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Production overall debugging skills

In Electronic Infomation Category: P | on February 09,2012

Overall debugging is to ensure that the machines technical specifications and NE575N datasheet and design requirements, to describe the various static and NE575N price and dynamic debugging circuit assembly with the related unit test, debug circuit to solve the unit can not solve the problem.

(1) six superheterodyne radio static debugging
six superheterodyne radio circuit shown in Figure 5--27 shown. Adjustment is the DC current meter forward from the level after level of the transistor collector followed in series with the circuit (schematic Office), adjust the bias circuit at all levels of the corresponding components (usually on the base bias resistor), respectively, to transistor collector DC current levels in line with the current technical specifications set forth in the value.

adjustment should be noted: a) in the absence of external signal input case, otherwise not allowed to transfer, this can be double-variable capacitors CA, CB all the spin, or short-circuit the input circuit with a wire ; b) DC current meter strings were the collector circuit, the best parallel across a table T 0.1 ~ 0. 47 VF bypass capacitor; c) if the potentiometer adjustable base bias resistor, potentiometer resistance to a string appropriate fixed resistor, adjust, the measured resistance value required then put on a fixed bias resistor, adjusted to zero to avoid Pot, burned transistors.

six superheterodyne radio circuit, the quiescent current measurements at various levels are as follows:

current measuring point D is generally 1. 5mA, if the measured current is zero, you can use metal objects (such as a screwdriver) touch the transformer primary or potentiometer input, to see whether the speaker audible, if not sound, then look at the speaker if there are problems; followed by measuring the resistance R7 ~ Rl0 correct; C9-side potential of the three investigations about whether 1.SV; four electrical capacity of C9 to see whether 100VF.

current measuring point C should generally be 2mA, if the measured current is zero, then look at the transformer position is correct, that pin is connected correctly; second look at whether the transformer winding path, that is the primary measure coil resistance of about 180fl,, secondary resistance
about 90fl.

current measuring point B should generally be 0. SmA, if the measured current is 0, the first measuring coil C in the week whether the open circuit conditions, if any, will have to be replaced; second look at the transistor model is to choose the right, and NE575N suppliers and pin it upside down.

current measuring point A should generally be 0. 3mA, if the measured current of O, then look enameled wire c, d both ends of the scraper is good, otherwise easily lead to the phenomenon is still insulated; second test in two weeks whether the circuit of the coil case, and if so, will have to be replaced; three transistor models to see whether to choose the right (high frequency tube should be selected here), and pin it upside down.

(2) system tune AM radio heterodyne AM radio tracking
provisions of 535-1605kHz frequency range, it is through double-variable capacitor, from the smallest to the largest capacity to spin to achieve this continuous tuning. In mass production, in order to meet the requirements of frequency coverage, regarded in the radio band frequency range of design in the 520-1620kHz range, a slight margin over the requirements.

general, the entire frequency range of 800kHz below the double-spin variable capacitor or larger in the position of the maximum capacity is called the low-end; 1200kHz above, that is double the capacity of even the smallest rotary variable capacitor or position as the smaller end; 800 ~ 1200kHz position as the middle. Clothes had not been adjusted for the radio, or tune the radio the old chaos, its frequency range is often inaccurate. For example, the frequency is not just from the 535 ~ 1605kHz. But from 700kHz ~ 2.1MHz or 500 ~ 1500kHz, are called high or low frequency range; the other from 535 ~ 1500kHz or 600 ~ 1605kHz, and are called high-frequency range is low or low-frequency range of deficiencies. Therefore, the newly installed radio and tune the old chaos radio system must be adjusted to achieve the desired targets.

