Connecting HDTV to PowerMac G4 - Works, then doesn't?

Background information from my system profile, the question follows:

OS 10.5.5
______________________________________________
Model Name: Power Mac G4
Model Identifier: PowerMac3,5
Processor Name: PowerPC 60? (2.1)
Processor Speed: 1.73 GHz
Number Of CPUs: 2
L2 Cache (per CPU): 1 MB
Memory: 1.5 GB
Bus Speed: 133 MHz
Boot ROM Version: 4.2.5f1
______________________________________________
ATI Radeon 7500:

Chipset Model: ATY,RV200
Type: Display
Bus: AGP
Slot: SLOT-1
VRAM (Total): 32 MB
Vendor: ATI (0x1002)
Device ID: 0x5157
Revision ID: 0x0000
ROM Revision: 113-91701-222

Displays:
VA1912wSERIES:
Resolution: 1440 x 900 @ 60 Hz
Depth: 32-bit Color
Core Image: Software
Main Display: Yes
Mirror: Off
Online: Yes
Quartz Extreme: Supported

Display Connector:
Status: No display connected
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I have a Radeon ATI Video Card. The VGA output is connected to a 19" Viewsonic VA1912w screen. Works well. I'm trying to attach the ADC port to a HDMI port on my Sony Bravia KDL-40V4000.

I obtained a Belkin Apple Monitor Adapter - ADC to DVI - and a DVI to HDMI cable. Everything connected properly. No problems.

With both screens attached and powered on I power on the G4. The grey "boot up" screen with the Apple logo and spinning wheel appears on the HDTV screen, meaning the Mac has found it and is using it. While this is happening the Viewsonic is grey.

Then both screens go black, the Viewsonic goes blue, then puts up an old desktop picture, while the HDTV remains black. And that's all that happens.

I have to disconnect the HDMI cable from the HDTV, power down the Mac, then power on the Mac again to get it back on the Viewsonic screen.

I've tried adjusting the display settings (1360 x 768 60Hz and others etc), and frequencies, before powering down and trying it all again, in case such settings effect the HDTV, all to no avail.

Can anyone tell me what's happening? Why the Mac finds the HDTV during bootup, but then loses it, while it finds the Viewsonic, but won't complete the startup sequence. I though OSX would just autodetect the HDTV.

Many Thanks in advance.

Unfortunately, the ADC port does not provide enough power to run today's HDTV's. The primary reason it was discontinued.

bobtomay said:

Unfortunately, the ADC port does not provide enough power to run today's HDTV's. The primary reason it was discontinued.

Click to expand...

Well, that's disappointing to learn.

So why does it manage to do it for that brief period during bootup?

Would I be correct if I assume that doesn't require much power?

Just trying to fill in the blanks.

Am not that technically knowledgeable to provide specifics.

My best guess would be that initially it's loading only a minimal set of drivers similar to every Win & Linux box during the boot process.

bobtomay said:

Am not that technically knowledgeable to provide specifics.

My best guess would be that initially it's loading only a minimal set of drivers similar to every Win & Linux box during the boot process.

Click to expand...

Very much appreciate the feedback. And it does seem to explain my problem.

Anyway, just to find out I moved the Viewsonic closer to the mac and attached it to the ADC port using the adaptor and a DVI cable, (which was supplied withthe screen but about 3ft to short for my needs and the old VGA was already in place), and used some spare VGA cables to hook up the HDTV, which had a PC port.

And it all worked.

So at least I know the video cards OK, and it does seem to confirm that the ADC port connected via adaptor to a HDTV HDMI port can't run a HDTV.

So, a cautionary tale for anyone else trying what I did with an older Mac and uisng an ADC connector/adaptor to HDMi to HDTV.