considered writing a book? I think there would be a big demand to read this practical advice rather than pages of intimidating mathematics as in certain books! Iam thinking of the superb book, "The Art of Electronics" which without a great deal of mathematics manages to convey a very in depth discussion on most aspects of electronics. John Potter or anyone else reading who is still relatively new to electronics, I would heartily recommend the aforementioned book. Anyway spec I would read your book if it was full of this sort of practical and non mathematical advice on power supplies.

Wow GB, that is very kind of you, and very gratifying to know that my posts are of some interest.

I have written quite a bit of technical stuff over the years, and funny you should mention it, but I have had ideas for a number of books on the back burner for years, ranging from, 'Writing', 'Maximizing your Position in Life', and also a load of electronics subjects. But the trouble with me is actually getting around to do things.

Yes, 'Art of Electronics', was s a revaluation when it first came out, and cut across a load of the BS that you so often get; I am currently reviewing the latest issue.

Most of my views come from a need to understand exactly what is going on. I used to drive the teachers mad at school continuously asking questions, especially as half the time they could not answer them.

But where I really appreciated the benefits of a simple, short, and accurate approach was when I was servicing RADARs on aircraft where, quite honestly, many of the manuals were were abysmal. This made the servicing work much more difficult than it need be. Then I joined industry and learned how to do electronics from coal-face engineers, who really understood what was going on. I was also liaison engineer for the apprentice training school at work, which was an education in-itself for me.

spec

 

[John Potter]

Yes, some electrically insulating washers are also pretty good thermal insulators. The rundown on heatsink material in order of lowest thermal conductivity is:

(1) Beryllium oxide: lowest thermal resistance (apart from diamond), brittle, highly carcinogenic, highly expensive.
(2) Aluminum oxide: brittle, medium cost, best choice, if you can get it
(3) Anodized aluminum: danger of puncturing anodized surface, expensive
(4) Mica: excellent electrical and thermal characteristics, brittle, low cost. Unless you buy from top-line manufacturers, like Avid, the thickness of the mica varies greatly, and thus the thermal resistance also varies accordingly. Mica is also a good choice.

And, quite simply, the other materials are not worth bothering with, if you need low thermal resistance that is.

The common thru-hole cases are:
(1) TO3: Rolls-Royce, in all respects, low thermal resistance, even and consistent contact, high reliability, does not need a clamp, expensive, getting rare.
(2) TO220: compact, easy to mount, needs a clamp for consistent thermal contact and reliability, cheap, the most common thru-hole package
(3) TO218; bigger version of TO220, with correspondingly lower thermal resistance. Also needs a clamp for even pressure and consistent heat sinking. A rare package now. Will fit to a TO3 PCB footprint.
(3) TO264/TO247: even bigger bigger version of TO220, with correspondingly lower thermal resistance. Also needs a clamp for even pressure and consistent heat sinking. A nice package.

**broken link removed**​

**broken link removed**

But thru hole cases are rapidly being phase out, and many of the latest and greatest power devices, especially MOSFETs, are only available in surface mount (SM).

There are a bewildering number of different SM cases and the industry has made an awful mess of case identity- inevitably on data sheets the same case will be referred to by different reference numbers in different places, so it is practically impossible to determine which case is which, and when you get a data sheet that covers multiple devices and multiple cases, you may as well give up. Why this situation has arisen, I do not know.

(1) TBD

**broken link removed**​

spec

Remember please I am speaking from Class A ignorance. I had wondered why the mounting hole for the LM's is - to be blunt - stupid. It should have an extended base plate with another screw. Some of the ones I have the case material has spread onto the mounting plate. The larger bridge rectifiers have a hole in them, I have used them when a lower current one would have been acceptable simply because they are easier to mount. I have collected quite a few various 'things' from the PC power supplies when I stripped them. I call them 'things' spec simply because I don't have any idea what they are. They are categorised as 'electronic gubbins'.

The 2SC5200 (npn) & 2SC1943(PNP) are nice linear gain power transistors and as such are popular with audio amplifier builders. I expect they could be useful in power supply circuits too. I have read elsewhere that good amplifiers and good power supplies have a lot in common.

Spec: this thread is an absolute treasure trove on practical power supply building, have you considered writing a book? I think there would be a big demand to read this practical advice rather than pages of intimidating mathematics as in certain books! Iam thinking of the superb book, "The Art of Electronics" which without a great deal of mathematics manages to convey a very in depth discussion on most aspects of electronics. John Potter or anyone else reading who is still relatively new to electronics, I would heartily recommend the aforementioned book. Anyway spec I would read your book if it was full of this sort of practical and non mathematical advice on power supplies.

There are hundreds of power bipolar junction transistors (BJTs) that outperform the 2N3055/MJ2955.

The 2N3055/MJ2955 suffer from the following shortcomings:
(1) Current gain falls off badly after about 4A
(2) High thermal resistance, junction/case, of 1.5 DCW
(4) High saturation voltage, collector/emitter
(5) High base/emitter voltage
(6) Low, frequency response of 300KHz and 2.5MHz, depending on which version of the 2N3055 you get.
(7) Relatively low (for a power transistor) collector/emitter voltage of 70V
(8) Relatively limited SOA

The TIP3055/TIP2955 are plastic case versions of the 2N3055/MJ2955, but there are some differences in the specification and in my opinion the TIP35C/TIP36C would be a better substitute.

