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).
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).
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
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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I like the circuit very much but those complementary matched J-fets......hard to come by these days. I'd probably have to change the Zener voltage reference with lower noise CCS/resistor.
you're definitely right about the jfet pain, cbs240
for this circuit, i would cheat and make 2 positive regs with separate transformer windings, separate rectifiers and caps.
mlloyd1
for this circuit, i would cheat and make 2 positive regs with separate transformer windings, separate rectifiers and caps.
mlloyd1
The low gm cascodes Q7, 8, 9 & 10 are still available in P & N channel.
The high gm Q6a & Q6b will be the difficult to source Pchannel.
Even the dual Nchannel high gm (Q5a&b) will be rare and probably expensive.
The high gm Q6a & Q6b will be the difficult to source Pchannel.
Even the dual Nchannel high gm (Q5a&b) will be rare and probably expensive.
will at least ease the component sourcing.
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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
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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Done, cap 8 is dead. I replaced the 470uF 16V to 470uF 35V and look forward that it can sustain longer life.
I know that some forum members built Borbely shunt regulators. On some high res.regulators pictures R21 and R22 are 1K but on some are 10K. I wish to know original values. Thank you in advance.
Thank you very much. Unlike Borbely series all-fet regulators, R17 and R 18 are 1K ( 10К in series ).
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
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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I am sure that D5 and D6 are 1ma J-505 CCD in TO 92 case. E-202 is 2ma and is not available in to92.Take look at the picture in the second post.
I am only informing you about some mods.
The TO 92 in the post 15 picture is the D1, D2 - E 102 / 2N5486 cascode
The TO 92 in the post 15 picture is the D1, D2 - E 102 / 2N5486 cascode
Hi ticknpop. It's seems difficult to pull together a Boberly SS.
Any opinion on the Partial kit or PCB from Jims Audio in Hong Kong?
Best rgds,
Denis
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.
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.