Tek 465B with less than good focus


George Headley
 

Hello Group: This is my first post but I feel that I know all of the regulars. I'm very impressed with your knowledge and have learned a lot from your experiences. I an an old computer tech , retired but not ready to give up the challenges relating to Tektronix scopes. I have been buying them mostly for the challenges found in the repairs but somewhat out of respect for equipment that is fun to work on because of the quality. I have several 465B that have poor focus. Not really bad but not good enough. There is some improvement when I limit to 20MHz. I dont have a HV probe but I suspect HV problems. I know from experience that low HV will cause a blooming of the trace. I have adjusted the CRT bias as per the manual. Slight improvement, astig and sweep ckts within spec. If I can trouble you for a minute of your time do you have any suggestions. one more thing , it may be my imagination but the rise and fall lines seem to be sharper than the time base lines..
George Headley

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Denis Cobley <denis.cobley@...>
 

Hi George
These are getting old (like all of us).
The CRT's lose sharpness with age - my best suggestion is to get a 2200 CRT
(154-0861-00) from any 2213A, 2215A, 2220, 2221/A 2230, 2232, 2235/A 2236.
These CRT's were much sharper new and will always give better results.
You can buy a dead / damaged unit on ebay very cheap.
Pull the CRT, remove the trace rotation coil and it's a perfect fit (gains
and timing will be very close).
This CRT can then be you test tube - swap it into each scope - if the trace
is still bad you have a fault - if it comes good then your old CRT is beyond
it's useful life.
Regards
Denis
Regards
Denis Cobley
Newtek Support Pty Ltd
11 Lyon Park Rd
North Ryde 2113
Australia
Ph 61 2 9888 0162
Fax 61 2 9888 0125
www.newteksupport.com

----- Original Message -----
From: "George Headley" <georgeheadley@mybluelight.com>
To: <TekScopes@yahoogroups.com>
Sent: Friday, November 21, 2003 12:46 PM
Subject: [TekScopes] Tek 465B with less than good focus


Hello Group: This is my first post but I feel that I know all of the
regulars. I'm very impressed with your knowledge and have learned a lot from
your experiences. I an an old computer tech , retired but not ready to give
up the challenges relating to Tektronix scopes. I have been buying them
mostly for the challenges found in the repairs but somewhat out of respect
for equipment that is fun to work on because of the quality. I have several
465B that have poor focus. Not really bad but not good enough. There is some
improvement when I limit to 20MHz. I dont have a HV probe but I suspect HV
problems. I know from experience that low HV will cause a blooming of the
trace. I have adjusted the CRT bias as per the manual. Slight improvement,
astig and sweep ckts within spec. If I can trouble you for a minute of your
time do you have any suggestions. one more thing , it may be my imagination
but the rise and fall lines seem to be sharper than the time base lines..
George Headley

Sign up for Internet Service under $10 dollars a month, at
http://isp.BlueLight.com




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--- In TekScopes@yahoogroups.com, "George Headley" <georgeheadley@m...> wrote:
Hello Group: This is my first post but I feel that I know all of the regulars. I'm very impressed with your knowledge and have learned
a
lot from your experiences. I an an old computer tech , retired but not ready to give up the challenges relating to Tektronix scopes. I
have been buying them mostly for the challenges found in the repairs but somewhat out of respect for equipment that is fun to work
on
because of the quality. I have several 465B that have poor focus. Not really bad but not good enough. There is some improvement
when I limit to 20MHz. I dont have a HV probe but I suspect HV problems. I know from experience that low HV will cause a blooming
of the trace. I have adjusted the CRT bias as per the manual. Slight improvement, astig and sweep ckts within spec. If I can trouble
you for a minute of your time do you have any suggestions. one more thing , it may be my imagination but the rise and fall lines seem
to be sharper than the time base lines..
George Headley
The Broadband noise of the amplifiers often makes the beam to apear "thick" and "out of focus".
As you describe, if you limit the bandwith, it reduces the tracewith significant, than the tracewith is
caused by the broadband (johnson et al) noise from the vertical amplifiers and other noise sources (resistors)
inside the vertical chain.
In my opinion, if you could see a significant difference between ful bandwith and bwl it to abt 20MHz than
the focus is usualy good.
But also not to forget is the astigmatism control, also often correctible (inside) which influences the trace thickness,
but not soo big as the focus does.

Jorgen
dj0ud