5v power supplies

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ed
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#1 5v power supplies

Post by ed »

I needed a couple of 5 v linear supplies a while ago for cheap dacs because with the wall warts they rustle like autumn leaves...very soothing but crap when you want some refined music.....

anyway I put together a couple of pre tracking versions using lm339 and assorted caps...but they got a bit hot and very greedy on Tx requirements, wanted Tx I didn't have on hand...

so I thought I'd have a go with lt1083 and run a dac and Squeezebox off the same supply..just curious etc etc...I've never played with lt1083 so I bought one of these v.cheap kits to see...

https://www.ebay.co.uk/itm/NEW-LT1083-A ... SwpkFY7doB

assembled the kit and tested it with the only bulb I could find to try and load it....I adjusted to 5v which is what I wanted and measured the draw at 1.2 A which seemed reasonable, the bulb was lit but not bright..so far so good..the sink went to 60 degs and I began to feel uneasy, but left it to settle down over dinner. Came back after 1 hour and voltage had climbed to 5.3 whereupon I adjusted it back down to 5.00 and left it for another 1/2 hour. Came back and voltage had dropped to 4.8 and temp gone down to 44 degs.

mmm this is a high current reg, not supposed to wander.

anybody got any ideas or experience with these cheap kits??
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#2 Re: 5v power supplies

Post by Nick »

Never seen them wander, but the pot could be moving with the heat. The heat sink looks a little small to me.
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#3 Re: 5v power supplies

Post by ed »

sorted

dodgy joint on the adjuster leg. voltage rock solid and sink is not even warm just running the DAC. I think I'll get the 1083 off the board and on a bigger sink when I put a bigger load on it.

It's early days but these ebay boards with parts look like fantastic value. The spec for the kit does say good for 7 amps but I certainly wouldn't with that heat sink. I think they're just stealing the wording from the lt1083 datasheet.
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#4 Re: 5v power supplies

Post by andrew Ivimey »

I was seduced by the spec sheeted claims of 1083s. Putting 9 volts through the input to get, if I remember, 7.25volts at an amp for VT62s, the supplied heat sink, pcb and components were severely damaged into useless 'walking wounded'. I didn't even trust things with replacement 1083s (or 1084???- ). So I bought new kits complete and fixed the 1083s to the aluminium chassis of the amp and bingo! Steady, efficient success with only a little heat dissipating away around the amp. I was aiming at 10volts 3 amps for VT4c but gave up that plan.

I have been surprised at how acceptable are switched mode (computer) power supplies are for IDH valves when I thought they would really spoil the beautiful simplicity that SE amps can give. (Success with vt4c, GM70, GU48 and vt62s)
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#5 Re: 5v power supplies

Post by DSJR »

Not suitable for DIY, but 'The Doc' and I have nifty cheapo DACs costing under a tenner and where mine is most acceptable for purpose with its wall wart, he bought one of these for his -

http://www.ebay.co.uk/itm/Hifi-linear-D ... 1438.l2649

- and it seems to do a great job and looks well presented and made inside. I can't afford currently to get one, but it's on the shopping list. I made an adjustable 12V regulated one up and it's in the loft somewhere, but I don't think it was very successful. Maybe I should find it and have another look to see if it can be taken down to 5V and have another play...
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#6 Re: 5v power supplies

Post by DSJR »

Can I ask a question please?

