[Yuta Michimura, Haoyu Wang]

Following the klog#21952, yesterday we investigated the response problems of the channels which are used for transmission PDs of IR s-pol and IR p-pol at Xend. Signals of the two PDs go to Ch3 (IR s-pol) and Ch4 (IR p-pol) of the BNC Dsub Converter on the TMSX rack. Then the signal goes to whitening filter, then the Anti-Alias chassis (AOS TRPD in Fig. 1) on EX0 rack (slot 32), and then to ADC. The two signals go to Ch30 and Ch31 in Fig. 2. When we inject some signals to the two PDs, the offset in Ch30 doesn't change and the Ch31 does not change either. Even when we unplug the output of the whitening filter, the two channels don't change. So we thingk there is something wrong with the Anti-Alias chassis or the ADC. We swapped the PDs' signal (AOS TRPD) on Anti-Alias chassis with another input (AOS OPLV, which is not used at the moment), see Fig. 3. The AOS OPLV channel works well and we got correct signals from the two PDs. So there is something wrong with the AOS TRPD channel of the Anti-Alias chassis or the ADC. We cannot replace the Anti-Alias chassis as other channels are in use. (The two channels AOS OPLV and AOS TRPD are swapped back after this test.)