Tektronix 494AP Spectrum Analyzer Repair

[Jay_Diddy_B]

Hi Group,

Time to share a repair that I made to a Tektronix 494AP Spectrum Analyzer.

A friend gave me the SA to repair, it would not work at all, it would blow the main line fuse at the back of the unit.

Schematic



I did some poking around with a meter and I found that one the rectifiers in the bridge was short-circuit (CR3096 or CR4094). In addition one the main electrolytic capacitors was short-circuit (C6101 or C6111).

The rectifier was easy to repair, I used a 1N5408 3A diode.

Electrolytic Replacement

The original capacitor in the spectrum analyzer were manufactured by Aerovox. They have a 5 pin base. This was probably chosen by Tektronix for mechanical stability.




I decided that I would make some adapter boards, so that I could use two pin snap-in electrolytic capacitors as a replacement.






I went to all this trouble with the adapter boards, because the end of the capacitor pokes through a hole in the chassis. The replacement capacitor has to be in the same place as the original.





Working again


The Spectrum Analyzer works fine now that the capacitors and the rectifier have been replaced.



I found the Service manuals at:

http://www.ko4bb.com/manuals/

Regards,

Jay_Diddy_B

[w2aew]

Sweet!

[Muxr]

Very cool.

[photon]

Thanks for posting. I always find such repairs very instructive.

[Vgkid]

Very cool, those are the same style of caps used in the 3456A's infamous power supply. I just used a radial cap, and bent the pins for best fit.