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FIXED - Sanyo TV + 17PW20.1
dumpystig:
First post here so hello to all you experts who I am hoping can shed some light on the following dilemma.
The TV is a Sanyo CES37WSD7-B, 17PW20.1 PSU, 17MB22-2 A/V I/O. The fault is similar to (but not the same as) many I have read about the past few days, regarding the standby freeze/LED staying on. Here is the sequence of what happens:
- Plug TV in; LED off
- Enter Standby by pressing button on TV; LED illuminates brightly for a split second then immediately dims to around half that initial brightness. TV buttons and remote have no influence - only the Standby button will work.
- Leave TV in above state; after anywhere between 5-40 minutes the backlight will come on, the screen comes to life and then functions as normal. Slight buzzing from bottom right area of PSU, faint but audible when I get near.
All the caps have been visually inspected (I don't have the appropriate test equipment, just a DMM) and none show any bulging domes/splitting sides or any leakage. What I have spotted is that the main smoothing cap (C819) has been replaced - it should be 220uF but the replacement is 150uF. I have done a shed load of resoldering to try and eliminate any dry joints. Once the set is up and running all voltages are as indicated on the schematics.
My thoughts are that the smoothing cap being a lower value is probably the culprit, but confirmation of this or any other indicators of the fault would be welcome.
Thanks,
Mark
watteau:
Hi Mark,
Have you checked the stand-by voltage on D823, when the
fault is present (it should be about 11.5V).
If it's low, the most common problem are the two 4700u 6.3v
caps. C818, and C857, in the stand-by secondary circuit.
Regards,
John.
dumpystig:
Hi John, thanks for reply.
Voltage at D823 = 10.5V, would you regard this as being low?
dumpystig:
And PL805, pin 12 (+5VSTBY) = 5.08V
watteau:
Yes that voltage should be Okay, there should also be a 3.3V on 11/12 of PL805, and the 5V
on pin 13, when in stand-by.
The power-supply 'run' voltage goes in at pin 6, of PL803, and should be 1.7V when in
stand-by, and 0V when running.
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