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nathaniel630
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« on: June 26, 2008, 08:50:34 » |
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Old and dirty boards can cause intermittent operation.
they respond to heat and cold treatments.
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nathaniel630
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« Reply #1 on: June 27, 2008, 00:15:04 » |
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INTERFERENCE symptoms may occur at certain times of the day.
Check for interference sources that go into operation at these hours.
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nathaniel630
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« Reply #2 on: June 29, 2008, 21:35:07 » |
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VIDEO CKT. TROUBLESHOOTING:
keep in mind, the INPUTS to the video loop are CONVENTIONAL BASEBAND VIDEO SIGNALS that can be monitored and traced back to the source(IF/ audio module or jack pack).The OUTPUT from the loop are CONVENTIONAL RGB SIGNALS that can be monitored and traced to the video output module.
if the input is GOOD and the output is BAD,,,you have isolated video problem.
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nathaniel630
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« Reply #3 on: June 30, 2008, 04:13:36 » |
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as in the case of any digital device, if the RESET LINE is open,shorted to ground or to power (5 or12V), the ICs will NOT RESET , or will remain reset, no matter what control signals are applied. this brings the entire digital operation to a halt.
So if you find a RESET LINE (or pin) that is always high, always low, or apparently connected to nothing (floating), check the line carefully...
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nathaniel630
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« Reply #4 on: July 02, 2008, 03:15:56 » |
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The General procedure for checking all types of chips, large or small, is as follows:
1. Check the symptoms at the system output.
2. Check the relevant input and output devices that are associated with the symptoms.
3. Check yhe output amplifiers that drive the relevant system output devices.
4. Check the relevant IC signal input pins and circuits.
5. Check the IC supply-voltage pins and circuits.
6 Check all relevant Control pins and circuits.
7. Check the relevant "automatic feedback control pins". Introduce substitute cotrol voltages.
8. Check the peripheral capacitors, coils, and crystals associated with the relevant IC pins.Remove and
substitute these parts if necessary..
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nathaniel630
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« Reply #5 on: July 03, 2008, 06:45:02 » |
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A shorted CHIP will often run warmer than normal.
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nathaniel630
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« Reply #6 on: July 03, 2008, 06:52:49 » |
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A complete loss of action or defective output can be the result of line
conflicts..
check all the enable pins and all chips that output to the lines involved.
check the "timing ckts." to all the enable pins involved.
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pardeep
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« Reply #7 on: July 03, 2008, 22:13:15 » |
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respected friends--IF YOU HAVE A GOOD MOOD THEN CHANCES OF SUCCESS (TO FIX FAULTS ) IS BRIGHT. SO FIX THE FAULT WITH GOOD MOOD AND WITHOUT TENSION. BE HAPPY DONT WORRY
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BE HAPPY DONT WORRY
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nathaniel630
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« Reply #8 on: July 03, 2008, 22:58:32 » |
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VCR repair:
End- of -tape ensor LED can burn out,tigerring AUTOSTOP during recording and playback.
Also, a worn or dirty idler tire can cause internal tape spillage and autostop.
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nathaniel630
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« Reply #9 on: July 03, 2008, 23:12:18 » |
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VCR
Bad Servo controller IC can cause the machine to run by itself and inore front -panel controls.
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nathaniel630
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VCR
Loading mechanism can shift out of adjustment, preventing operation of REWIND and FAST FORWARD modes.
Also, cold solder joints in HEAD AMP area can cause "intermittent color playback problems."
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nathaniel630
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VCR
spindles might become loose, causing STREAKS in picture or total "loss of tracking." Carefully readjust the spindles until the picture is clear.
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nathaniel630
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Capacitors have a high failure rate. Small low-voltage electrolitics fail most often.
Other types of low voltage capacitors fail very often, too.
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nathaniel630
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Electrolitic capacitors tend to open more often than they short.
This means that jumping all the electrolitics when something goes wrong is not a bad idea.
Use one or two large-value, high-voltage capacitors for checking all the capacitors.
The ratings should be higher than that of the capacitor tesed. Turn off the power when connecting the jumper capacitors.
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nathaniel630
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...The LENGHT OF TIME it takes for a ckt. breaker to cut out after turn-on gives a clue as to where the trouble lies.
....IMMEDIATE CUT-OFF indicates a short in the power-supply or power output ckt. A FEW SECONDS delay indicates a low power ckt.
....VERY LONG PERIODS of normal operation before cutoff could mean that the ckt. breaker itself is defective. Replace it. Chances are very good that this will solve the problem. If the problem persists, you have at least elliminated one possible cause...
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