Power Supply Quicksilver Acbel APIOPC24 tick-tacks and hums

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Power Supply Quicksilver Acbel APIOPC24 tick-tacks and hums

Hello everyone,

this is my 1st post on this forum. Other Mac forums could not solve the problem.

Since mid december 2008 my QS 733 & 933 have problems going to „deep sleep“. For some seconds the white lamps of the start button and the ADC Studio Display „breathe“. A short time after the QS completely shuts off and cannot be awaked.

It is a known problem of instability of this power supply. A specialist for power supplies (> 1000 Acbel repairs) renewed inside my 3 power supplies: field effects transitor, capacitors, resistors, and the vent ... maybe some more things. Voltages measured correctly as shown in the PDF „Apple Service Source PowerMac G4“.

After repair the QS powers on and shuts off right. System Profifer shows correctly the processor type in MHz, the RAMs inside their banks ... But when sending to „deep sleep“ ... as written above. The power supply tick-tacks three times per second and hums. The voltage of 5V various about 2.5 to 4 V changing alternately.

What may hurt the power supplies? The repairs long for now 3 month and no final results.

QS 733+933 MHz, PB 550 MHz, mini, Mac OS 9.2.x

Posted on Mar 18, 2009 8:02 AM

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Answer 1

Black Eddy Author

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Mar 18, 2009 8:10 AM in response to Black Eddy

correction:

tick-tacks and chirps (not: hums)

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Answer 2

Black Eddy Author

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Mar 19, 2009 5:28 AM in response to Black Eddy

New test results:
There is a chip called „World Trend“ or „Welttrend“ which is defective. This chip is at the exit of the power supply and traces the mainboard funktions, esp. 12 V and 5 V. That is the reason for the alternating voltages. The alternating voltages destruct hard disks. When testing this hard disks, the hard disks test program shows: „Safe delete of free memory will not work. A media with mount point has to be used.“ Using Disk Warrior, Onyx, and the original Tiger cd the hard disk doesn't appear. So be careful with your hard disks inside Quicksilver because of data loss and make backups.

I'll keep you informed ...

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Answer 3

direwolf8

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Mar 19, 2009 8:58 AM in response to Black Eddy

I'll assume "tick tacks" means that you hear a ticking sound. The ticking is usually the switching supply coming up and shutting down and the chirp is the oscillator not getting up to speed. That all points to excessive load on the power supply, so the problem is most likely near the output, or you have a shorted load connected to it. Disconnect everything but the motherboard and see if the problem persists.

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Answer 4

Black Eddy Author

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Mar 19, 2009 9:34 AM in response to direwolf8

The Acbel is taken out of the QS and plugged to 220 V but no other connections to motherboard, hard disks, cd burner; so there is no load. Per second there are three ticks and 1 pause.

A metal paper clip is used to shorten green to black. Only the vent of the Acbel is running and as you may expect 3 short runs and 1 pause per second. As I wrote the voltage varies per second from 2.4 to 4 V permanently instead of 5 V.

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Answer 5

Black Eddy Author

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Mar 23, 2009 5:20 AM in response to Black Eddy

Does someone know the „Welt Trend“ chip 7515 [soldered in SMD-technic]? Manufacturer or replacement manufacturer? A URL?

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Answer 6

Black Eddy Author

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Mar 23, 2009 12:55 PM in response to Black Eddy

Problem solved!

The guy repairing Acbels found out it was the Welt Trend chip 7515! He took this chip from another Acbel PCB and changed both crosswise. It works!

And you won't believe: It's me as the 1st one to which it happened a defective Welt Trend 7515 chip inside the Acbel!

So if your Acbel is ticking remember of this chip.

direwolf8: Thank you for help.

Black Eddy

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