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Old 10th April 2012, 10:24 AM   #3481
johnm is offline johnm  United Kingdom
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Quote:
Originally Posted by KatieandDad View Post
Funny I did suspect the PSU earlier

#3438

What kind of PSU are you using ?

Some will not like the high inrush current of C1.

Either try substituting C1 with a smaller say 1000uF cap or try the series resistor as I have mentioned.

C2 is not such a problem because is has R2 in series with it.


There probably isn't anything wrong with the PSU, that particular one just doesn't like a highly capacitive load.

Andy
Hi.

The psu is detailed a few posts above - standard LM317T implementation. Post 3474.

Well yesterday I tried it with the 100R in place of the 1R. No likey! This is without C1 in place too. I haven't tried a 1000uF cap there so could quickly solder one in and recheck.

Altered the R2 resistor by the LM317T to get 20V instead of 24V. Didn't improve anything. This thing just doesnt seem to like being loaded! This evening I'll try it with the different load resistors as you/Andrew have suggested.

Cheers,

John

Last edited by johnm; 10th April 2012 at 10:26 AM.
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Old 10th April 2012, 10:33 AM   #3482
AndrewT is offline AndrewT  Scotland
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Do you have the leadouts of the 317 correctly identified?
Do you have the decoupling caps fitted at the In & Out?
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Old 10th April 2012, 10:36 AM   #3483
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The LM317 MUST HAVE >3V across it to work.

Are you sure 1) The LM317 is OK and 2) The circuit is correct and 3) There is at least 24V at its input.

You must also have the 0.1uF at the input and 1uF at the output as close to the LM317 as practical.

With the huge C1 of the B1 you must also use the two protection diodes across the LM317, failure to use these will result in failure of the device. Failure may not occur immediately but is due to the Load (ie C1) trying to operate the LM317 in reverse.
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Old 10th April 2012, 10:42 AM   #3484
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Quote:
Originally Posted by KatieandDad View Post
The LM317 MUST HAVE >3V across it to work.

Are you sure 1) The LM317 is OK and 2) The circuit is correct and 3) There is at least 24V at its input.

You must also have the 0.1uF at the input and 1uF at the output as close to the LM317 as practical.

With the huge C1 of the B1 you must also use the two protection diodes across the LM317, failure to use these will result in failure of the device.
Andrew/Andy - Yes - Approx. 24V before the rectifiers. 29-30V after. It's just a textbook implementation of the simplest LM317T circuit, with a 1000uF/50 cap after the rectifiers, and a 1000uF cap after the reg. 1uF (in National's dastasheet it says either 0.1uF film cap or 1uF tantalum) tantalum caps at the input/output right next to the 317 legs. 10uF cap across R2, which sets the output voltage to reduce ripple further, again according to the datasheet. Pin outs all correct. I HAVEN'T added the diodes but I wouldn't have thought that would hurt as most leave them out anyways, and 6L6 (posted his link a page back) used the same PSU board and setup as myself with no problems. However he may have used a different brand of LM317T (mine's ST). I think the finger of blame must point towards the 317 really - it just doesn't seem to want to perform when connected to a load, but measures the correct voltage when unloaded. I have another PSU here I can use which I'm going to setup later, but the curious side of myself would love to know what's wrong with it all the same.

Universal Power Supply PCB

Last edited by johnm; 10th April 2012 at 10:46 AM.
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Old 10th April 2012, 10:47 AM   #3485
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Default Using Protection Diodes with LM317T

The National Semiconductor Datasheet says you must use the diodes.

Especially as C1 is 15000uF.

It'll be interesting to see if it works with a resistive load.
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Old 10th April 2012, 11:12 AM   #3486
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Quote:
Originally Posted by KatieandDad View Post
The National Semiconductor Datasheet says you must use the diodes.

Especially as C1 is 15000uF.

It'll be interesting to see if it works with a resistive load.
True, but I've seen others using high values without the diodes to no ill effect (I believe Naim use a huge 15000uF / 63V cap after with the LM317T in their Hicap too). Plus in my build I would have thought the 1000uF directly after the reg would have eased the inrush from the 10,000uF (not 15,000uF in my case) C1 on my B1?

I've also tried the PSU without C1 and it still won't work.

I'll see what happens with a resistive load later today (fingers crossed) and perhaps that will shed some light on it.
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Old 10th April 2012, 11:32 AM   #3487
AndrewT is offline AndrewT  Scotland
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Just because some builders ignore manufacturer's recommendations, is no reason for you to do so.
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Old 10th April 2012, 06:14 PM   #3488
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Noted Andrew - it was advice I actually read on here aeons back, but it obviously has resulted in a damaged LM317T. Lesson learned.

Have subbed in another PSU I had (for a Creek phono stage) and it's working beautifully, and sounding rather nice too! Very pleased indeed

Busy for the next few days but going to build another LM317T PSU - have ordered some 1N4002 diodes to play it safe this time.

Back to some music listening! Thank you for all the help today chaps.

- John
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Old 10th April 2012, 06:18 PM   #3489
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When you get around to it, try a Salas Shunt Reg you will be amazed at the difference that that will make.

You can buy the DCB1 board at DIYAUDIO.com and just use the Regulator end of it.
Its not expensive and really makes a big difference.

I made my own PCB, its that easy. The Europe shop is out of stock but the US shop will supply at about 18.00 (incl P&P).

I did build the DCB1 but stayed with my B1 in the end. I had the spare DCB1 PCB but that was quickly snapped up when I offered it for sale with all the components.

You can view the result at Post #3405 in this thread, together with the LM317 version in the following Post #3406.

Last edited by KatieandDad; 10th April 2012 at 06:23 PM.
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Old 10th April 2012, 06:29 PM   #3490
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Sound interesting - I actually have an unused DCB1 'Mezmerize' board but would rather have something a little smaller, especially if I'm only going to use the shunt reg. part of it anyways. Do you have the URL of the UK shop perchance Andy? Cheers.

Will check out that post now.

Quote:
Originally Posted by KatieandDad View Post
When you get around to it, try a Salas Shunt Reg you will be amazed at the difference that that will make.

You can buy the DCB1 board at DIYAUDIO.com and just use the Regulator end of it.
Its not expensive and really makes a big difference.

I made my own PCB, its that easy. The Europe shop is out of stock but the US shop will supply at about 18.00 (incl P&P).

I did build the DCB1 but stayed with my B1 in the end. I had the spare DCB1 PCB but that was quickly snapped up when I offered it for sale with all the components.

You can view the result at Post #3405 in this thread, together with the LM317 version in the following Post #3406.
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