Re: 475 Probe Calibration problem with x10 probes

n2msqrp
 

Thanks. Has anyone tried Caig Labs Deoxit?

Mike N2MS


On October 24, 2018 at 9:44 AM "Colin Herbert via Groups.Io" < colingherbert=blueyonder.co.uk@groups.io
wrote:

This might indeed help, but be cautious when doing it. There are posts on
this forum where the correct technique is laid out - it is very easy to
damage the cam-operated contacts. Also, note that the material of the
attenuator board is a bit special and is easily damaged by heat and
various solvents. Briefly, the technique is to put a little IPA (isopropyl
alcohol) onto a sliver of ordinary paper and use that to clean the
contacts. Check that the contacts are open, slide the ipa-wetted paper
between them, close the contacts and then carefully pull the paper out
level with the board, as far as possible. This can be done a few times to
get all the contaminants off. You can probably ascertain which of the
attenuator contacts need cleaning by checking in the service manual as to
which attenuators are in circuit when the poor bandwidth is seen.
Good Luck, Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto: TekScopes@groups.io ] On Behalf Of
ef804s tubes
Sent: 24 October 2018 14:27
To: TekScopes@groups.io
Subject: Re: [TekScopes] 475 Probe Calibration problem with x10 probes

I have two 475 scopes. Both have developed a similar probe calibration
problem on one channel. I am using the scope calibration signal. I have
verified results with multiple probes

First scope - Channel 1 probe calibration tests fine with x1 and x10
probles. Channel 2 calibration tests fine with a x1 probe but the waveform
has a sloped rise and fall time when testing with a x10 probe on a
vertical sensitivity setting of .5v/div and above.

Second scope - Channel 1 probe calibration tests fine with x1 probes but
the waveform is a spike when testing with a x10 probe with vertical
sensitivity setting of .5v/div and above. Channel 2 probe calibration
works fine with x1 and x10 probes.

Has anyone seen this problem?

Mike N2MS

Hi,

please clean the attenuator contacts ans the pins of the attenuator blocks
as well.

Fred





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