I own an Hameg 204 analog oscilloscope.
Unfortunately the x-axis oscillation on the CRT screen is broken. I am looking for advice on how to fix this.
My background: I have fixed several little electronics devices. Examples include networks switch with burnt capacitors. This oscilloscope is much more complicated and a little above my level to handle it myself.
Precise description of the issue
- Expected behavior: the CRT ray moves from the far left to the far right of the CRT screen.
Actual behavior: the CRT ray is stuck at 60% of the x-axis of the screen (y-axis works fine). The x-pos button does nothing from 100 down to 50% and move the line start further right when turned from 50% to 0%.
When I activate the "x magn x10" button, the ray moves from 60% to the far right.
Basically, with the "x magn x10" trick, I have a working oscilloscope with only 40% of the original screen width. These "40%" do not depend on the time resolution.
What I already did
The following was made with "x magn x10" always activated.
First thing I did what to get the schematics: http://www.sky-messtechnik.de/images/PDFs/HM204-1.pdf .
I then used a working (digital) oscilloscope to check "from S281" point (it is not only 'from CT' as stated in the manual but also 'from timebase'). Here I see the x-oscillation I expected to see, with 0V in the middle (see image below). I can also confirm that x-pos (bottom left) works as intended (-12V to 0V).
"Inside" the x-final amplifier though, the situation is very different. I always see the same pattern (at both 'W2-6 CRT', Chp12, ...) but obviously with different voltages. depending on the location in the amplifier (see image below; minimum value is very close to 0V).
EDIT: I also checked all power rails and all are at their expected voltage.
Where you can help
As the board is quite difficult to take apart (so I would like to do it only once), I am looking for some advice on how to precisely locate the faulty component so I can order a replacement.
I am hoping that for an experienced eye, the pattern would be typical of a specific component failure.
If needed, I can make further measurements.
EDIT: new measurement:
T2101, base (to R2101):
T2101, collector (to R2110):
T2101, emitter (to R2100/R2101/R2108):
T2102, base (to R2103):
T2102, collector (to R2112):
T2102, emitter (to R2109, VR2100, VR2101):