iMac G3 power supply, unidentifiable component blown

[stenstrop]

Hi all! I home this is the right place to post this.
I got a working iMac G3 recently out of a recycling bin for free recently and it worked! at least for a while. After a few boots the power supply blew and it stopped working. I've taken it apart and found a blown ceramic capacitor. I would just look up the model of it and order a new one however, the label side is damaged and I can't make out the model.

The capacitor is on the CRT power supply board and marked as "TH902" and socketed in "P903". The board part number is "6870T173D10", it's branded LG. I'll attach some pictures.

If someone could identify this part I would love you forever!

 

[CooperBox]

I don't have an answer for you, but it may help others if you can state the exact model of iMac G3 you have and the processor GHz speed. The models range from iMac1 (M4984) through to PowerMac4,1 (M5521).

 

[stenstrop]

It's a 333MHz iMac,1 M4984.

 

[philgxxd]

Can't help you much as I don't have that particularly model (iMac DV 400Mhz here) but that looks like a thermistor.
It acts like a fuse so that it's socketed makes sense.
I found it rather difficult to find a replacement for that kind of components as it looked to me they vary a lot but maybe some electronic expert could chime in.

 

[Eriamjh1138@DAN]

I think thats a transorb. Is the designator TH902 or P903?

 

[bobesch]

It's a 333MHz iMac,1 M4984.

A 333MHz fruit-color tray-loader with no fire-wire?
If yes - at home I have the very same model in working condition and may take a picture of that black thing, but unfortunately not before the end of next week ...

 

[CooperBox]

Whilst waiting for bobesch to get back to you, you could post your same query complete on the 'Apple Collectors' sister forum, or just the text, and link to your photos. On that particular forum, MacTech68 is extremely knowledgeable on a great deal of older Mac hardware, and may possibly have or know where to locate the schematic for that iMac.
I note that he's not posted on this particualr forum since end 2015, but is a regular reader of the Apple Collectors forum and does post there regularly.

 

[stenstrop]

I think thats a transorb. Is the designator TH902 or P903?

P903 is the socket (plug 903?) and TH902 is the component (Thermistor 902?)
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A 333MHz fruit-color tray-loader with no fire-wire?
If yes - at home I have the very same model in working condition and may take a picture of that black thing, but unfortunately not before the end of next week ...

Yeah, that seems to be it! Thank you!

 

[bobesch]

Today I had some time to tinker with my iMac and I read the official repair guide: for the first time I figured out, that getting access to the power-supply board does mean to expose the CRT-part of the iMac.
I have to admit, that I have neither experience or courage nor the right equipment to get close to the high-voltage CRT, so I won't be able to give you support about that specific part of the power-supply board. I'm really sorry about that!
(Especially because I've got a Strawberry-flavor iMac with probably also a defective power-supply board and I now recognized that I do not dare to even think about trying to open that relevant part of the iMac.

 

[stenstrop]

Today I had some time to tinker with my iMac and I read the official repair guide: for the first time I figured out, that getting access to the power-supply board does mean to expose the CRT-part of the iMac.
I have to admit, that I have neither experience or courage nor the right equipment to get close to the high-voltage CRT, so I won't be able to give you support about that specific part of the power-supply board. I'm really sorry about that!
(Especially because I've got a Strawberry-flavor iMac with probably also a defective power-supply board and I now recognized that I do not dare to even think about trying to open that relevant part of the iMac.

It's pretty easy to discharge the CRT https://www.wikihow.com/Discharge-a-CRT-Monitor If it has been off for a while (A few days) it should be perfectly safe.

 

[bobesch]

It's pretty easy to discharge the CRT https://www.wikihow.com/Discharge-a-CRT-Monitor If it has been off for a while (A few days) it should be perfectly safe.

Sorry, I won't try that ... The iMac and me we are both in a working condition yet and I don't want to put that on risk...

 

[ifrit05]

Sorry, I won't try that ... The iMac and me we are both in a working condition yet and I don't want to put that on risk...

It's not risky at all. I have had to do this a ton of times for old Macs with CRTs.
Just leave it unplugged for at least a day or two and you should be fine if you don't want to poke around the anode.

 

[MggAndr]

Hi, old thread here but maybe you are still looking for the info and by the way you could also help me.
I have an iMac G3 233MHz (M4984) and acoording to this IFIXIT article https://es.ifixit.com/Guía/iMac+G3+Model+M4984+Power+Supply+Replacement/1566 it has the same LG motherboard as yours (P/N 6870T173D10 see photo 15) .
I plan to add an SSD and change the Stock fan to reduce noise mainly.
I've read somwhere that the stock fan is a 92mm 5V 2 pins cooling fan. But I've seen this guy putting a 12V fan inside

I have no knowledge about eletronics, I mean zero!

Question: do you know what's the voltage delivered by the power board in that 2pin connector for te fan? Is it 5V or 12V?

Once I find all the appropiate components I plan to open the iMac and it happens (according to the Service Manual) that I have to access to that power board in order to plug the 2pin fan connector. Once I do it I can take a photo of that component and also help you.

So let me know if you have the info

 

[ifrit05]

Hi, old thread here but maybe you are still looking for the info and by the way you could also help me.
I have an iMac G3 233MHz (M4984) and acoording to this IFIXIT article https://es.ifixit.com/Guía/iMac+G3+Model+M4984+Power+Supply+Replacement/1566 it has the same LG motherboard as yours (P/N 6870T173D10 see photo 15) .
I plan to add an SSD and change the Stock fan to reduce noise mainly.
I've read somwhere that the stock fan is a 92mm 5V 2 pins cooling fan. But I've seen this guy putting a 12V fan inside

I have no knowledge about eletronics, I mean zero!

Question: do you know what's the voltage delivered by the power board in that 2pin connector for te fan? Is it 5V or 12V?

Once I find all the appropiate components I plan to open the iMac and it happens (according to the Service Manual) that I have to access to that power board in order to plug the 2pin fan connector. Once I do it I can take a photo of that component and also help you.

So let me know if you have the info

You can safely run a 12V fan with 5V (it will just run about half the speed it is rated for), but I'm pretty sure it's 12V.

 

[MggAndr]

You can safely run a 12V fan with 5V (it will just run about half the speed it is rated for), but I'm pretty sure it's 12V.

Thank you for the quick reply. At the end I´m going to put an IDE HDD I've found on ebay: delivery is expected in november 18+-. As soon I recieve it I'll do the whole upgrade and post the photo of that component. But maybe I'll do the fan upgrade first so it would be sooner (29-30 october+-). Thanks!

 

[ifrit05]

Thank you for the quick reply. At the end I´m going to put an IDE HDD I've found on ebay: delivery is expected in november 18+-. As soon I recieve it I'll do the whole upgrade and post the photo of that component. But maybe I'll do the fan upgrade first so it would be sooner (29-30 october+-). Thanks!

I would of installed a SATA SSD with an IDE converter but that works too! Good luck!

 

[MggAndr]

Hi, I'm sorry but finally my power supply board has not the same serial number (mine is P/N: 6870T139D11).
It's still made by LG so l looked for a similar capacitor and I found this one labeld TP 8D15 and there are two of them on this board:
By the way the connector to the fan is on the display board in my system, so maybe it has also a different voltage too , who knows.
I hpoe it helps you