Topics

7b92


 

Found in the newsgroup "sci.electronics.design" and i thein it 's
worth to forward it to here:

"Betreff: Re: 7904A oscilloscope with 7B92A time base - viewing
delayed trace?
Datum: Thu, 19 Jul 2001 19:32:39 GMT
Von: "Mitch Berkson" <berkson@...>
Firma: Excite@Home - The Leader in Broadband http://home.com/faster
Foren: sci.electronics.design


After obtaining a copy of the 7B92A manual, I was able to troubleshoot
the
problem. Since it is the same problem on two time bases, it may be
worthwhile to document it here.

It is a mechanical problem. Behind the Time/Div knob, there is a
plastic
bobbin which activates a lever switch depending on whether the
Time/Div knob
is pulled out. The lever switch spring is also what pushes against
the
bobbin to return it to its position.

The bobbin became stuck and the lever switch spring was unable to
return it
to its position. Since the bobbin held the switch closed, the time
base was
not aware that the knob was pulled out and did not behave as if
delay/intensify mode were on.

I cleaned the bobbin/shaft with WD40 and now both time bases work
fine.

Mitch Berkson"

Jorgen
dj0ud


Miroslav Pokorni <mpokorni@...>
 

It might be worth considering effect of WD40 on plastic parts.

I am almost certain that plastic is nylon of some variety, most likely not
filled (no filler like glass). WD40 is silicon but has smell of petroleum
product, that might be propelant.

Regards

Miroslav Pokorni

-----Original Message-----
From: @dj0ud [mailto:@dj0ud]
Sent: Wednesday, July 25, 2001 9:24 AM
To: TekScopes@...
Subject: [TekScopes] 7b92

Found in the newsgroup "sci.electronics.design" and i thein
it 's
worth to forward it to here:

"Betreff: Re: 7904A oscilloscope with 7B92A time base -
viewing
delayed trace?
Datum: Thu, 19 Jul 2001 19:32:39 GMT
Von: "Mitch Berkson" <berkson@...>
Firma: Excite@Home - The Leader in Broadband
http://home.com/faster
Foren: sci.electronics.design


After obtaining a copy of the 7B92A manual, I was able to
troubleshoot
the
problem. Since it is the same problem on two time bases, it
may be
worthwhile to document it here.

It is a mechanical problem. Behind the Time/Div knob, there
is a
plastic
bobbin which activates a lever switch depending on whether
the
Time/Div knob
is pulled out. The lever switch spring is also what pushes
against
the
bobbin to return it to its position.

The bobbin became stuck and the lever switch spring was
unable to
return it
to its position. Since the bobbin held the switch closed,
the time
base was
not aware that the knob was pulled out and did not behave as
if
delay/intensify mode were on.

I cleaned the bobbin/shaft with WD40 and now both time bases
work
fine.

Mitch Berkson"

Jorgen
dj0ud


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