Tag Archives: crt donor

HP 8569A Spectrum Analyzer: Any organ (ehh, CRT) donors out there

This 8569A came from the US, purchased by a local HAM operator, and in need of repair. Some switches don’t move nicely, so it seems liked a regular repair job of a 8569A.

First issue, 5 minutes after turn-on, where not the switches, but a blown mains capacitor (aging X2 grade capacitor). Well, this is easy to fix.

With the instrument powered on, it quickly became evident that the there is some distortion of the display, in particular, in the upper section of the CRT. This is not a common fault, and hard to explain other than by a broken deflection system of the CRT.

To be absolutely sure that no other assemblies are causing this defect, the X-Y deflection signals were coupled to a working 8569A, and indeed, no distortion visible.

The CRT display of a working 8569A – with the X-Y signals of routed from the unit that shows the distortions:

Sure, the display is not quite synced (also because of the extension leads with alligator clips). How to proceed? Well, this will need a 8569A CRT for repair, from a donor unit. Let’s hope, at least for the HAM friend that one will come around soon.