Cambridge audio Dac 3 schematic needed - diyAudio
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Old 23rd May 2007, 09:03 PM   #1
mgm31 is offline mgm31  France
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Default Cambridge audio Dac 3 schematic needed

Hi,

Could you help me with the service manual or the schematic for this cambridge audio dac 3 ?

The CD input seems dead and the DAT input seems OK.

I found a copy of the output stage for the Dacmagic II/3 but unfortunaly this is sheet 3/5.

I suppose the missing sheet are describing the input stage ?

Sorry for my frenchy english

Thanks a lot
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Old 10th September 2009, 03:23 PM   #2
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Default Stan Curtis

Search for Stan Curtis on the net he will have them if it is the old DAC3
and E-mail him
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Old 14th November 2009, 11:50 PM   #3
havar is offline havar  Norway
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Quote:
Originally Posted by mgm31 View Post
Hi,

Could you help me with the service manual or the schematic for this cambridge audio dac 3 ?

The CD input seems dead and the DAT input seems OK.

I found a copy of the output stage for the Dacmagic II/3 but unfortunaly this is sheet 3/5.

I suppose the missing sheet are describing the input stage ?

Sorry for my frenchy english

Thanks a lot
Hi!

Did you ever find any solution to this? I'm asking, as I've got an old Dacmagic 3 myself, also with a dead CD input.

Thank you for reading.
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Old 15th November 2009, 10:57 AM   #4
mgm31 is offline mgm31  France
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It's a long time ago and I sold this dac with the input dead.

I can't remember exactly but seems to be the input buffer and someone solved it with a replacement.

Didn't found the link on my favorite.
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Old 15th November 2009, 11:47 AM   #5
JohnW is offline JohnW  Hong Kong
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Hi,

The Dac is one of my designs, you need to replace the 8-Pin DIP 9637 - its located close to the input SPDIF's BNC's.

These are damaged when exposed to High Earth Leakage currents on the SPDIF inputs - never a problem when using BNC to BNC - but if you use BNC to RCA, then the center conductor of the RCA plug makes contact first - before the Ground - resulting in any Earth leakage current to flow via the center RCA pin to the input circuit.... With BNC connectors, you don't have this problem as Ground is always made first during connection, and broken last during disconnection.

John
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Old 15th November 2009, 12:11 PM   #6
havar is offline havar  Norway
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Thank you guys!

Now I know what to do, if I bother... I guess that I will fix it though, as I just can't handle the fact that something isn't working properly...

It is probably as "JohnW" says, as I was using a RCA-cable, and the BNC/RCA adapter was already inserted in the input.

Thanx a lot!
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Old 15th September 2010, 12:09 PM   #7
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Quote:
Originally Posted by JohnW View Post
Hi,

The Dac is one of my designs, you need to replace the 8-Pin DIP 9637 - its located close to the input SPDIF's BNC's.

These are damaged when exposed to High Earth Leakage currents on the SPDIF inputs - never a problem when using BNC to BNC - but if you use BNC to RCA, then the center conductor of the RCA plug makes contact first - before the Ground - resulting in any Earth leakage current to flow via the center RCA pin to the input circuit.... With BNC connectors, you don't have this problem as Ground is always made first during connection, and broken last during disconnection.

John
Thank you for this advice - this reason was new for me. The UA9637 about
UA9637 Datasheet pdf - DIFFERENTIALE VERDOPPELUNGLINIE EMPFÄNGER - Texas Instruments
I have replaced several times by my service work arround 1995 until today. At all the time I can't find an explantation for the reason.
P.S. great developing work, still great sounded DAC.
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Old 20th November 2011, 11:49 AM   #8
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Hello to all involved on this old threat

I've read it and that's my problem!! My DacMagic 3 has dead BNC connections and only Optical working... After switching my DVD Player to a brand new Blu-Ray player and using frequencies higher than 48Khz (me, as an idiot, do select 96 Khz and even 192 khz)

This morning I was starting to accuse the BR player

Well, let's locate the 8-Pin DIP 9637 and replace it.

Have a nice Sunday morning!!
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Old 20th November 2011, 01:35 PM   #9
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Default DS9637A vs. UA9637A

The most used versions of this line drivers from DACMAGIC and DAC3 are the follow:
1) DS9637A (National Semiconductor)
http://www.national.com/ds/DS/DS9637A.pdf
2) UA9637A (TI)
Interface - RS-422 - UA9637A - TI.com

Because I have not thrown away all faulty devices, can I note, that the damaged devices are the TI version (UA9637A). The also often used version from National Semiconductor, the DS9637A is obviously better immune against high input voltage peaks (perhaps internal suppressor diodes present?). Thus I use only this version for replace.

There are also additional this versions on the marked (no own experiences):
UA9637AP/SN65LVDS9637AD (TI)
http://www.ti.com/lit/ds/symlink/sn65lvds32a.pdf
http://www.micropik.com/PDF/UA9637.pdf
LVT9637PI90LV9637U
PI90LV9637U* datasheet and application note, data sheet, circuit, pdf, cross reference, pinout | Datasheet Archive

this follow types is not suited (other internal function unit):
L9637D
http://www.st.com/internet/com/TECHN...CD00000234.pdf

Last edited by tiefbassuebertr; 20th November 2011 at 01:37 PM.
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Old 20th November 2011, 04:43 PM   #10
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Many thanks for this info

I'm going to fix this unit with the help of a friend who's much better than me using the soldering iron and he will be back in town next week.

Once he's able to work with my Cambridge Audio, we will search for a replacement such as DS9637A (National Semiconductor) and keep my DAC covered for future damages.

Probably also I will spend little money in some upgrade of the machine. There's a well-know article from Hi-FI News date January 1999 that proposes a lot of changes. I'll take this like a guide for upgrading.
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