420vdc supply for a tube amp - Page 2

12E1 · 27th May 2012, 10:23 AM

Quote:

Originally Posted by pergo

In my amps there are always 3 DC-DC converter (12-->+-40V, +40V --> 300V, +40V ---> 6.3V)

On Ebay you find the Nixie power supply, large as a dollar-coin, from 12V up to 450V@10mA or 225V@20mA.

I mean no disrespect to anyone here, but both of these scenarios are a long way from the power supply that the OP was asking about. The fact that the OP was asking the questions that they were suggests that they might not have a full understanding of the implications. The types of DC-DC converter that you are describing are a world apart from those found in the power supply under consideration.

Kay Pirinha · 27th May 2012, 10:52 AM

Yes, it's the rectified supply rail after an active PFC - thus not isolated from the mains! In an active PFC the rectified DC voltage has to be higher than the peak AC input voltage (AC voltage times square root 2), otherwise the PFC regulation wouldn't work.

Best regards!

flatheadmurre · 27th May 2012, 10:58 AM

Rewind the transformers in the smps or use voltage doubling.

After that you still have noise issues to deal with.

Tried a few mods of computer PSU´s but still like the linear approach.

srinath · 27th May 2012, 12:08 PM

I will check for continuity but I should tell you there is a transformer and maybe 6 or 8 transistors in that 1/2 of the psu before the 420v output. From here on to the output there is 2 more transformers and 10-12 transistors. I will check for continuity though.
I should put a few pics up too I guess.
Cool.
Srinath.

srinath · 27th May 2012, 11:50 PM

Its got continuity, somewhere around 1,800,000 ohms. Oddly that is the resistance from either of the 2 outputs to the 2 + and - input prongs. So lets call it prong 1, 1 to + ac input = 1.8m ohm, prong 1 to - ac input = 1.8m and prong 2 to + ac is 1.8m, as is prong 2 to -.

So what does it mean.

I will post a pic in a bit.

Cool.
Srinath.

srinath · 28th May 2012, 02:11 PM

The power supply pics are attached.

420vdc across that white 2 pin plug. 42vdc out from the plug in the back - and there is about 1.8m ohm from there to the 2 pin plug as well. I cant measure anything over 2m ohm and I read over that or open from the full on output pin to the ac input -

Cool.
Srinath.

astouffer · 28th May 2012, 03:49 PM

Doesn't look isolated.

srinath · 28th May 2012, 08:49 PM

I measure continuity between the B+ and B- prongs on other amps too, my onkyo tx-ds-555 and a few others read less than 1.8 m.
Cool.
Srinath.

astouffer · 28th May 2012, 08:58 PM

You'll read that through a bridge rectifier. Its still NOT isolated. Hook it up to something with an earth ground and you have a 50/50 shot of seeing fireworks.

srinath · 28th May 2012, 09:05 PM

I dont quite understand - this SMPS also has a rect. bridge etc etc ...
Cool.
Srinath.

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27th May 2012, 10:52 AM	#12
Kay Pirinha diyAudio Member Join Date: Oct 2011 Location: Tauberbischofsheim, Germany	Yes, it's the rectified supply rail after an active PFC - thus not isolated from the mains! In an active PFC the rectified DC voltage has to be higher than the peak AC input voltage (AC voltage times square root 2), otherwise the PFC regulation wouldn't work. Best regards!

27th May 2012, 10:58 AM	#13
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	Rewind the transformers in the smps or use voltage doubling. After that you still have noise issues to deal with. Tried a few mods of computer PSU´s but still like the linear approach.

27th May 2012, 12:08 PM	#14
srinath diyAudio Member Join Date: Feb 2010	I will check for continuity but I should tell you there is a transformer and maybe 6 or 8 transistors in that 1/2 of the psu before the 420v output. From here on to the output there is 2 more transformers and 10-12 transistors. I will check for continuity though. I should put a few pics up too I guess. Cool. Srinath.

27th May 2012, 11:50 PM	#15
srinath diyAudio Member Join Date: Feb 2010	Its got continuity, somewhere around 1,800,000 ohms. Oddly that is the resistance from either of the 2 outputs to the 2 + and - input prongs. So lets call it prong 1, 1 to + ac input = 1.8m ohm, prong 1 to - ac input = 1.8m and prong 2 to + ac is 1.8m, as is prong 2 to -. So what does it mean. I will post a pic in a bit. Cool. Srinath.

28th May 2012, 03:49 PM	#17
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Doesn't look isolated.

28th May 2012, 08:49 PM	#18
srinath diyAudio Member Join Date: Feb 2010	I measure continuity between the B+ and B- prongs on other amps too, my onkyo tx-ds-555 and a few others read less than 1.8 m. Cool. Srinath.

28th May 2012, 08:58 PM	#19
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	You'll read that through a bridge rectifier. Its still NOT isolated. Hook it up to something with an earth ground and you have a 50/50 shot of seeing fireworks.

28th May 2012, 09:05 PM	#20
srinath diyAudio Member Join Date: Feb 2010	I dont quite understand - this SMPS also has a rect. bridge etc etc ... Cool. Srinath.