NEC FS-6805S

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Hi, I have a friends TV at home, complete frame collapse. I replaced
all of the electro's in the vertical section & the vertical output ic
(LA 7838) checked the Vcc reistor from the flyback transformer,
switched on & nill change. I know that it is probably  not economical
to fix, but, she can't really afford a new one & I've got the time to
play with it. I haven't got the voltages with me at the moment, but pin
1 has 12V, & pin 13 has 27V. I've checked the deflection coil, plugs &
sockets for continuity.
Any help greatly appreciated. Thanks, Ian S.


Re: NEC FS-6805S


My notes

LA7838 Vertical O/P
13 Pin SIP

pin 11 =Grd
pin 12 =Output[12&11] 13 Meg
pin 1 12% Volt
pin 8 28% Volt

If you go between pin 12 & 11 there should be about 13 Meg Ohms
on a faulty IC there is only  0-6 Ohms


Hi, I have a friends TV at home, complete frame collapse. I replaced
all of the electro's in the vertical section & the vertical output ic
(LA 7838) checked the Vcc reistor from the flyback transformer,
switched on & nill change. I know that it is probably  not economical
to fix, but, she can't really afford a new one & I've got the time to
play with it. I haven't got the voltages with me at the moment, but pin
1 has 12V, & pin 13 has 27V. I've checked the deflection coil, plugs &
sockets for continuity.
Any help greatly appreciated. Thanks, Ian S.



Re: NEC FS-6805S


So My notes were not complete then, how about this

LA7838 Vertical O/P
13 Pin SIP

pin 11 =Grd
pin 12 =Output[12&11] 13 Meg
pin 1 =power supply, 12 Volt
pin 8 = power suply 28 Volt
pin 13 = power supply for output stage

If you go between pin 12 & 11 there should be about 13 Meg Ohms
on a faulty IC there is only  0-6 Ohms


Hi, I have a friends TV at home, complete frame collapse. I replaced
all of the electro's in the vertical section & the vertical output ic
(LA 7838) checked the Vcc reistor from the flyback transformer,
switched on & nill change. I know that it is probably  not economical
to fix, but, she can't really afford a new one & I've got the time to
play with it. I haven't got the voltages with me at the moment, but pin
1 has 12V, & pin 13 has 27V. I've checked the deflection coil, plugs &
sockets for continuity.
Any help greatly appreciated. Thanks, Ian S.




Re: NEC FS-6805S



Eric wrote:
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Hi Eric, thanks for the response.
I have pin 1 = 12V
         pin 8 = 28V
         pin 13 = 27.39V
         pin 12 = 16.66V
Because of other parallel conections, I couldn't measure the resistance
between pins 11 & 12 but in circuit it is a couple of K.  If I have
16.66V
to ground on pin 12 the ic doesn't have a short circuit output. There
is no sawtooth waveform on the output, hence no drive to the yolk coil.
Does the output ic need a trigger input from the jungle ic on pin 2 to
oscillate ? I suspect that this is the reason for the no frame drive.
Looking forward to you response,
Ian Sutherland.


Re: NEC FS-6805S



sutherland snipped-for-privacy@yahoo.com wrote:
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