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8753B A3 Source Problem

Question asked by nueron on Sep 18, 2011
Latest reply on Aug 27, 2015 by Dr_joel

I have connected my 8753B for the "Test 21 R&A Op Check" with a 20dB attenuator on the RF source and 11667A splitter connected to R and A and receive a fail. If the source power is varied from -10dBm to +10dBm, the R or A trace is quite flat with a 26dB lower level. However, if the RF source power is increased to +20dBm, the R & A traces become slopes with the following values (I should be seeing around -6dB from 300kHz to 3GHz):-

300kHz: -6dB
2GHz:   -12dB
3GHz:   -15.5dB

As power is increased from +10dBm to +20dBm the frequencies from 3GHz downwards appear to 'limit'. I've checked the RF output on a spectrum analyzer and it shows the same (so it's not the receiver circuitry).

I don't know if this is a problem with calibration constants or with the A3 source module. The A3 schematics would be helpful, but no-one seems to have them. I'm wondering if there is a fault with the ALC circuitry (hopefully something on either the 08753-60103 Source Bias PCB or 08753-60203 ALC BD. and not the ceramic modules).

Any help would be appreciated.