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The power supply's schematic probably lives in one of many Chinese
power supply manufacturer's archives. By the time the 70000K series came around, it was common for HP to buy their power supplies from outside vendors (OEMs). The OEM's supplies were inexpensive (a relative term), and were considered to be interchangeable. They were not generally repaired, but rather swapped out as a unit. Switching supplies have been refined to a point where the IC's, etc are arranged so that they can be used on single sided boards. For safety, because of the voltages involved, they were laid out in a straight forward way. UL requires the line side, and the grounded side be well marked with zebra lines, and warnings. There are only two topologies in common use: 1) bootstrapped, and 2) power factor correcting. Bootstraped will always have a pair of largish HV electrolytic capacitors on the AC end of the supply that rectify/double the power line voltage. You can count on there being a 120V/240V line selection switch/strap somewhere. Power factor correcting will usually have a single large HV electrolytic capacitor, 900V or so, that can take any line voltage from 90V to 300V, without any user intervention. Anyway, there are books galore on the two normal topologies, and once you have determined which you have, it is quite easy to follow the signals across the circuit board... the board is as good as the schematics the Chinese made for these supplies. Those that fix these sorts of boards don't use schematics, but rather use their senses (eyes, nose...), ESR meters, and knowledge of the parts that generally fail. -Chuck Harris On Tue, 23 Nov 2021 19:52:15 -0800 "Gene Silvernail" <genesilvernail@...> wrote: Working on the PS board of the 70900A and bought the CLIP from Artek. |
