Strictly Linear PSU's

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Re: Strictly Linear PSU's

Postby sureshot » 20 Jan 2016, 20:19

I was drawn to the SCR as well for some reason, probably given by what you've said you already replaced. The only real way is follow the trail with a meter until it goes cold ! Beyond will be the fault in the circuit. Given that you've made good the components you have already replaced. One wrong termination is all it takes for a fault situation, check and double check all leads to and from the transistors and other replaced components. But do look at that SCR.
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Re: Strictly Linear PSU's

Postby Crusader » 20 Jan 2016, 21:03

SCR??

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Re: Strictly Linear PSU's

Postby sureshot » 20 Jan 2016, 21:10

Thyristor sorry known as an SCR.
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Re: Strictly Linear PSU's

Postby sureshot » 20 Jan 2016, 21:12

Go with what Rob said it makes sense for a plan of action, check for any accidentally made solder bridges as well, easily overlooked.
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Re: Strictly Linear PSU's

Postby sureshot » 20 Jan 2016, 21:43

The plan now.. Box up the 10 Amp model, add a crowbar to the output, with the already regulator and output fuses. As i don't have a big enough linear transformer yet (put to xbox psu's in series for the input) (already tried and tested at full load current) And test the circuit on an old porta pak with extension speaker, and a RM KL203P FM only for now. As with converted smps, use over real time is the best test. Nearly forgot, as this is veroboard all tracks carrying high current are soldered the entire length, the board on its own with no extra current carrying ability is a hazard.

If it proves good, then i will attempt the 30 Amp version, point to point wiring though as no room or means for pcb production.
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Re: Strictly Linear PSU's

Postby cjay » 20 Jan 2016, 21:56

sureshot wrote:
Mattylad wrote:The circuit for the PW Marchwood is an excellent PSU for this if you can find it. (wish I could).

Also have a look at http://warc.org.uk/?page_id=404

To the best of my knowledge your link is the Marchwood project Matt.Its a super design, not beyond mine or many other hobbyists ability. The components count is much higher, but for complexity and quality its to be expected.


Mhmm, that's the Marchwood. Cracking supply.

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Re: Strictly Linear PSU's

Postby sureshot » 20 Jan 2016, 23:24

Post again soon... Hopefully not having blown any radio gear lol.
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Re: Strictly Linear PSU's

Postby Gw0wvl » 12 Feb 2016, 22:29

ive got the full information on the P.W Marchwood here.. Full schematics and componant layouts, Parts list etc... My home made supply uses the same Over voltage circuit as in the Marchwood.. Using the Motorola MC-3423 .... Ive a video on youtube of the full powersupply...
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Re: Strictly Linear PSU's

Postby sureshot » 15 Feb 2016, 00:04

Gw0wvl wrote:ive got the full information on the P.W Marchwood here.. Full schematics and componant layouts, Parts list etc... My home made supply uses the same Over voltage circuit as in the Marchwood.. Using the Motorola MC-3423 .... Ive a video on youtube of the full powersupply...

Its a very nice PSU, the Matchwood unit. I'm in persuit of simplicity functionality and reliability, and safety as well. Since I posted the circuit at the start of this thread (The voltage regulator emitter follower element) Its working extremely well. I started with a single TIP2955 PNP transistor, and have since built, two, three, and now four transistor versions. I'm yet to go to six transistor version, although 30 Amps from a six transistor version is pushing it. My findings on current voltage drop, and heat as the enemy.

If the input to output is kept as low as possible the circuit performance is very good. My findings lead me to a four transistor unit as a 10Amp unit, this way nothing is driven to hard. So if I wanted 30 Amps for comfort I'd be using 12 transistors, sound exesive, but mounted they take little room. I've been using a two transistor version (pictured start of this thread) for about 4 weeks now with no problems. Its not a complete supply yet, as the AC source is separate from the PSU circuit for this extended test. But its looking good enough to build a 30 Amp version. I'm using a zener and fuse for output protection, its not perfect protection I know, but on a final cased build I'll use a crowbar for protection. The two transistor unit is powering a TTI 881 Radio, and a RM KL 203P total load is 8.4 Amps. Voltage drop is negligible.

I like the Matchwood PSU, but I really like simplicity, that extends to other stuff equally. Maybe one day if I can get some PCB production going I'll build it.
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Re: Strictly Linear PSU's

Postby sureshot » 15 Feb 2016, 00:34

Its the small ABS box bottom of this old pc table, the input is a bit high at 24 volts, but its just a test rigged up for the minute. if all goes well i will go out and get a 300 VA transformer for the big one.
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Re: Strictly Linear PSU's

Postby sureshot » 05 Mar 2016, 23:54

Well its been a few weeks now, and although the radios been quiet, I have had a few overs with the amp and radio with this linear circuit. Its a winner !

Before I build the big 6 x transistor version, I've been investigating higher powered transistors with massive hfe gain. The TIP2955's in use are 90 watts max a pop each, but I'm now looking at using the MJ11015 and the MJ11033 power transistors. These are rated at 30 and 50 Amps each, imagine x 6 ! If the model goes well, I should have the big one built not to far in the distant future. This circuit (beginning of this thread) is or looks simple, but its very efficient indeed !
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Re: Strictly Linear PSU's

Postby sureshot » 05 Mar 2016, 23:56

Double post deleted.
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Re: Strictly Linear PSU's

Postby sureshot » 10 Apr 2016, 11:00

100 watts linear 4 x TIP29955s, time for a bigger heatsink and 6 x MJ2955s, all good, very stable plenty of power. Its the CPU heatsink that's been the bottle neck up until now.
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Re: Strictly Linear PSU's

Postby Techquest » 11 Apr 2016, 22:46

Mattylad wrote:The circuit for the PW Marchwood is an excellent PSU for this if you can find it. (wish I could).

Also have a look at http://warc.org.uk/?page_id=404


There you go Mattylad
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Re: Strictly Linear PSU's

Postby sureshot » 12 Apr 2016, 01:26

Techquest wrote:
Mattylad wrote:The circuit for the PW Marchwood is an excellent PSU for this if you can find it. (wish I could).

Also have a look at http://warc.org.uk/?page_id=404


There you go Mattylad
http://www.mediafire.com/download/2s7lx ... ood053.rar

This would, with a bit of adaptation make a really good lab supply. But means to an end as and absolute bruit power, the simple emitter follower is all that's needed. With added protection. Unless its a labour of love.... You just want to power that high current amplifier ! But its a very nice PSU design. But for quick efficient " huge " current the linear voltage regulator and pass transistors is easy on your pocket, and archives the objective efficiently.
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