Hi Folks,
Just got our <new> quantar in, and it has a power supply issue. (I knew
about this when it was purchased).
It is a dual powersupply - AC/DC, and the DC section works - hook up
24 volts to it, and the repeater functions properly.
Sooo, the AC section is shot. No visible flames have been here, the
fuse is OK, the switch works properly, the rectifier diodes are ok...
just wondering if anybody else has seen this.
I know there are no 'official' schematics around, but mebbie someone
has done some work on these before and can point me in the right
direction.
Next step is to visually look at all solder joints, then resolder everything.
Thanks!
Tim
Quantar Power Supply CPN1048A Help
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Re: Quantar Power Supply CPN1048A Help
Found some traces that weren't there anymore! Also one of the large
caps (450v) had something strange on it's bottom. The plastic wrapper
was also stretched/broken, so there's something wrong with it.
Replaced the traces... popped the fuse.
An additional question.... since the LV portion of the supply works ok,
can I take the AC portion from an AC only supply & put the DC section
on it, or does it have different connections to the ribbon cable?
Thanks,
Tim
caps (450v) had something strange on it's bottom. The plastic wrapper
was also stretched/broken, so there's something wrong with it.
Replaced the traces... popped the fuse.
An additional question.... since the LV portion of the supply works ok,
can I take the AC portion from an AC only supply & put the DC section
on it, or does it have different connections to the ribbon cable?
Thanks,
Tim
Re: Quantar Power Supply CPN1048A Help
Found a dual diode in a TO-220 package at the end of the
heatsink that has one of the diodes shorted...
More to come later.
Tim
heatsink that has one of the diodes shorted...
More to come later.
Tim
Re: Quantar Power Supply CPN1048A Help
At least you're able to get to the parts and replace them.
I had a similar issue with an MTR2000 power supply. Worked great with an external 28V supply (which is what I eventually bought and will run it that way) but the AC side seemed dead. I could see some goop around the bottom of two 450VDC caps inside, and I suspect some burnt foils, but I can't get the board out without destroying it or a dozen components that are screwed and glued to the heat sink (thanks ABB). No schematics of course, just a block diagram.
The theory is fairly straight-forward. Incoming AC is rectified to about 350VDC. That runs through a switching oscillator to make AC, which is lowered by a small transformer to something around 20VAC. They rectify and filter that to get 28VDC which is also further regulated down to the lower voltages.
The incoming AC usually goes through an automatic voltage sensor that operates some sort of switch. If it sees something above about 180VAC, the input rectifier operates as a four-diode bridge to convert the (roughly) 240VAC to 350VDC. If the voltage is less than about 180VAC, the input rectifier operates as a two-diode voltage doubler to convert the (roughly) 120VAC to 350VDC. Because of the voltage doubler, the DC filter caps are usually arranged in two separate banks, so there are often pairs of equal value caps to handle the job. This lets them use lower-voltage rated caps as they're operated at around 200VDC each.
End of "Switching Power Supplies 101".
Bob M.
I had a similar issue with an MTR2000 power supply. Worked great with an external 28V supply (which is what I eventually bought and will run it that way) but the AC side seemed dead. I could see some goop around the bottom of two 450VDC caps inside, and I suspect some burnt foils, but I can't get the board out without destroying it or a dozen components that are screwed and glued to the heat sink (thanks ABB). No schematics of course, just a block diagram.
The theory is fairly straight-forward. Incoming AC is rectified to about 350VDC. That runs through a switching oscillator to make AC, which is lowered by a small transformer to something around 20VAC. They rectify and filter that to get 28VDC which is also further regulated down to the lower voltages.
The incoming AC usually goes through an automatic voltage sensor that operates some sort of switch. If it sees something above about 180VAC, the input rectifier operates as a four-diode bridge to convert the (roughly) 240VAC to 350VDC. If the voltage is less than about 180VAC, the input rectifier operates as a two-diode voltage doubler to convert the (roughly) 120VAC to 350VDC. Because of the voltage doubler, the DC filter caps are usually arranged in two separate banks, so there are often pairs of equal value caps to handle the job. This lets them use lower-voltage rated caps as they're operated at around 200VDC each.
End of "Switching Power Supplies 101".
Bob M.