Power Mac G4 MDD "Mirror-Door" won't power up

[cyclones]

I have a second G4 that has decided not to power up. The fuse is NOT blown. When you press the power button, the power button's light turns on for as long as it is pressed, but from there, nothing happens. I have checked and I do get 25V on the 25V "trickle" line.

This happened after a power outage. I have already tried pulling the NVRAM battery and pressing the CUDA switch. No difference. I therefore assume it's the power supply.

This is the Apple P/N: 614-0224, Samsung PSCF401601.

Any suggestions on where to go from here?

[seanc]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Measure the voltage on the battery, try unplugging the monitor. If it powers up with the monitor unplugged, plug it back in once it's on and see if it keeps running.

[iKitsune]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

I have a second G4 that has decided not to power up. The fuse is NOT blown. When you press the power button, the power button's light turns on for as long as it is pressed, but from there, nothing happens. I have checked and I do get 25V on the 25V "trickle" line.

This happened after a power outage. I have already tried pulling the NVRAM battery and pressing the CUDA switch. No difference. I therefore assume it's the power supply.

This is the Apple P/N: 614-0224, Samsung PSCF401601.

Any suggestions on where to go from here?

It's the PSU. MDDs had notoriously bad ones. Open it up and see if it had simultaneously thrown every cap like my Samsung one had, or if it's got a scorch on the back of the circuit board like another one I saw.

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Battery is 3.6V. I was already trying w/ monitor unplugged.

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

It's the PSU. MDDs had notoriously bad ones. Open it up and see if it had simultaneously thrown every cap like my Samsung one had, or if it's got a scorch on the back of the circuit board like another one I saw.

It appears normal. Didn't notice anything odd when I had it open the other day. But I'm pretty sure you're right about it being bad.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Samsung's on no-start are a few small caps down behind the PWM board next to the center/larger heatsink with the primary switchers on it. The little board is mounted upright next to the heatsink and the caps to be replaced require you to remove the entire heatsink and components. MIND THE THERMISTOR!!! Desoldering station makes it a 5 minute job. Wick and iron, 10 minutes.

Again, check the primary cap as you have on the other G4. If it's CapXon HP, replace it. These can go "weak" and not blow the fuse or switchers.

Toast

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Is this panasonic a good model to replace the cRapXon cap?

Manufacturer:
PANASONIC
Order Code:
1198628
Manufacturer Part No:
EETED2G471EA
RoHS : Yes
Description
CAPACITOR, 470UF, 400V
Capacitor Dielectric Type:Aluminium Electrolytic
Capacitance:470uF
Capacitance Tolerance:± 20%
Voltage Rating:400V dc
Effective Series Resistance:282mohm
Series:TSED
Height:40mm
Outside Diameter:35mm
Capacitor Case Style:Radial Leaded
No. of Pins:2
Mounting Type:Snap-In
Lead Spacing:10mm
Operating Temperature Range:-25°C to +105°C
AC Ripple Current:2.01A
AC Ripple Current @ 120Hz:2.01A
Application:High Temperature
Body Diameter:35mm
Case Style:Radial
ESR Frequency:120Hz
External Length / Height:40mm
Max Operating Temperature:105°C
Min Temperature Operating:-25°C
Operating Lifetime:3000h
PCB Hole Diameter:2mm
Ripple Current Frequency:120Hz
Ripple Current Temperature:105°C
Terminal Type:Snap-In
Tolerance, +:20%
Tolerance, -:20%
Voltage Rating DC:400V

Thanks Toasty!

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

[QUOTE=cyclones]Is this panasonic a good model to replace the cRapXon cap?

Manufacturer:
PANASONIC
Order Code:
1198628
Manufacturer Part No:
EETED2G471EA
RoHS : Yes
Description
CAPACITOR, 470UF, 400V
------------
Turns out I need 420V, but other than that is it OK?

[stj]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

why 420v?
rectified 240v - the highest you ever need is about 360vdc
a lot of mains caps are only rated at 380v

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

why 420v?
rectified 240v - the highest you ever need is about 360vdc
a lot of mains caps are only rated at 380v

420v is the rating on the original cap.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Cyclones - Where are you located. Please fill out the location in your profile. Since that cap info seems to be a direct copy from Farnell....., Europe?


My choices have been Panasonic HB, HC; CDE 381L*; UCC KMQ (390uF/450v).

Toast

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Not in Europe; farnell was the first result that came up which had ripple current listed.
updated profile.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Ooooo.....!

Tornado Alley!

Auntie Em!, Auntie Em!

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

OK, so toasty are these the ones you speak of?

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Yes

[JOHNBOY]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

How the hell do you guys get those heatsinks out. There must be a way to pull the caps without taking it off. I can't see myself desoldering all that. what if you just unscrew the components and pull away the heatsink.

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

You are welcome to try, liebchen.

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

How the hell do you guys get those heatsinks out. There must be a way to pull the caps without taking it off. I can't see myself desoldering all that. what if you just unscrew the components and pull away the heatsink.

You need a good desoldering iron. If you don't have one, it's a great investment. Without one, you might as well not even try. You want a vacuum one. A decent one (non-motor) is in the $50 range I think. The one I have was given to me as a gift. DON'T mess with the crappy bulb-type ones at radio shack. They're just above worthless.

I'll post pictures of the board shortly that show which you need to desolder in order to get it out.

The thermistor is a real b*tch. That is the only issue. So you must have everything desoldered fully and then SLOWLY work the heat sink up EVENLY.


Also, here's an update. I replaced those three caps with new Panasonics and now the G4 powers up every time. THANKS TOASTY!!!!

[Toasty]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Excellent work! Thanks for posting the results & glad you got it fixed!

Hint on the thermistor: Unsoldering it first relieves the tension on its legs. Make sure its wires are *completely free* in the holes. Then proceed to unsolder the rest of the components.

Toast

[cyclones]

Re: Power Mac G4 MDD "Mirror-Door" won't power up

Here are the photos as promised. Hopefully this will be helpful in the future.