The ON Semiconductor, MJ15003G/MJ15004G, are generally considered to be the the modern replacements for the 2N3055/MJ2955.

A really nice pair of transistors are the, MJL3281A/MJL1302A (just look at the flatness of the current gain graph).

And if you want to handle some serious current and power, the MAG6332/MG9412 are the boys.

spec

PS: Afraid to say that, apart from audiophile power amplifiers, power MOSFETs have completely replaced power BJTs

DATASHEETS
(1) http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF
(2) http://www.onsemi.com/pub_link/Collateral/TIP3055-D.PDF
(3) http://www.onsemi.com/pub_link/Collateral/TIP35A-D.PDF
(4) http://www.onsemi.com/pub_link/Collateral/MJ15003-D.PDF
(5) http://www.onsemi.com/pub_link/Collateral/MJL3281A-D.PDF
(6) http://www.rlocman.ru/i/File/dat/Semelab/Transistors_Bipolar_BJT_Single/MG9413.pdf
(7) http://www.rlocman.ru/i/File/dat/Semelab/Transistors_Bipolar_BJT_Single/MG9412.pdf

Steady on spec my friend. You know in the good old days when you got that little rotating arrow in the middle of the screen whilst a film was buffering, my brain is rather close to that. 2 months ago (1) though (8) would have meant nothing to me. Now (1), (2), (7) and (8) I understand. (4) and (5) are rather grey but OK and (6) I can understand but the numbers are meaningless. I expect (3) is on holiday. I am going to go through your data sheets, how much I will comprehend I have no idea but I'll do my best.
I think it best due to my ignorance though that we try and keep this circuit relatively simple - at this point in time. That circuit you showed is fine, I'm pretty sure I can manage that. I have to agree with Gas (I hope that OK with you Gasboss775). I never thought that when I started this thread it would become so helpful, not only in regard to the power supply but electronics in general which is for me more important. I don't mind, in fact it's a good idea, if I use more modern and better components. Providing I can look at the circuit with reasonable confidence as a Mark1 build I'll be more than happy. Apart from the battery charger and a Joule thief it's the first time that 50 year my old Multicore solder has been used. I do have some new stuff, LEAD of course. I tried the new kit and didn't like it much. Made from old car wheel balance or fishing weights I expect. I can't find my old wooden handle 100W iron, very useful for surface mount.

Just a bit of light reading before lights out. You must be joking, I gave that sort of thing up years ago - and I was never any good at it then.

I think I got out of page sink with this reply spec. I did look up the data sheets on the advert but there was no thermal resistance - just a blank. I know the old mica ones are rather Victorian, we should get on well.

Thank you Gasboss775, that's a good idea. There is one slight snag though. I spend hours trying to get my head around what spec is so kindly advising. I find that in the early hours of the morning, with the dog quietly breaking wind on her bed next to me, for some reason is the best time. I still have my library card and I'll get them to find your book for me if it's not on the shelves. If I can understand it I'll get my own copy.

 

[John Potter]

Nice transistors. They are member of the audiophile power transistor family that the Japanese companies pioneered in the 1980s. ON Semiconductor (was Motorola Semiconductor Division) now makes similar devices since the Japanese have pulled out of the market, to an extent.


Wow GB, that is very kind of you, and very gratifying to know that my posts are of some interest.

I have written quite a bit of technical stuff over the years, and funny you should mention it, but I have had ideas for a number of books on the back burner for years, ranging from, 'Writing', 'Maximizing your Position in Life', and also a load of electronics subjects. But the trouble with me is actually getting around to do things.

Yes, 'Art of Electronics', was s a revaluation when it first came out, and cut across a load of the BS that you so often get; I am currently reviewing the latest issue.

Most of my views come from a need to understand exactly what is going on. I used to drive the teachers mad at school continuously asking questions, especially as half the time they could not answer them.

But where I really appreciated the benefits of a simple, short, and accurate approach was when I was servicing RADARs on aircraft where, quite honestly, many of the manuals were were abysmal. This made the servicing work much more difficult than it need be. Then I joined industry and learned how to do electronics from coal-face engineers, who really understood what was going on. I was also liaison engineer for the apprentice training school at work, which was an education in-itself for me.

spec

I spent weeks looking through the Internet trying to understand the 'gubbins' that goes into making a power supply. I have a friend of over 60 years who is a brilliant electronics engineer, designed CPU's, but totally incapable of explaining even the simplest item without wandering off into something entirely unrelated. I joined 3 Forums and found many replies very helpful, some unfortunately were not, emitter resistor, purpose and value for example. In one Forum they even used the worst language possible about each other. I didn't expect that. I am very lucky to have found you spec and this Forum is very lucky to have you. I concur with GB 100%.

