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Apple a2m6014 monitor need some help to repair

wolfpup

wolfpup

New Member
Joined
Nov 3, 2022
Messages
8
Hi, im new here I want to fix a old apple monitor i have replaced all the electrolytic caps and the IC401 LA7824 this has made no difference the monitor has what kinda looks like vertical collapse
but has wavy lines only in center I have a video of there


anybody have any ideas could this be a bad yoke ? any help on this id be most grateful.
 
Hi wolfpup and welcome. I wish you would have posted here before attempting a repair. I have worked on a ton of these a2m6014 monitors. NONE HAVE NEEDED CAPACITORS REPLACED. I highly doubt your issue is cap related.

You might be onto something with the yoke comment. Have you checked the horiz and Vert winding on the yoke for breaks? Do a continuity check with the cables unplugged from the video pcb. Make sure the yoke connector on the pcb has no broken solder joints. Make sure the ground leads are all connected. Its not vertical collapse as its not a thin line. The yoke might not be on correctly as well.
 
yoke.JPG
Hi, Verault I have it still open on my bench i took some readings off the yoke, take a look maybe you can tell if this looks bad not really sure what it should read.
the yoke is disconnected from the board wile I took these readings.
scop1.JPG
my other cheap scope is reading 600/650V on the HV output collector this not seem low ? in the day 20-24KV was what I would see. that was 20V division with a 10X probe

let me know what you think .
 
VERAULT said:
Give me a day or two and I will get you the readings from one of my good monitors. (y)
Click to expand...
Thanks that would be fantastic, i kinda hope its not the yoke or the flyback both of them will be hard to get.
 
Well I need you to check on the underside of the flyback. Solder-side of the pcb. Look for cracks. Lots of monitors are shipped badly and the weight of the flyback and crack the pcb. Look for hairline cracks or broken solder joints. I have repaired a bunch with this issue. Including the same model as yours. Look at this post I did to know what I mean: https://forum.vcfed.org/index.php?threads/1992-sony-trinitron-monitor-repair.78920/

And again, look at the pcb solderside connection of where the yoke cable connectors to the pcb for broken solder connections.

Also some deoxit in the H-sync and Vsync board pots (or any pots) works wonders for fine tuning... not necessarily related but something else to do in the interim.
 
VERAULT said:
Well I need you to check on the underside of the flyback. Solder-side of the pcb. Look for cracks. Lots of monitors are shipped badly and the weight of the flyback and crack the pcb. Look for hairline cracks or broken solder joints. I have repaired a bunch with this issue. Including the same model as yours. Look at this post I did to know what I mean: https://forum.vcfed.org/index.php?threads/1992-sony-trinitron-monitor-repair.78920/

And again, look at the pcb solderside connection of where the yoke cable connectors to the pcb for broken solder connections.

Also some deoxit in the H-sync and Vsync board pots (or any pots) works wonders for fine tuning... not necessarily related but something else to do in the interim.
Click to expand...
I'll take a look now, I already used deoxit5 on the larger trim pots, and resoldered the FBT I didn't inspect the yoke connector I'll do that now.
 
Well i just ordered the LA7822 from Ebay, that is the last IC in there that will rule out all the IC's so its can be the yoke or the FBT I think the HV may be low, Im going to borrow a HV prob from a friend i used a scope to check the saw wave form off the horizontal output transistor it was 650 volts peak to peak can't remember if that was normal on these I use to work on tube TV's 30 years ago i just cant remember the normal range for this. its coming back to me slowly lol..
 
Last edited:
Sorry I havent gotten the readings yet. Im in the process of cleaning up my office and work area as too many projects are scattered about.

You say the last IC.. but what about all the transistors?
 
@wolfpup how'd you come to the conclusion it's a bad yoke? I have the earlier, less-common IIC monitor (A2M6014) with a similar issue:iic-monitor.gif

It's been difficult to track down troubleshooting info for this specific issue, and for this specific monitor (the SAMS facts info/schematic are for a different version of the same IIc monitor).
Like you, I replaced the caps, and think I've verified all transistors are good - so trying to dig up some more troubleshooting info.
 
thisisben said:
I have the earlier, less-common IIC monitor (A2M6014)
Click to expand...
Thats an A2M4090 Not an A2m6124

I have had the windings on my 9" iic monitor go bad as well. Looked similar to that. Again if you read his post you can check the horizontal and vertical windings for continuity AND for Ohms and compare them against what you find online for correct readings. On my IIc monitor when I took the yoke off you could see patches of green areas where the enamel failed and the copper corroded. IT could not be saved.
 
VERAULT said:
Thats an A2M4090 Not an A2m6124

I have had the windings on my 9" iic monitor go bad as well. Looked similar to that. Again if you read his post you can check the horizontal and vertical windings for continuity AND for Ohms and compare them against what you find online for correct readings. On my IIc monitor when I took the yoke off you could see patches of green areas where the enamel failed and the copper corroded. IT could not be saved.
Click to expand...
Sounds good, I'll take a look at the windings and see what I can find. Appreciate it!
 
Hi, I ended up picked up another dead monitor same model, and repaired that one, needed Cap's and a STR power regulator so I checked its yoke and found i was reading across a resistor i had to unsolder the vertical windings once i did that i found I had an open winding. from what I can see the glue used to attach magnets and hold windings together has turned from the normal yellow color to a dark brown color and corroded the yoke on some parts of it. i have seen this in other repairs in the past. on main boards the brown glue would eat traces. i asked the Manufactured about why they use this glue but they tell me they have no idea about that brown glue.

but I did so much work on the first monitor I still want to revive it anybody know where i can get a used yoke ?
 
@wolfpup good info about the glue causing the yoke winding breakdown. I have also seen this in the past as you described on circuit traces. Had you posted this earlier on another forum ? I remember seeing the wavy center line and suggesting it could be the yoke. If it wasn't you I'd like to find that person and tell him what you found.

Larry G
 
wolfpup said:
View attachment 1248225
Hi, Verault I have it still open on my bench i took some readings off the yoke, take a look maybe you can tell if this looks bad not really sure what it should read.
the yoke is disconnected from the board wile I took these readings.
View attachment 1248227
my other cheap scope is reading 600/650V on the HV output collector this not seem low ? in the day 20-24KV was what I would see. that was 20V division with a 10X probe

let me know what you think .
Click to expand...

@wolfpup Sorry for the really late response but this was the first chance I actually had to take measurement. Again this is from one of my Working monitors. I know you already drew conclusions it was the yoke but I wanted to post results regardless.
yoke.JPG
 
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