SSLV1.1 builds & fairytales - Page 205

Billc · 15th December 2012, 04:14 PM

I do. I have oscillations! I should have checked that first.
Lowering R7 makes them worse. The output cap changed to 100uF improves things but only loading the supply down so that 100 mA is shunted by the transistor makes it go away... and then the voltage is stable. I varied the output cap from 47uF to 1800uF and found 1800 to be much worse. 100uF is best.
Here are my choices as I see them:
I can now run the CCS at 500 mA, let my circuit draw 100 mA and add a resistor to draw 300 mA. Then the shunt transistor will dump 100 mA. Or, lower the CCS to 200 mA.
The other option is to build another positive regulator and use it for the negative supply by connecting the positive output to ground. I have all isolated supplies so that will not be a problem.
What do you recommend?

Salas · 15th December 2012, 05:08 PM

What kind of caps are installed on rails at load side? Since its oscillations with the load, maybe more R value in R7 for damping, or 0.1R in series with the load to buffer it.

Billc · 15th December 2012, 06:40 PM

The oscillations occur with or without the load. I am using just a resistor to simulate the load. My actual circuit that will be the load is currently being built.
The variable seems to be the amount of current through the shunt transistor.
I do not think that buffering the load will help but I will alter the value of R7 and see how that works.
It may be that I need to use all positive regulators to run the amount of current that I want to. That will be a lot more work to do because my heatsink will need to be drilled and tapped for the positive circuit board.
Thanks for your help.
Bill

Salas · 15th December 2012, 06:45 PM

You talked about varying load and I thought something real. But you did not mean dynamically so. Just changing consumption. Got it. How is it at 200mA spare?

Billc · 15th December 2012, 08:31 PM

Sorry for any confusion. At 200 mA via the shunt transistor it oscillates. I have been checking out my positive regulator with the oscilloscope and it is rock stable at any load.
At this point, I plan to build more positive regulators and use them for the negative power supply. Do you think that there is a problem with that? My transformers and diodes are all separate for the positive and negative side.
Bill

Salas · 15th December 2012, 08:49 PM

I don't think its that different to the positive. I will have a closer look with the currents you refer and let you know more.

Salas · 15th December 2012, 08:50 PM

P.S. Are your builds p2p or on PCBs?

Billc · 15th December 2012, 08:57 PM

I am using the circuit boards from tea bag.
One of the FET's has g shorted to d instead of s.
Changing that did not make a difference.
Bill

Salas · 15th December 2012, 09:20 PM

Try 100 Ohm gate stoppers on the 610s.

Salas · 17th December 2012, 12:54 PM

Quote:

Originally Posted by samoloko

I am looking to buy some films for Vref and Vout
I am struggling between Auricap and Sonicap
would you recommend which can be better to power line aplication - UGS V3
of course you can recommend some other brand
I would like to use Obbligato Gold but It Is so long

There was a builder reporting very favorably for Sonicap there.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Frugel-Horn Mk3 Builds & Build Questions	planet10	Full Range	814	10th May 2013 04:20 PM
Call for MyRef-C Builds & Photos	bcmbob	Chipamp	0	1st October 2010 10:57 PM
"Magga Amp Workshop" builds again (Simple 45 Project)	Niila	Tubes / Valves	1	3rd February 2009 08:51 PM
so who here builds amps	amp builder jb	Tubes / Valves	29	15th July 2005 08:23 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

15th December 2012, 04:14 PM	#2041
Billc diyAudio Member Join Date: Jun 2002 Location: CT	I do. I have oscillations! I should have checked that first. Lowering R7 makes them worse. The output cap changed to 100uF improves things but only loading the supply down so that 100 mA is shunted by the transistor makes it go away... and then the voltage is stable. I varied the output cap from 47uF to 1800uF and found 1800 to be much worse. 100uF is best. Here are my choices as I see them: I can now run the CCS at 500 mA, let my circuit draw 100 mA and add a resistor to draw 300 mA. Then the shunt transistor will dump 100 mA. Or, lower the CCS to 200 mA. The other option is to build another positive regulator and use it for the negative supply by connecting the positive output to ground. I have all isolated supplies so that will not be a problem. What do you recommend?

15th December 2012, 05:08 PM	#2042
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	What kind of caps are installed on rails at load side? Since its oscillations with the load, maybe more R value in R7 for damping, or 0.1R in series with the load to buffer it.

15th December 2012, 06:40 PM	#2043
Billc diyAudio Member Join Date: Jun 2002 Location: CT	The oscillations occur with or without the load. I am using just a resistor to simulate the load. My actual circuit that will be the load is currently being built. The variable seems to be the amount of current through the shunt transistor. I do not think that buffering the load will help but I will alter the value of R7 and see how that works. It may be that I need to use all positive regulators to run the amount of current that I want to. That will be a lot more work to do because my heatsink will need to be drilled and tapped for the positive circuit board. Thanks for your help. Bill

15th December 2012, 06:45 PM	#2044
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	You talked about varying load and I thought something real. But you did not mean dynamically so. Just changing consumption. Got it. How is it at 200mA spare?

15th December 2012, 08:31 PM	#2045
Billc diyAudio Member Join Date: Jun 2002 Location: CT	Sorry for any confusion. At 200 mA via the shunt transistor it oscillates. I have been checking out my positive regulator with the oscilloscope and it is rock stable at any load. At this point, I plan to build more positive regulators and use them for the negative power supply. Do you think that there is a problem with that? My transformers and diodes are all separate for the positive and negative side. Bill

15th December 2012, 08:49 PM	#2046
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	I don't think its that different to the positive. I will have a closer look with the currents you refer and let you know more.

15th December 2012, 08:50 PM	#2047
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	P.S. Are your builds p2p or on PCBs?

15th December 2012, 08:57 PM	#2048
Billc diyAudio Member Join Date: Jun 2002 Location: CT	I am using the circuit boards from tea bag. One of the FET's has g shorted to d instead of s. Changing that did not make a difference. Bill

15th December 2012, 09:20 PM	#2049
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Try 100 Ohm gate stoppers on the 610s.