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Insights from full recap and restore of Trayloader G3 iMac

68krazy

Well-known member
Hey everyone,

I've just wrapped up what ended up being an extraordinarily involved project: the full teardown, recap, and restoration of a G3 iMac trayloader.  She's a 266mhz Tangerine, and she's a beaut:

IMG_5788.JPG

This has been one of my most involved Macintosh projects to date, and the only thing that got me through it is that I absolutely adore the original iMac and I wanted to see her thoroughly, thoughtfully, and meticulously restored.  it was a labor of love and I'd think twice before doing it again.  The restoration consisted of:

1. Replace the picture tube with a new-old-stock one from an all-in-one Molar Mac.  The reason is that I found one on eBay, and I couldn't say no to a fresh picture tube

2. Recap the power supply

3. Recap the CRT driver board and replace the flyback transformer

4. Recap the motherboard with solid polymer caps, install a fresh Tadiran battery

5. Reinstall the operating system

6. Thoroughly clean along the way

Here are pictures of all the boards after the recapping:

IMG_5778.JPG

IMG_5780.JPG

IMG_5786.JPG

I didn't document the process very closely — this is the fourth or fifth Mac I have restored to this extent, so it's not novel enough for me to document step-by-step anymore.  That being said, here is some insight from the experience:

1. HOLY COW THIS THING HAS AN INSANE AMOUNT OF CAPACITORS.  I have NEVER recapped a computer that had anywhere near this amount.  I spent $100 on caps alone.  If you want to recap one of these... beware.

2. It seems as though LG did all of the engineering and production of the monitor, power supply, metal sub-frame, and even the power LED and switch.  Everything in the computer, other than the plastics and the logic board cage, was stamped with LG logos and production dates.  Apple must have worked closely with them when designing this computer.  LG's build quality on this machine is... ehhh... it's okay.  The picture tube seems decent.  The driver board seems to be made out of mid-grade materials, I accidentally lifted a few traces and it didn't feel as robust as other PCBs I have worked on.  The power supply seemed fine.  The flyback was, as we all know, a notorious failure point.  It seems as though LG monitors from this era all suffered from unreliable flyback transformers.

3. The power supply board has five "Samwha" brand capacitors, 3300uf value on the output stage, and they were all leaking.  There were two Korea Chemi-con capacitors on the CRT driver board that seemed to have a little electrolyte underneath as well.  Every other capacitor inside the machine was absolutely fine, including the SMD ones on the logic board.  I'd say this machine has overall decent quality capacitors, and if you own one, I wouldn't be in a rush to recap.

4. The plastics were in okay condition on mine.  Not horribly brittle like a lot of the slot-loader iMacs are.  That said, they didn't feel particularly robust either, and I exercised extreme caution in disassembling and re-assembling the machine.

5. The picture tube that I installed from a AIO Molar Mac was a definite upgrade.  It's sharper than the standard iMac tube, and the face of the tube has noticeably darker phosphor — it seems to be a high-contrast tube.  I have an excellent picture on the screen after adjusting the color using the Display Adjustment Utility.

6. The tray-loading CD-ROM drives on these really struggle to read CD-R disks.  I have a restore disk for this iMac, but, because the drive won't read the disk reliably and because these machines don't seem to want to boot off of USB, I haven't been able to re-install the OS.  I still want to wipe the drive and do a fresh install, but I'm going to have to brainstorm and research a bit to figure out how to do it without using the CD drive.

All in all, I'm really glad I recapped this machine.  I did it out of love for the original iMac, and also as a preventative measure.  I am documenting it here because I haven't seen a ton of board-level work done on these, and I love them, so I wanted to contribute at least one forum thread about this lovely machine.  Thanks for reading!

IMG_5789.JPG

 
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joshc

Well-known member
Great write-up, thanks so much for taking the time to do this. I chickened out trying to restore an iMac G3 so I can safely say you are a much braver soul than I am. These, and the eMacs, are definitely not for the faint of heart. I am glad you put this level of effort into a tangerine - one of my favourite iMac colours!

 

Daniël

Well-known member
This is a very useful thread! I'm currently in the process of collecting all the Trayloaders, and while I initially set out to just fully recap/restore them in one go, that total cap price certainly has given me some hesitation. Do you happen to have a capacitor list somewhere for these systems? Also, could you share your source for new flybacks? I want to at least stock up on a good few of those. I'm personally trying to see if smaller fans could be placed discreetly in the CRT area, to aid airflow, as well as potentially upgrading the original fan, to try and keep the FBT as cool as possible. 

 

68krazy

Well-known member
I agree, it's going to be really neat to see them all together in one place!

Daniël, I would be happy to share my capacitor list with you.  The only caveat is that as far as I understand, there were two revisions of the analog board and power supply for the trayloader.  (This is not to be confused with the different revisions of the machine, as they are not directly correlated.)  I think most trayloaders came with the first revision of the analog board and power supply, which is what my caps list is for.  From what I understand, if your flyback transformer is marked "6174z-1003g," you have the first revision, and my caps list should work well for you.

For flyback replacement, I used HR Diemens part # 46176.  It seems to be a high quality replacement.  It feels well made, uses a muRata (high quality Japanese OEM) focus block, and works perfectly, so I feel confident that it's a worthy replacement for the original.  I bought it from a distributor in the USA, but these guys might be cheaper for you in the Netherlands:

https://www.electronic-spare-parts.com/catalogue/line_output_transformers/hr_diemen_line_output_traformers/hr_46176.html

I've also attached my capacitor list.  Let me know if you have any questions about the formatting, etc.

