Thanks to my generous scientist father, I am now the owner of a Tektronix 5111A 'scope and Wavetek signal generator. Both seem to function fine.

I've got a Fisher 400 with an intermittent crackling that I cannot diagnose. I changed out many of the carbon comp resistors in the power section and replaced the coupling caps. Swapped tubes, etc. Still can't locate the source. It's intermittent, but usually happens at some point while the receiver is on.

I know this sort of thing is much easier to diagnose with a scope, but I have no idea how. Could someone explain troubleshooting with the benefit of a scope and signal generator? I also have an audio signal tracer that I made out of a little Radio Shack amp...

Just excited to put the scope and stuff to work, but really don't know how...

Thanks a million.

I'm working on getting a scope and gen. Congrats on your score. This is probably a dumb suggestion, but have you cleaned all the pots. Just a thought. Jay

I just need probes........

You might try cleaning the tube socket pins where the tube plugs in and the tube pins as dirty pins can cause intermittent connections which can cause the crackling

I cast a vote for cleaning tube sockets/pins, too. I have "fixed" many old pieces (especially tuners) just so.

Of course, old carbon comp resistors can get 'sizzly', too.

Finally, if the crackles are tuner-specific, there's another possible cause. See #3 in the following thread:
http://audiokarma.org/forums/showthread.php?t=51715&highlight=craftsmen

Just excited to put the scope and stuff to work, but really don't know how...


Best thing is to do is get a book on O'scopes and "just do it"... starting with the basics and going from there.

Here's a few sites I found just doing a Google search... hope they help.

Link 1 (http://www.zerobeat.net/g3ycc/scope1.htm)

Link 2 (http://www.doctronics.co.uk/scope.htm)

Link 3 (http://www.facstaff.bucknell.edu/mastascu/eLabs/Scope/Scope1.html)

Scott

Also (if not included above):
http://www.tektronix.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes/XYZs/&FrameSet=oscilloscopes

BTW, you can 'make' a scope probe by just adding a small ceramic cap in series with your probe tip (e.g., a standard meter probe).