rack
Newbie level 4
Hello.
I've a "horizontal" problem with my HungChang analog oscilloscope mod. 5502, 20MHz dual tracks.
The instrument shows the tracks only in the left part of screen.
If I turn the "X-POS" control knob the track moving only on the left part of screen, on the right direction the track "collapse" or overwrite the the one that exist.
I supposed the problem was in "horzontal stage" so I've checked all the transistors and diodes: they seems all ok.
There aren't burned resistors or swollen capacitors.
The solders seems good and I redoing some ones with a bad look (poor).
Vertical controls works fine.
here the schematics about "horizontal stage":
**broken link removed**
**broken link removed**
Measuring the out voltage for the "H+" and "H-" plates (see red marks in schematic), with "TIME/DIV" sets in "XY" :
"X-POS" knob at min (left) -> "H-"=160V, "H+"= about 4V.
"X-POS" knob centered -> "H-"=about 3V, "H+"= about 3V.
"X-POS" knob at max (right) -> "H-"=about 0V, "H+"= about 5V.
So the problem should be in "H+" output voltage.
If i turn the "TIME/DIV" control, sometimes the track fill all the screen and in this case the "H+" voltage reaches the 160V (157V).
The calibration signal (square, 1Vpp, 1KHz) is shows fine but only in the short left part of screen but, when the "X-POS" knob is turned, the square wave stands over the one that exist.
I have replaced the transistors for the output stage (Q809,810,811 and 812) and some of the polarized capacitors in this schematic part.
Any helps about identify the trouble are welcome.
Thanks in advance for answers.
I've a "horizontal" problem with my HungChang analog oscilloscope mod. 5502, 20MHz dual tracks.
The instrument shows the tracks only in the left part of screen.
If I turn the "X-POS" control knob the track moving only on the left part of screen, on the right direction the track "collapse" or overwrite the the one that exist.
I supposed the problem was in "horzontal stage" so I've checked all the transistors and diodes: they seems all ok.
There aren't burned resistors or swollen capacitors.
The solders seems good and I redoing some ones with a bad look (poor).
Vertical controls works fine.
here the schematics about "horizontal stage":
**broken link removed**
**broken link removed**
Measuring the out voltage for the "H+" and "H-" plates (see red marks in schematic), with "TIME/DIV" sets in "XY" :
"X-POS" knob at min (left) -> "H-"=160V, "H+"= about 4V.
"X-POS" knob centered -> "H-"=about 3V, "H+"= about 3V.
"X-POS" knob at max (right) -> "H-"=about 0V, "H+"= about 5V.
So the problem should be in "H+" output voltage.
If i turn the "TIME/DIV" control, sometimes the track fill all the screen and in this case the "H+" voltage reaches the 160V (157V).
The calibration signal (square, 1Vpp, 1KHz) is shows fine but only in the short left part of screen but, when the "X-POS" knob is turned, the square wave stands over the one that exist.
I have replaced the transistors for the output stage (Q809,810,811 and 812) and some of the polarized capacitors in this schematic part.
Any helps about identify the trouble are welcome.
Thanks in advance for answers.