Power Supply Voltage problem

[42001]

Hi,

Can anyone tell me what I'm doing wrong here?

2 x 25V 500VA toroid results in 68VDC ???? Should be around 36V I imagine.... What am I doing wrong??

Thanks!

 

[fastvideo]

Check where is the C.T.

 

[42001]

Hi fastvideo, what do you mean?

 

[Preamp]

Guess he means the center tap. How are the two secondaries wired up?

 

[42001]

Hi Preamp,

I have built the SPS-01 power supply from Per-Anders Sjostrom. I have the scematics here, but can't upload them here.... maybee I can mail it to you?

 

[42001]

Here it is:
http://sjostromaudio.com/hifi_pics/hifi_100pr/sps01r0schema.png

I use the 25V 500VA toroid....

Regards, Sjoerd

 

[Preamp]

No need for a schematic. What about a picture of your wiring? Or at least, tell us what's printed on the transformer's label about the wiring colors and how you connected them.

 

[42001]

Let me inform you about what I built:

Power supply with 8 x 22000uF/63V slit foil caps.

I am wondering: Is higher voltage normal without load?

Wiring is as to be seen when you follow the link I provided. first secondary on AC1, second one on AC2.

When I power up, the DC voltage increases slowly to 65 to 68 VDC. But again, without load, only my multimeter

Its a Aplimo toroid type 88016.

SEC.2x25V 10.00A RED/YELLO.BLEU/GREY

So RED/YELLO on AC1 and BLUE/GREY on AC2

Helpfull?

Regards, Sjoerd

 

[sofaspud]

Both halves measure 68V, or one half measures high and one half measures correctly, or you're measuring incorrectly?

 

[42001]

Hi sofaspud,

Both halves measure the same..... But when measured via ground I do get 36VDC.... But between NEG and POS I get 68VDC.....

 

[Preamp]

25V secondaries should give you a DC in the range of 35V (roughly). Unloaded will be a couple volts more, due to transformer regulation. Your 68V sound like you're measuring both rails in series and not each one referring to ground.
Did you use a finished PCB or did you do one yourself?

 

[Preamp]

Hi sofaspud,

Both halves measure the same..... But when measured via ground I do get 36VDC.... But between NEG and POS I get 68VDC.....

That's exactly what this PSU is supposed to do...

 

[sofaspud]

Then I don't see the problem. The 68V measurement is the voltage of both the secondaries. Ground should be the reference here, with a ±36V bipolar supply resulting. From your link, the measurement across the full supply would be 126VDC.

 

[tinitus]

Then I don't see the problem. The 68V measurement is the voltage of both the secondaries. Ground should be the reference here, with a ±36V bipolar supply resulting. From your link, the measurement across the full supply would be 126VDC.

yes, +/-36V looks perfectly normal...but then there ought to be 72V between pos and neg, no ?

 

[sofaspud]

72VDC, yes, but there could be circuit/measurement subtleties that alter that value. I'm not confident enough to say the difference is cause for concern, but I don't believe it would be.

 

[42001]

Ok guys, I just slammed my head against the door..... I'm a nitwit POS GND is 36VDC and NEG GND is 36VDC... Perfect!!!

I thougt I had to connect the amp only on POS and NEG, measuring 72VDC.... And I got spooked because the voltage should be +-35VDC..... (Hiraga amp)I forgot that ground is the reference.... No problems here! Sorry to have bothered you

Kind regards,
Sjoerd

 

[Preamp]

Now you'll know it next time .

 

[42001]

Yes! Thats true.... Learning all the time!

Thanks for your patience