| Modelo |
Defeito |
Solução |
| SC-428VS |
Sem vídeo, pouca emissão do
TRC. |
Substituir C502G, C502R e C502B – 47uF / 50V. C505G, C505R e C505B – 1uF / 50V.
Fazer ajuste de corte e equilíbrio do branco para que o monitor funcione corretamente. |
| SC428 |
Grampo no campo vertical |
Trocar TDA8351. |
| SM430 |
Sem video,tela preta com alta. |
Trocar capacitores C112/C114 1000UF. |
| SC431VII |
COLD POOR TUBE REDUCE |
R120+ADD 470UF16V TO HTR FEED 6.5V< |
| SC431 |
Apito vindo dasbobinas de deflexao. |
Verifique a cola na bobina e retire-a. |
| SC428VS |
Estreitamento na largura horizontal. |
TDA4950 |
| SC428PSL |
Imagem ruim, baixa tensao de filamento |
Capacitores na placa de video(1UF160V).
|
| SC-428PSL |
Pale white background and text is green or other primary colour. A slight burning smell may also be noted. |
Check the 70V supply to CRT base PCB. If this is low it normally indicates that excessive current is being drawn by the video driver circuits. Any smell is usually caused by R600 70V feed resistor overheating on the main PCB and/or diodes overheating on the CRT base PCB. Check all the diodes on the tube base PCB they often suffer a high resistance reverse leakage, which does not always show on an ohm meter. If any diodes are suspect it is best to substitute them, or remove them and test for reverse leakage with a bench PSU set to around 30V. Connect the diode under test in series with a 1K resistor across the supply with the cathode to positive. If there is a voltage drop across the resistor, this indicates a reverse leakage and the diode should be replaced. The 1N4148 diode faults normally show on an ohm meter but the BAV21 diodes at locations D104R, D104B and D104G can have a reverse leak which will only show on a PSU test. These diodes have a 250V reverse voltage rating and must be replaced by a similar type. Voltages on the video output chip IC102 type LM2406T while displaying a DOS screen, starting from the top pin, are as follows. 72.2V, 2.7V, 72.2V, 2.9V, 71.8V, 74.4V, 0V, 1.4V, 1.4V, 11.6V, 1.4V. Also check for 72V across each BAV21 diode. We have had a few examples like this, the last had 6 duff diodes and a duff chip, this may have been caused by a flash over in theCRT. |
Click aqui e veja o cartão do cresce net |