 

[John Potter]

Hi spec. It might be an idea to review the components for this power supply. I'm happy to use better power transistors, etc. and very happy to add current control. I will be guided by your advice. Give me a while to look at those data sheets and absorb your reply in general. Like you I too have my problems. Shopping. I'm still trying to work out how the hell I ended up doing so much cooking. Good job we have a dog that'll eat anything.
Thanks again - JP

 

[spec]

Hi spec. It might be an idea to review the components for this power supply. I'm happy to use better power transistors, etc. and very happy to add current control. I will be guided by your advice. Give me a while to look at those data sheets and absorb your reply in general. Like you I too have my problems. Shopping. I'm still trying to work out how the hell I ended up doing so much cooking. Good job we have a dog that'll eat anything.
Thanks again - JP

Hi John,

Thanks again or your kind words. Like you, I am annoyed by the trolling that goes on on some other sites: I just cant understand it- perhaps an alpha mail thing. I have had PMs from quite a few members that have had to suffer ignorant behavior in the past from some sites.

Anyway back to your power supply, if you like, I will do a full design that you can build (I hope it works).

I may have mislead you: 2N3055s will be perfectly adequate for this PSU, especially, as I have mentioned before, with you excellent cooling arrangements. I only described other transistors because you asked. I did not mean to imply that 2N3055s are useless, far from it.

The detailed circuit will use four of 2N3055 transistors and, as I mentioned in a PM.

To keep the PSU simple only single value current limiting (at 3A+) will be provided. This means that the PSU can run for ever into a dead short.

The zero volts and all other voltages will have source and sink current capability, to a degree,. Don't worry about this for the moment: it is no big deal to do, but it gives a much better output voltage performance.

The output voltage will be continuously adjustable from 0V to 40V (may be higher).

Don't worry, this circuit is dead simple, and a similar architecture has been used for a very long time.

There will be no transformer switching: the full 52V will be used.

If you would like me to go ahead and do a detailed circuit as described, please let me know.

spec

 

[John Potter]

Hi spec
I still pop back to the other 2 sites. There were some nice helpful people there. One I met remembers gas masks in London during the war. We're into email now. It would be rude to abandon the threads completely although they are very quite now. I really don't think I could handle 3 like you, thank God there's only one spec. That's wrong, every Forum should have at least one.

I honestly doubt you misled me, just brought to my attention there is more modern stuff about. I'm quite happy to use dinosaur teeth. The Sinusonasus had nice even teeth. (Don't panic I looked the spelling up) Maybe when the dust has settled with this power supply we can compare the newer ones but for now KISS (keep it simple stupid) is a good idea. I am managing to keep up but I need a bit of time to re read your PM's. I don't want you to have to repeat yourself too much at a later date. I am wondering if I can copy paste this whole thread. Have you ever been likened unto hens teeth spec.

Sorry but I am not sure what single value current limiting means. If it means the current is limited to 3A to stop meltdown then I'm all for it. That is what I did in my own very crude way with those 2 x 55W bulbs in the battery charger. It was OK after an hour with a direct short. Even the roof was OK to touch - just. I was so confident of my work I did it outside on concrete and kept the dog and wife indoors. Apart from popping that cap deliberately I haven't had any smoke yet, feel rather like a virgin. I'm absolutely certain I am perfectly capable of rectifying that situation.

I do have this 60V 400W (you must be joking) Banggood step down buck converter that has V & A adjustment (still not arrived) and 3 little 1.25V to 40V 5A (maybe 2A at a push) V adjustment buck convertors (arrived) that hopefully will enable me to see what these switch mode / buck things can do. You can't expect much at 3 for £4.

10 x 0.1Ohm 1W resistors arrived today from CPC along with a few other bits. I had read that it's best to get all 4 x 2N3055's at the same time to hopefully ensure they have similar characteristics. I did this but they seem a bit odd to me.

Should I get 4 more from Farnell?

They are not expensive and I can use the others for odd projects I'm sure. Bit annoyed that CPC Farnell don't stock the same items as Farnell. As for Maplin they are a joke, they were OK once though.

I don't think I will need any resistors. About 400 came from CPC and 1500 from Banggood. I checked the later they seem within tolerance. Blue background, not easy to read but the Fluke will.

I don't have a clue how to make a printed circuit board but I think I made a pretty neat job of those valve amps all those years ago. My MOD engineering apprenticeship started when I was just 15 and finished at 21.
I expect they still do tag strip, if needed, and I have 5 copper prototype boards. I have a few small ceramics and caps. No big stuff apart for the 10,000uF. CPC don't do big stuff, hardly anything above 16/30V. I have plenty of heat shrink, a third hand and tools OK for the job.

As for 'excellent cooling' I have no idea where you got that idea from. I have to admit though that 'stick a big heat sink on it' seems to be the general rule on DIY kit. Fan's are not the 'in thing' it seems. The last fans I worked on were 2 that soaked up 33kW each. I don't think I would trust anybody to go from 33kW to 6W. In my line of work we called heat sinks - 'radiators' LOL.

I would very much appreciate a circuit spec. Please, there is no need to rush, I really need to go through this thread and absorb the words according to the ARC Angel spec. And it came to pass that on the eighth day ...............

Thank You spec

JP

 

[spec]

Hi John,

...I am not sure what single value current limiting means. If it means the current is limited to 3A to stop meltdown then I'm all for it.

Yes, that is what I meant. The PSU would have a maximum current output, Once that maximum current has been reached the current out put would stay at that value. So, for example, if you shorted the output of the PSU, the output voltage would be zero and the current would be the set maximum current. Later you could think about adding a variable current limit.

