For the benefit of future generations troubleshooting an IFR 2398.
Initially:
0) All self cal pass exept the Level cal
1) I got SWR 4:1 or worse (antenna analyser looking into spec an input, spec an switched on, SWR the same regardless of attenuation selection (0 to 50 db, 10 dB step).
2) I see the spec an built in cal 40 MHz signal at -42 dBm (should be -30 dBm) and any signal provided to the input of the spec an was over 20 dB less than what it should be.
My thinking:
3) I focused to the circuit directly at the input of the spec an (as indicated by the SWR behaviour). Thanks to George for the schematic.
My actions (so far):
4) I supplied -12 volts to the board, then measured the voltage on each of the two control pins of every AH002R2 RF switches. All of them had ~-8.8V and 0V but the first one had -1V and 0V.
5) I removed the first AH002R2 switch
6) I connected directly with a short jumper to connect the N-type input to the rest of the attenuator chain (pin1 to pin7 from memory).
7) Re-installed the RF module. All self CAL failes exept the YIG - expected as there's no connection to the 40 MHz internal cal signal. SWR is now 1:1 (yey!!!)
Just for fun, added an external 40 MHz about -30 dBm signal to the input of the analyser and rebooted it. It passed all tests! Under these conditions, it behaves as you would expect but the amplitude seems to be out by ~3 dB. Given the dodgyness of the calibration, that's hardly a surprise.
I have ordered a AH002R2 from eBay (fingers crossed) and will report what happens when I install it.
cheers
Dimitris