Monday, September 23, 2019

Marconi 2024 RF Signal Generator Error 508: Amplitude modulator unlevelled Repair

I have recently bought a used Marconi 2024. But instrument was partially faulty having issue a minor issue with LCD screen and a comparatively major issue with Error 508 : Amplitude modulator unleveled. So it needed a repair First i will try to fix issue Error 508 because replacement compatible LCD will arrive later.

This post is going through will be mostly what to look for when you are attempting to fix same issue in your marconi/IRF or now aeroflex 2024 or similar marconi 2023.

This article will quote  service manual for this instrument multiple time, service manual can be easily found with just simple internet search or on ko4bb

As i have already fixed my issue now i know with my instrument issue was with carrier RF signal level being too low. But issue with other instrument many be different so  i will still describe here how i traced to the faulty component.

I assume all power supply voltage are fine with voltage and ripple.

There are two version of service manual available. old service manual have There are a quite a few error in newer service manual's schematic.

As per Maintenance manual  Error 508: Amplitude modulator unlevelled appear when pin diode based modulator loop is running into issue with either AM level or the level of carrier RF signal or detection circuit of AM modulated RF signal.