Ceramic filter test methods

Ceramic filters are divided into two categories according to their amplitude-frequency characteristics: band-stop filters (also known as notch filters) and band-pass filters (also known as filters). They are mainly used in frequency selection networks, intermediate frequency tuning, frequency discrimination and filtering circuits to separate currents of different frequencies. They have the characteristics of high Q value, good amplitude-frequency and phase-frequency characteristics, small size and high signal-to-noise ratio. They have been widely used in household appliances such as color TVs and radios and other electronic products.
Ceramic filters mainly use the piezoelectric effect of ceramic materials to realize the conversion of electrical signals → mechanical vibrations → electrical signals, thereby replacing the LC filter circuit in some electronic circuits and making them work more stable.

At present, there are two types of ceramic filters: two-terminal and three-terminal. Their circuit symbols are shown in the attached figure.
Common models of bandpass filters in color TVs are LT5.5M, LT6.5M, LT6.5MA, and LT6.5MB ceramic filters; 10.7MHz intermediate frequency filters commonly used in FM stereo recorders and radios are LT10.7MA, LT10.7 MB, LT10.7MC, etc., and intermediate frequency filters in AM radios are LT455, LT465, etc.
Common models of band-stop filters (notch filters) in color TVs are XT4.43M, XT5.5MA, XT5.5MB, XT6.0MA, XT6.0MB, XT6.5MA, XT6.5MB, etc.

Ceramic filters can be tested with a multimeter, the specific methods are as follows:
1. Set the multimeter to R×10k;
2. Use red and black test leads to measure the forward and reverse resistance between any two legs of a two-terminal or three-terminal ceramic filter, both should be ∞. If the measured resistance is small or 0Ω, it can be determined that the ceramic filter is damaged; It should be noted that measuring the forward and reverse resistance to be ∞ cannot completely determine that the ceramic filter is intact. Under amateur conditions, the substitution method can be used for testing.