I had read that it's best to get all 4 x 2N3055's at the same time to hopefully ensure they have similar characteristics. I did this but they seem a bit odd to me. Should I get 4 more from Farnell?

Matching transistor characteristics is important for some applications, audio amplifiers for example, but in this application it is not important, providing that each transistor meets the datasheet parameters.

I don't have a clue how to make a printed circuit board... I have 5 copper prototype boards.

A good layout on a prototype board will be fine for the PSU.

As for 'excellent cooling' I have no idea where you got that idea from.

Your cooling arrangement is excellent- nice low thermal resistance heatsinks... and a fan to boot. It shows that you have got your priorities right. So often when people attempt to build power supplies, they do not understand how important heatsinking is.

I would very much appreciate a circuit spec.

My pleasure John- will do.

spec

 

[John Potter]

Hello Alan - and spec
Alan was the first person to help me spec, he's on another Forum but we send little emails to each other and he reads this thread. He just told me what a mosfet is, I forgot to ask you.

Do you actually mean I understood. There's hope yet. As I wrote above I was worried about overloading and around 3A will be fine.

It would be very useful to be able to have variable current regulation but only for low mA. I do like messing about with LED's. I have quite a few strings from Poundland which I'm going to covert to mains. I have a carrier bag full of low voltage mains adaptors and those and a few resistors should be fine. It's a 'political' thing, my wife will see something other than bits all over the dining table. There are plenty of small V&A buck convertors that can give me variable mA but all I need is a few resistors for most LED's. I can play with those LM317's I have while I'm waiting for bits.

I'll have to use a 60V LM317AHVT for the fans, 17V is too much, wire wounds are OK but I can adjust the fan speeds with an LM.

Once again I was a little misled. One article more or less inferred that the emitter value depended on how close the 2N3305's were in tolerance. From what you say if they are widely out it could make a difference.

Using a prototype board is fine with me. My only comment is that tag strips are easier to change components on. That's how I got 410V across my nose. Maybe we should stick to prototype board, I expect you could hold all the bits in one hand.

The only reason I gave cooling any consideration was because many times the problem of heat generation with linear supplies cropped up in various Internet designs and then almost ignored. Putting 1 x 2N3055 in the middle of a 15" x 4" finned heatsink is very inefficient. That and the small linear supply a friend made me for a digital camera that I put in my trouser pocket and the swine burnt me. I am going for the MKII design, it does mean both sides of the heat sink get cooled by the fan and should the 2N3055's get too hot I have a few ideas other than more volts to the fan or another fan. I will cut a hole in the base of the case and put the whole lot on legs. I can check the 2N3055 case temp. with the infra red thermometer I have.

It's redundant now but I still fancy a thermal switch with a red LED. I suppose I could have 3 - Green, Amber and OOPS!. I'll add them to these Chinese regulators - I know they are going to need them.

From a mechanical engineers point of view linear power supplies are a bit 'orf' aren't they. I understand they produce a much cleaner DC but the 'greenies' would be horrified. I suppose I could put a heat exchanger on this beast and use it to run a bath or perhaps some sort of coffee machine. Either way I'm making it at the right time of year. Quite looking forward to getting stuck in but I must try and copy this thread and other bits here and there. That book sounds a good idea too.

Thanks again spec.

JP

 

[spec]

Hi John,

As I wrote above I was worried about overloading and around 3A will be fine.

As I have mentioned before, with your cooling arrangements there is little worry about over temperature with four 2N3055s. My main concern is frequency stability.

It would be very useful to be able to have variable current regulation but only for low mA.

OK, I will see what can be done simply. In the power supply, essentially, one resistor defines the current limit; call the resistor, Rcl.

Thus, the power supply current limit is defined by, 0.6V/Rcl. The high current ranges are the problem. So, off the top of my head, what you could have is switched current limits of, 3A, 2A, 1A, 0.5A, 0.2A, 0.1A, and variable 0.05A to 0.001A. Later, we can work on a continuously variable current limit of, 0A to 3A. By the way, I propose precision ten-turn potentiometers for the voltage adjustment and current adjustment (as stated).

Once again, I was a little misled. One article more or less inferred that the emitter value depended on how close the 2N3305's were in tolerance. From what you say if they are widely out it could make a difference.

Yes, that is true, but, because the cooling is so good and distortion, does not matter, like in an audio power amplifier, exact current sharing between the power transistors is not essential. You could even use different transistor types. Remember that the objective is to produce a power supply. The objective is not to ensure perfect current sharing.

Using a prototype board is fine with me. My only comment is that tag strips are easier to change components on.

My advice is to use a prototype board for the low-level electronics and tag-strips for the heavy electronics. For example, the resistors, including Rcl, would be mounted on tag-strips physically close to the power transistors. On the schematic, I will indicate all this.

It's redundant now but I still fancy a thermal switch with a red LED. I suppose I could have 3 - Green, Amber and OOPS!. I'll add them to these Chinese regulators - I know they are going to need them.

You can have as many bells and whistles as you like once the basic power supply is up and running. I would advise fitting a voltage and current meter to your PSU. Suitable units are available on ebay for a few quid (£UK). **broken link removed**

From a mechanical engineers point of view linear power supplies are a bit 'orf' aren't they. I understand they produce a much cleaner DC but the 'greenies' would be horrified.

