Shunt Regulator Issues/ Questions

LucasAdamson · 03:25 PM

I bought a 500mA Class A (+/-)Shunt Reg Kit from eBay Hong Kong, for use with an RIAA circuit I built.

The RIAA requires 2x 27v DC and pulls about 20-30mA per channel.

I can't get the shunt reg to work as I'd hoped. I have a toroidal with 18v secondaries, as recommended for the kit, and when I wire it up I get 13.7v DC per side. When I use it bipolar, of course, I get 27.4vDC, very close to my desired voltage, but I also get some small voltage fluctuations, and I can't get more than 1 volt difference with the whole range of the pots, so I don't think that's ideal at all.

I'm not sure if it is regulating properly, as I had thought I would be able to tune the voltage with the pots, and I expected absolute voltage stability.

If anybody can advise me, I would be most grateful. Here's the schematic:

ikoflexer · 13th February 2010, 03:10 PM

If you have a 470R or 500R resistor, or two 1k in parallel, test your reg first with this passive load.

It's possible your reg is oscillating.

The schematic does not show.

LucasAdamson · 13th February 2010, 03:16 PM

OK Thanks. Image fixed now I think! I will test with a passive load.

ikoflexer · 03:31 PM

I still can't see the image. You could attach an image to the post if you don't want to rely on the site where the image is hosted.

You should probably describe the psu before the reg, bridge, CRC filter, what value C, R, and C, etc.

Edit: probably something wrong with the site that the diyaudio attachments uses.

dodo · 13th February 2010, 04:00 PM

Lucas
You need around 40-42V AC on the transformer secondaries , to get 27V DC with your shunt

ikoflexer · 13th February 2010, 04:18 PM

+1

Definitely you need higher voltage before the shunt.

richie00boy · 13th February 2010, 04:42 PM

Looking at the notes on the schematic it says that 18V in gives you 13.5V out, so it seems you have it working perfectly.

LucasAdamson · 13th February 2010, 05:58 PM

OK that makes sense. Thanks to you all.

I wasn't sure if I could get the full range of voltages out of an 18v transformer, as I've never built a shunt reg before.

I tried with the jumper leads in, and it seems I can go up to about 24v DC before the lights start flickering and then go out. Without the jumper leads I get 27v DC and no lights and it's impossible to tune the voltage by more than +/- 1volt.

I'll get a 40v traffo then. Many thanks, Lucas

LucasAdamson · 13th February 2010, 06:08 PM

If I have dual 18v secondaries, that are actually reading 20v on the DMM, can I wire them in series to get 40v? I have little experience of AC multiplying, so I am a bit cautious to try it as an experiment, and I also don't want to waste the transformer.

Thanks
Lucas

richie00boy · 13th February 2010, 08:19 PM

No, you will have to get another identical transformer if you want more voltage and don't want to modify the power input board into a half wave voltage doubler.

13th February 2010, 02:57 PM	#1
LucasAdamson diyAudio Member Join Date: Feb 2009	Shunt Regulator Issues/ Questions I bought a 500mA Class A (+/-)Shunt Reg Kit from eBay Hong Kong, for use with an RIAA circuit I built. The RIAA requires 2x 27v DC and pulls about 20-30mA per channel. I can't get the shunt reg to work as I'd hoped. I have a toroidal with 18v secondaries, as recommended for the kit, and when I wire it up I get 13.7v DC per side. When I use it bipolar, of course, I get 27.4vDC, very close to my desired voltage, but I also get some small voltage fluctuations, and I can't get more than 1 volt difference with the whole range of the pots, so I don't think that's ideal at all. I'm not sure if it is regulating properly, as I had thought I would be able to tune the voltage with the pots, and I expected absolute voltage stability. If anybody can advise me, I would be most grateful. Here's the schematic: __________________ Lucas Last edited by LucasAdamson; 13th February 2010 at 03:25 PM. Reason: To hopefully make the image show up!

13th February 2010, 03:16 PM	#3
LucasAdamson diyAudio Member Join Date: Feb 2009	OK Thanks. Image fixed now I think! I will test with a passive load. __________________ Lucas

13th February 2010, 03:25 PM	#4
ikoflexer diyAudio Moderator Join Date: May 2008 Location: Toronto	I still can't see the image. You could attach an image to the post if you don't want to rely on the site where the image is hosted. You should probably describe the psu before the reg, bridge, CRC filter, what value C, R, and C, etc. Edit: probably something wrong with the site that the diyaudio attachments uses. Last edited by ikoflexer; 13th February 2010 at 03:31 PM.

13th February 2010, 04:42 PM	#7
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Looking at the notes on the schematic it says that 18V in gives you 13.5V out, so it seems you have it working perfectly. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

13th February 2010, 05:58 PM	#8
LucasAdamson diyAudio Member Join Date: Feb 2009	OK that makes sense. Thanks to you all. I wasn't sure if I could get the full range of voltages out of an 18v transformer, as I've never built a shunt reg before. I tried with the jumper leads in, and it seems I can go up to about 24v DC before the lights start flickering and then go out. Without the jumper leads I get 27v DC and no lights and it's impossible to tune the voltage by more than +/- 1volt. I'll get a 40v traffo then. Many thanks, Lucas __________________ Lucas


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13th February 2010, 03:10 PM	#2
ikoflexer diyAudio Moderator Join Date: May 2008 Location: Toronto	If you have a 470R or 500R resistor, or two 1k in parallel, test your reg first with this passive load. It's possible your reg is oscillating. The schematic does not show.

13th February 2010, 04:00 PM	#5
dodo diyAudio Member Join Date: Dec 2004 Location: Bydgoszcz , small town in Poland	Lucas You need around 40-42V AC on the transformer secondaries , to get 27V DC with your shunt

13th February 2010, 04:18 PM	#6
ikoflexer diyAudio Moderator Join Date: May 2008 Location: Toronto	+1 Definitely you need higher voltage before the shunt.

13th February 2010, 06:08 PM	#9
LucasAdamson diyAudio Member Join Date: Feb 2009	If I have dual 18v secondaries, that are actually reading 20v on the DMM, can I wire them in series to get 40v? I have little experience of AC multiplying, so I am a bit cautious to try it as an experiment, and I also don't want to waste the transformer. Thanks Lucas __________________ Lucas

13th February 2010, 08:19 PM	#10
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	No, you will have to get another identical transformer if you want more voltage and don't want to modify the power input board into a half wave voltage doubler. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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