Leader LBO-514A Chanel 1 problem

[georgian]

Hello guys,

Could someome help me to fix my very old oscilloscope?
The Chanel1 lokk like dose't like very low voltages.
I have a ramp signal that gose from 0V to 2.56V (Atmega32 with AD557 DAC)
The Chanel 2 seams to work just fine but the Chanel 1 dosen't show the ramp as it should.

I do have some electronic skills and an original manual with schematics from this oscilloscope.

See the attached pictures for a clear details. Thank you.

[georgian]

Chanel 2

[rmserroni]

Okay, if you have the manual it is easier to check the attenual resistors at the input of the channel, you can inject a signal and compare between channels 1/2 in which component the signal is different, this component is defective.
good luck

[georgian]

Could you help me indentify this resistor? Is it one ofe this 3?

[georgian]

After reading https://www.eevblog.com/forum/repair/leader-lbo-514a-strange-tail-on-square-wave/50/ post on the forum I realized I have the same problem. I turned the VC1201 10pF capacitor all the way and it solved the problem.

Thank you,
Georgian Borca