Tek 475 no horizontal


Warren Brewster
 

Hi,

I have a Tek 475, that I recently repaired ( faulty cap in voltage divider for HV circuit).
I tested the scope and checked as per service manual - worked perfectly.
Turned off and unplugged power lead

When putting the cover back on the edge of the cover caught a single wire connecting the DM44 to the timing board - breaking the wire off the timing board.
I reversed to cover removal and then unplugged other end of the wire.

Re tested scope and all functions work perfectly - so powered down and left overnight.
Next day decided to re-solder wire back onto timing board.
- Removed A8 Trigger / Z-axis board and A7 timing board as per service manual.
- Re-soldered wire ( easy to see where as came from) to trigger board
- Refitted A7 and A8 boards ( I also took pics of all cables just in case) - all cables returned to correct positions.
- Powered up - no horizontal trace :-((

If I set input to display CH1 and CH2 - 2 dots appear.
- Vertical adjust on CH2 moves CH2 up/down
- Vertical adjust on CH1 moves CH1 diagonally right/up.
- Horizontal adjust no effect.

Tested with spare scope - getting square wave from J399, TP526 shows 250mv square wave @~1Mhz.
U520 outputs also show square wave
- Waveform at Q566 is small square wave ( approx 8Mv p-p)

Suggestions of where fault may be - or where to test
Horizontal amp and sweep gen - no saw tooth waveform - probably due to trigger fault???


Regards,

Warren

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