Linear power supplies are beautiful, like class A amplifiers, and, yes, they generate little noise, around 3mV compared to around 100mV for a switching PSU of the size you are proposing.

The solar constant is 1KW per square meter, so what is 150W between friends. Most greenies are charlatans or worse, and cost civilization billions- beware of anyone taking a moral stance. That does not apply to genuine greenies though. I hope I am a greenie in the later sense.

That book sounds a good idea too.

Yes, 'The Art of Electronics' is a great book.

spec

 

[debe]

Been an interesting thread Guys, im not a great fan of SMPS after having spent years repairing them in TVs & VCRS. Generaly fail in a big way. My adjustable bench supply is a linear one using heavy transformer & 2 x 2N3055s, gives me 5v to 24v DC about 8Amps max with internal fan heating & has survived the last 25 years. Too old now to even try & repair surface mount equipment TVs are that cheap now just throw them out as theres hardly any thing worth salvaging in faulty LCD TVs.

 

[spec]

Been an interesting thread Guys, im not a great fan of SMPS after having spent years repairing them in TVs & VCRS. Generaly fail in a big way. My adjustable bench supply is a linear one using heavy transformer & 2 x 2N3055s, gives me 5v to 24v DC about 8Amps max with internal fan heating & has survived the last 25 years. Too old now to even try & repair surface mount equipment TVs are that cheap now just throw them out as theres hardly any thing worth salvaging in faulty LCD TVs.

Hi debe,

There are SMPs and SMPs. I had three at work. They were as quiet as a mouse, generated plenty of current, and ran as cool as a cucumber, compact too, and they never missed a beat. But, hell, were they expensive.

The early SMPs were a touch shaky, especially the off-line SMPS in coutries with 240V mains supplies, and many TVs were poorly designed or used components to their limit. Now though, apart from the odd common fault, TVs seem to be pretty reliable.

As you say, DIY repairs are near impossible with modern sets, apart from changing modules and perhaps the odd capacitor. One component you can salvage from modern TVs are some very nice polymer electrolytic capacitors and, maybe, the odd SMPS inductor (or just the core).

By the way, I was drooling over an LG, 55 inch, 4K, OLED (Organic LED), curved-screen, model 55C6V TV in Bristol UK yesterday. Amazingly the screen is only 1/4 inch thick and there is no border to speak of. It was only £2KUK, but my missus is being quite unreasonable by mandating that our current plasma TV is quite adequate.

spec

​

 

[spec]

POST Issue 3 of 2016_12_02

Hi John,

Below is the third draft of the bench power supply circuit. I haven't analyzed or optimized it yet, and for simplicity, only a 3A current limit is provided at the moment

spec

 

[John Potter]

Hi spec
I managed to get a bit done today. Another couple of days and hopefully the triple case will be ready. I have to get the leaves from 14 fruit trees off the lawn. I can leave the pruning till March. It was a good year.

Don't worry too much about the mA regulation, somewhere between here and China there are various items that might work. It would be nice though to have it all in one place eventually.

I have a meter ready and waiting 0V - 100V and 0A to 10A.
**broken link removed**
Whether this one is going to be good enough I'm not sure. It was as always a compromise. I thought I could use the Fluke until I knew more. Then, thankfully, the ARC Angel appeared out of the sunset.

I had also added ones like you suggest to the next order to Banggood. They are for that little 4A V Supply I'm making as a fill in whilst waiting for bits.
**broken link removed**
https://www.banggood.com/0_56-Inch-...nt-LED-Panel-Meter-p-933676.html?rmmds=search

I do wish though that that friend who made that tiny regulator for me had fitted a little heat sink. At a guess I would say it was loosing about 3W/6W. The camera charged in a few seconds, I don't think the poor regulator would have lasted much longer. It was a 1.3 MP Digital Dream camera, took 2 x AA batteries. I found that Toshiba batteries would last for 4 flash charges. Duracell 2. I can't remember now what 'power pack' I ended up with. It wouldn't work on 2.4V rechargeable batteries.

I am afraid so many have jumped on the greenie wagon to make money that it's very difficult to separate the truth from greed. What worries me most is that anyone who disagrees is vilified. Not a very scientific approach.

I was joking about the klaxon and large red LED. I did add a thermal switch to the battery charger as I had the one that was used on the transformer. It said on the case of the battery charger I stripped that it was normal for the charger to switch on and off during use. I can only assume they relied on this thermal switch to stop the transformer from going into meltdown. As the thermal switch was lying on the floor of the case I'm surprised the transformer wasn't cooked.

Like you I have a large plasma TV. It's old, gets a tad warm and weighs a TON. My wife and I can't lift it. The main electronics are in a separate box about the size of a VCR with a cable thicker than my thumb going to the screen. I am more fortunate than you insomuch as it has started to make a sound like hail stones on a tin roof going full chat out of the speakers. The colder it is the longer it takes for this sound to go away. It uses about 180W. The 26" LED VDU I am using now uses a 19.6V x 2.1A power supply that runs cold with a volume less than a cigarette packet.

Circuit.

This I will have to digest.

