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Problem Philips Oszilloskop 3233 (Elektronik)

verfasst von asko, 03.03.2012, 13:45 Uhr

So, hab mich mühselig eingelesen. Meiner Meinung nach kann es an zwei Dingen liegen: Hold-off Schaltung oder Austastung. Ich tippe auf die Hold-off Kondensatoren, die man mit dem TIME Schalter auswählt. Was meint ihr?

Auszug aus dem Handbuch:

3.1.4.2. Hold-off circuit

Due to the effect of diode GR504, the charge of the hold-off capacitor selected with TIME/cm switch SK2,
cannot follow the decay of the sawtooth voltage.
The capacitor voltage will then decrease with an RC time which is sufficiently large to allow the sawtooth to
reach its zero level and to ensure the decay of the switching phenomena. During this RC time, the input level
of the sweep-gating multivibrator is so high that incoming trigger pulses have no effect.

3.1.6.4. Blanking circuit

The blanking circuit blanks the c.r.t. during the fly-back of the timebase and unblanks the c.r.t. during the
sweep and constantly if TIME/cm switch SK2 occupies position X via A.
The blanking circuit operates on a low voltage level and comprises an a.c. and a d.c. path.
Transistor TS706 is driven by the collector signal of transistor TS504 in the sweep-gating multivibrator.
Transistor TS706 forms together with transistor TS704 a single-ended push-pull circuit.

- A.C. Path: The amplified a.c. components of the blanking signal are fed direct to the Wehnelt cylinder of
the c.r.t. via H.T. capacitor C707.
- DC. Path: For the d.c. component of the blanking signal, the signal of oscillator TS702 & TS703 is used.
The oscillator signal is modulated with the blanking signal. The amplified modulated signal on the collector
of transistor TS703 is via capacitor C706 fed to demodulator GR702-R713. After demodulation, also the
a.c. component of the blanking signal is available.

The ac. and d.c. amplifications are equalized by means of potentiometer R71 1.