Re: Power Mac G4 MDD "Mirror-Door" won't power up
Hi to the group,
Revisiting the thread after a long hiatus. The MDD that I fixed due to help from this thread is still going strong some years later in constant use.
I just picked up today a better base MDD system also with a bad PS. As it happens, it's the same MDD I referenced earlier in the thread that had its PS replaced with one bought off ebay, so it was on it's second supply when it failed again.
As a quick check of the system, I plan to swap in the repaired supply from my working...
Ed in SoDak
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Last Activity: 12-01-2018, 02:09 PM
Joined: 07-04-2010
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
Listen to Toasty on this one for sure. That CapXon main filter cap is the root cause of the typical failure mode in this power supply.
Kinda funny, since Mac always seemed to have a superior build-quality. But, CapXon capacitors are universally condenmed as worthless and just about guaranteed to fail.
My first repair is still humming along fine using Nichicon caps. I went for a 450volt main cap and made sure I chose 100C temp ratings for all of the caps.
A friend just gave me...Leave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
I tried to edit my post to add this, but it had run past the 10-minute editing window.
I made sure I ordered 105 degrees C caps to match the originals and also matched the original voltage and capacitance, without trying to find an "over-rated" part. I could have chosen a higher temperature, voltage or capacitance parts as a sort of safety factor, but the larger size of a beefier cap might be an issue iin this already overly-cramped board.
I did notice while testing the power supply...Last edited by Ed in SoDak; 07-26-2010, 12:58 AM.Leave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
Hi Johnboy,
I went with Nichicon as I've had good experience with them in other gear that used them from the factory. I ordered everything from Digikey and had to choose one Panasonic for a 1000uf 35v as it wasn't available in Nichicon. That's one of the 13 additional caps I bought as insurance, and I have not installed those yet . It has thus far been working fine with just the 6 caps mentioned above, plus the TH2 and Q1/Q2 pair. Toasty recommended changing out C135, 137 and 141. I threw in C129 and 130...Leave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
Finally I have some results to share! I'm happy to report the MDD is up and running. I placed an order with Digikey on July 5th and was surprised to see email notification they shipped that same day. Odd, I thought, as it was a postal holiday. Two weeks later, no package, so a couple emails to Digikey and a no-charge replacement order was in my hands yesterday, just three days later. I had the parts in and running last night!
For TH2, I selected a 7 Ohm, 10 Amp replacement, that was the colsest I could find...Leave a comment:
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Re: clearing solder tubes
I use a desoldering iron with attached bulb. Like most of the other methods, you may need to flow more solder and try again, but I find I can catch the end of the lead in the tip's hole and move it to or fro while sucking to free it and center it up in the hole or help in uprighting a bent lead.
For braid, I've read it needs to be clean. Much old stock has oxidized, so a little light sandpaper will expose fresh copper.
-EdLeave a comment:
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Re: Stumped this weird G4 power supply problem
I'm pretty new at this game myself, but an old car mechanic's trick might help track the clicking sound. Just use a length of plastic tubing, put one end in your ear, and probe around with the other end for the sound.
-EdLeave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
>>R350 perhaps ??<<
Hmm, could be, I'm just going by memory as it's very crowded there and I think the board marking for it is beneath the part. It just threw me for a bit as I hadn't come across any of these before. You are correct, it is part of the fan speed circuit and senses current.
There's no reason to suspect it as bad. I pulled it in a search to locate TH1 to compare it to my "unknown" TH2, as I still wasn't sure what the heck that was. I'd assumed it was an MOV...Leave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
Thanks for the prompt reply, Toasty! I've been digesting the other threads on this PSU and I'm seeing the similar failures in most of them.
I originally thought TH2 might be a surge protector, but covered the bases by also ordering an inrush limiter. I began my testing by substituting a 60w bulb for TH2. It glowed brightly and I hadn't uncovered any shorts at that point, so I assumed the lamp glowed as it was across the AC line. Not quite correct, but I measured AC line voltage across TH2's solder points,...Leave a comment:
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Re: Power Mac G4 MDD "Mirror-Door" won't power up
Hello to the group! I joined the forum to view the pics in this thread. Thanks to Cyclones and Toasty for the images and info.
On my MDD, the fuse was blown and thermistor TH2 was smoked, blown in two. It reads about 6 Ohms, so that's a fail and probably why it was blowing fuses!
The main filter cap was open, so I replaced it and the TH2 thermistor with parts from Digi-Key. At that point, the supply at least stopped blowing fuses, but isn't showing any voltages on the output connector. ...Leave a comment:
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