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IC testing, how can I tell if vertical IC is bad?

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Robert Morris

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:roll: My vertical IC to Zenith television model SR2552S, has white horizontal line, the voltage measurements on the vertical IC read, .003v-vert. output,31v vert output power supply, .030v-input,1.6v-OSC blocking pin, 32v - Vcc1, and 29v- pump up output. I checked surrounding components for shorts and opens.
 

Sebi

Active Member
This is only a vert. power stage. Try inject AC voltage to input for checking. (1...2V 50 or 60Hz.)
 

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Robert Morris

New Member
Vertical IC replaced, cured problem, thankyou...however..

Sebi,
Thanks for taking the time to send me the schematic diagram to this circuit, it helped out and saved me time.I replaced the vert. IC LA7833 & the raster came back up, there were horizontal lines on the top, replacing C2100 near the vert. IC ([email protected])
cured the problem. However, all my work was undone when I powered up the set, and failed to clear the speaker terminals from under the chassis, caused the fuse to blow, replaced fuse, does not blow, but has no sound or picture. After all that work, discouraged, but carrying on. What next? I read the voltages on High Voltage Horiz Output transistor, and they read collector to base-160v dc///collector to emitter-160v dc///emmitter to base
001v dc..(This was NTE2302). Cannot see or smell any damage to power supply, read nearby reistors and diodes and they appear to be ok";
 

Sebi

Active Member
Auuuu.... As i read from Your post the hor defl. transistor bad. First desolder it, and solder a 230V 60W bulb to collector and emitter place, for PSU check. If the lamp lite, the PSU O.K. (160V, maybe with load lower.) Check the transistor with diode-tester or battery torch (+to base - seriel with bulb, bulb another pin to collector (lite) and to emitter (lite). With reverse polarity no lite this is O.K.
Here is a primitive drawing the most common FBT circuit.
 

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Squintz

New Member
Are the lines sort of on a slant. If so try adjusting the Vertical Sync Potentiometer located inside the TV housing on the circuit board. I had the same problem with thin horizontal lines but i think the problem may be the same.
 
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