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| Blueberry 2nd Gen iMac White screen, crinkling noises, no startup chime? What is wrong? | |
| Posted by: Froggy814 on 2026-08-30 16:45:25 I got a iMac G3 today and went to power it on as a test, and I heard a crinkling noise coming from the inside and there was no startup chime. Which was not unexpected considering the person I bought it from said that it didn't work. Research indicates either the PSU or the Flyback transformer is bad for the crinkling noise and that the no startup chime is a dead PRAM battery. But I want second opinions before tearing into a lethal case. (PSU and CRT can be deadly if handled improperly.) I beleive the hard drive spins up, but cannot be 100% certain. Any help would be appreciated to get the middle man working in my collection! Thanks! - Froggy | |
| Posted by: Froggy814 on 2026-08-31 07:45:46 Alright, I am going to try a PRAM reset to see if it chimes with that. Then I'll report back. | |
| Posted by: Froggy814 on 2026-08-31 08:06:11 Alright. It chimes! But I still have the white screen. Were going to need to fix that. What I hear: On startup there is crinkling inside the iMac. I hear the hard drive working After the crinkling stops there is a faint buzzing noise. Not from HD or CD drive. It is like not so faint you have to put your ear to the iMac shell but it is easier to hear that way. If anyone has anything to tell me so I can fix it, that would be appreciated! Thanks! | |
| Posted by: Froggy814 on 2026-08-31 08:22:34 Boy it sure is unfortunate that the 350Mhz G3 iMac's didn't have a VGA plug on the back! That would make troubleshooting a lot easier, such as seeing if it's the PSU, CRT, or something else entirely... | |
| Posted by: treellama on 2026-08-31 08:52:26 There are pads for one--does anybody know whether soldering one on would just...work? | |
Posted by: Froggy814 on 2026-08-31 08:55:57There are pads for one--does anybody know whether soldering one on would just...work?I didn't know that there were pads for one! Maybe I could try putting a VGA plug on and then... Do you know if it's a connector or a standard VGA plug layout? If someone has the pinout... | |
| Posted by: Froggy814 on 2026-08-31 08:57:04 Also, the power light comes on as well. How should I discharge the PAV board so that I will be at least partly safe before I start to tear it down? (I don't want to die from heart failure because I was stupid) | |
| Posted by: Froggy814 on 2026-08-31 10:42:13 Okay. Found a lead (I think) someone on reddit posted about a CRT just being white like mine in the iMac. And a commenter said: I think I've seen a handful of other people that had this issue. I don't remember if/how they fixed it though. It's like there's a short somewhere on the input side and RGB are all blasted to max voltage which would make white. I am still going to do research, I don't know what would cause the short either though... | |
| Posted by: Froggy814 on 2026-08-31 11:02:41 This guy says that it is usually caused by capacitors... Is that really the fix for everything this age now!?! From reddit thread: This is a super common phenomenon and particularly common with large JVCs. It's really just a power thing; white signals are often the most electrically intensive to produce and as sets age and their electrolytic capacitors get a little more resistive, they "groan" a bit when trying to create white light. Replacing capacitors is usually the go-to solution in this situation. You'll want to replace the capacitors eventually anyway if you want the TV to stay operational for a long time but if this is bothering you right now, at least replacing the capacitors used in the power supply circuit might suffice. I'll let someone else chime in with their opinions on this but the tl;dr is you're probably not doing anything wrong and there's probably not anything seriously wrong with your set; CRTs are just old and many are showing strong signs of their age nowadays. | |
| Posted by: Froggy814 on 2026-08-31 11:05:49 And the other suspect is most likely the Flyback Transformer... Mac ClassicTips and tricks to help keep your Mac OS 9/Early Mac OS computers usable today. Software downloads, guides, hacks and news.
