Strictly Linear PSU's

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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 10:04

The CPU heatsink lends itself to a small footprint, up to 100 watts, depending on heatsink. One's TO220 the other TO3 package. Both have a footprint no bigger than a playing card. Admitted these two are 5 Amp units, but the voltage regulator transistor emitter follower is going to be a very compact unit.
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 10:10

Better picture of the 100 watt model, all the silicone on one common heatsink. The next build 6 x transistors will move away from a CPU heatsink, but the PCB will still be very compact for a 20 Amp unit. But I'm toying with the idea of 12 x transistors and water cooling.
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Re: Strictly Linear PSU's

Postby Buick Mackane » 12 Apr 2016, 10:12

Nice work dave
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 20:26

PLL02A wrote:Nice work dave

Thanks pal ! Hope a few try this circuit out. 13.80 Volts can be achieved by using the 78S15cv and dropping the final output. the regulator only carries less than an Amp. R7 value determines how much work the regulator does. I have tried the MJ11015 high power darlingtons, but ran into oscillation problems )-: shame as they can dissipate 200 watts each. had a long 9 page plus on a popular electronics forum thrashing this out, but no joy with darlingtons for now. the TIP2955 0r MJ2955s look the best bet for now. But i'm still on a quest for a higher power package.
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 20:26

PLL02A wrote:Nice work dave

Thanks pal ! Hope a few try this circuit out. 13.80 Volts can be achieved by using the 78S15cv and dropping the final output. the regulator only carries less than an Amp. R7 value determines how much work the regulator does. I have tried the MJ11015 high power darlingtons, but ran into oscillation problems )-: shame as they can dissipate 200 watts each. had a long 9 page plus on a popular electronics forum thrashing this out, but no joy with darlingtons for now. the TIP2955 0r MJ2955s look the best bet for now. But i'm still on a quest for a higher power package.
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 20:26

PLL02A wrote:Nice work dave

Thanks pal ! Hope a few try this circuit out. 13.80 Volts can be achieved by using the 78S15cv and dropping the final output. the regulator only carries less than an Amp. R7 value determines how much work the regulator does. I have tried the MJ11015 high power darlingtons, but ran into oscillation problems )-: shame as they can dissipate 200 watts each. had a long 9 page plus on a popular electronics forum thrashing this out, but no joy with darlingtons for now. the TIP2955 0r MJ2955s look the best bet for now. But i'm still on a quest for a higher power package.
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 20:28

Sorry multiple posts kept saying 500 server error.
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Re: Strictly Linear PSU's

Postby Buick Mackane » 12 Apr 2016, 20:47

sureshot wrote:Sorry multiple posts kept saying 500 server error.


It posts the first time dave, Even though you think it hasn't, Just refresh the page. Yeah i'm in the process of tarting up an old 3 amp PSU i had laid about. You know the details about that as you posted in my thread :) Finished the cosmetic work, Just need to get motivated and wire it up, First time i've mucked about with a PSU. Receivers is more my thing, But wanted a nice clean linear supply with variable voltage for powering projects etc, Was browsing ebay last week and seen a nice 24v - 10.5 amp transformer for £22, Its gone now, Should have snapped it up, The price of them has rocketed, Would have been nice for a future project.
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 22:06

PLL02A wrote:
sureshot wrote:Sorry multiple posts kept saying 500 server error.


It posts the first time dave, Even though you think it hasn't, Just refresh the page. Yeah i'm in the process of tarting up an old 3 amp PSU i had laid about. You know the details about that as you posted in my thread :) Finished the cosmetic work, Just need to get motivated and wire it up, First time i've mucked about with a PSU. Receivers is more my thing, But wanted a nice clean linear supply with variable voltage for powering projects etc, Was browsing ebay last week and seen a nice 24v - 10.5 amp transformer for £22, Its gone now, Should have snapped it up, The price of them has rocketed, Would have been nice for a future project.

Yes seen your restoration psu, the LM338K is a nice regulator.
Being a power junky lol, and watching the pennys, i'm interested in the best quickest most reliable cheap quality linear supply. But as nice as the marchwood project is... its pointless for my pursuits of raw power.

The point i'm in it for, both smps and linear is that very high current. 60 Amps will realise my linear goal, and the voltage regulator transistor emitter follower can achieve this, and saving a lot of money as well. What's the price of a 60 Amp smps or linear supply O-: I had my doubts at first on this circuit on page 1 of this thread, but its as good as any other linear supply i've ever used. The addition is protection, over voltage, over current on the output. Very little expense indeed.

