Erno Borbely super shunt regulator

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I purchased 320 Phono and EB906/255 super shunt regulator from Erno Borbely a few years ago. Last year, I changed the regulator to Dexa and put aside the 255. Recently, I wish to use it again for another diy kit but I could not find the 255 circuit diagram again. The new diy kit uses only 20mA that the current setting at 240mA would make the power transistor red hot.

I remember there is a formula to calculate the resistor value but I can't find it. Can anyone give me the formula, or the value for 30mA or Erno's email addres (I wonder if he still reply email today).
 
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You can find a schematic for the EB906/255 on the old Borbely Audio website. That website is no longer online but you can find it either in the web archive or you can download a copy of the website from Zenmod's website Zen Mod Blog | Buddha is everywhere …….

Once you find a copy of the old Borbely website, look under the "Special Articles" section for the article by Are Waagb on Shunt Regulators.

Resistors R1 and R2 set the total current available to the load and to the shunts. The total current is roughly -.6v/R1. So if you are sourcing about 240ma then R1 should be around 2.5 ohms. Raising R1 to 15 ohms would set the total current available to 40ma which should be fine for a 20ma load.
---Gary
 

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Hi GaryB,

I just noticed that one of the Q4 is getting quite hot in the circuit while all others are only mildly warm. I measured the input voltage and they are the same among all inputs. What could be the cause of this?

Conditions are:
Input 28.5V, output 24V, current 240mA

Sunny
 
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I purchased 320 Phono and EB906/255 super shunt regulator from Erno Borbely a few years ago. Last year, I changed the regulator to Dexa and put aside the 255. Recently, I wish to use it again for another diy kit but I could not find the 255 circuit diagram again. The new diy kit uses only 20mA that the current setting at 240mA would make the power transistor red hot.

I remember there is a formula to calculate the resistor value but I can't find it. Can anyone give me the formula, or the value for 30mA or Erno's email addres (I wonder if he still reply email today).

What are the values of R21 and R22?
 
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I was told the D5 D6 were replaced with 1k5 later on.
I think constant current source is better, but I think the E 202 had too much variation in value to work some times.

You can cascode D1 , D2 with 2n5486 - higher impedance greater psrr

You can also change LM 329 to 4 green /red leds (not blue, too noisey)
Lower noise

The Blackgate FK and N caps I can’t find more, maybe new ones this year from Audio Note
 

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Opps, never revisted the thread to answer you Dennis.
I built 12 Borbely shunts for me and another 8 for friends.
Jim’s audio board works OK.
I can’t say if his parts are real, I think I bought a few semiconductors from him over the years with no problems, but I don’t know whats in this kit. I have a few spare parts left so let me know what you need.
 
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