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Old 12th January 2007, 11:17 PM   #1
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Default Help with Audio Sector NOS DAC

Hey All,

I just finished up the Audio Sector NOS DAC and it's not working. It didn't blow up and nothing got hot. That's good, but all I'm getting out of it is 120hz hum.

Any ideas what to check out first?

I'm using the green board with transformer off the board.

Thanks

Vince
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Old 12th January 2007, 11:33 PM   #2
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Did you install the jumper on CS8412?

What are the voltages after all 4 regulators ?

How did you connect RCAs output, any pics?
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Old 13th January 2007, 01:46 AM   #3
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Hi Peter,

I got these voltages:

Facing reg flat side-
U1- 2.74-0-2.79
U2- 2.76-0-2.79
U3- 2.79-0-2.79

Voltage after rectifier coils
L1- 4.41v
L2- 4.54v

I suppose these are all low? These should be around 8-9v after the regs.

The transformer secondaries 9v in parallel. But I have a feeling I don't have the transformer wired right.

Is there orientation on J1 and J2?
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Old 13th January 2007, 01:48 AM   #4
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These are the best my old digital camera can do at close range.
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Old 13th January 2007, 01:57 AM   #5
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Last pic...
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Old 13th January 2007, 03:44 AM   #6
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Quote:
Originally posted by vdi_nenna
I got these voltages:

Facing reg flat side-
U1- 2.74-0-2.79
U2- 2.76-0-2.79
U3- 2.79-0-2.79

Voltage after rectifier coils
L1- 4.41v
L2- 4.54v

I suppose these are all low? These should be around 8-9v after the regs.

The transformer secondaries 9v in parallel. But I have a feeling I don't have the transformer wired right.

Is there orientation on J1 and J2?
The voltage after regulators should be 5V and 8V on DAC.

Both secondaries need to be used here, so they cannot be connected in parallel. One secondary powers input buffer and receiver and connects to J2, the other powers DAC chip and connects to J1. The voltage after rectifiers is approx 12V, after ressitors approx 11V. You have 2.5V which is way too low.

There is no orientation on J1 and J2.
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Old 13th January 2007, 01:55 PM   #7
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I rewired in parallel and I got:

5.05-0-12+ on U1-4

No hum, but no sound either.

On SN75179 Pin 1 is 5v.
On TDA1543 Pin 5 is 4.43v. Is this too low for digital?

Can't tell on CS8412.
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Old 13th January 2007, 03:27 PM   #8
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It looks like you got right the PS in the receiver section, however the supply voltage on TDA1543 (U7) is too low. You need to get 8V on pin 5. The unregulated supply here is made the same way as for the receiver, so you should be able to find what went wrong comparing voltages in both sections.

Just make sure the secondary from transformer (connected to J1) is separate from secondary connected to J1 and has similar AC voltage rating (9V or so).
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Old 13th January 2007, 05:44 PM   #9
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I think I found the problem. I ordered all AN8005s! U4 is a AN8008! DETIALS!

Thanks for your help!

Vince
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Old 13th January 2007, 05:50 PM   #10
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But 4.43V after U4 is still low, even for 5V regulator. What is the voltage before regulator?

The DAC will work with 5V, although not as good. Contact me through PM and I will ship you 8V regulator.
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