The old QED DAC I use sounds great with two supplies on it. One is a QED Positron, which claims twin 15VDC supplies. Only one is used, so is the other one loaded or filtered internally but not connected in a kind of 'mirror' arrangement? I had a couple of leaking supply caps in the Positron on receipt a few years ago and replaced them, but it seems the 'unused' supply terminates in a film cap and possibly resistor from memory - wish I could 'read' circuits better :(

* If anyone has an old QED Positron linear supply not in use, could they consider selling it to me - a few have come up but with DACs at increasingly higher prices - it's not THAT bloody good...)*

The other supply is a Beresford Caiman smps plus S-Booster (adding the S-Booster seemed to help a little so it stayed) and this has one conventional DC output.
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#7 Re: 5v power supplies

Post by pre65 »

Dave, these adjustable filament supply kits are a lot more "affordable" if you want a more DIY solution.

http://www.ebay.co.uk/itm/Tube-Amp-Fila ... 1438.l2649
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#8 Re: 5v power supplies

Post by ed »

andrew Ivimey wrote: Sat Nov 11, 2017 12:01 pm I have been surprised at how acceptable are switched mode (computer) power supplies are for IDH valves when I thought they would really spoil the beautiful simplicity that SE amps can give. (Success with vt4c, GM70, GU48 and vt62s)
I am minded to recall the fiasco with the coleman regs on the SV572s...after a succession of more powerful Tx and larger sinks and more ripple-capable caps the replacement smps supplies was a breath of fresh air.....so I'd say I was successful even with direct heating...but I did feed the smps into the coleman regs which is cheating slightly.
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#9 Re: 5v power supplies

Post by ed »

It's further occurred to me...

we went through a period of fiddling with smps for other purposes and if I recall Paul tried to serial connect some of those 48v ones but discovered that the negative output was tied to ground on sone supplies so as soon as 2 were connected there was a dead short.

I briefly resurrected the idea because I wanted to use 2 for a balanced supply to try with one of my mosfet amps. It didn't get far but the ebay supplies in perforated cases proved ok with floating outputs.

so, moving on....I'm wondering what the output looks like if you feed one of the 9v smps into the lt1083 board without its bridge....I wonder if the hf hash will be affected in any way. A 9v 5a smps is way cheaper than an equivalent toroid..

watch this space...I'm curious.
Last edited by ed on Sat Nov 11, 2017 12:59 pm, edited 1 time in total.
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#10 Re: 5v power supplies

Post by pre65 »

Ed, are the 572s still an ongoing project ?

One day I will try Coleman regs on the 833a, possibly fed by a SMPS PSU.
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#11 Re: 5v power supplies

Post by andrew Ivimey »

Oops I said ' indirect'and then talked exclusively about DH valves. Apologies - I'm fast losing what I might not have had much of before.

Amps for DH triodes!!!! says I.

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#12 Re: 5v power supplies

Post by ed »

pre65 wrote: Sat Nov 11, 2017 12:28 pm Dave, these adjustable filament supply kits are a lot more "affordable" if you want a more DIY solution.

http://www.ebay.co.uk/itm/Tube-Amp-Fila ... 1438.l2649
Philip, it doesn't look like you read the first post.....
pre65 wrote:Ed, are the 572s still an ongoing project ?
there is a breadboard somewhere gathering dust and fully fitted amp in purple chassis somewhere...but the answer is no...I have a box of NOS valves which will go on ebay in time for Christmas I hope. I'm thinking there might be people out there looking for replacements by now.

oh oh look: https://www.ebay.co.uk/sch/i.html?_from ... 2&_sacat=0

it's great when you find you have something you don't want and they're becoming unobtanium...I sold a quad of semisouth jfets last week and felt I'd done a good deed for a person in need..
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#13 Re: 5v power supplies

Post by pre65 »

[quote=ed post_id=152773 time=1510405562 user_id=27]

Philip, it doesn't look like you read the first post.....

[quote]

The ones I linked to are soft start, so slightly different.
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#14 Re: 5v power supplies

Post by IslandPink »

I've got two new Taylors upstairs. Don't think they are going to get used.
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#15 Re: 5v power supplies

Post by ed »

IslandPink wrote: Sat Nov 11, 2017 2:55 pm I've got two new Taylors upstairs. Don't think they are going to get used.
Taylors what? 211s?

oh hang on, I think I know what you meant...was it 572Bs?
Last edited by ed on Sat Nov 11, 2017 3:26 pm, edited 1 time in total.
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