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-   -   I need Help with my F5.... (http://www.diyaudio.com/forums/pass-labs/155846-i-need-help-my-f5.html)

rtate 29th November 2009 03:54 AM

I need Help with my F5....
 
3 Attachment(s)
I have just started to commission my F5 and I have a problem with the power supply,
Using cviller amp, PS and bridge pcb's
I am using a variac for all preliminary tests.
I checked the transformer and got 18VAC
I then hooked up the bridges and got 24VDC form both.

Now here's the problem,
When I hook the rectifiers up to the capacitor banks the readings were all over the place as I brought up the variac so I stopped.
A couple of the caps got very warm to the touch and the variac started to hum quite loud.
I think that I shoud read +24v from V+ to gnd and -24v from V- to gnd and 48v between V+ and V-
IS this correct??
When i got as far as 10VDC from V+ to gnd(red to green) I only measured
4VDC from V- to gnd(black to green)

I rechecked all my solder joints and they are ok
The resistors were all checked with a meter before installation
I don't know what to check next!!
Could some of the caps be bad??
they are 15,000uf 63v from Apex Jr.
Is there a way to check them while they are still on the board?
I know that I have missed somthing simple but just can't figure it out :headbash:

There is no physical connection from the PS to Earth or chassi ground, but from all the pictures that I have looked at this seems to be correct...

Nelson Pass 29th November 2009 04:27 AM

If the caps got warm, it's because they are being run backwards.
Either they are installed backwards, or the wiring to the
board is reverse polarity.

:cool:

tinitus 29th November 2009 04:34 AM

You are aware that + from bridge negative rail side of supply is connected to ground/center tap, together with - from positive rail side ?

I say it because your use of red/black wire looks "fishy"
But I dont know Cvillers supply design

Oh, Nelson posted faster
But on the same matter
I have looked at Cvillers manual, and cap mounting seems ok

Maybe also check that theres no shorting connection on your switch diodes to their heatsinks, to verify they are properly isolated

Yes, your connection from negative bridge definately appears to be reversed

rtate 29th November 2009 01:47 PM

If the caps were run backwards for a very short period of time and at a lower voltage, say 10-14 Vdc would the electrlytics be permanently damaged already??
They did get warm and if Ilistened very closley, I think that they were starting to boil :eek:

AndrewT 29th November 2009 02:34 PM

Hi,
this is another example where a bulb tester would prevent damage to an incorrectly wired project.
The bulb would glow bright and reduce the input voltage to the mains transformer to just a few Vac.

Nelson Pass 29th November 2009 07:24 PM

Quote:

Originally Posted by rtate (Post 1996106)
If the caps were run backwards for a very short period of time and at a lower voltage, say 10-14 Vdc would the electrlytics be permanently damaged already??

Good chance of it. You can always correct the problem and
try them, but I would stand back.

:cool:

jleaman 29th November 2009 07:29 PM

Looking at your picture it shows that you have the positive red wire on the negative terminal, is this your error ?


Notes, this picture, you should shorten your wire exposure, those are quite long and if you wire everything up and you pull on a wire and it shorts then you will get a big nasty suprize when you turn on your amplifier,

http://www.diyaudio.com/forums/attac...5-100_1784.jpg


This image, shows that on the left the positive and negitve are backwards. See that the cap's are all negative on one side, but the red positive wire is on the negative side of the cap ? This looks to be your error.

http://www.diyaudio.com/forums/attac...5-100_1785.jpg

rtate 29th November 2009 09:03 PM

jleaman, thanks that was my problem.
When i was hooking it up I assumed(I know what "Assume" stands for)
that both negative wires went to the connections marked gnd.

All is good now and everything checks out perfectly!!!

Should I still be concerned about the caps even though it checks out ok with
full voltage applied??

jleaman 29th November 2009 11:31 PM

Quote:

Originally Posted by rtate (Post 1996498)
jleaman, thanks that was my problem.
When i was hooking it up I assumed(I know what "Assume" stands for)
that both negative wires went to the connections marked gnd.

All is good now and everything checks out perfectly!!!

Should I still be concerned about the caps even though it checks out ok with
full voltage applied??

Id keep my eye on them like nelson said, to be sure, order a few spare :)

J'

AndrewT 30th November 2009 08:56 AM

would reforming the reversed caps help make them survive?

The reverse current (many amperes by the sound the transformer was making) may have removed the insulating effect of the oxide film.


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