tuned superheterodyne radio circuit There are three types: a) intermediate frequency tuning circuit: it is fixed to adjust in 465kHz, after a good tune, when used without adjustment; b) the local oscillator tuning circuit: it adjust the radio frequency scale than the high frequency of 465kHz discs instructions on the location, after a good tune, adjust the variable capacitor used, continuous change of the local oscillation frequency, in order to achieve the purpose of animal husbandry, heterodyne access; c) Input circuit: it adjustment in the local oscillation frequency than the low frequency of 465kHz position. Among them, the low, middle and high-end, there should be three points coinciding with the frequency scale corresponds to the value set of instructions (the other points should be as close as possible). In the superheterodyne radio, decided to receive the frequency (that is, determine the frequency scale) is the local oscillation frequency and IF frequency difference, rather than the frequency of the input circuit (Direct-radio frequency receiver input circuit is determined of), so the difference between the rate the school frequently. In the local oscillation circuit, the change in the oscillation coil inductance (ie, changes in the core) can significantly change the more low-end of the oscillation frequency (but high-end has a greater impact). Fine-tuning of the oscillation change capacitance, can significantly change the high-end (oscillator with spin to the capacity of the minimum position) of the oscillation frequency. Therefore, when the calibration frequency scale: low-end should be adjusted to the coil core oscillation, the oscillation should be adjusted to fine-tune the high-end capacitor.

the local oscillation frequency and the IF frequency to determine the frequency of the received external signal input circuit with the addition to the resonant frequency of the signal or not, the relationship between the superheterodyne radio sensitivity and selectivity, so adjust the input circuit to make it resonant with the external signal frequency, can receive the high sensitivity, good selectivity. So, usually adjust the input circuit to adjust said compensation.

adjust compensation, low-end transfer bar magnet coil circuit on the input position, adjust the antenna trimmer capacitor end.

oscillation circuit and the input circuit by adjusting, use the double-time as long as the adjustment variable capacitor, you can make two circuits (oscillator input) while the frequency of occurrence of continuous change, so that the two loops to maintain the difference in the frequency of 465kHz, the so-called synchronization or tracking. But in fact, make the whole band to reach every point within the synchronization is not easy to achieve, in order to make the whole band can get the basic synchronization, oscillation circuit in the design and input circuits, require it in the middle frequencies (such as Polish lOOOkHz ) to achieve synchronization, and low-end antenna by adjusting the magnetic inductance, high-end fine-tuning the antenna by adjusting the capacity of the low and high end also achieve synchronization, so that the frequency of other points also do not differ too much , so in the superheterodyne radio range of the entire band is tracking three points, it is also known as synchronous or three three-point adjustment system.

In summary, the purpose of calibration frequency scale, is to make the radio range of the entire band can work while listening to the radio, the frequency scale pointer that receives the radio frequency and corresponds to adapt input circuit track points; the purpose of compensation is to make receiver sensitivity, the whole sensitivity and selectivity of uniformity to the best extent, and adapt to the oscillation circuit of the track point. They are usually referred to as calibration frequency scale and tone compensation, and these two adjustments referred to as poor tracking system tune.

(3) of the TV tuner, TV tuner debug
debugging in Figure 5-29 (a) below. The scanner (BT -3) output probe to tuner input, the input scanner detector probe to the output frequency tuner (a 75Cl in the termination resistor load). Commissioning steps are as follows (in large screen color TV Toshiba 289X8M movement example):

1) HB-band (channels 6-12) debugging - in the HB and MB tuner plus 12V terminal voltage ( LB and UB Rui voltage is 0). This time from the scanner to see the characteristic curve should be a single peak, and the sound carrier frequency fs and the image carrier frequency fp of the beat
fs - fp) as 6.SMHz, fp is not less than 50%, as Figure 5-29 (b) below; the same time, adjust the tuning voltage, the normal curve to move from the 12 channels 6 channels, the voltage gain of 20 ~ 30dB; do not meet the requirements should be adjusted accordingly inductive loop line
The distance and coupling the high frequency characteristics of the resonant point falls below the specified frequency range.

2) LB band (channels 1 ~ 5) debugging - in the LB and MB tuner plus 12V terminal voltage (HB and UB voltage is 0). Scanner shows the high-frequency characteristic curve should be a single peak, (fs - fp) as 6.SMHz, fp not less than 50 010, as shown in Figure 5 -29 (b) below; change the tuning voltage characteristic curve from the 5 channels to move a channel, the voltage gain of 20-30dB; if errors should be adjusted accordingly or inductance coil inductance coil in the oscillator and capacitors, to conform to the indicator.

