Products > Test Equipment
Tektronix 335 teardown
mnemotechnika:
Hi everyone, I'm new to this forum. Please help me figure out what might be wrong with this old device. This is what appears on the screen no matter what I adjust. The center part moves slightly when adjusting the horizontal position. Thanks.
frantisek:
First of all you need to check all voltages and ripple of the power supply to make sure they are OK! Then we will see.
David Hess:
After checking the power supply voltages, investigate the focus resistor chain and measure the CRT cathode voltage if you have a suitable high voltage probe.
TurboTom:
Some time ago, I had a 335 with a damaged CRT. Two of the glass rods that align the electron gun assembly were cracked so there was some distortion, though the trace was still half-way visible. But I can imagine that more severe damage inside the tube may also lead to the effect that you're reporting. I hope that's not the cause in your case.
It may as well be one of the deflection amplifiers being completely out of balance. You may want to check the voltages at the deflection plates and if they change (within the pairs) in a mirror-like way when you adjust X- and Y-position.
I used my broken 335 as a parts donor for another damaged scope but may have most of the components still here, so if you need an "unobtainium" spare (except for the CRT) I may be able to help.
David Hess:
--- Quote from: TurboTom on October 11, 2024, 06:31:40 am ---It may as well be one of the deflection amplifiers being completely out of balance. You may want to check the voltages at the deflection plates and if they change (within the pairs) in a mirror-like way when you adjust X- and Y-position.
--- End quote ---
Oh, that would do it also. If the beam is far enough off the screen, then the reflections make shadows like that. More than once initial inspect revealed that one of the deflection plate connections fell off.
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