I don't have a clue about your method of connecting the transformer. I'm sure it's correct but I see in my ignorance the output as 0V 36V 0r 0V 18V + 0V 18V.
Do I take it the 10,000uF cap is now redundant ? I might have a home for it.
Do Farnell do 1000uF caps as CPC Farnell don't (maybe 16V ones).
I take it a mere mortal can get an account with Farnell. CPC Farnell seem to be lacking components in several areas.

If I might suggest we leave the 3A current limit as it is for now. I am not adverse to a MK2 through to MK762/A revised Oct 2019. I want to learn spec, just enough to be able to look at a circuit and not think it's a map of the London Underground. I don't care how long it takes in a way.

I'm more than happy right now. We should also bare in mind I can't even stand yet let alone walk...................

I take it the LM358N SPARE is not actually a spare - or is it?
Should I take a video of the smoke ascending unto heaven when I first switch it on, I will wire it up incorrectly you know.
Don't take me too seriously spec, I've always had a strange sense of humour.

I must take that welder to bits, it looks positively lethal.
I have just found a lovely 140 mm fan. I am not going to use it unless I have to. It's on my spare 800W PC power supply. I doubt it's any more watts than the smaller one I'm using.

Occasionally one meets someone who puts a bit of faith back into ones thoughts about the human race.
I have met 2 and some very close calls since I started these Forums.
Best thing I've done in years.

Thanks
JP

 

[spec]

Hi John,

I don't have a clue about your method of connecting the transformer. I'm sure it's correct but I see in my ignorance the output as 0V 36V 0r 0V 18V + 0V 18V. Do I take it the 10,000uF cap is now redundant? I might have a home for it.

It is not surprising that you do not have a clue about the method of connecting the transformer... because I have made an error and missed out the 10,000uF reservoir capacitor, a somewhat vital component. The circuit of post #92 is now updated to include the 10,000uF reservoir capacitor.

Do Farnell do 1000uF caps as CPC Farnell don't (maybe 16V ones).
I take it a mere mortal can get an account with Farnell. CPC Farnell seem to be lacking components in several areas.

CPC are good, but they do not carry the stock that the mainline distributors do. Anyone can buy from Farnell, RS, DigiKey UK, Mouser UK, Arrow UK. The latter three distributors are US, but they have UK divisions. eBay and Alibaba are the two big low-cost component sources. Then there are many other useful distributers, many specializing: Arduino and Raspberry Pi, model aircraft, batteries.

Postage and packing charges can add significantly to your costs, but often, postage is free. Farnell, DigiKey, Mouser, and Arrow make no charge for orders over £30UK, and RS make no charge at all. From what I can tell, DigiKey is everyone's favorite distributor.

If I might suggest we leave the 3A current limit as it is for now. I am not adverse to a MK2 through to MK762.

Very wise. After frequency stability, current limiting is the difficult part with a bench power supply. I am thinking about a couple of ways of doing a simple adjustable precision current limit anyway.

I want to learn spec, just enough to be able to look at a circuit and not think it's a map of the London Underground.

Yes, electronics is a fascinating area. Don't worry we all have the 'map of London underground' feeling, but just to reassure you, there is nothing in the slightest complicated about the bench power supply circuit of post #92. My opinion is that anyone, with a logical mind can learn the essentials of electronics theory quite quickly. The secret is to start with the basics and work up.

I take it the LM358N SPARE is not actually a spare - or is it?

The LM358 has two opamps in one eight-pin package. In the circuit of post #92, only one of the opamps is used, so yes, the other opamp is spare. But you must put spare sections of any chip into a defined state or the spare sections can misbehave, and in the extreme, even destroy themselves and the whole chip. That is why the spare opamp has its inputs connected to the (0V) and (-15V) supply lines.

In case your wondering why use a dual opamp, when you only need one opamp, the answer is for practical reasons. Because of its low cost, flexibility and ease of use, the LM358 has been the most ubiquitous opamp chip since the late 1970s, and is used extensively in hobby and professional electronics. As a result of the LM358s wide use, and thus high volume production, it is dirt cheap (£0.40UK). Oddly enough, a chip with a single LM358 opamp, is rarer and much more expensive. Incidentally, you can get a 14 pin chip (LM324), with four LM358 type opamps in it, for about the same low price as an LM358.

spec

 

[John Potter]

Hello spec
I sat here and read your words - 'I made an error and missed out the 10,000uF reservoir capacitor'. You do know what that means for me to notice that I'm sure. It means that I am very slowly beginning to understand. Please don't raise you hopes up too much, we have a long, long way to go. I will be quite honest. Your circuit will be challenging, especially as I don't know what a lot of it does. I will rephrase that, You have told me whet this circuit does but I'm not sure what parts of the circuit do what it does. Do forgive me, that's terrible English. The problem is I don't know what I am talking about.

If you could possibly break down the circuit into 3 or 4 areas and crudely explain, perhaps not in detail, what bit does what it would help me immensely. I do feel I'm asking an awful lot of you spec.

The next thing once you have got to the point where I can start burning the cork floor tiles that are protecting the dining table is to order the parts. I think I'll go to Farnell. I have checked up and they seem to have the items that CPC don't stock. Would 63V 1000uF capacitors be OK ? Perhaps there are some components I'm likely to destroy or worth holding and should order 2 or 3 ?

