Digital Power Supply Tester

I can’t believe I waited all this time to make an investment in a power supply tester for PC computers. This tester will pay for itself in one use.

Manhattan Digital Power Supply Tester
Manhattan Digital Power Supply Tester Model 101530

Given that many of us have more than one PC in our homes or businesses, and the fact that given enough time all electronic items will fail and die, the quick and easy digital power supply tester is the one tool that everyone should have.

After looking at all the pros and cons and reading the Amazon online reviews of the various digital power supply testers, I decided on the Manhatton Digital Power Supply Tester for ATX, 20- or 24-pin connectors.

Here is what can be done with it:

  • Quickly diagnose power supply units, saving time, avoiding system damage, and data loss.
  • Accepts 20- or 24-pin ATX, 4-, 6-, and 8-pin CPU, 4-pin FDD, 4-pin Molex (HDD) and SATA power connectors.
  • Voltage indicator safely and accurately detects voltage presence.
  • Easy to read, backlit LDC display with audible alarms and LED indicators.
  • Sturdy, lightweight, and compact aluminum case; ideal for carrying in a toolkit or having it on the technician’s bench.
  • Lifetime Warranty.

The instructions are included with the device, though you have to look inside the sandwiched cardboard display sleeve to find them.

The directions are easy and is actually very simple to use.

  • Make sure the power supply and all the connections are removed from the computer.
  • Plug in the main 20- or 24-pin ATX connector from a power supply that you want to check.
  • Two beeps indicate that the liquid-crystal display (LCD) has updated each voltage and power-good (PG) value based on what is currently being tested.
  • The 12 V, 3.3 V, and 5 V LEDs will light if their corresponding power outputs are good, and reamian off if the power outputs fail. (The voltage sources are to be tested one by one.)
  • Test any of the component voltage cables one at a time by attaching a 4-, 6-, or 8-pin CPU connector, 4-pin FDD or Molex (HDD) connector (+12 V1 / +5 V), or SATA (+12 V1 / +5 V / +3.3 V) connector to the tester, checking the appropriate LEDs for output indications.
  • Remove each non-ATX connector after each test. Caution: Besides the 20 or 24-pin ATX connector, do not plug more than one additional power connector at a time into the tester.
Normal Voltage Range* Display Voltage Range*
Lower (A) Higher (B) Min. (C) Max. (D)
+5 V +4.75 V +5.25 V 4.0 V 6.0 V
-12 V -11 V -13 V -10 V -14 V
+12 V1 +11 V +13 V 10 V 14 V
+12 V2 +11 V +13 V 10 V 14 V
+3.3 V +3.14 V +3.47 V 2.0 V 4.5 V
+5 VSB +4.75 V +5.25 V 4.0 V 9.0 V
PG 0 ms 990 ms

* +/-5% for +5 V, +3.3 V, +5 VSB; +/-10% for +12 V1, +12 V2, -12 V.

Voltage Table and Readings

  • Abnormal voltage will not display on the LCD.
  • “LL” displays when no voltage or voltage lower than a minimum acceptable value is detected.
  • “HH” displays when voltage is higher than a maximum acceptable value is detected.
  • If the detected voltage is lower than table value (A) or higher than table value (B), an alarm beeps.
  • If the detected PG value is lower than 100 ms or higher than 900 ms, an alarm beeps and the reading blinks on the LCD screen.

The tester works as advertised. Quite a handy device.

Check it out: Manhattan Digital Power Supply Tester


Measuring iMac G5 Power Supply Voltages at Connector Plug Pinouts

Exactly how how do you test the PSUs out on the Apple iMacs?
How do you turn on the iMac G5 power supply when it is out of the computer?

