Big B+ voltage drop using diode rectifier. - Page 3

TheGimp · 13th November 2012, 04:09 PM

Get rid of the RC and just run a CLC. This will minimize your DC losses.

Use a large C2 value (330uF) and adjust the first cap value to set your B+.

tomchr · 13th November 2012, 08:23 PM

If PSUD won't dance for you, PSpice, LTspice or regular spice will.

Just place two inductors, L1 and L2 along with a 'K' spice directive: K1 L1 L2 0.999
This makes a transformer with a coupling coefficient between primary and secondary of 0.999 (99.9 %).

Include the DCR of all the components - including both the primary DCR and secondary DCR of the transformer.

~Tom

vingenz · 14th November 2012, 07:46 AM

It's better PSU then LTspice for transformers....i think

DavesNotHere · 02:53 PM

Quote:

Originally Posted by vingenz

Hello folks!
I've built an amp with 2x6l6gc P-P AB1 in the power section. There is problem that I can't solve: after full wave rectifier, B+ is 460VDC (372VAC on secondary) at idle, and 395VDC (350VAC on sec.) at full power.
Power transformer specs are: 250mA; 372-0-372VAC.
6l6 are biased (fixed bias) at 35mA each. Diodes are 1n5408 (1000v, 3A)
Well, i need more clean headroom and I can't understand why it's sagging too much . Suggestion? Tricks?
Thanks!

well the best thing is to increase regulation. about another 100Uf or so in the power supply would work nicely. but regardless of how stiff you make the power supply, it supposed to sag slightly without inducing power supply noise.

like this power supply : this is for 4 6l6's and 4 12ax7's the 2H choke was deleted in final design that mesa boogie uses.

Copyrighted schematic deleted by Moderation

DavesNotHere · 14th November 2012, 02:58 PM

If you really want to increase headroom in the amp. Make the B+ hotter like 480-500V to the plate. But this path should be left for the ones who are not afraid of pushing the envelope. And making sure they adjust the bias when upping the plate voltage.

DavesNotHere · 14th November 2012, 03:14 PM

and I encourage use of the series caps with bleed resistors as this safely discharges the circuit when the unit is turned off.

vingenz · 14th November 2012, 05:04 PM

Quote:

Originally Posted by DavesNotHere

If you really want to increase headroom in the amp. Make the B+ hotter like 480-500V to the plate. But this path should be left for the ones who are not afraid of pushing the envelope. And making sure they adjust the bias when upping the plate voltage.

How?

DavesNotHere · 15th November 2012, 01:10 AM

Sorry, moderator deleted my schematic. I'll have to make one instead of posting my originals ( even though they settled on a different design).

O.k. with using public domain knowledge, we'll walk you through the designing phase. So give me a few minutes as I will have to setup some sort of flicker accoun

Enzo · 15th November 2012, 01:21 AM

Several people suggested it, did you provide us the DC resistance of the power transformer windings? From your report, your AC voltage at the transformer was dropping considerably. If that voltage drops, then so will the resultinbg rectified and filtered DC. You can consider the resistance of the winding to be in series with it and causing voltage drop with current flow.

tomchr · 15th November 2012, 01:26 AM

You also need to consider the resistance of the primary. The total resistance that should be considered to be in series with the secondary winding is:

Rtotal = Rprimary*(Vsecondary/Vprimary)^2 + Rsecondary

~Tom

13th November 2012, 08:23 PM	#22
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	If PSUD won't dance for you, PSpice, LTspice or regular spice will. Just place two inductors, L1 and L2 along with a 'K' spice directive: K1 L1 L2 0.999 This makes a transformer with a coupling coefficient between primary and secondary of 0.999 (99.9 %). Include the DCR of all the components - including both the primary DCR and secondary DCR of the transformer. ~Tom __________________ 21st Century Maida Regulator, Universal Filament Regulator, 300B Driver PCBs, and more... Neurochrome : : Audio - http://www.neurochrome.com/audio - Engineering : : Done : : Right

15th November 2012, 01:26 AM	#30
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	You also need to consider the resistance of the primary. The total resistance that should be considered to be in series with the secondary winding is: Rtotal = Rprimary*(Vsecondary/Vprimary)^2 + Rsecondary ~Tom __________________ 21st Century Maida Regulator, Universal Filament Regulator, 300B Driver PCBs, and more... Neurochrome : : Audio - http://www.neurochrome.com/audio - Engineering : : Done : : Right

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
Toroid transformer and big voltage drop	Fredde79	Power Supplies	5	27th June 2012 07:56 AM
need to clear about voltage of diode rectifier for psu	mdm102	Power Supplies	2	17th July 2010 09:17 AM
Rectifier voltage drop question	jrenkin	Tubes / Valves	2	7th March 2010 08:39 PM
rectifier voltage drop	dsavitsk	Tubes / Valves	8	10th November 2006 05:52 AM
Voltage drop AZ1 = AZ11 = RGN1064 rectifier tube	Klimon	Tubes / Valves	2	29th June 2005 10:19 AM

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

13th November 2012, 04:09 PM	#21
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	Get rid of the RC and just run a CLC. This will minimize your DC losses. Use a large C2 value (330uF) and adjust the first cap value to set your B+.

14th November 2012, 07:46 AM	#23
vingenz diyAudio Member Join Date: Dec 2010	It's better PSU then LTspice for transformers....i think

14th November 2012, 02:58 PM	#25
DavesNotHere diyAudio Member Join Date: Jun 2011	If you really want to increase headroom in the amp. Make the B+ hotter like 480-500V to the plate. But this path should be left for the ones who are not afraid of pushing the envelope. And making sure they adjust the bias when upping the plate voltage.

14th November 2012, 03:14 PM	#26
DavesNotHere diyAudio Member Join Date: Jun 2011	and I encourage use of the series caps with bleed resistors as this safely discharges the circuit when the unit is turned off.

15th November 2012, 01:10 AM	#28
DavesNotHere diyAudio Member Join Date: Jun 2011	Sorry, moderator deleted my schematic. I'll have to make one instead of posting my originals ( even though they settled on a different design). O.k. with using public domain knowledge, we'll walk you through the designing phase. So give me a few minutes as I will have to setup some sort of flicker accoun

15th November 2012, 01:21 AM	#29
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Several people suggested it, did you provide us the DC resistance of the power transformer windings? From your report, your AC voltage at the transformer was dropping considerably. If that voltage drops, then so will the resultinbg rectified and filtered DC. You can consider the resistance of the winding to be in series with it and causing voltage drop with current flow.