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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to aus.electronics,sci.electronics.repair
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NEC FS5197 TV, Blank screen, sound okay
Any one help on an NEC FS5197. Has a blank screen, EHT and heaters okay,
sound is okay. I replaced Q681 which was faulty but that didn't fix the fault. Circuit around Q681 appears okay. (Unfortunately I don't have a schematic.) Thanks for any help in advance TJB |
#2
Posted to aus.electronics,sci.electronics.repair
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NEC FS5197 TV, Blank screen, sound okay
TJB wrote:
Any one help on an NEC FS5197. Has a blank screen, EHT and heaters okay, sound is okay. I replaced Q681 which was faulty but that didn't fix the fault. Circuit around Q681 appears okay. (Unfortunately I don't have a schematic.) Thanks for any help in advance TJB If EHT and heaters are ok, the problem must be manifesting on cathodes or grids. (Emission so dire you cant see a thing is pretty unlikely, but I have come across it once.) I dont see that theres anything to suggest other than metering those and working back from them. Of course the cause may be far away from the cathodes, possibly as far away as in the tuner. Without a cct diag youre going to have a hard life! NT |
#3
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NEC FS5197 TV, Blank screen, sound okay
And what is Q681 "bingo"?
is it the HOT or what" wrote in message oups.com... TJB wrote: Any one help on an NEC FS5197. Has a blank screen, EHT and heaters okay, sound is okay. I replaced Q681 which was faulty but that didn't fix the fault. Circuit around Q681 appears okay. (Unfortunately I don't have a schematic.) Thanks for any help in advance TJB If EHT and heaters are ok, the problem must be manifesting on cathodes or grids. (Emission so dire you cant see a thing is pretty unlikely, but I have come across it once.) I dont see that theres anything to suggest other than metering those and working back from them. Of course the cause may be far away from the cathodes, possibly as far away as in the tuner. Without a cct diag youre going to have a hard life! NT |
#4
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NEC FS5197 TV, Blank screen, sound okay
"Frank" wrote in :
And what is Q681 "bingo"? is it the HOT or what" wrote in message oups.com... TJB wrote: Any one help on an NEC FS5197. Has a blank screen, EHT and heaters okay, sound is okay. I replaced Q681 which was faulty but that didn't fix the fault. Circuit around Q681 appears okay. (Unfortunately I don't have a schematic.) Thanks for any help in advance TJB If EHT and heaters are ok, the problem must be manifesting on cathodes or grids. (Emission so dire you cant see a thing is pretty unlikely, but I have come across it once.) I dont see that theres anything to suggest other than metering those and working back from them. Of course the cause may be far away from the cathodes, possibly as far away as in the tuner. Without a cct diag youre going to have a hard life! NT Thanks guys but ----- A big sorry -- I forgot to mention that the on screen display is working fine. The crt and it's voltages are okay. The problem is in one of those multi-legged devices or in a switching transistor(s). Video In or TV just produces a blank screen. Setting the onscreen menu to display a blue background for no signal also produces a blank screen. I started poking around the transistors located around the tuner/video stage. Unfortunately as I said I don't have a circuit so it's a bit tough to find out where each stage is and what each section does. TJB |
#5
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NEC FS5197 TV, Blank screen, sound okay
TJB wrote:
"Frank" wrote in : wrote in message oups.com... TJB wrote: the tuner. Without a cct diag youre going to have a hard life! Thanks guys but ----- A big sorry -- I forgot to mention that the on screen display is working fine. The crt and it's voltages are okay. The problem is in one of those multi-legged devices or in a switching transistor(s). Video In or TV just produces a blank screen. Setting the onscreen menu to display a blue background for no signal also produces a blank screen. I started poking around the transistors located around the tuner/video stage. Unfortunately as I said I don't have a circuit so it's a bit tough to find out where each stage is and what each section does. So how do you expect to check the voltages and waveforms at all the key points if youve got no cct diag? How are you going to narrow the fault down until you find it with no such info? NT |
#6
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NEC FS5197 TV, Blank screen, sound okay
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