Help with Audio Sector NOS DAC

[vdi_nenna]

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

 

[Peter Daniel]

Did you install the jumper on CS8412?

What are the voltages after all 4 regulators ?

How did you connect RCAs output, any pics?

 

[vdi_nenna]

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?

 

[vdi_nenna]

These are the best my old digital camera can do at close range.

 

[vdi_nenna]

Last pic...

 

[Peter Daniel]

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.

 

[vdi_nenna]

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.

 

[Peter Daniel]

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).

 

[vdi_nenna]

I think I found the problem. I ordered all AN8005s! U4 is a AN8008! DETIALS!

Thanks for your help!

Vince

 

[Peter Daniel]

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.

 

[vdi_nenna]

I just ordered 2 an8008s.

The problem I'm having is the transformer secondaries have 4 leads: 9-0-9-0. For series they say join brown and red wires. This will give 18v-0-18v. In parallel I get 9v, but then there will only be 9v-0 leads. Can this connect to th power supply J1 & 2?

Did I order the wrong voltage transformer? Should I have used a smaller one?

 

[Peter Daniel]

If the transformer have 4 secondary leads it means dual secondaries.

So you connect one set of 9-0 to J1 and second set of 9-0 to J2. It should work fine then:

9 --> J1
0 --> J1

9 --> J2
0 --> J2

 

[vdi_nenna]

Ok, I got 5v+ on all regulators and 12.95v to 13v after both coils. Just under 13v right before regulators on lead on right if facing flat side of regulator.

You said it should still function with 5v on DAC? Data sheet says 5v too.

Maybe I fried the CS8412?

 

[Peter Daniel]

Yes, it should work with 5V. It's hard to say what's wrong without using scope. You can always ship it to me, and I can look it over.

 

[vdi_nenna]

I actually own a 10 mhz scope. I don't know how to use it very well. I've been wanting to learn. Maybe you have some tips?

I'd be willing to ship it to you if you'd look at it. You might find a broke part I don't have on hand...like all major ICs.

We can talk about arrangments off-line.

Thanks,

Vince