3) high level (RFAGC) adjustment. URFACC voltage (from 0.SV to 7. 3V), the gain can be evenly tuner changes the bandwidth characteristics meet the target requirements.

4) AFT adjustment. Voltage (6. SV +4 V), high-frequency characteristic curve can move around, a sensitivity of 0. 3MHz / V.

5) Similarly UB frequency band (channels 13-68) debugging - in tuner plus UB and MB-side voltage of 12V (LB and HB voltage is 0), adjust the tuning voltage and the corresponding resonance inductance, the high-frequency characteristic curve in line with the indicator.

(4) put the TV image in the image
put debug debug connection shown in Figure 5-30 (a) follows (in large screen color TV Toshiba 289X8M movement for example). Before commissioning, the combination of the first line of the main circuit board (SL -1) is disconnected, as shown in Figure 5-30 (b) below. Put off the contact with the tuner will switch to standard NTSC system (3.58MHz) position, scanner input table with the FSB probe, as shown in Figure 5 -30 (c) below. Pre-release access in the emitter tube V181, sweep signal output terminal of the main circuit board to put cut point, the main circuit board
with 12V regulated voltage, adjustable frequency transformer T181, to 33. SMHz frequent punctuation put in the amplitude-frequency characteristic curve in the concave bottom; adjust IF transformers T182, to 32. OMHz punctuation is located in the discharge frequency amplitude-frequency characteristic curve of the concave bottom.

(5) telephone technical performance of the test
phone performance testing, usually need to use specially designed telephone tester, it can provide for the telephone and telephone transmission lines similar to the DC power supply, ringing signals, dial tone signals. In addition, it can automatically detect the telephone dial, ringing call and performance testing. Telephone tester has many types, and can be divided into pulse-tone telephone and audio-tone telephone tester tester. Such as MODEL-1080, JP8000, and WHJ-B, etc. is the pulse-tone telephone tester, MODEL-2102, MODEL-1061 and the JT-2000 is the audio-tone telephone and other tester. The following telephone to MODEL-1080 tester, for example, shows telephone performance detection. 1) tone detection.
a) with MODEL-1080 phone testers, telephone access to the measured Ll, L2 test port.
b) telephone on-hook, press the test instrument "BELL" key should be the normal telephone ringing, ringing should not be distorted.

current PBX user loop to the ring detect signal. In the absence of MODEL-1080 phone testers cases can be directly used to detect the ring communication network. Is: will test telephone with outside line (communication network feeder) and a good connection, dial the number 111 (Shanghai area), then hang up after a few seconds, PBX will send a ringing signal, if the telephone ringing circuit is normal, will be able to send ringing .
c) hook, phone should stop ringing.

2) by the words of detection.
Press tester "R" key, and whether the receiver to listen to telephone dial tone, with or without sound small, distortion or noise and so on.
3) transmitter testing.
Press Tester "T" key, to send telephone microphone aimed mouth blowing, listening to receiver if there were "involved in the sand" sound. While also observing the call level meter pointer is to the right head tilt, the greater the magnitude of deflection pointer to the right, indicating the higher sensitivity of the phone, whereas the lower sensitivity.

4) pulse dialing detection.
with MODEL-1080 phone testers, order number if dial-up, pulse rate, intermittent than meet the requirements, the instrument will "beep" sound issue, indicating that the test target to meet the requirements. If the indicator does not meet the test requirements, it is not audible, while the parameters of non-compliance indicators will be lit in the corresponding indicator in the instructions.

5) telephone DC resistance testing.
required two multimeter, a multimeter set to 10V DC voltage block, in parallel in the outside telephone line, telephone outside the test voltage, while the other multimeter with a current of 50mA DC block, outside the loop in series with the telephone , the test current, the measurement results of calculations, the phones DC resistance, DC resistance and then determine whether to meet the technical specifications.

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