The simplistic Salas low voltage shunt regulator - Page 515 - diyAudio
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Old 12th July 2012, 08:42 PM   #5141
Salas is offline Salas  Greece
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Looks like oscillation to me. What happens if you will stick 100uF directly across the sense lines?
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Old 12th July 2012, 09:15 PM   #5142
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Nothing really.... still same noise/oscillation

- Please note that my regs share a groundplane with their load (tda1541a). The S0 and F0 are directly connected to the gnd plane. I don't think this should create these oscillations, but may be worth mentioning.

- I am using a 220uF nichicon for C201, and a 3.3uF Wima for C204

- C203 and C202 are unused
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Old 12th July 2012, 09:21 PM   #5143
Salas is offline Salas  Greece
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If you use 1R in series at the +V receive node?
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Old 12th July 2012, 09:36 PM   #5144
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You mean at the -15v output? Or at the -25v input?
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Old 12th July 2012, 09:41 PM   #5145
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Sorry not (+) in this case, at the (-)V node that your application feeds. Where the -F, -S go.
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Old 13th July 2012, 06:31 AM   #5146
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I put a 1R0 in series with the output, this reduces the amplitude of the oscillation (to about 20mVpp when loaded)....
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Old 13th July 2012, 07:00 AM   #5147
Salas is offline Salas  Greece
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Are there small value film or ceramic caps across the (-) rail on your application circuit?
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Old 13th July 2012, 07:26 AM   #5148
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Can someone please confirm to me that the following applies to the Salas 1.2R circuit diagrams in post 3200 on page 320.

Q8 (2n5457) gate and drain are tied and connected to the collector of Q7 (BC550C) in the positive versions. In the negarive versions the gate and drain of Q8 are still tied, but this time connected to the negative output.

There is no Drain labelled in the negative circuits and I don't want to get the orientation (or my PCB) incorrect.
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Old 13th July 2012, 07:30 AM   #5149
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Hi Salas,
Not exactly sure what you mean, but these are the caps I use:

- I am using a 220uF nichicon for C201, and a 3.3uF Wima for C204
- I am using a 1uF decoupling cap right at the load <-- I guess that's what you mean, it's an acrylic film cap
- C203 and C202 are unused
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Old 13th July 2012, 07:53 AM   #5150
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You did not forget R207 also I suppose. Can you take that 1uF out and check the scope again?
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