2445B focus problem

I have a 2445B scope on which I can not adjust focus to obtain a clear sharp trace. The best focus is achieved somewhere in the middle of the range of the focus pot which leads me to believe that this isn't just a pot which has drifted.

This is a scope purchased under warranty. Should I return it or try to repair it? Any ideas what may be wrong?

To email me see

formatting link

Thanks!

Grant Erwin Kirkland, Washington

Reply to
Grant Erwin
Loading thread data ...

How about the astigmatism control, usually a screwdriver adjustment on the front panel? Between that and the focus pot it should be possible to get a clear trace everywhere.

Does it do this with no input signal, or only when you have it connected to something? The 20 MHz bandwidth switch cleans the trace up nicely on my

2445, otherwise it is fairly broad.

If that doesn't do it, I'd go for the warranty first.

Reply to
Bob M.

"Bob M." wrote in news: snipped-for-privacy@comcast.com:

This is good advice.IF all this fails,then you need a service manual,and check out the circuit description for the HV circuitry.The worst thing would be a bad Z-axis hybrid IC;not made any more,not available new,just from parts scopes.

--
Jim Yanik,NRA member
remove null to contact me
Reply to
Jim Yanik

Tweezing the astigmatism pot did actually help quite a bit. It's now probably usable. I was just looking at the DC traces and the lettering. This scope was shipped without proper (original) packing material and it may have just bonked the front panel pots a little.

My big concern is if the CRT is gassy - that is a killer when buying old Tek scopes. Even when you could get replacements they would cost as much as adding a room on your house!

I've heard that on 2215 scopes there is a resistor string focus setting network which drifts. I've looked at the schematic for the focus control electronics on the 24XX scopes and it is an actual DC amplifier. I don't think this is a resistor drift issue.

As I do have a parts scope available, I do also have the option to swap the high voltage boards. I don't know if that would cause the scope to go out of calibration, however.

Grant Erw> How about the astigmatism control, usually a screwdriver adjustment on the

Reply to
Grant Erwin

Grant Erwin wrote in news: snipped-for-privacy@corp.supernews.com:

I've seen some of the small value ceramic tubular caps cause focus/astig problems.Leaky or shorted caps. This scope has dynamic focus tracking(with intensity changes). If you do swap the HV boards,recalibration should be done.

--
Jim Yanik,NRA member
remove null to contact me
Reply to
Jim Yanik

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.