Apple iMac G5 PSU With Ambient Light Sensor Shown

iMac G5 Power Supply Connector – P-1

1. +3.3 – BlackA3B 12. +3.3 – BlackA3B
2. +3.3 – BlackA3B 13. +12v – BrownA3B
3. GND – BlackB4B 14. GND – BlackC4B
4. +5v Gray/PurpleA4B 15. On/Off – Gray
5. GND – BlackB4B 16. GND – BlackC4B
6. +5v Gray/PurpleA4B 17. GND – BlackC4B
7. GND – BlackB4B 18. GND – BlackC4B
8. PG – Blue 19. +12v – BrownA3B
9. +5.1Vsb – Purple 20. +5v Gray/PurpleA4B
10. +12v – BrownA3B 21. +5v Gray/PurpleA4B
11. GND 22. +20v to +24v – Brown

On the 661-3350 power supply and other similar PSUs, jumper pins 15 (gray) and 16 (blk/gnd) to turn the PSU on. With the power supply on, you should be able to read all the voltages listed above with a DC voltage meter. Between pins 22 and any GND pin, you will see approx. 24vdc, which is needed for the backlight. Note that the plug is numbered on the wired side of the connector plug. You will need some good lighting to see the numbers. A small flashlight comes in handy.

When reading the voltages, it is always a good idea to check both for proper DC voltage and AC ripple voltage. Note that AC ripple voltage should be relatively low, in the low millivolts range.

From what I have been able to tell, the other power supplies in both the 17 inch and 20 inch iMac G5 computers all used the same DC voltage pinout arrangements. I believe the voltage pinout arrangements are different on the Intel iMacs and some of the iSight models.

Please read the detailed information for repairing Apple iMac G5 power supplies.

Note: (see below) PG acronym represents the Power Good signal and VSB represents Voltage Stand By.

If anyone has more information for any of the power supplies (especially the pinout arrangement) used on the various Mac products, including the various PPC models, Intel Models, and Power Macs, please send it to me.

Thank you.



Voltage pinouts listed above cover the following Apple PSUs: 661-3350, 661-3289, 614-0353, 614-0296, 614-0297, 661-3351 614-0923 614-0352 614-0294, AP14P46, 614-0398, 614-0326, 661-3625, 661-3289, AP13PC97, 614-0279, DPS-180SB, A 614-0334, 614-0366, 614-0326, 614-0398, 614-0353, 614-0328, 661-3627, 614-0327, 614-0325, 614-0365, 614-0329, 661-3290, Manufacturer Part Numbers: DPS-180QB-1A Rev 01, API4PC47, DPS-180QB ) along with a number of different manufacturers including: (ACBel API3PC96 – Celetronix Q45B – NPFC), and additional manufacturers’ part numbers than what is listed here.

PG acronym represents the Power Good signal. I found the following reference in the Wikipedia when it comes to talking about power supplies in general for PCs.

In addition to the voltages and currents that a computer needs to operate, power supplies also provide a signal called the Power-Good signal, sometimes written as Power_OK or Power_Good or you can distinguish it by its gray color. Its purpose is to tell the computer all is well with the power supply and that the computer can continue to operate normally. If the Power-Good signal is not present at startup, the CPU is held in reset state. If a Power-Good signal goes down during operation the CPU will shutdown. The Power-Good signal prevents the computer from attempting to operate on improper voltages and damaging itself.

The ATX specification defines the Power-Good signal as a +5 volt (V) signal generated in the power supply when it has passed its internal self-tests and the outputs have stabilized. This normally takes between 0.1 and 0.5 seconds after the power supply is switched on. The signal is then sent to the motherboard, where it is received by the processor timer chip that controls the reset line to the processor.

Apple iMac G5 Take Apart Procedure 1st and 2nd Generation

Here is the procedure that I used to replace the capacitors on the Apple iMac G5 MOB.

