Re: 7A26 transient response 5 nS all atten

Colin Herbert

I think I am remembering correctly when I say that Tektronix recommended the use of IPA (isopropyl alcohol, isopropanol, propan-2-ol) because many other cleaning agents could damage the substrate of the attenuator boards. The boards are made from polyphenylene oxide. On P.41 of my Service manual (Rev. May 1974) on cleaning, it reads:

"Avoid the use of chemical cleaning agents which might damage the plastics used in this instrument. Special care should be taken when cleaning the Polyphenylene Oxide attenuator boards. Do not apply any solvent containing ketones, esters or halogenated hydrocarbons. To clean, use only water soluble detergents, ethyl, methyl or isopropyl alcohol."

I hope that clarifies the situation sufficiently. It would be a great shame for someone to ruin a fine instrument by employing the wrong solvent to clean the contacts on the attenuators.


-----Original Message-----
From: [] On Behalf Of Dennis Tillman W7PF
Sent: 22 January 2020 00:20
Subject: Re: [TekScopes] 7A26 transient response 5 nS all atten

I believe the service manuals mention what is safest to use to clean the contact fingers. They are delicate so be very careful. I use IPA soaked into thin cardboard. Others believe that DeOxit is good. It used to be called Cramolin 30 years ago. Still others use a shot of contact cleaner but that will eventually (many years from now) leave a residue behind that may harden.

Dennis Tillman W7PF

-----Original Message-----
From: [] On Behalf Of Albert Otten
Sent: Monday, January 20, 2020 1:00 PM
Subject: Re: [TekScopes] 7A26 transient response 5 nS all atten

Hello Jon,

I don't have much experience with cleaning those attenuators. I think I used a squirt of Ipa when there was no access with a soaked strip of postcart.
In an old message here I saw a link to .
Scroll down to dismantled 7A26. Looks interesting at first sight, didn't read it in detail.


Dennis Tillman W7PF
TekScopes Moderator

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