Ersterhernds iMac G5 (iSight 20 A1145) Project

[justein230]

Build Log 16 - First Boot with Case Closed

A big day for me today, the first closing up of the machine for testing. It all fit perfectly back together and all components work great. Initial temperature observations are warmer than the 17" G5 I completed last month. Idle is around 58-60. YouTube 1080p fullscreen video puts up to a steady 74 degrees. The fans are running at bare minimum speed to keep the machine quiet. I cannot believe how clean the system looks, considering it was so beat up when I first got it home.


The first photos of the iMac G5 20" project in its closed-up state

The slot cut out of the the bottom of the iMac where the brightness control slider is located. LCD brightness control works flawlessly via fingertip control.

The 'breathing' pulse function of the LED while in sleep mode

[video=youtube;gM3zcV7ultA]https://www.youtube.com/watch?v=gM3zcV7ultA[/video]




Onwards with further testing now, but a pretty exciting moment to see it working for the first time!


Ersterhernd

Once again, unsurprisingly, a wonderful job. This machine I'm sure will be a joy to use.

 

[ersterhernd]

After a full day of testing the system in it's closed-up state, I could only find one issue that needed fixing. The bluetooth connectivity (which I hadn't tested yet) was very choppy with the Magic Trackpad. Using System Information, the RSSI read in excess of -80 dBm. Most of the other builds that I've completed to date with internal Bluetooth are in the -60 range, which is acceptable for a smooth mouse or trackpad.

I used one of the included WiFi antennas from the Intel NUC to fix the Bluetooth issue. I ran the wire to the bottom of the iMac (where the white holes are) and affixed it there. I closed the machine up with the front bezel reinstalled and booted it up. The Bluetooth RSSI was significantly improved at -55 dBm.

Trackpad and Magic Mouse functionality are now liquid smooth, even 3 feet away from the iMac.



Ersterhernd

 

[ersterhernd]

Issue number 2 cropped up yesterday. I was using the system as per usual, and the room was very quiet, much quieter than usual; there was no ambient noise whatsoever, just the purring of the 2 case fans in this iMac.

I noticed somthing very unusual while scrolling a long web page with the Magic Trackpad. There was a very faint 'electricity sound', a kind of hum, that was happening every time I activated the Trackpad to scroll the content on the screen. It also occurred as I panned over the OSX dock and the icons magnified. The faint hum was coming from both iMac speakers, and was non-existent when the LCD image was stationary.

I did a quick google search and found this to be a widespread problem, even on production machines. Some form of ground loop or EMI was making its way from the video circuit into the audio. As it turns out, it can be quite an elusive problem that isn't easily fixed.

I first tried to wrap the wiring to/from the 5V PAM8403 amplifier with EMI shielding foil taken from the iMac. This actually helped a little; the feedback through the speakers wasn't as pronounced as before, but still was present. I then installed a heavy ferrite ring around the wiring, which really didn't help at all. The humming 'electric' noise was still noticable when the cursor moved over certain icons or scrolling was done on a long web page.

I worked on this for several more hours and finally found the solution. The 5V/GND for the audio amplifier is being supplied by the NZXT USB hub. This was done because of feedback issues I encountered on my previous 17" iMac project when the amp was powered via the PicoPSU. I routed the ground wire from the amp to the PicoPSU and left the 5V coming from USB. Then I soldered a 56 Ohm resistor into that ground wire. Upon reboot, the hum noise issue was fixed.

It appears that the small amount of added resistance to the Audio Amp circuit fixed this issue, why I'm not sure. As it stands now though, the speakers remain dead silent at all times other than when sound is played by the system.




Ersterhernd

 

[ersterhernd]

Here's a few results for power consumption. All values were measured using a Kill-A-Watt meter plugged into the wall. The biggest difference in power usage comes from the adjustment of the screen brightness.

Power Off (standby) = 3.6W

These are a few peak results achieved with the LCD at minimum/maximum brightness...

OSX 10.9.2 Desktop = 31.9/60.1
Google Chrome (google.ca) = 37.2/63.5
Fullscreen 1080p YouTube = 41.0/71.4
GeekBench 2 64 bit = 45.7/76.3
Elgato EyeTV (FullScreen) = 40.5/71.3

The internal power brick, a PowerStream PST-YD-100W in this system will handle the requirements easily with plenty of overhead room. This 20" iMac runs on average about 15 degrees C warmer than its 17" little brother with the same hardware. The LCD panel in this one throws off a lot more heat, because of the additional backlights inside.

Using the iMac in bright sunlit room requires the brightness adjustment to be set at around 3/4 of maximum for a perfectly usable experience. This puts the typical wattage requirement of the system around 50W. The minimum brightness level is usable when ambient lighting conditions are very dim, such as late in the evening with only a table lamp on the desk.


Ersterhernd

 

[kiwisincebirth]

... Then I soldered a 56 Ohm resistor into that ground wire. Upon reboot, the hum noise issue was fixed.

It appears that the small amount of added resistance to the Audio Amp circuit fixed this issue, why I'm not sure. As it stands now though, the speakers remain dead silent at all times other than when sound is played by the system.

Ersterhernd

Please clarify, when you say into that ground wire, do you mean in-series i.e. so ground is not directly connected but via the resistor, or something else ?

