Need help fixing Adcom GDA700 DAC

oldsguy · 15th January 2006, 05:03 PM

My Adcom DAC went down this week and I've been told right from Adcom 'good luck finding parts for it'.

It appears that the problem is likely the Ultraanalog digital receiver. Assuming I can't get one, how hard would it be to change it something a little more common?

I'd appreciate if anyone could give me some leads tho.

Jason

rfbrw · 15th January 2006, 05:44 PM

What comes after the Ultraanalog receiver?

rfbrw · 15th January 2006, 05:47 PM

There was someone selling a UA rx.
http://www.diyaudio.com/forums/showt...ht=#post770852

oldsguy · 15th January 2006, 08:02 PM

The UA is labeled AESC003.

The next chip has a sticker labeled OMICRON3, SPAL1R0

And then of course the next in line is the PMD100 HDCD decoder.

What's the status on HDCD? Is it a dead technology now that microsoft took it over, or is it just an unadvertized part of the newer 24/96 and faster convertors?

Jason

oldsguy · 15th January 2006, 08:02 PM

The omicron labled chip is is just a PALce16v8q PLC.

Jason

rfbrw · 16th January 2006, 02:33 PM

It is easy to connect a replacement rx to the PMD100 but if you want to retain the mutiple inputs you will have work out where the selected input enters the UA rx and you may also have to change the current input format of the PMD100. To that end perhaps Adcom will provide you with a schematic.
HDCD in its current incarnation seems to be available only as code for programmable DSP chips.

oldsguy · 16th January 2006, 05:48 PM

Adcom did provide a schematic. But's all they can provide.

The input switching is done through multiple relays before hand, and it looks like 1 pair of signal lines into the RX, the data lines through to the PMD100 and L + R data out to the DACs.

Any hints on figuring which of the two is bad? I've got signal in before the RX, nothing out to the DACS. Just not sure what to look at between the two of them.

Thanks
Jason

rfbrw · 16th January 2006, 09:02 PM

What tools do you have? An oscilloscope would be nice but failing that do have any other digital IC's or dac chips or even a complete dac ?

oldsguy · 17th January 2006, 02:05 AM

I've got a old 10meg scope.
Can I send you a copy of the schematic so we are looking at the same thing?

Jocko Homo · 17th January 2006, 02:11 AM

Oh boy.........you are going to need something faster than that.

Jocko

15th January 2006, 05:03 PM	#1
oldsguy diyAudio Member Join Date: Jan 2006 Location: British Columbia	Need help fixing Adcom GDA700 DAC My Adcom DAC went down this week and I've been told right from Adcom 'good luck finding parts for it'. It appears that the problem is likely the Ultraanalog digital receiver. Assuming I can't get one, how hard would it be to change it something a little more common? I'd appreciate if anyone could give me some leads tho. Jason

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15th January 2006, 05:44 PM	#2
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	What comes after the Ultraanalog receiver?

15th January 2006, 05:47 PM	#3
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	There was someone selling a UA rx. http://www.diyaudio.com/forums/showt...ht=#post770852

15th January 2006, 08:02 PM	#4
oldsguy diyAudio Member Join Date: Jan 2006 Location: British Columbia	The UA is labeled AESC003. The next chip has a sticker labeled OMICRON3, SPAL1R0 And then of course the next in line is the PMD100 HDCD decoder. What's the status on HDCD? Is it a dead technology now that microsoft took it over, or is it just an unadvertized part of the newer 24/96 and faster convertors? Jason

16th January 2006, 02:33 PM	#6
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	It is easy to connect a replacement rx to the PMD100 but if you want to retain the mutiple inputs you will have work out where the selected input enters the UA rx and you may also have to change the current input format of the PMD100. To that end perhaps Adcom will provide you with a schematic. HDCD in its current incarnation seems to be available only as code for programmable DSP chips.

16th January 2006, 05:48 PM	#7
oldsguy diyAudio Member Join Date: Jan 2006 Location: British Columbia	Adcom did provide a schematic. But's all they can provide. The input switching is done through multiple relays before hand, and it looks like 1 pair of signal lines into the RX, the data lines through to the PMD100 and L + R data out to the DACs. Any hints on figuring which of the two is bad? I've got signal in before the RX, nothing out to the DACS. Just not sure what to look at between the two of them. Thanks Jason

16th January 2006, 09:02 PM	#8
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	What tools do you have? An oscilloscope would be nice but failing that do have any other digital IC's or dac chips or even a complete dac ?

17th January 2006, 02:05 AM	#9
oldsguy diyAudio Member Join Date: Jan 2006 Location: British Columbia	I've got a old 10meg scope. Can I send you a copy of the schematic so we are looking at the same thing?

17th January 2006, 02:11 AM	#10
Jocko Homo Banned Join Date: Feb 2002 Location: As far from the NOSsers as possible	Oh boy.........you are going to need something faster than that. Jocko

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