HP 54502A Oscilloscope screen not working

[habibrenjie]

My HP54502A scope has stopped working. When I turn it on I hear a relay ticking faster and faster, the screen doesn't turn on save for a few faint flashing of the "copyright hp" screen. Any advice on how to fix this or how to diagnose the problem is greatly welcomed.

[Smith]

Sounds like a power supply failure. These power supplies are notorious for failing.

Most failures are due to bad caps. Mine had several of them. Finding them can be dificult, as many of them are put in parrallel. Thankfully the HP service manual does have an overview of the voltages and tollerances. If I remember correctly you can only adjust one voltage (5,2V).

These power supplies are not a HP design, but manufactured by another 3rd party. There are some non official schematics on the interweb, but they are not 100% accurate.