The simplistic Salas low voltage shunt regulator - Page 385 - diyAudio
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Old 1st April 2011, 01:54 PM   #3841
AndrewT is offline AndrewT  Scotland
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When do we insist that the Forum prevents 1020kB being downloaded from a remote server.
Pbase is too slow!
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Old 1st April 2011, 03:44 PM   #3842
canvas is offline canvas  Taiwan
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Quote:
Originally Posted by Salas View Post
Make a schematic by following your build's connections, see if there is a mistake in the execution or in some value. Show it here too. Does it have a dummy load when measuring? Are the 2 Mosfets fully isolated? Gate stoppers really near to gates? R8 1K? 1.2R is easy to tame, lets debug. Nice and clean work by the way.

Salas,

I put a 100R 3W as the dummy load. Mosfets are fully isolated. Gate stopper is not far from the gate. (1~2cm maybe?) R8=1K. I even switched the 9540 to 9610. After all, it still oscillates! I will try to trace the connections and draw it on a paper. The circuit is based on this schema. I modified the layout, so that the space and length for 4.7uf pp is sufficient.


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Last edited by canvas; 1st April 2011 at 03:50 PM.
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Old 1st April 2011, 05:10 PM   #3843
Salas is offline Salas  Greece
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Use the proper film cap C3, we don't know the ESR of a 4u7 BG lytic there. Use 9530,40 Q5 not 9610. But 9610 Q1! Lower R6 to 2K2 when 5V app. Check around the Jfet cascode and the BJT driver Q6 for the output Mosfet that there are no pin reversals and connections are right.
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Old 1st April 2011, 05:25 PM   #3844
AndrewT is offline AndrewT  Scotland
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Salas,
have you built a 5V regulator with q9 drawing ~160uA.
I have not, but I can't see the circuit as posted working correctly.
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Old 1st April 2011, 06:06 PM   #3845
Salas is offline Salas  Greece
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I have built the circuits I posted in #3200. The 5V with 27K are only reported by others here. He can go 10K and see. I mostly suspect the 4.3K and the CCS practical implementation, the 4u7 lytic's ESR also (C3). IF Q1 is indeed 9540 as depicted in above schema, is highly suspect.
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Old 2nd April 2011, 03:39 AM   #3846
canvas is offline canvas  Taiwan
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Hi Salas,

As for C3, I got 3.3uf Silmic 2, 4.7u OSCON and 4.7u BG N. The largest film I got is Rifa 450 1uf. Q1 is surely 9610 as you mentioned in other post. Last time, I tried 9540 for Q1 and it did not help. Follow your instruction, I tried 2.15K for R6(2*4.3k), vout becomes 3.85v oscillated and it can't be ajusted through VR!
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Old 2nd April 2011, 06:50 AM   #3847
Salas is offline Salas  Greece
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Weird, orelli's works with 1k8 R6. Must be something layout practical that bugs. Q6 should be intimate to Q5. Is it? Try to have their +V pins junction physical point the same. Is that horizontal resistor the R5, and goes all the way long pins from Q6 to Q5, and R6 isn't at the emitter junction as it should but comes later, the one light blue with yellow band? Check and fix such details. Use the Rifa also.
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Old 2nd April 2011, 09:51 PM   #3848
orelli is offline orelli  Italy
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hi Salas, I agreed with you , the layout of Canvas maybe is the cause of oscillations. Too long are the resistor's leads; they can works like antennas and suck the very hi frequencies. I realized the 5V version 1.2r working on the layout that you posted on this thread. Sorry, I don't remember the nr post, but it was a dual type(v+ and V-), and it was black with the rails orange, and realized by a friend of you.It was a 1.2 version,not a revisited one.I hope you understood.
I've modified the 1.2 in 1.2r (very simple job) and realized the CCT on a 2mm teflon board. The cct like exactly the one you posted. I used Mundorf MCap for the 4.7 value,
IRF 8A fred diodes and Pan FC in the raw supply. I used cheap film resistors.
And finally the sound! I'm VERY satisfied! The sssv1.2r substitute a TPA Placid shunt reg to feed a Buffalo II with own Trident shunt regs mounted on it. The first 2 things I noted
was dynamic and soundstage. These are a lot better than a previous reg, and remain the same also at very loud volume. After 20 or so hours, the CCT revails also the fine nuances that aren't so apparent at first listening.
I don't check about oscillations,cause, sincerly I don't care(and I've not a oscope).

Thanks again
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Old 2nd April 2011, 10:13 PM   #3849
Salas is offline Salas  Greece
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It would not play without strong stability problems if it was oscillating, especially if feeding analogue there is wide spread harmonic noise all over an FFT I.e. strong hum & buzz masking noise on the speakers, inescapable & equivalent to no go. Nice that you like it subjectively also. Congrats. Maybe you can post front and back pictures that may help others for constructing if you got a camera or a capable cellphone. Regards.
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Old 2nd April 2011, 10:16 PM   #3850
RCruz is offline RCruz  Switzerland
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Hi Canvas

Make it tighter... I had the same issues and solved everything by making the smallest possible connections.

Can you draw your layout in a paper so we can follow the gnd connections too ?
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