Here is the link location of the Apple service manuals, with step-by-step instructions in PDF document form for removal and replacing everything on iMac G5 computers and other Apple products including: Cinema Displays, MacMinis, Laptops, eMacs, iPods, iMacs, and Towers. (link opens in new window)

When you take it apart, start with this order:

  1. Lay the iMac face down on a soft, protected surface.
  2. Back cover removal. (Loosen the three screws on the bottom lower edge, then lift up carefully from the bottom up).
  3. Take close up pictures of your G5 mother board and inside the iMac for your reference in case you need to refer to something for proper installation.
  4. Power supply removal ( ).
  5. Verify Power Supply capacitors are not bulging or blown out.
  6. Hard drive removal.
  7. CD removal.
  8. Memory cards removal.
  9. Right fan cover removal.
  10. Lower left two small plug connectors undo by carefully taking needle-nose pliers and tug the plugs upwards to disconnect them.
  11. Fan plugs – disconnect.
  12. Airport option removal, being careful not to break the very delicate antenna wire clip. You might want to leave the wire attached and just move the Airport out of the way.
  13. Then remove the Torx mounting screws. See the special 12-in-1 screwdriver with Torx and Phillips bits.
  14. Carefully lift out the MOB, making sure all the mounting screws were removed. Do not force it.
  15. Heat up the soldering iron, with a wide tip attached, and working from the bottom and the top of the MOB, with the MOB tilted up on edge, heat up one leg of a capacitor on the backside and rock the capacitor slightly from the top. Then do the other leg, and the cap will come out of the hole.
  16. Remove all capacitors in the groups.
  17. Once the holes are clear, (pins work well), then place the high quality low ESR capacitors in the holes, making sure the positive and negative legs of the capacitors are properly situated in the holes. Do not install caps backwards. Major damage will most likely result.
  18. Apply Arctic Silver thermal paste heat sink compound to the small area (make sure it is cleaned with isopropyl alcohol), on the bottom of CPU. Cover it and the matching heat sink area with a thin layer (not to excess). Use a small razor blade as a scraper to remove the excess. Keep it thin, thin, and thin.
  19. Reassemble the motherboard, (don’t forget the white light tube that displays the “power on” light on the front cover of the iMac), hard drive, DVD/CD Super drive, cables, plugs, fan covers, memory modules, and make sure you don’t have any extra screws left over.
  20. Double check and triple check your work.
  21. Place the back cover on.
  22. Plug everything back in and turn it on.

Important Notes:

  • Don’t forget to put new heatsink compound back on the bottom of the processor chip, which is located on the bottom of the MOB, and the solid plate heatsink assembly located on the chassis: Arctic Silver. Several heating up and cooling down cycles is required for maximum thermal heatsinking effectiveness.
  • At least a 60 watt soldering iron is recommended and a good solder sucker and some plastic headed sewing pins for heating up and push removing solder from holes. Read the article: Soldering Tips for Lead-Free Solder for more detailed information.
  • Use rosin core solder only. Do not use acid core or acid flux. Use lead free, or, in my opinion even standard 60/40 leaded solder will work (although there are few lead-free caveats) for soldering the new caps. Just make sure there are no cold solder joints.
  • How to Tip: Use a few small pins to clear the holes when the soldering iron is used to heat up the holes to remove the old solder.
  • Don’t try to bypass this advice. Highly recommend replacing all the caps in both groups. Even though one or two caps might be visibly bad, the others are more than likely weak or on their way out too.
  • It’s up to you if you want to attempt the repair. It depends on how comfortable you feel about doing it yourself. The degree of difficulty on MOB caps replacement on a scale of 1 to 10, with 1 being the easiest and 10 being the hardest; a 7.
  • Double check your power supply unit. Open the PSU to check those capacitors too.
  • Degree of difficulty on PSU caps replacement on a scale of 1 to 10; a 3.

The procedure above is going off of memory.


  • Layout your screws as you go.
  • Have lots of room to lay it out.

Refer to my articles, read carefully, and suggest printing them out for reference.

iMac G5 Motherboard repairs procedure
iMac G5 power supply repairs

Feel free to contact me if you have any further questions.