Flyback transformer failure (common) Can either prevent the iMac from powering on, or cause varying levels of electrical arcing. Typical symptoms of arcing are a static popping sound accompanied with a horizontal line briefly appearing across the CRT screen. The arcing may even be visible within the case. Electrical arcing can become a dangerous fire hazard. It is not recommended to continue using a CRT with an arcing flyback transformer. The flyback transformer can be replaced, however they are no longer produced and it's almost impossible to find a supplier that has "new old stock". This is a specialist job! The PAV board is a high voltage area that contains dangerous charges that can kill even when the machine is turned off. But Capacitors sounds a little bit easier and cheaper 😛 | |
| Posted by: pl212 on 2026-08-31 11:08:29 Three things, two of which cause 'crackling': 1) Flyback transformer <- crackling. Can be easy or very hard to find a replacement depending on the exact part number 2) caps 3) dirt/debris between anode cap and rubber cover, dried-out dielectric grease, etc. <- crackling Start with #3 as it's free, that's what I'm planning to do with my iMac. And as always, be very careful around CRTs, practice safe discharge procedures, one hand behind your back, treat everything as if it is live, etc. | |
Posted by: Froggy814 on 2026-08-31 11:12:32Start with #3 as it's free, that's what I'm planning to do with my iMac. And as always, be very careful around CRTs, practice safe discharge procedures, one hand behind your back, treat everything as if it is live, etc.Understood! Thanks for the info, I guess it's about time I just tear it down and check the problems. Crossing my fingers it's not the flyback! | |
| Posted by: Froggy814 on 2026-08-31 13:13:07 Alright the last find before I work, from a repair manual? It talks about the problem of the White screen that I get. 11.14) White/gray retrace linesWhere all colors are involved - the lines are essentially white or gray (or with a slight tint due to slight unequal settings of the color adjustments), look for something common like an incorrectly adjusted screen (G2) or master brightness/background/bias control or a problem in one of these circuits, a defective power supply or a problem in the blanking circuitry: * Screen (G2) or master brightness/background/bias control - mark setting and then see if a slight adjustment removes the retrace lines. See the chapter: "Monitor Adjustments". Of course, if this happened suddenly, the problem is not due to a misadjusted control though a dirty pot is possible - turn it back and forth - this might clean it and restore normal operation. * Power supply or connection to CRT neck board - insufficient voltage will result in the CRT never totally blanking. Check (usually scan derived) power supply components (from flyback). * General power supply - check B+ for correct value and ripple. A main power supply fault might result in these symptoms (and usually many others). * Blanking circuit - this may be a part of the video/chroma chip or separate. Check waveforms to determine if the blanking pulses are making it to the video output. | |
| Posted by: Froggy814 on 2026-08-31 18:48:06 I found the pads @treellama was talking about. There are a bunch of components around it that are missing. Is there anyone that has a schematic for the G3 iMac or is there a willing person who can take their iMac apart and tell me what components I need to add and tell me the values. Otherwise I have to go on a whim... I don't want to do that! Picture coming: | |
| Posted by: Froggy814 on 2026-08-31 19:16:06 Alright here are some photos. If someone could help me to fill it out, that would be nice! 🙂 | |
| Posted by: Froggy814 on 2026-08-31 19:55:56 Here is a VGA picture from this ebay listing. It looks like they eliminated a part and just have 4 of the pins have things on them, do all of the pads need to be filled in then?  Ebay link | |
| Posted by: Froggy814 on 2026-08-31 19:57:58 Alright, I would need the component values from a 400Mhz one. https://www.ebay.com/itm/3770038421...WiQfEp1dT11lxhdsojoJJzIg==|tkp:Bk9SR4SVmq6LaA | |
| Posted by: Froggy814 on 2026-08-31 20:01:52 Photo of components in place   I want to know why ebay listings are the best place to get pictures! | |
| Posted by: Froggy814 on 2026-08-31 20:16:12 Nevermind about the 400Mhz only. It's the 350 as well, maybe more. It does need to have that specific double chip layout though. | |
| Posted by: Froggy814 on 2026-09-01 08:14:20 I have deduced with looking at pictures, in order to get VGA out of the board you need to add 2 resistors and 3 inductors. That looks like that's it. With the plug of course. I think that the resistors are just 0 ohm, but the inductors and resistors I am not certain on what the values are. I will continue to surf the web. But boy is it hard to find info on these. All I see is pull the cannon. And I don't think anyone has attempted this before. @pl212 does your G3 have the VGA port with the Vram chips behind it? If it does do you think you can look at the values? Thanks! | |
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