Last year, a colleague of mine very kindly gave me this Toshiba SD-23VB VHS/DVD combi player, which was apparently completely dead, likely a fault with the internal PSU.
I tested it when it arrived, and it was indeed completely dead – there was no response to the power button or any other button at all, and nothing on the display.
I removed the internal PSU for inspection, but nothing was obviously visually wrong (cracked solder joints, bulging electrolytic capacitors, burning or scorch marks, etc) – I removed all of the electrolytic capacitors one by one and tested them with my Peak ESR70 and they seemed OK so I reinstalled them.
The Toshiba SD-23VB has a pretty comprehensive service manual which includes a block diagram, schematic, and diagnostic flowchart for the internal PSU.
The flowchart recommends checking the fuse F101 (which was OK), then the bridge rectifier BD101 (which was OK), then the power resistor at R101 (which was OK), then the power supply to pin 7 of the main switching IC at IC101 (ICE2B265) – there wasn’t any power here, so I checked D102 (RL104F 400V 1A Schottky rectifier diode) but this was OK.
The datasheet for the ICE2B265 also includes quite a useful reference schematic which explains in a bit more detail about its support components.
I tested the start-up resistor at R105 (22R 1/8W) just after D102, and this had failed open-circuit switching IC IC101 – I replaced this with a 1/4W part, and the player started up OK!
I reassembled everything for testing, and both VHS and DVD works well – a successful fix for a unit condemned because of one faulty resistor.
