The simplistic Salas low voltage shunt regulator - Page 513 - diyAudio
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Old 9th July 2012, 07:01 PM   #5121
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First things first, I have found heavy oscillations in the preregulator which preceeds the Salas reg. (darlington capacitance multiplier)
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Old 9th July 2012, 09:23 PM   #5122
Salas is offline Salas  Greece
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Skip that, no real need.
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Old 9th July 2012, 10:10 PM   #5123
Salas is offline Salas  Greece
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Quote:
Originally Posted by studiostevus View Post
Plain BC547's...

I just noticed that on both my negative regs, the bc547's get really hot
You need PNP in the negative, that one you use is NPN.
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Old 10th July 2012, 09:04 PM   #5124
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Sorry i used a bc557.

In the meantime i have fixed the prereg, and replaced the bc557 with a branded bc560. The intermittent flickering stopped (for the moment, i havent done an endurance test). The bc560, like the bc550 yesterday gets verrrry hot... I burnt my finger on it!

Does the bc560 usually require a heatsink, o r do you think there is an error? Didnt see anything funny on the scope now....
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Old 10th July 2012, 10:47 PM   #5125
Salas is offline Salas  Greece
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All they can have across is the Vo-shunt Mosfet's VGS. All they can have through is the U$23 IDSS. Thus I would expect ~10mW in your (-)15V one if normal. They still cope without mini-sinks near 50V in some of my phono builds but with 2-3mA IDSS cascoding Jfets (V1.2R). What are your shunt Mosfets there?
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Old 11th July 2012, 03:49 AM   #5126
agussug is offline agussug  Indonesia
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Quote:
Originally Posted by studiostevus View Post
Sorry i used a bc557.

In the meantime i have fixed the prereg, and replaced the bc557 with a branded bc560. The intermittent flickering stopped (for the moment, i havent done an endurance test). The bc560, like the bc550 yesterday gets verrrry hot... I burnt my finger on it!

Does the bc560 usually require a heatsink, o r do you think there is an error? Didnt see anything funny on the scope now....
Mine is V1.0, BC560 in my circuit is not hot. Vin is -21V, Vout -11.4V, Iout about 30 - 40 mA.
I don't know if this situatioin apply to your circuit as yours is BiB.
After the cicuit is on, Vout is -12.04, after about 5 minutes, it settle to -11.4V and never drifts again even after used more than 2 hours.

Regards
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Old 11th July 2012, 08:47 AM   #5127
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Quote:
Originally Posted by Salas View Post
All they can have across is the Vo-shunt Mosfet's VGS. All they can have through is the U$23 IDSS. Thus I would expect ~10mW in your (-)15V one if normal. They still cope without mini-sinks near 50V in some of my phono builds but with 2-3mA IDSS cascoding Jfets (V1.2R). What are your shunt Mosfets there?
MOSFET = IRF620

But... I am using 2SK170 as U$23! That's then probably where the problem is, isn't it? (is K170 typically higher IDSS than K117?)

If I replace the U$23, I would probably have to replace the K170 on the other side as well, no? (sorry I don't fully understand the function of that one).
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Old 11th July 2012, 08:56 AM   #5128
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Measure IRF620's VGS. Probe at U$23's to BC collector junction on the scope. What are the results? (BIB- is for 560C, 2SK117, IRF530 other combinations I can not predict).
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Old 11th July 2012, 09:04 AM   #5129
jambul is offline jambul  Belgium
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Dear Salas,

so the cap multiplier as prereg is useles/waste?

regards
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Old 11th July 2012, 09:12 AM   #5130
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The multiplier is a filter, does not regulate anything. No matter how much harmonic noise it will cut, the intrinsic wide band noise of the regulator's output will be the same. The regulator itself has a CCS with enough rejection ratio for ripple and its error amp to regulate, not to find significant benefit beyond gross input ripple levels. The filters are good for eating noise to absolute minimum when situated last in the chain before very sensitive high gain low signal no PSRR circuits. Their Achilles' heel is high impedance.
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