G3 AIO Molar CRT Flickers

[Johnnya101]

Hello everyone,

Just got my Molar G3 the other day. Oh my GOD THAT THING IS HUGE!

Anyways, onto the problem.

The first boot, it went fine. I was on Internet Explorer, when the screen quickly blanked out and cracked/clicked. This was for like 0.5 seconds. Then, the second boot, right after the Mac OS 9.2 screen, it cracked, and then went to the loading screen.

Now. I DO know a little about CRTs. So this I think could either mean:

Bad solder joints?

Bad analog board capacitor(s)?

Dust on yoke?

What does this sound like to you? The PRAM battery IS dead (Time resets to 1956), so I have to replace it today.

Some specs of the AIO

233 MHz

120 (Forgot exactly) MB ram

4 GB HD duel boot OS X and OS 9

Thank you for your help!

 

[Johnnya101]

Oh, probably should have posted a little more info.

It has a sticker saying May 1998. 

It also seems to happen randomly.

I can post photos if needed, although I think everyone knows what  the molar looks like

 

[EvilCapitalist]

The ticking sound makes me think flyback is on the way out.  I had a studio display doing the exact same thing and that's what it turned out to be.

The G3 AiOs certainly are heavy beasts.  There was a guy out my way selling 20 of them and I briefly thought about buying them and tossing them in a storage unit but shipping them would be murder.

 

[Johnnya101]

What makes it seem like that? Not trying to say that in a rude way, just want to know how you would know...

If it is the flyback, are they hard to get?

Thanks!

 

[EvilCapitalist]

How you had described it, the picture going away for a split second while making a ticking sound is exactly what happened on the Studio Display I had.  There was a thread somewhere on here about flyback transformers going bad on certain machines and monitors which I can't find but it mentioned things in more detail.

I never ended up fixing the problem, just waited until it got bad enough that the monitor was unusable and switched to a different one.  Obviously not an option in your case but perhaps one of the more technically-inclined folks will chime in with what replacing it entails.  Though if you haven't already cracked the case open and blown dust out (if there is any) do that, you might luck out and have that be the root of the issue.

 

[Johnnya101]

Ive only taken out the motherboard tray, and the crt is enclosed as far as I can tell. 

A note to others: I dont mind working on a crt. Although I have never done it, the grounding seems easy enough.

 

[Gorgonops]

You could check and reflow the solder joints on the analog board and see if that helps, that's supposedly been of use in some of these bad flyback cases. But that's almost certainly what it is, nearly all of Apple's CRT AOI's succumb to bad flybacks eventually.

 

[Johnnya101]

Does anyone here know what I need to look for when buying another? And would anyone here do the major work of replacing it? 

John

 

[CelGen]

The snapping is high voltage arcing about. Usually when a lot of dust accumulates it starts to happen and doesn't always mean a bad joint or a failing flyback however excessive arcing can damage windings on the yoke and causeexcess current draw on the flyback.

Open it and remove all dust around the deflection yoke and around the flyback, including the underside of the board.

Failing that, you can try reflowing the joints around the flyback but if it was a cold joint the symptoms would be occurring far more often.

Failing that, get rid of the Molar Mac because it's a beige turd and you'll be spending more than it's worth to replace the flyback.

I had a studio display doing the exact same thing and that's what it turned out to be.

I'd like to point out the CRT studio displays were fire hazards. Recycle them on sight and never attempt to use one.

 

[Johnnya101]

Thanks CelGen, Ill check out that. The CRT as I said is enclosed in like metal box, so I have to figure out how to open that first. Theres a really dusty fan above the motherboard leading to the CRT... I wonder if that could have sucked up dust and moved it to the CRT?

 

[Johnnya101]

One other thing. This computer SHOULD have a bleeder since its newer, right? 

 

[belgaonkar]

You don't want to leave it up to fate.

In the past I have used a flat head screw driver and a car jump lead to ground the CRT.

 

[Johnnya101]

Ill definitely discharge the CRT, but Im just wondering if it has a bleeder... just in case.

I might not even have to do anything. Im just going to remove the CRT casing and see if theres dust on the FBT. If there isn't, the FBT is the problem. If there is, then its probably a dust issue.

 

[CelGen]

Dust it anyways. It can't hurt to give it a cleaning.

I never assume a bleeder is present. even when there is there's always the potential it has failed with a high resistance which makes it either slow to discharge or completely ineffective. A screwdriver with a piece of wire wrapped around it to the chassis and a poke under theanode cap for a few seconds is all you gotta do to be positive.

 

[Johnnya101]

This is what I found online to discharge. Im assuming this is correct?

1. Get a long screwdriver, use wire wrapped around and taped to screwdriver shaft.

2. Attach the other end of the wire to something grounded (If I do it outside, a grounding rod)

3. Push the screwdriver under the cap and touch the metal piece a few times.

 

[CelGen]

That's all there is to it.

 

[Johnnya101]

UPDATE ON PROGRESS

Found a repair manual online for the AIO. Took off the shell and the EMT cover for the CRT. Man, there is a pretty thick layer of dust for being covered! Well, not THICK but still... Theres dust webs...

Ill be cleaning that later today.

 

[Johnnya101]

Cleaned off the dust webs and some of the dust. Don't want to touch the actual tube or the red FBT wire... So couldn't do too much. If anyone wants to know, the FBT is model:

6174Z - 1009A

3TD23

The only replacement I could find was $69.

I also purchased a VGA adapter so I can use a monitor without using the CRT.

Ill see if theres any flicker I guess when its back together. Theres no way that something on the motherboard can cause this, right? 

 

[techknight]

I had two of these back when they were in service at school, do the very same thing. The flyback is bad.