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Old 8th February 2013, 07:49 PM   #501
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I also never had a single problem from the regulators. My build in two years ols.

D.
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Old 8th February 2013, 08:36 PM   #502
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Hi Owen. The capacitance is in fact less than specified in the circuit - Pana FC 1000/63, raw dc is about 53v. Not sure if the bypasses might have anything to do with it but they are as specified.

My guess is that the short circuit protection in the regulators kicks in while trying to charge the output caps and the particular make of regulators may be to blame. The ones i use say OnSemi and were most probably bought in Joburg, so there is a decent chance they are fake.

Nikola, certainly keen to find out what you did. Already ordered higher spec regulators...
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Old 8th February 2013, 08:46 PM   #503
qusp is offline qusp  Australia
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never had any issue with lock-ups, i'm running the LT 1085/1033 though
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Old 8th February 2013, 09:22 PM   #504
opc is offline opc  Canada
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Quote:
Originally Posted by analog_sa View Post
Hi Owen. The capacitance is in fact less than specified in the circuit - Pana FC 1000/63, raw dc is about 53v. Not sure if the bypasses might have anything to do with it but they are as specified.

My guess is that the short circuit protection in the regulators kicks in while trying to charge the output caps and the particular make of regulators may be to blame. The ones i use say OnSemi and were most probably bought in Joburg, so there is a decent chance they are fake.

Nikola, certainly keen to find out what you did. Already ordered higher spec regulators...
Based on the above I would hazard a guess that you either have fakes, or possibly just poor specs on the on-semi parts.

I always use the Fairchild 317/337 parts, but I'm not sure what's available where you are.

Both yourself and Nikola are from the same area, so maybe it was a bad batch, or fakes...

Anyone else seen this issue?

Pick up either the Fairchild parts, or the LT parts as suggested and see it that fixes the problem.

Cheers,
Owen
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Old 8th February 2013, 09:29 PM   #505
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Both yourself and Nikola are from the same area, so maybe it was a bad batch, or fakes...
That certainly makes excellent sense but i am inclined to think i brought mine from South Africa... probably even more likely to be fakes.

Just took off the Lundahl transformers and am back to single phase cap coupled. There is simply no comparison, never thought the amorphous Lundahls were so bad.
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Old 8th February 2013, 09:32 PM   #506
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Owen

In case i wasn't clear i think your I/V stage absolutely rocks, even if only half of it is in use at present
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Old 8th February 2013, 10:48 PM   #507
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Originally Posted by analog_sa View Post
That certainly makes excellent sense but i am inclined to think i brought mine from South Africa... probably even more likely to be fakes.

Just took off the Lundahl transformers and am back to single phase cap coupled. There is simply no comparison, never thought the amorphous Lundahls were so bad.
Normally, Lundahls transformer require long run-in time, more than 300 hours.
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Old 10th February 2013, 07:48 AM   #508
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Hi Owen,

- What is the input DC voltage? - 50V
- What is the output DC voltage? - 43V
- What is the input capacitance? - 1000 uF/100V Nichicon FW bought from digikey
UFW2A102MHD Nichicon | 493-3185-ND | DigiKey
- What is the output capacitance? - same as the input ones
- What is the bypass capacitance? - I suppose it is the adj. terminal capacitance - 10uF.
- What 317/337 brand / type are you using? - pictures attached.

I tried to cope with the problem with reversed schottky diodes at the regulator outputs. Did not solve the latch-up completely.
Tried to use tracking (see sch.), but decided I'd better not, because of cross noise/hum issues.
Solved the problem with thermistors at secondary side of the transformer windings. Before rectifier diodes.

It's funny that the only guys having problems are from Bulgaria, those evil bastards The only thing that I can think of is that the LMs are fakes and that caused the problems, everything else was bought from digikey, I am not sure where the LMs were sourced from... Anyway, it's been working for almost a year without a problem and sounds wonderful, that is why I've never mentioned it, it was clear that it had to be taken care of in one way or the other.
Attached Images
File Type: jpg IMAG1089.jpg (708.1 KB, 322 views)
File Type: jpg IMAG1090.jpg (644.3 KB, 307 views)
File Type: jpg tracking.jpg (31.7 KB, 287 views)

Last edited by Nikola Krivorov; 10th February 2013 at 07:55 AM.
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Old 10th February 2013, 09:20 AM   #509
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Originally Posted by bigpandahk View Post
Normally, Lundahls transformer require long run-in time, more than 300 hours.
This particular pair has been running for even longer. To be honest my hearing is probably not so sensitive as i hear very insignificant change in transformer sound over time.
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Old 10th February 2013, 09:48 AM   #510
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Originally Posted by Nikola Krivorov View Post
The only thing that I can think of is that the LMs are fakes and that caused the problems,

My LMs look nothing like yours, as mentioned previously they are marked OnSemi. Last night hooked a variac and reduced the incoming mains voltage by about 10% - all latch-up problems seem to have gone away.

Somewhere in the back of my mind i have some strange recollection that not all 317s work the same as far as the protection goes. Some may limit the output current to the max allowed, while others shut down and only a hard reset will get them going again. Not sure if this has any basis in reality but i think it's not the first time i encounter this problem.

A low ESR capacitor, coupled with a low DCR mains transformer may easily exceed 1.5A of charging current during start-up. Why the variac fixes this i am not quite sure, nor am i sure if the high input voltage has any effect on the protection circuit.
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