Osciloscope hameg 512-4 channel 2 no horizontal line

[Armand alla]

Hi to all ,i have an old osciloscope hameg 512-4, i have a problem with channel 2 ,i have not the second horizontal line in the screen ,i push the button mono/dual but it do not come and when i rotate the vertical button of channel 2 it rotate the horizontal line of channel 1,also signals put in channel 2 and volt/div button let say all the function of channel 2 control horizontal line of channel 1 , i have changed all 1uf tantalium caps to new ones but i do not have the second horizontal line of ch2.
Please help me .

 

[KlausST]

Hi

Please show a photo of the scope where we can see all the setup and the screen.

Klaus

 

[Armand alla]

Thankyou for answering .Those are the buttons .if necesary i take a video what it do on my problem

 

[KlausST]

Hi

No need for a video. A photo is sufficient.
* switch ON the scope
* press the "dual" button
* press the "chopper" button
* set timebase to 0.1ms/div
* set trigger to "auto" (fully left?)

If you see one horizontal line:
* move Ch 1 vertical offset. Check whether the line moves
* move Ch 2 vertical offset. Check whether the line moves

Klaus

 

[Armand alla]

I did and 1 horizontal line is present.and it moves also with ch1 ofset and ch2 ofset up and down.it also can move without pressing dual and chopper button. I have clean the switch in dual button but second line no come.i didnt fimd on circuit where ch1 and ch2 signal is going together to check.it looks that ch1 and 2 use the same x line on crt

 

[KlausST]

Hi

If there is a single line (we don't see on your photo) and it moves eith Ch1 offset as well as with Ch2 offset, then most probably you have an "ADD Ch1 + Ch2" enabled.

Klaus

 

[Armand alla]

Yes klaustst is like you have sayed .Look like there is an Add ch1+ch2 .
I will verify later putting 2 dc voltage one 5v other 9 v and see if its an add ch1+ch2.as i see the front pannel of scope does not have such a button ADD button

 

[Armand alla]

I also do have nothing when i push Hor.ext button .it should be X-Y plot but no point on the screen.

 

[D.A.(Tony)Stewart]

Start by checking voltages for Vce , or Vb,Ve, Vc on the chopper and Channel mutivibrator page which does the alternate sweep features.

 

[Armand alla]

Thankyou tony for responding i have checked a bit the voltages on the mutivibrator and i have seen that some voltages are 4v low.i have checked some resistors there and instead of 51 ohm i have 32 ohm ,.will take the X board out and to check for those resistors +/- 5% and change them as is in the manual after i gave info.it will take a while i think

 

[D.A.(Tony)Stewart]

Follow the inputs from chop/alt to all the outputs to Y amp

 

[Armand alla]

Ok sir thankyou for the advice.i will begin from Y board to check

 

[D.A.(Tony)Stewart]

Ok sir thankyou for the advice.i will begin from Y board to check

Better to start from middle then look for switch settings effects, then go forward or backward to find error.

 

[Armand alla]

Yes it looks like is an ADD fuction of both signals on my oscilloscope .i put a squere vave in ch1 and a sawtooth wawe in channel 2 .it show me a sawtoth signal 90 degre of squere signal.so those 2 signals are mixed somewhere and i want to divide them .as y ofsset ch1 and ch2 up and down is arranged by 1 ch Xline.infact if dual is not press on this osciloscope y offset of both channel can move the line verticaly ,when i push dual another second X line should come but is not coming so i am looking to bring it back .thats it

 

[Armand alla]

Sir Stewart ,
I just get out the Y board to check and i have some resistors that has more than 50% ohm down ,(anyway will verify after getting those resistors out the circuit),but there is a change to the transistor of ch1 and 2 ,i checked the manual on the photo and 2 of them are not as the manual look .2 of them are reversed i send a photo of manul and my board .i think that there should be the problem anyway i will check those 4 transistors from the manual book the connections .(i never have change those both they guy before me hav dome that i think) anyway thankyou