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VK3AXI
Guest
I am in need of a circuit diagram for Philips PS 353 Series 5 - 2A 13.8v power supply. I now have my shed organised and attacking project No 2
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VK3YNV
Guest
I think that's a re-badged Arlec PS 353, if so it will be a simple linear supply using a Fairchild UA78CB 13.8V regulator, there should be a TO3 package mounted on a heatsink, see what the markings on that are.
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VK3AXI
Guest
I think you are correct Ray. There appears to be two diodes on the board. One is very cooked, so much so its totally in half. The other one looks fine. I assume they are the same type.
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VK3YNV
Guest
Check the transformer connections, if there are three wires coming from the transformer, and just two diodes, then it's a center tapped transformer with the center tap going to ground and the other two taps going through the two diodes to a filter capacitor.
That gives full wave rectification with just two diodes instead of the four that would be normally required for a full wave bridge.
The two diodes will be the same.
That gives full wave rectification with just two diodes instead of the four that would be normally required for a full wave bridge.
The two diodes will be the same.
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VK3AXI
Guest
Before spending any more time on the power supply i though i should check the transformer. Unsoldered the 3 wires from the circuit board, connected a multimeter and powered it up. Nothing at all. Disconnected power and checked continuity. Dead short between centre tap and the active taps. My conclusion, dead transformer.
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VK3ZYZ
Guest
Is the primary open?
A lot of transformers have thermal fuse in the primary.
If it is open, it can often be shorted out to get the transformer going again.
A decent current transformer may have very little resistance in the secondary windings.
A lot of transformers have thermal fuse in the primary.
If it is open, it can often be shorted out to get the transformer going again.
A decent current transformer may have very little resistance in the secondary windings.
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VK3AXI
Guest
Removed transformer from casing and found the wire running from the tab to the transformer had melted away very close to the winding. No lead coming out of the transformer winding to the tab. There was still a little of the lead on the tab but you could see a blob of melted copper on the end where it should join the winding. By the way, this is not my good power supply it was just one in the junk box that i thought i might be able to get going. Nothing ventured, nothing gained.
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VK3YNV
Guest
That type of open primary failure can be caused by a high voltage spike, my son Matthew used to live in a flat in South Yarra, and a car hit a nearby power pole causing a high voltage spike on the mains, It blew the primary windings on a number of his appliances, the ones that survived were the ones with transient supression on the mains side. None of the destroyed appliances had blown fuses. Very weird. From memory there was a clock radio, a stereo cd player, and a couple of plug packs that died. His computers survived ok.