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R2001C CRT Display Wavering and Noise on startup

Posted: Sat Dec 22, 2012 11:51 pm
by N1CTF
Greetings,
The display on my R2001C oscillates up and down vertically at a very slow rate - maybe 1 cycle per second. It is a very slight wavering movement, and it is still totally useable, but I am wondering if this is an indication of a developing problem.
The previous owner shotgunned the electrolytic caps in it, but I don't know how long ago. I think he got them all, but I am not certain.
Where might I look for problems?

Also, the same service monitor makes a lot of squelch noise when it is first turned on. It lasts for about 10 seconds. It almost sounds like there are tubes in it warming up, but I am pretty sure this is a solid state unit. Otherwise it works fine after it settles down. Is this normal, or an indication something is on its way out?

Thanks in advance for your help.
John, N1CTF

Re: R2001C CRT Display Wavering and Noise on startup

Posted: Mon Apr 01, 2013 6:14 pm
by bernie
My two bits worth:
The reason that your display is distorting is caused by a 60 hz AC field beating with the vertical scan rate.
Nearby transformers are often the cause, a soldering station, or some other device.

You can also have stray fields from the power transformer. I have seen missing shoulder washers on the transformer mounting causing the problem
The wiring on the fan relay can also be the problem. Be sure that the wires are all as far as possible from the CRT.

The CRT is very sensitive to external magnetic fields. This is why the entire unit must be degaussed prior to CRT alignment.
I do not think that the squelch is a problem.

Re: R2001C CRT Display Wavering and Noise on startup

Posted: Tue Apr 02, 2013 7:30 pm
by DJP126
Another cause of the oscillations is poor grounding of the AC line input filter. The filter has a tab on it that you can solder on a short piece of wire & ground it to the chassis.