Analog Oscilloscope vertical cahanels linked

[darkness_electro]

I have a problem with a tesla bm 566 oscilloscope. It had some z amplifier problems, but i sorted it out (partially). Now i have another problem. Channel a and b seem to be linked together. The position controls from a changes the position of b and vice versa. Also, when i apply both cannels is seems to sum them up. Also, both seem inverted. Moreover, it doesn't go all the way, meaning it cannot be calibrated. I apply a 4 volt signal p-p and it only goes to max 3 divisions (1v/div)  When i apply a positive voltage the beam goes down. Do you have any idea how to sort this out?

[tautech]

I have a problem with a tesla bm 566 oscilloscope. It had some z amplifier problems, but i sorted it out (partially). Now i have another problem. Channel a and b seem to be linked together. The position controls from a changes the position of b and vice versa. Also, when i apply both cannels is seems to sum them up. Also, both seem inverted. Moreover, it doesn't go all the way, meaning it cannot be calibrated. I apply a 4 volt signal p-p and it only goes to max 3 divisions (1v/div)  When i apply a positive voltage the beam goes down. Do you have any idea how to sort this out?

Invert and/or Add functions enabled?

[darkness_electro]

No, they aren't, but they use ganged switches and are on a quite inacessible board. Can they be internally shorted?

[tyguy2]

That sounds like a likely cause. Try testing the continuity on the switches. You may also have an issue with the scanning on the CRT.

[mikerj]

Try giving the switches a squirt of contact cleaner followed by a good workout to remove any contact oxidation.

[darkness_electro]

i tried wiggling the switches, but it doesn't seem to be working. also, in alt or chop mode i still have only one trace.