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Salas SSLV1.3 UltraBiB shunt regulator
Salas SSLV1.3 UltraBiB shunt regulator
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Old 13th June 2019, 07:59 AM   #1541
Salas is online now Salas  Greece
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Salas SSLV1.3 UltraBiB shunt regulator
Quote:
Originally Posted by nano35 View Post
Hi,
what is the most possible cause of UltraBiB reg output voltage drop?
Without load, the reg output voltages are normal: +/-15V.

Then, I connected UltraBiB regs to an amp: needs positive and negative 15V.
The UltraBiB reg voltages dropped to +11V and -9V.

Strange.....

Most likely reason (when not faulty) is less CC setting than the load's current demand. That brings current limiting and output voltage drop. A form of protection.

A way to confirm is replacing with a known lighter load. A dummy load test resistor of 150 Ohm will require 100mA at 15V for example. When the CC setting is 200-250mA as recommended, there is no reason for the output voltage to drop with that test load. Else, there is likely a fault in the PSU's build or a bad part.

Most unusual will be an oscillatory situation between the PSU and some circuit as load. An oscilloscope can clearly show that and some rearrangement can be found.
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Old 13th June 2019, 09:35 AM   #1542
nano35 is offline nano35  Hong Kong
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Thank you so much Salas. I will do the tests.
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Old 14th June 2019, 05:42 AM   #1543
nano35 is offline nano35  Hong Kong
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Hi Salas,

I put a pair of 180Ω/1W resistors at Regs' output for testing. It was fine.
The output voltages remain +/-15V.

I am actually experimenting on powering my Whammy headphone amp with different PSU types, including UltraBiB and an opamp based regulator. Input voltage is set at +/-15V.

For R1 value, I took the stock output bias 60mA (with 10Ω resistors I am using) and add 100mA; that's how I got the 3.3Ω resistors for R1.

What should I pick for R1 if 3.3Ω is not adequate enough? 2Ω or lower?
Thank you!
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Old 14th June 2019, 09:32 AM   #1544
Salas is online now Salas  Greece
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Salas SSLV1.3 UltraBiB shunt regulator
It's either you will go searching by chance to meet that Whammy build's consumption with R1 substitutions, or you will measure it with a DMM set as A-meter so to plan accordingly.

In the first case 2Ω is next logical step.

It's not only about an amplifier's bias current. Think about its subsystems and its max output on worst load possible. Also possible fault if it's a first time power on test.
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Old 14th June 2019, 10:04 AM   #1545
nano35 is offline nano35  Hong Kong
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Great! thanks Salas for the help.
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