One day i will splash out for the bells and whistles Marchwood project, but for now its really about the power, and final cost. This circuit is so simple to build, all the test points reading under load add up, and with the TIP2955s or similar its very stable. And above all it cost peanuts. As i've yet to get a decent toroidal transformer... I have been running 100 watt 4 x transistors from two xbox psu's in series, so 24 Volts input. And for a TTI881 and a RM KL203p its been super reliable.

I've since been thinking away from a regular transformer, and converting two HP 1200 watt DPS server supplys, then run that into my high current linear circuit. The former as a pair can be picked up very cheap on ebay. Yes its been mentioned before, its just a dropper, but so is any linear secondary circuit. Possibilities are endless, and for very little outlay. I know above 100 watts its point to point wiring for me, but for those with pcb production means ! Its slow at the moment, i'm still looking for the ideal heatsink and cooling arrangement, but its coming together be it slowly.
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Re: Strictly Linear PSU's

Postby wardster » 12 Apr 2016, 22:09

If I'm allowed to give a heads up here, I'm making a listing on the for sale page for some Linear PSU kit that is gathering dust and I just don't have the time to get a project up off the ground. I have 3 very heavy 240v to 15v transformers at at least 20A output - a link to one project is here;

http://m1kta-qrp.blogspot.co.uk/2016/03 ... -7103.html

I think I also have a couple of 240v to 28v transformers at 10A output too.

There are also 4 off MJ2955 power transistors on big bad ass heatsinks tested working too :)

Hope this helps someone to save these poor old bits of kit get saved from more dust!
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Re: Strictly Linear PSU's

Postby sureshot » 13 Apr 2016, 10:13

wardster wrote:If I'm allowed to give a heads up here, I'm making a listing on the for sale page for some Linear PSU kit that is gathering dust and I just don't have the time to get a project up off the ground. I have 3 very heavy 240v to 15v transformers at at least 20A output - a link to one project is here;

http://m1kta-qrp.blogspot.co.uk/2016/03 ... -7103.html

I think I also have a couple of 240v to 28v transformers at 10A output too.

There are also 4 off MJ2955 power transistors on big bad ass heatsinks tested working too :)

Hope this helps someone to save these poor old bits of kit get saved from more dust!


Hope someone contacts you and can make use of this gear your offering. My needs are going to exceed 60Amps to get that as a continuous output up to that rating. But for more more modest high current builds 2 x of your transformers in parallel give a very high current as a base to build from.
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Re: Strictly Linear PSU's

Postby sureshot » 17 Dec 2016, 22:05

Some progress, although I've scaled it down from 30 Amps. I'm never going to need more than 20 Amps.

Its going to be the schematic on page 1. But I've gone for MJ4502 power transistors, larger head room in terms of current. Each transistor only has to handle 5 Amps, these have collector currents of 25 Amps continuous. Bit pricey at £4 each, but its not about cost.

The case was £10.95, the transformer is 300 VA with twin 10 Amp secondaries, 15 Volts. Measures 16.90 Volts AC no load. I've used 15 Volt secondary before, its enough head room for 12 .50 Volts, what I'm after. You can use 18 Volt secondary if you wanted 13.80 Volts at the output.

I've not long finished rebuilding an old Alti 3 - 5 Amp with the single regulator boost circuit on page 1 of this thread, using an LM317K to set up the voltage, and test out the MJ4502 in real time. No issues powering radio and 25 watt Amp 3 weeks in now.

So some early shots offering up the transformer, I'm hoping to not use fans, at 12 Amps continuous 15 Amp 50% duty cycle, and 20 Amp peak power. Its slow progress, but i will be back when there's more to show. On the output i am going with a full crowbar circuit for output protection.
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Re: Strictly Linear PSU's

Postby sureshot » 24 Dec 2016, 21:36

Little bit more progress, voltage regulator and transistors fitted. Transformer in now, and i think most of the harware. Found a cute AMD heatsink for the 35 Amp bridge rectifier, that should do fine.
As the case was an ebay find, there where constraints of 4 x 12mm holes do sort out. Two are the fuse and on / off switch. There are two more at the rear right corner, caps in them at the moment. But might fit something in them at a future date, blanking caps came with the case.
Just got to order some M4 85mm to 90mm bolts for the pcb, mounted above the transformer. Back in the not to distant future.
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