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After using my Macintosh SE/30 for about half an hour, it starts to make a very high pitched, continuous sound at a low but annoying volume. (It sounds like tinnitus.) After another few minutes, it becomes more intermittent. I'm guessing it's some capacitor(s) getting noisy at a certain temperature range. I've had the analog board recapped a year ago and the logic board I bought previously recapped (don't know how long ago). I haven't recapped the power supply. What is the most likely culprit?

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Posted (edited)

What’s this component circled in red called? I found that when I tap it with a pen, the sound goes away momentarily. Is this the flyback transformer you're talking about?

24691508-7FF3-4FAC-8D05-115FCEAC0880.jpeg

Edited by nonzero
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The component you have circled is the flyback transformer. The glue looks to be in very poor condition. It is the brownish stuff around the edge. When these machines come from the factory, it starts off as a tan color. Computers that were used for a very long time and been very hot have transformers that look like yours. I would probably not recommend touching this part of the analog board when it is energized, at least not without some further research about analog board operation. This part likely had thousands of volts running through it when you poked it. I think you'll need to find a replacement part to fix this issue.

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Thanks, yea I figured it was high voltage so I used the back of a plastic pen to tap it. I'm reading I could remove the glue and epoxy it, but it requires a lot of work, including fastidious scraping, baking out moisture, and using a vacuum chamber. Is there a quick and dirty solution that will stop the sound even at the cost of a lower life expectancy for the transformer?

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That flyback has had a hard life - the dark colour there indicates its been used for a high number of hours.

Depending on where you are in the world, obtaining a spare SE analog board with a flyback in better condition is probably your best option IMO - they come up on eBay and there might be someone on the forum who can spare one as well...

 

Finding a replacement flyback on its own is an expensive task.

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The Plus, SE, SE/30 and Classic can use the same flybacks.

 

The ones used by the colour models (Colour Classic and Colour Classic II) are different.

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On 3/7/2021 at 10:35 PM, nonzero said:

Thanks, yea I figured it was high voltage so I used the back of a plastic pen to tap it. I'm reading I could remove the glue and epoxy it, but it requires a lot of work, including fastidious scraping, baking out moisture, and using a vacuum chamber. Is there a quick and dirty solution that will stop the sound even at the cost of a lower life expectancy for the transformer?

 

What? Just remove the glue and add some fresh glue. let it run down the core and fill it up. 

 

It will be fine. However, you need to do this sooner rather than later, becuase core ringing can lead to core saturation which will produce alot of heat and eventually destroy the transformer. you have to do this. 

 

Also I cant hear the noise anymore, im too old. 

Edited by techknight
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Which gorilla glue?

Everyone should stop saying “gorilla glue”

There are many different types, for many different applications. 

No. Don’t use gorilla glue.   FOR ANYTHING!!!

https://www.google.com/search?q=gorilla+glue&source=lmns&tbm=shop&bih=666&biw=1024&client=safari&prmd=nvi&hl=en-US&sa=X&ved=2ahUKEwiSp6yhvKrvAhUI3awKHZhODNUQ_AUoBXoECAAQCA

Edited by jimjimx
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On 3/10/2021 at 6:47 PM, techknight said:

 

What? Just remove the glue and add some fresh glue. let it run down the core and fill it up. 

 

It will be fine. However, you need to do this sooner rather than later, becuase core ringing can lead to core saturation which will produce alot of heat and eventually destroy the transformer. you have to do this. 

 

Also I cant hear the noise anymore, im too old. 

Dang, one of my Wells & Gardner RGB monitors has some irritating flyback whine. Normally I just replace them (they aren't expensive and are still in (re)production), but I may give this a try before I do. The picture is fine, the sound is just annoying as hell. In all honesty, I would never have thought to re-glue the cores, lol.

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On 3/11/2021 at 6:32 PM, warmech said:

Dang, one of my Wells & Gardner RGB monitors has some irritating flyback whine. Normally I just replace them (they aren't expensive and are still in (re)production), but I may give this a try before I do. The picture is fine, the sound is just annoying as hell. In all honesty, I would never have thought to re-glue the cores, lol.

 

Yea I do whatever i can saving flybacks. the plastic is getting brittle and cracking open on some old ones too, and you have to reseal those with HV rated silicone. like corona dope. 

 

And as far as new flyback production? thats news to me. according to @maceffects the parts for flybacks arnt made anymore. so eventually the worlds supply will run out. 

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That's right, last time I checked the parts to make new flybacks aren't being produced anymore.  In the OPs case, this sure is a flyback issue.  If anyone does find a source for new flybacks or even parts needed to make new ones, please let me know.  I'd be interesting in buying some for myself or producing some if parts become available. 

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Mac flybacks? No clue there. As far as the arcade world goes, though, K7000-compatible flybacks have been reproduced for years (along with a bevy of other manufacturers and models). They are certainly of lesser quality than OEM W&G or Electrohome flybacks, but they've kept a ton of monitors alive. Most of the games in my garage have had their flybacks replaced, as they were on the cusp of death. About the only monitors that are impossible to get repro flybacks for (and require a transplant or a worth-its-weight-in-gold OEM unit) are fairly uncommon color vector displays.

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