Apple Monitor II A2M2010P

[ojt1998]

Hi all,

I'm in the process of restoring a monitor ii that I purchased not working. Upto now I have recapped the main board and the unit now powers on. The rear controls and contrast knobs are now functioning since the recap however it doesn't want to display an image. At best I have a slight outline of the Raspberry Pi boot logo however the image is very distorted and wavy. Looking at the circuit diagram of the monitor would I be right in thinking it is possibly the transistors that are on the video in - Q101 and Q102?

My main electronics experience is with audio amplifiers and such. I have discharged the CRT and understand the risks assosciated with the high voltage.

Many thanks.

 

[retrogear]

you should be able to turn up the brightness control in the back to get a green raster even with no video cable plugged in.
Can you get a green raster ? If so then the next common cause of no video or weak/wiggly video is the jack itself either cracked joints/traces or oxidized

Larry G

 

[VERAULT]

Video or still images would help. I do have two A2m2010 monitors I have been unable to fix wavyness which snaps and collapses after a period of time. Just to say we covered it. Have you tried a really well made shielded Composite cable (not the cheap stuff they make and sell from china which costs a few cents?) Sometimes a good cable fixes these issues.

 

[ojt1998]

I’ve tried a couple of different cables. The top tight line is an outline of a raspberry then the two sort of horizontal highlighted lines are the Pi’s login text. The controls on the back do adjust the image with brightness etc

 

[VERAULT]

Well scale back the brightness, you are quickly wearing out the tube.

Have you used contact solution on the dirty pots?

Is the bottom right just an artifact of the rolling refresh rate or is it black? Because if its a dark corner the issue is your yoke has a break.

 

[ojt1998]

I scaled the brightness back after getting a decent enough photo. The screen shows the full raster - that’s just the refresh rate. I’ll try some contact solution on the dirty pots and see if that does the trick

 

[VERAULT]

I take it your trying to make some retro Pi setup?

 

[retrogear]

As long as you got the correct values/polarity for the coupling caps C101,C102,C104 then yes it could be one of the video amp transistors Q101,Q102 or shorted diode D101.
The voltage readings on those transistors might provide a clue as well. Be aware that cap polarity markings on boards aren't always correct.

Larry G

 

[VERAULT]

I think only the monitor IIc has incorrect silk screening. I havent come across an a2m2010 with incorrect polarity. Then again this is a PAL system, I am guessing it uses a different board I am unfamiliar with.