"Dick" wrote in message
...
My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

You need the Tekscopes group:

Leon