I purchased a Philmore PS123 from ebay.com for \$10. The unit was still in the box with original one-page flyer that passes as the operator's manual. The unit's schematic was shown, but doesn't quite match the wiring in the cabinet. It's almost identical to the circuit I traced out and previously blogged about. The filter capacitor is 2200 uF, rather than 2000 uF as shown in the schematic. The schematic shows a single 1K resistor from the collector of TR1 to the anode of the zener diode. The actual circuit has a 5.6K resistor from the collector of TR1 to the negative side of the 500 uF capacitor, then a second 5.6K resistor from the negative side of the 500uF capacitor to anode of the zener diode.
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The reverse engineered circuit is shown below.
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A photo of the PS123 is shown below.
The performance curves of load regulation and ripple vs. load are given in the included flyer.
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