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DIYbanter » Do - it - Yourself » Electronics Repair > power supply sometimes works
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orange
 
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Default power supply sometimes works
I've got problem with one PSU. Its occasionaly working.
Sometimes when I turn the switch ON nothing happens and then when I
turn it OFF, for a sec it starts and (normally) shutsdown immediately.


what could be the problem?

It is very old Amiga 2000 switching PSU, similar to PC (+12V,
+5V..etc).

please help

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  #2   Report Post  
mike
 
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orange wrote:
I've got problem with one PSU. Its occasionaly working.
Sometimes when I turn the switch ON nothing happens and then when I
turn it OFF, for a sec it starts and (normally) shutsdown immediately.


what could be the problem?

It is very old Amiga 2000 switching PSU, similar to PC (+12V,
+5V..etc).

please help


The supply may require some minimum load on one or all outputs
to function.
mike

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orange
 
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it behaves the same, load or no load, sometimes it works but its pure
luck

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kip
 
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Bad filter caps in PS...
kip
"orange" wrote in message
oups.com...
I've got problem with one PSU. Its occasionaly working.
Sometimes when I turn the switch ON nothing happens and then when I
turn it OFF, for a sec it starts and (normally) shutsdown immediately.


what could be the problem?

It is very old Amiga 2000 switching PSU, similar to PC (+12V,
+5V..etc).

please help



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Check your heat sink & the heat tranfer cream, it could due to poor
heat tranfer to the
heat sink, i have this problum also.

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Bob Parker
 
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Startup resistors gone high in value?


"kip" wrote:

Bad filter caps in PS...
kip
"orange" wrote in message
roups.com...
I've got problem with one PSU. Its occasionaly working.
Sometimes when I turn the switch ON nothing happens and then when I
turn it OFF, for a sec it starts and (normally) shutsdown immediately.


what could be the problem?

It is very old Amiga 2000 switching PSU, similar to PC (+12V,
+5V..etc).

please help



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Ron(UK)
 
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orange wrote:
it behaves the same, load or no load, sometimes it works but its pure
luck

It`s probably going to be a failing electrolytic in the mains side of
the chopper circuit - I dont have a diagram but I`d expect it to be in
the region of between 1 and 10 uf. Be aware that there are dangerous
voltages around there, maybe even when it`s unplugged.

Ron

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kip
 
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To start with blow out the **** from the PS..
kip
"orange" wrote in message
ups.com...
I have uploaded hires (1Mb each) photos he
http://orange.users.sbb.co.yu/Amiga/psu/P7180008.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180009.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180010.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180011.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180012.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180013.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180015.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180016.JPG

could you tell me which one capacitor is most likely to be the cause?



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Ron(UK)
 
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orange wrote:
I have uploaded hires (1Mb each) photos he
http://orange.users.sbb.co.yu/Amiga/psu/P7180008.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180009.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180010.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180011.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180012.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180013.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180015.JPG
http://orange.users.sbb.co.yu/Amiga/psu/P7180016.JPG

could you tell me which one capacitor is most likely to be the cause?

It would be my guess that it`s one of the little orangey ones with the
black stripe under the silver heatsink, The type visible in pic 0011,
right on the edge of the board. Also look for one similar near the
chopper transistor - That`ll be the one on the black heatsink I reckon.

You`d really need to check all the electrolytics with an esr meter to be
sure. First off I'd get all that crap out of there if I were you, and
remember that there might be a charge stored in those 200 volt smoothers.

Ron

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www.lunevalleyaudio.com
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budgie
 
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On 18 Jul 2005 01:23:43 -0700, "orange" wrote:

I've got problem with one PSU. Its occasionaly working.
Sometimes when I turn the switch ON nothing happens and then when I
turn it OFF, for a sec it starts and (normally) shutsdown immediately.


what could be the problem?

It is very old Amiga 2000 switching PSU, similar to PC (+12V,
+5V..etc).

please help

Serious question: Have you tried replacing the switch?
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orange
 
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ok thanks all, I was going to clean it thoroughly but since
electrolytics can leak I thought experienced users might see signs of
leakage if not cleaned,
I was also hoping it might be the switch, but after checking with
ohmmeter it works ok.

err, what exactly is esr meter?
My voltmeter can check capacitance (but I need to desloder them and put
in special place for checking probably because of cable capacitance,
right?) and it can see if capacitors are shorted.

I can check resistance between various points, if that could be of any
help for solving the problem?

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kip
 
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Why don't you just replace the filter caps and end your misery.

kip
"orange" wrote in message
oups.com...
ok thanks all, I was going to clean it thoroughly but since
electrolytics can leak I thought experienced users might see signs of
leakage if not cleaned,
I was also hoping it might be the switch, but after checking with
ohmmeter it works ok.

err, what exactly is esr meter?
My voltmeter can check capacitance (but I need to desloder them and put
in special place for checking probably because of cable capacitance,
right?) and it can see if capacitors are shorted.

I can check resistance between various points, if that could be of any
help for solving the problem?



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orange
 
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OK, kip, but which ones ARE filter caps? Please have a look at photos
and tell me..

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orange
 
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Ok, I'll start replacing them all. But before I try finding them, could
you tell me what does '4700/16 V1' on capacitor mean? what is the
capacity and voltage ?
( http://orange.users.sbb.co.yu/Amiga/psu/P7190003_up.jpg )

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kip
 
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Thats a 4700/16 Volts

kip

"orange" wrote in message
oups.com...
Ok, I'll start replacing them all. But before I try finding them, could
you tell me what does '4700/16 V1' on capacitor mean? what is the
capacity and voltage ?
( http://orange.users.sbb.co.yu/Amiga/psu/P7190003_up.jpg )



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orange
 
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and 4700 is 4700 microfarads?

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kip
 
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yep

"orange" wrote in message
oups.com...
and 4700 is 4700 microfarads?



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James Sweet
 
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"orange" wrote in message
oups.com...
ok thanks all, I was going to clean it thoroughly but since
electrolytics can leak I thought experienced users might see signs of
leakage if not cleaned,
I was also hoping it might be the switch, but after checking with
ohmmeter it works ok.



They can leak, but usually they fail without any visible signs. That wave of
caps made with bad electrolyte did tend to bulge and leak though.


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orange
 
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unfortunately, somethings terribly wrong ((((
I have replaced all caps except the two BIG ones (680uF, 200V) and one
small 1,5uf 50V; couldn't find replacement for them (actually I got
1uf-could it replace 1,5uf?)

I also connected a car light as load for 12V, but 5V was with no load.
The power supply (again) sometimes works, BUT instead of 12V I get 7V
while car light is connected. when its disconected, voltage goes up to
10V

it seems that there is no solution but to modify new atx psu

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James Sweet
 
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"orange" wrote in message
oups.com...
unfortunately, somethings terribly wrong ((((
I have replaced all caps except the two BIG ones (680uF, 200V) and one
small 1,5uf 50V; couldn't find replacement for them (actually I got
1uf-could it replace 1,5uf?)

I also connected a car light as load for 12V, but 5V was with no load.
The power supply (again) sometimes works, BUT instead of 12V I get 7V
while car light is connected. when its disconected, voltage goes up to
10V



That's normal, with no load on the 5v the 12v won't regulate.


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orange
 
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you were right, when I put load on 5v it works
still sometimes it won't start, I'll try to find replacement for those
2 big ones 680uF 200V, hope it will solve it

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