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Greetings!

I have an SC504 on the bench. What is the 250 ohm trimmer pot that is on the Hv Board? I can’t find any documentation on this mod.

Insight would be appreciated!

Barry

I can't even tell what is the latest circuit configuration. Anyone have an idea?

Just a guess, but after some digging I suspect there is a different HV board layout/configuration for the 2 different CRT's available... anyone has any insight?

Regards,

Barry

Suggest you get the exact service manual for the model and serial number of the scope

Most HV trim pots and control are megohms not 250 Ohm

Jon

Jon,

The trimmer has “250R” markings and measures 250 ohm.

I have downloaded SC504 manuals from several sources. They are all the same version. I don’t know where else to look.

Thank you!

Barry

Here is a photo of the HV board showing the trimmer.

/g/TekScopes/photo/300558/3883505?p=Created%2C%2C%2C20%2C2%2C0%2C0

Regards,

Barry

Does anyone have a copy of the “REV B” manual? If so, does the HV board show a trimmer?

Many thanks!

The bus,wire is,perhaps an indicator of a mod,perhaps b y previous repair attempt.

Suggest you Remove the Trim pot see the,original PCB.

Jon

Jon,

I have 2 SC504. Both of these units have this exact mod. I found some documentation that stated that a later crt required a circuit mod.

Thanks, still putting the pieces together.

Barry

There is a revised Service Manual that shows the trimmer on the HV Board. That manual is labeled "REV B May 1980" on the first page of the Table of Contents. So this was a Tektronix factory modification that probably allowed the HV Board to be tuned for different versions of the CRTs.