[BUILD] 1176 Rev A - Back to the beginning...

[Echo North]

I think you're on the right track.  Keep GR off and get the signal passing through the signal and line amp correctly.  Tripple check all of your wire connections.

 

[Lucin Niega]

The problem was a grounding issue. I stripped the paint off the inside of the case where the output tx is attached and it works like a charm. Sounds beautiful. Now to calibrate the meter.

 

[Volume11]

I know this is going to sound stupid but, which fet exactly does the qbias adjust the voltage to?

 

[Echo North]

I know this is going to sound stupid but, which fet exactly does the qbias adjust the voltage to?

Q1 and Q11.  The GR and Meter FET.  You're setting them to a point just slightly into conduction.

 

[Lucin Niega]

Q Bias completed. Working on discrete meter calibration. I 'm measuring across tp10 and tp11 and can't get any closer than .16v at 0vu on the meter. Any ideas?

 

[acoustix]

You have to perform this step a lot of time.

0V between the TP point,
Readjust the 0VU
Readjust the 0V between TP point ....

In my case, with the 2k trimmer i can't perform this, i put the 5K trimmer... good or not i don't know, but it's works 

 

[Lucin Niega]

Thanks acoustix! I will replace with a 5k.

 

[Stagefright13]

  Populating A Rev A board right now. Such A nice board to work on. Never ceases to amaze me how nice these boards are and how incredible they sound. Number 6 in the works Mako! You rock at making boards. And thanks for the fast shipping!

John

 

[w!ll]

I'm having a problem at the input stage here, I'm measuring a voltage at the input connector, both side of the input attenuator, and the input to the input transformer, but nothing on the other side. I've checked the wiring, transformer orientation and chassis ground connection. all good. Can't fathom it, could anyone offer a suggestion?

Will.

 

[acoustix]

Do you perform this with the Output of the input transf plugged ?

Maybe post comes good pictures 

 

[w!ll]

Everything is wired up if thats what you mean?

 

[Echo North]

One of the input pads on the pcb is ground and the other is signal in.  Remove the input wires (from the transformer) and use a continuity tester to make sure the pads are not shorted together.

 

[w!ll]

Ok, continuity test suggests they are. How would that happen and how can I solve that?

 

[Echo North]

Ok, continuity test suggests they are. How would that happen and how can I solve that?

With the input attached? 

The input will make it appear shorted because of the secondary of the input is a solid wire.  It'll have a low resistance (I forget what exactly but low).

 

[w!ll]

That's with the input wires to the transformer removed.

 

[Echo North]

That's with the input wires to the transformer removed.

That doesn't seem right at all.

Is the 270R (R4) resistor shorted?

 

[Echo North]

Have a look at the input circuit.

You should not see a short with the input unattached.  Unless I'm really missing something?

 

[3nity]

hey Mike.
is that a dual op-amp preamp you got on your avatar....ala jensen twin.??
more pics?
Merci.

 

[Echo North]

hey Mike.
is that a dual op-amp preamp you got on your avatar....ala jensen twin.??
more pics?
Merci.

There's an internal pic and a block diagram in my WM thread.

I'll have full release and frontpanel pics by the weekend.  It's not a twin servo.  It's a fully differential design.

 

[w!ll]

Right, I misunderstood sorry. I thought you meant the input pads of the input transformer pcb. The input pads to the main pcb do not short with the wires unattatched.