Kiwi

 

[ersterhernd]

Please clarify, when you say into that ground wire, do you mean in-series i.e. so ground is not directly connected but via the resistor, or something else ?

Kiwi

Yes, Kiwi that is correct. I cut the ground wire between the amp and Pico, soldered a 56 Ohm resistor into it, protected it with shrink tubing and then reinstalled the wire as before.

It completely fixed the audio feedback/interference coming somewhere from the video circuit.


Cheers!

 

[ersterhernd]

Build Log 17 -- Project Completed Photos and Summary

After several days of testing, troubleshooting and overcoming several issues, I'm at the point where I can fairly confidently say the iMac 20" G5 project is complete. I will report further if anything else crops up, but for now it is working very well in it's closed-up state running 10.9.2 Mavericks.

I purchased this Brand New in Box Apple USB keyboard locally on Craigslist for 20 dollars.

Project Overview

This 20" build was considerably more difficult than the 17" iMac G5 that I completed last month. Although the two look very similar from the exterior, they are worlds apart on the inside. This model gave challenges in places where the smaller one simply worked straight away. The 24V supply to the Inverter was especially troublesome, as the PicoPSU was immediately shutting down upon the press of the start button due to some kind of amperage overdraw. Next in line was the video/audio interference detailed a couple of posts up. It was a simple solution once found, but very elusive to troubleshoot. Heat continues to be somewhat of an issue, but not to the point of concern. The 20' LCD and Backlight system creates considerably more heat than the 17", as it consumes over 3x the wattage.


Final Hardware Summary

The final hardware list ended up as follows...

- Intel NUC DC3217BY with i3 processor
- 8 GB 1600 Mhz DDR3 RAM
- 128 GB mSATA Plextor SSD Storage
- Apple A1181 Bluetooth
- Broadcom ’N’ Series WiFi
- Powerstream PST-YD-100W Notebook Power Adapter (internally mounted)
- Internal PicoPSU WI-25-120 PSU
- 12V to 24V 3A 72W DC/DC Upconverter
- Apple iMac G4 20" inverter PN 922-6129
- Apple iMac G4 20" Neck (for extraction of LCD and Inverter Cables only)
- BC547B Transistor actuated PicoPSU on/off control
- Adjustable Grove Potentiometer Slider on bottom of the iMac for LCD brightness control
- Picaxe 08M2 Micro-Controller for pulsing sleep using original iMac LED
- Startech HDMI to DVI converter with MOLEX PN 74320-4004 connector
- ISD1820 audio recorder with Apple iMac G4 Speaker (Mac Startup Chime)
- NZXT IU01 internal USB Hub
- Original iMac G5 cooling fans x 2 (center fan replaced with 17" version)
- StarTech ICUSBAUDIO Stereo Audio Adapter
- PAM8403 Mini Digital Audio amplifier
- Internal iMac Speakers
- Internal Microphone utilization
- Apple iSight Camera
- Apple IR Receiver
- 3 x USB 2.0 external port
- Original Power Plug
- Original Power Button
- Hard Reset button
- Apple BT Trackpad and brand new white Apple USB Keyboard
- No Ethernet Port utilization
- No DVD-ROM installed


This project was definitely amongst the more difficult that I've completed to date. So far, it is a pleasure to use; very quiet, reasonably fast and fully functional as planned.


Regards,

Ersterhernd

 

[MacTester57]

Nice work Ersterhernd - as always!

I've bought a non working 17" G5 iMac (A1058 model with back access) last week. I've only paid 16 bucks.

Currently I'm working on my own Arduino based SMC. I have the ambition for writing as much own code as possible. The backlight works so far and I'm able to control its brightness, The original fans work and can be controlled from one wire temperature sensors via the Arduino. However, the TMDS to HDMI mod is not yet done.

I will start a new thread later...

MacTester

 

[ersterhernd]

Nice work Ersterhernd - as always!

I've bought a non working 17" G5 iMac (A1058 model with back access) last week. I've only paid 16 bucks.

Currently I'm working on my own Arduino based SMC. I have the ambition for writing as much own code as possible. The backlight works so far and I'm able to control its brightness, The original fans work and can be controlled from one wire temperature sensors via the Arduino. However, the TMDS to HDMI mod is not yet done.

I will start a new thread later...

MacTester

Thx for the positive comment, MacTester!

I think you'll really enjoy your G5 mod. Several people that have come into our home and seen the G5 running current software have been really awe inspired.

On another note, both you and Kiwi seem to be well onto the Arduino platform, perhaps I should break out the textbooks as well...

Looking fwd to seeing your thread when it begins.


Cheers!

 

[MacTester57]

Thx for the positive comment, MacTester!

You're welcome. It's unbelievable for me, how much energy you put in your projects. Compared with yours, my projects take veeeeery much time until they are completed.

On another note, both you and Kiwi seem to be well onto the Arduino platform, perhaps I should break out the textbooks as well...

No, I'm still a beginner, but I've learned a lot during all the tests for the new project. Many thanks to Kiwi for his excellent support.

Yes, I think you should order an Arduino and do some tests. I've ordered this Pro Micro: http://www.ebay.com/itm/Leonardo-Pr...ni-/181177987693?ssPageName=ADME:L:OU:CH:3160 It's a terrific product and offers much more features than a Picaxe. At the beginning I had some problems with the C++ language, but now I will never go back to the Picaxe.

MacTester