Tektronix 2252 - repair and preventive maintenance

[22euu]

Hi all,

Recently I am the happy owner of an oscilloscope wanted since childhood - Tektronix 2252. The oscilloscope arrived in pretty good shape but when I turned it on, I noticed a few things I didn't like:

1. What is displayed on the screen seems to have a slight flicker (a kind of visibly annoying "refresh rate") and the display is not sharper like my old 2215A Tek.
2. When I turn it off, the waveform remains on the screen and gradually fades out, focusing on the middle of the screen (like old CRT TV).
3. The fan sounds very noisy.
4. I opened it and in the high voltage area, traces of "smoke - high voltage burnt dust" can be seen on the cover and underneath. I google it and comparing with the photos of other oscilloscopes, the area should be clean...

Relying on your knowledge in troubleshooting Tektronix oscilloscopes, please help me to solve the above problems and also please indicate, based on your experience which components should be changed as preventive maintenance and to extend the life of the oscilloscope.

Thanks.

[David Hess]

1. What is displayed on the screen seems to have a slight flicker (a kind of visibly annoying "refresh rate") and the display is not sharper like my old 2215A Tek.

The single beam is time multiplexed to produce the readout which causes flickering in the waveform display.  The readout can be shut off to prevent this.  Some oscilloscopes have a mode where the readout is only generated between sweeps, but I do not remember that any of the 22xx or 24xx series support this.

3. The fan sounds very noisy.

Both of mine are almost completely silent, so your fan bearings might be worn.  Oiling them (motor oil is good) will likely improve the situation.

4. I opened it and in the high voltage area, traces of "smoke - high voltage burnt dust" can be seen on the cover and underneath. I google it and comparing with the photos of other oscilloscopes, the area should be clean...

The high voltages electrostatically collect smoke and dust from the environment.  This likely indicates many hours of operation and is not something to worry about.

[22euu]

1. What is displayed on the screen seems to have a slight flicker (a kind of visibly annoying "refresh rate") and the display is not sharper like my old 2215A Tek.

The single beam is time multiplexed to produce the readout which causes flickering in the waveform display.  The readout can be shut off to prevent this.  Some oscilloscopes have a mode where the readout is only generated between sweeps, but I do not remember that any of the 22xx or 24xx series support this.

I thought some kind of capacitor was responsible for this. It's OK, I'll disable read out.

4. I opened it and in the high voltage area, traces of "smoke - high voltage burnt dust" can be seen on the cover and underneath. I google it and comparing with the photos of other oscilloscopes, the area should be clean...

The high voltages electrostatically collect smoke and dust from the environment.  This likely indicates many hours of operation and is not something to worry about.

That's good, I thought I had to change the high voltage capacitors from there.

Many thanks, David!