In the case of xinhua sy168-a (distributed on the circuit map), for example, the radio segment failure analysis:
First, the fm band is normal and does not receive am-band signals: check for 7v voltage at both ends of the c128 filter cap; if no r/t switch or c128 penetration is required。
C128 at two ends of normal voltage, check for 6. 6 v voltage at t104
1, none: poor contact with fm switches
2, yes: check the corresponding band switch, is the point of contact good? The c127 two-end voltage shall be 5. 7 v, if low or jump: the common failure is a mid-week internal trough of l109 through or out of battery. If the c127 two-end voltage is 5. 7 v, the common failure is the lack of internal contact within the c124 caps, which causes the middle wave to stop。
Two, no fm frequency signal. Fm frequency is normal:
Check if fm switches are in contact, e. G. Normal: measure t101, t102, t103 levels of voltage, test l203, l204, mid-week loops, d202, d203 diodes. C164, c110 and c116, respectively, need to be checked for penetration if t101, t102 or t103 are to be launched at low extreme voltage。
Xinhua sy168-a radio part transistor work with a number of toes voltage values:
Three, the fm band signal is available, but the stereo signal is not on:
Measuring the ic201 model: an362 foot voltage values, an abnormal need to replace integrated circuits, e. G., if normal, adjust tr201 when signal is available to synchronize the rate of oscillation of the ic201 internal pressure-controlled oscillator with the frequency of the radio signal's conductive frequency signal, and general trt201 to give ic201 foot 6 a 6. 5v voltage, indicating light。
Ic201, an362, working voltage values:
Four, am and fm are silent:
Check t501 set electrodes for 12v voltage, if there is no need to check whether the whole-stream diode d501 is pierced, c505 and c506 are pierced and the fuse is burned
If t501 sets 12v voltage is normal, it is necessary to check t201, t202, t203 cavity voltage, and the common failure element is the discharge of the polar cap c201, c203, c205 through or out of the electrical system, so that the transistor is shut down。
Five, there's a noise in the am band:
(a) the sound of the steamboats: c505, c506, insufficient capacity
Blast sound: often l109 has a leak or poor exposure to internal circuits。
Shouting: t501 discharges a polar voltage above 8. 2 v, resulting in excessive middle discharge power voltage, resulting in medium-frequency self-restraint。
The circuit map of the recorder is very different, and can this machine overhaul be useful in overhauling other models
