Help with M1212 Display

[Jockelill]

Hi!
New to the forum here, but hoping to get some advice.
In my collection of old macs, I have 2 M1212 display. Both are in working order, but they make a quite annoying high pitch noise. I don’t think it’s the usual “coil wine”, because the frequency is much lower.
I’ve identified it to the high voltage transformer, and posted a small video below.

my question Is simply, any advice on how to get rid of this problem?

Any help is highly appreciated!

br
Joakim

 

[Byrd]

Hi Joakim,

In a dark blacked out room can you notice any arcing (small sparks, flashes) coming from the flyback transformer (where you are touching)? If so these will eventually need replacement; I'd also reflow solder on the underside. Dust too won't help - time for a good blast out using compressed air.

After a re solder if it seems OK and the monitor is performing well, there is special epoxy/high temp hot glue you could use to stop the vibrations and whining around the flyback.

JB

 

[Jockelill]

Thanks for the tip, I’ll try it again in a dark room. Yeah, it needs cleaning for sure! I did recap my other M1212 and cleaned it thoroughly, but it’s making the same noise. Haven’t tried the reflow, but I’ll give that a try as well.

If the flyback needs replacement, are these available somewhere?

do you know the brand of that glue?

 

[Byrd]

A high temp silicone sealant would do, at a pinch the high temp hot glue sticks.

The later the monitor the better chance of finding a cheap flyback - google or eBay the part no.

 

[9166188]

My M1212 also suffers similar noise issue. Did yours get fixed with silicon sealant and re solder?

 

[Jockelill]

Haven’t tried it yet, but I got some high temp epoxi yesterday that I will try out. I’ll keep you posted. Interesting is that also one of friends has one of these monitors and it does exactly the same, so seems “common”

 

[9166188]

Great, will wait for your update. BTW, I find this capacitor list. I might replace them while the case is open.

https://tinkerdifferent.com/resources/macintosh-color-display-m1212-capacitor-list-1-645-346-13.25/

 

[Jockelill]

Great, will wait for your update. BTW, I find this capacitor list. I might replace them while the case is open.

https://tinkerdifferent.com/resources/macintosh-color-display-m1212-capacitor-list-1-645-346-13.25/

Good find!! I’ve recapped one of my screens, but it had no impact on the coil whine.

 

[Jockelill]

Hi Joakim,

In a dark blacked out room can you notice any arcing (small sparks, flashes) coming from the flyback transformer (where you are touching)? If so these will eventually need replacement; I'd also reflow solder on the underside. Dust too won't help - time for a good blast out using compressed air.

After a re solder if it seems OK and the monitor is performing well, there is special epoxy/high temp hot glue you could use to stop the vibrations and whining around the flyback.

JB

No arching what I could, I tried in a dark room, but of course it can be internally.

 

[9166188]

According to this video, flyback transformer tends to go bad eventually. Is it possible to get a new compatible replacement nowadays? Looking at ebay, they don't seem to me having the same pins out configuration to fit necessarily and some have two adjustment knots not present in the original one in M1212. Any pointers to the right replacement appreciated!

 

[chiptripper]

I have the same squealing on my M1212, definitely the flyback. Seems like they're all falling victim to this trouble. The most likely source for a replacement would be someplace like HR Diemen. Seems they don't stock the exact replacement transformer anymore, but it's possible they have another one that'd match or could be adapted to fit this board.

HR Diemen

 

[Jockelill]

By coincidence I noticed a burnt resistor on one of mine. RL34, does anyone know the size of this? Or maybe someone has a schematic for the display?
I have reflown my flyback and if it does not help, I will attach it with epoxy.

 

[Jockelill]

One weird thing, my other M1212 does not have RL34! So must be different revision.
I did remove the resistor and it measures 22ohm in burnt condition, first line is red , so 22ohm does not sound very implausible, but a schematic would of course be nice

 

[9166188]

U mean this?

Apple M1212 Monitor Schematic

User Manual: Apple M1212 Monitor Schematic

usermanual.wiki

 

[Jockelill]

THANK YOU!

Only thing is that I can't find RL34 in this one... Likely this is the schematic for the first M1212, and then there is another one with "revision 2"...

 

[9166188]

Hello, want to test your sense of color? 110/220/330 Ohms

 

[Jockelill]

So, I finally got to test my screens again after reflowing the fly backs and changing the burnt resistor on one of them. And both seems to work just fine now!! I’ve tested them only a few hours, but the noise would come quite fast before. So, if you also have this problem, try to reflow/resolder the fly back first.

 

[9166188]

A belated update: re-solder didn't work for me. But after applying a thick layer of eproxy according to @Byrd, it stops humming. So, this settles the problem for now.

 

[Jockelill]

Cool, what epoxy did you use? Any picture?

 

[9166188]

I think most eproxy would do the job. I simply grab a random one from a local store.

But now, I hv a new problem. It can no longer power on.