Hi Gary,
The very first thing you need to do is to measure the low voltage test
points for DC level and ripple. They are marked on the board. These
scopes usually have bad electrolytic capacitors and you need to test for
that.
The service manual will tell you what to measure and what to expect.
The correct manual can be had here.
Regards,
Tom
On 9/20/2020 7:41 PM, gary@... wrote:
I have a 465B/DM44 that is new to me that I think has issues. I am a relative newby to scopes, but this one does not seem right. There is "compression" of the horizontal trace, but it varies. Sometimes the trace just shrinks to a width of about 1-1.2 major graticule (1/2" in the same spot), other times it only shrinks a bit, covering about 7.3 graticules, with the best it ever gets being about 9.6 (full screen = 10). This significant compression happens randomly, both when scope is relatively "cold' and after it is fully warmed up. It affects both channels. I've used different probes - no difference. I can impact this, by moving the sweep left to right with the horizontal position control. This sometimes moving the horiz position "fixes" it, other times not. If it is temporarily working OK, I can get it to shrink if I aggressively manipulate the horiz position knob. In addition the "timing" may not be correct - not sure I am saying this correctly, but the calibration square wave gets "smaller" horizontally as the trace moves from left to right. I would expect the length of the square wave to be the same all across the screen. I suspect this is related to the compression, but not sure - seems relevant to mention. The only thing I have done is removed the cover and made sure the connections to the deflection plates on the CRT were secure (they appeared to be). Everything looks clean and untouched inside, and overall the unit is clean and does not look abused. I have not cleaned any switches or controls, but that seems like a good place to start. If it matters, serial number is above 60xxx, which I believe makes it the later series. I have downloaded the manual from the TEK site, but they only have the low S/N version. If it would help I have photos and even short video of the bad behavior.
I come here seeking help, on how to proceed, possible causes, how to troubleshoot. Thanks in advance Gary.
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