If you do work on the tunnel diodes, be sure to use a heat sink right up
against the diode body. Ge tunnel diodes are easily ruined with heat.
?
However, I think David's comments are more likely the issue. That is
because of the external trigger working.
?
Do you have the correct service manual for your 475?
?
Regards,
tom
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----- Original Message -----
Sent: Friday, January 25, 2013 5:09
PM
Subject: Re: [TekScopes] 475 Triggering
Issue -- Will recent 468 Triggering Issue Thread Help Me?
?
On 01/25/2013 03:46 PM, stan_katz wrote:
?
I have an ancient 475 scope which works fine with an external trigger,
but will not trigger on any of the internal sources. Should I start by
reviewing the recent 468 triggering issue thread to get me going? If not,
can anyone recommend a thread I should start with? Of course, I'd be
delighted to receive help on this
thread.
Stan
Probably not.
Going from
what I had on 465Bs the triggering problem is often that
the tunnel diodes
have changed in value.
There are many! threads about this in the
archives.
It may be worth your time to try swapping the TDs from the B
sweep section
with the A section to see if things change.
I had this
problem come up when I was hunting for a process control network
problem
while working in factory in a different country.
I swapped the TDs and the
scope has been near perfect ever since.
Go figure.