I'd love to see pictures of your collection sometime, if you choose to share!  :cool:

View attachment iMac G3 266 Capacitor List.xlsx

 

Daniël

Well-known member
Thanks! I'll probably slowly buy up enough to replace the flyback of each iMac, with maybe a spare or two. With my plan for extra cooling, I should be able to get maximum life out of the new ones, if there's space for a small fan somewhere near the flyback. Though I would only replace the originals if they start having issues. Guess I will have to start taking each apart for an inspection of what flyback transformer they've got.

I will definitely share some pics once my collection's complete! I've currently got a decent condition Grape (bit yellowed on the gray inner plastics and missing the door though), a pretty good condition Tangerine (some scuffing on the front bezel), and two Bondis, one in good condition but entirely dead, and a lesser condition one that's working, that will combine into one. I'm trying to get all of them in good condition and relatively unyellowed, and I might buy a few in more common colors to swap colored parts with to make it possible. 

Also, if I have enough differently colored parts left over at the end, I plan to build what I dub the "Harlequin iMac". It'll use various colored parts across the machine, much like the namesake VW Harlequin. Though I'd also want to try and upgrade/mod it further, with a G4 (or Sonnet HARMONi G3 + FireWire card, if I ever get my hands on one), and the Game Wizard Voodoo 2 card if I ever manage to get one, as well as having the internal floppy, ADB and serial broken out to ports in the I/O section. I still have DB19 ports from scrap boards to do it with, and being able to connect an old Compact Mac era external floppy to an iMac G3 and use it under OS 8 would be pretty funky. I think that would be really cool, and a nice wacky iMac companion for my Flower Power.

 

CC_333

Well-known member
My first Mac was one of these! 

I thoroughly cleaned it a few years ago, but it doesn't look quite as nice as yours (I think it could've if I had polished the front bezel plastics).

I had used it relatively lightly, so it's in reasonable condition internally, but at this point, perhaps some preemptive maintenance might not hurt?

I also happen to have a dead G3 AIO (bad flyback, I think), and I'm pretty sure its CRT is in fairly good shape.  Hmm.....

c

 

CircuitBored

Well-known member
@68krazy did you simply replace every single electrolytic capacitor for this refurb or did you test each one and only replace those which didn't meet specification?

I am making some progress with my Performa 5400 and am curious about your methodology for testing and troubleshooting. 

 

68krazy

Well-known member
@PowerMac_G4 I replaced them all.  My philosophy of capacitors is that it takes more time and work to pull, test, and re-install than to just replace.  And since they’re a wear item anyway, I see a full replacement as good preventative maintenance if it’s a machine I really like.  That way they won’t eventually leak all over the pcb, or drift out of value and stress out other components, or any of the other things old capacitors sometimes do.

I don’t see recapping as a magical cure-all, but I do think of it as prudent preventative maintenance.

 

Juror22

Well-known member
I have a slot loading Tangerine and I love what you did for this trayloader (Incredible job by the way and I would never have thought a Molar Mac CRT would fit - how did you first come up with that?).

I worry about caps and such going bad in mine, but I have heard its difficult to take them apart (plastics breaking and the like).  Did you have a tough time getting the plastics apart or trying to crack at stress points?

 

CircuitBored

Well-known member
Hi @68krazy

I accidentally shorted and destroyed the flyback transformer in my Performa today... oops! 

How did you source a replacement for the transformer in your iMac? I noticed that you said you'd replaced it. 

 

68krazy

Well-known member
@PowerMac_G4 I saw your post about that in another thread — I'm sorry to hear about what happened!

I googled the LG part number (6174z-1003g) and found that there was a replacement from HR Diemen.  HR Diemen was a well-known manufacturer of flyback replacements back in the day.  When I found the HR Diemen part number, I googled their part number and found a few places that still had it.

Not sure if HR Diemen made a replacement part for your 5400, but it's worth a shot!

 

CircuitBored

Well-known member
@PowerMac_G4 I saw your post about that in another thread — I'm sorry to hear about what happened!

I googled the LG part number (6174z-1003g) and found that there was a replacement from HR Diemen.  HR Diemen was a well-known manufacturer of flyback replacements back in the day.  When I found the HR Diemen part number, I googled their part number and found a few places that still had it.

Not sure if HR Diemen made a replacement part for your 5400, but it's worth a shot!


Thanks for the tip! I found a handy replacement guide but sadly it doesn't have the exact model I need in it! I have 154-382D and all the guide has is values for A, B, F and G – agh!

Screenshot 2021-02-17 at 23.08.21.png

I'm tempted to just buy one equivalent to a similar number and give it a go but I feel like that's asking for trouble...

 

68krazy

Well-known member
Are you sure you need a new flyback?  You mentioned that you can still hear the high voltage "zzzzt" when you start the machine.

 

CircuitBored

Well-known member
It looks like HR Diemen have an equivalent after all, I was just typing it in wrong! 

154 382 D -> HR 46443

Now just to see if I can track that down. 

 

CircuitBored

Well-known member
Are you sure you need a new flyback?  You mentioned that you can still hear the high voltage "zzzzt" when you start the machine.


Not sure at all but I'm fairly sure that's what shorted. 

I hear the whole tube do the static crackly noise as usual, yes. It's rather confusing. 

I get no glow on the electron gun. Perhaps that's where I should be looking...

 

68krazy

Well-known member
Hmmm.  If there's no glow in the neck of the tube then you have issues with your heater voltage.  Not sure if that is connected to the flyback or not.

 

mistermac

New member
I'm also thinking of recapping some of mine G3's, just to be sure.

Because of the cost and work involved, I wanted to limit the recapping to the caps you found to be leaky. I'm at least replacing the 5 3300uf Samwha caps in the PSU. Do you remember what the value of the 2 Chemi-con caps was?

Also, would you recommend replacing the caps on the logic board with Tantalum caps? The reason I would like to recap the logic board is because I want to prevent damage to that board.
 
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