I must try and sort out my eBay account. I have not used it in years but I still have PW, etc. written down. My next door neighbour is 'well into' eBay, I'm sure she will help.

I am going to move the heat sink cooling fan to the bottom of the case. It's less likely my 4 year old granddaughter will stick a pencil in it. I have to rewire the transformer 'next door' anyway. Cutting large neat round holes in thin steel is not my favourite past time. Better than endlessly watching that dreadful woman at a gardening centre or that purple tied twit wittering on about PPI. Perhaps one day I'll explain what my 'Green Pineapple Treatment' involves. It's definitely X rated. I fancy some nice turned Victorian brass legs about 50mm long. I've gone off thermal switches.

'Anyone with a logical mind' - That's the second mistake you have made as far as I'm concerned. I have never used prototype board. I have no idea how to lay the components out other than the power transistor resistors. Should they be almost directly connected to the 2N3055's or can they be on a single tag strip mounted on the case and wired ?

Time for bed

Regards - JP

 

[spec]

I sat here and read your words - 'I made an error and missed out the 10,000uF reservoir capacitor'. You do know what that means for me to notice that I'm sure. It means that I am very slowly beginning to understand.

Yes, well done. I need someone with a logical mind to check my stuff. By the way, errors are a fact of life, especially with me.

If you could possibly break down the circuit into 3 or 4 areas and crudely explain, perhaps not in detail, what bit does what it would help me immensely.

It is no problem at all. Will do a breakdown and description of the bench PSU circuit.

Would 63V 1000uF capacitors be OK ?

Sounds like just the ticket. But post a link so that I can check- capacitors are a minefield.

Perhaps there are some components I'm likely to destroy or worth holding and should order 2 or 3?

Take a look at ETO article 'Core Components' @ https://www.electro-tech-online.com/articles/core-components.782/ I would recommend getting the following components for your spares box:
(1) BC546: NPN small signal bipolar junction transistor (BJT) [10 off]
(2) BC556: PNP BJT [10 off]
(3) TIP41C: NPN power BJT (TO220 case) [10 off]
(4) Power transistor mounting kits [20 off] (eBay)
(5) TO220 aluminum oxide thermal washers [10 off] (eBay)
(6) TO3 aluminum oxide thermal washers- you may have to settle for mica [10 off] (eBay)
(7) Thermal grease [one tube]
(8) LM358: dual opamp (8 pin plastic dual-in-line [DIL] package) [10 off]
(9) Turn-pin integrated circuit (IC) socket (only get turn-pin) [10 off] (eBay)

I have never used prototype board. I have no idea how to lay the components out other than the power transistor resistors. Should they be almost directly connected to the 2N3055's or can they be on a single tag strip mounted on the case and wired ?

A good layout is important but, don't worry, we can sort the physical side out a bit further down the line.

By the way, I haven't done the circuit detailed analysis, optimization, or component rationalization yet; there is certain to be some changes as a result.

spec

 

[John Potter]

Hi Spec - capacitors below
https://uk.farnell.com/panasonic-el...1jm102/cap-alu-elec-1000uf-63v-rad/dp/9693890

I do have the thermal grease and TO220 thermal washers, etc.
I'll try and sort this Ebay account out, I was getting email from PayPal but to be honest I ignored them due to 2 rather disastrous items from eBay. One was a UK company the other I can't remember. I expect the prices on Amazon are the same but you don't need a PayPal account - I think.

I expect though that I can get these items from Farnell if the worst comes to the worst. No doubt Banggood do them but their delivery ox cart has a broken wheel. (LOL)

One or two of the transistors -? have different variants. I bookmarked anything over 60V.

Any chance you could narrow this one down a bit as there are 110 hits on Farnell and I don't know what it looks like.
'Turn-pin integrated circuit (IC) socket'

Any idea what the correct name for a 'tag strip' is ?

I do have quite a section of small 3mm and 4mm nuts, self locking nuts, screws, washers, connectors, etc. I also have taps, dies, etc, etc. Most of it left over from the kit car days.

It looks like Farnell only do mica. The supply is about 30W / 2N3055 maximum. As the fan is moving underneath I can easily check the power transistor heat. I doubt I'll ever use 30W.

It's 50 years since I last had this hobby. I few more days or weeks or whatever won't matter at all. It is very kind of you to help me and no doubt others reading this thread.

If you make a mistake the only person that's going to be upset is you. From my point of view it might even be for the best, one only learns by ones mistakes - or in this case you may make an error but I KNOW I will.

Cheers - JP

 

[spec]

Hi John,

capacitors below
https://uk.farnell.com/panasonic-electronic-components/eca1jm102/cap-alu-elec-1000uf-63v-rad/dp/9693890

Nice- Panasonic components are pretty good and good value too.

I'll try and sort this Ebay account out, I was getting email from PayPal but to be honest I ignored them due to 2 rather disastrous items from eBay. One was a UK company the other I can't remember. I expect the prices on Amazon are the same but you don't need a PayPal account - I think.

Yes, best to get eBay and PayPal accounts sorted.

Not only are the prices incredibly low on eBay, but they have parts you cannot get anywhere else.

