Repairing a 577 that is pretty far gone.


Eric
 

I got most of the repairs complete on a 577 that was pretty trashed I was in to the calibration document to adjusting the vertical amp gain there was very little adjustment. Holding in the beam find button and moving the position know the trace moves up and down but also moves in a J pattern on the crt when moving the vertical position control from clockwise to full counter clockwise. I have tested all 4 transistors and all the resisters in the vertical drive section and they all test with in spec however the amp and drive transistors are VERY poorly matched when it comes to Hfe. Troubleshooting lead me back to U570 which should be a tek 156-0200-00 (AKA MC1456P) what was in the socket was a metal can labeled S 7939 1826 0569. the unit is a very early one display serial number is B010114 the chassis serial is B010124. Power supply checks out OK and is working. Any one know what I can use in replacement of a 156-200?

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