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

1 has 12V, & pin 13 has 27V. I've checked the deflection coil, plugs & sockets for continuity. Any help greatly appreciated. Thanks, Ian S.

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

1 has 12V, & pin 13 has 27V. I've checked the deflection coil, plugs & sockets for continuity. Any help greatly appreciated. Thanks, Ian S.

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.