PayPal is required to buy from quite a few vendors theses days.

One or two of the transistors -? have different variants. I bookmarked anything over 60V.

https://uk.farnell.com/fairchild-semiconductor/bc546btf/transistor-bipol-npn-65v-to-92/dp/2453787
https://uk.farnell.com/fairchild-semiconductor/bc556btf/transistor-bipol-pnp-65v-to-92/dp/2453802
https://uk.farnell.com/stmicroelectronics/tip41c/transistor-npn-100v-6a-to-220/dp/9804170

Any chance you could narrow this one down a bit as there are 110 hits on Farnell and I don't know what it looks like.'Turn-pin integrated circuit (IC) socket'

https://uk.farnell.com/harwin/d2608-42/socket-ic-solderless-8way/dp/1023046

Any idea what the correct name for a 'tag strip' is?

Farnell do not seem to do tag strips anymore.

https://www.google.co.uk/search?q=t...ved=0ahUKEwitmIjUxtnQAhWkBcAKHd2HADEQ_AUIBygC

It looks like Farnell only do mica.

The supply is about 30W / 2N3055 maximum. As the fan is moving underneath I can easily check the power transistor heat. I doubt I'll ever use 30W.

Mica insulating washers will be fine.

spec

 

[John Potter]

Hello spec
Well, that was too good to be true.
Some time ago I set up a 'basic' account with my bank just for any transactions over the Internet. I went to the PayPal site and added new valid card details and that appears to be that. Famous last words.

There is still one item that I have not received from Banggood. I sent an email and I have been asked to check if it was undelivered and wait another week, more or less what I expected. It's 3 weeks since it was 'shipped'.
Even if it never turns up I have saved so much on the other items I'll not really be out of pocket. It might turn up - fingers crossed.
Thanks for the links. If you know what an item is called or even what it looks like it helps - LOL

I hate LOL spec, it's just that with my strange sense of humour until people get to know me it does save confusion. I do have several American friends and you cannot imagine the fun I, we, they have, mainly due to the 'language barrier'.
The favourite one was where an American policeman in New York was complaining about the 'horses going to the bathroom all over the place'. I just mentioned ours use the toilet, it's more hygienic. Dave allen did a wonderful few minutes on S.H.I.T. Do look it up. 3 minutes 47 secs on.

I do have to be rather careful with 2 friends in North Carolina. They have quite strong opinions on certain subjects. I just keep my head down.

Panasonic are a pretty well known name and the last 2 capacitors I bought of theirs didn't spread them selves across the ceiling. They definitely are good value.
Right or wrong I order by cheapest first and then pick the one that seems the best value.

LM358 - Bit creepy this.
After I read your last posting I went to have a look at bigclives latest saga. Please watch it from 9 minutes 50 seconds. It really confirms your choice.

My present thoughts are to get the components I need from Farnell where possible. I can then 'stock up' on the items you recommended and some from 'Core Components' from eBay.
I will wait until you are happy for me to start the MK1 power supply and then send off for the components I need.

I have a very understanding wife. We have quite a large dining table, about 2m long - seats 8. There is just enough room left for us to eat. OOPS!. I have explained it's all your fault spec. I have been buying some little tool boxes, organisers from Poundland and scrounging anything else I can find. Everything looks tidy but even with 4 plastic boxes the size of beer crates stacked away things are getting out of hand. I have to get better organised.

I have just been informed we are having our daughters and grandchildren next weekend. The table has to be cleared. No rush for the circuit spec. 4 year old's and soldering irons don't exactly mix.

Thanks for the links, it'll get me started on the order.

JP

 

[spec]

Well, that was too good to be true.
Some time ago I set up a 'basic' account with my bank just for any transactions over the Internet. I went to the PayPal site and added new valid card details and that appears to be that.

Should be OK- PayPal are quite good to use.

There is still one item that I have not received from Banggood. I sent an email and I have been asked to check if it was undelivered and wait another week, more or less what I expected. It's 3 weeks since it was 'shipped'.

I recently ordered a large amount of stuff from the far east, mainly eBay. Every single item turned up, but delivery took from 2 weeks to six weeks. Nearly all the items were free post and packing.

Dave allen did a wonderful few minutes on S.H.I.T. Do look it up.

I loved Dave Allan- his shows were compulsory viewing. What a loss now that he is gone.
Have you seen these two ETO threads:
https://www.electro-tech-online.com/threads/want-a-good-laugh.143396/
https://www.electro-tech-online.com/threads/funny-images-thread.130358/

LM358 - Bit creepy this. After I read your last posting I went to have a look at bigclives latest saga. Please watch it from 9 minutes 50 seconds. It really confirms your choice.

Afraid the link didn't mention the LM358.

By the way, another ubiquitous, jelly-bean chip is the LM393 dual comparator.

My present thoughts are to get the components I need from Farnell where possible. I will wait until you are happy for me to start the MK1 power supply and then send off for the components I need.

Good move

I can then 'stock up' on the items you recommended and some from 'Core Components' from eBay

If you are planning to get into electronics, the 'Core Components' list would be a good start.

There is also a 'Core Equipment' article which you may like to have a peep at too: https://www.electro-tech-online.com/articles/core-equipment.787/

spec

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