8 Channel, 3U NEVE 1073 completed

[erikb1971]

can I check them while on the pcb?

 

[sgenevay]

At Least with color codes.... Are your 2 boards reacting the same ?

 

[erikb1971]

nope, the other board is completely dead

 

[sgenevay]

Mmmmmmm was near to ask you to compare your board with the other to check the difference.... But it's maybe not a good idea anymore then...
All your transistor voltages are ok ?
Sylvain.

 

[MicDaddy]

On my mixer I have to have the gain all the way down, and then I can run the out from the 1290 into any mic input and use the 1290 as a supplemental preamp for the console.  Is the gain on your soundcraft all the way down? 

Take some clear pictures and post them up here.

 

[erikb1971]

OK.
I made the right balanced output cable, and the clipping is not from my mixer.
I checked the transistor voltages from the document. 1,2 and 3 are exactly the same values as the document, but 4,5 and 6 are a mess:

TR4 C=1,4 B=0,6 E=0,1

TR5 C=0,9 B=1,5 E=0,8

TR6 C=23,5 B=0,9 E=0,3

So there seems to something eehhh wrong But what?

 

[MicDaddy]

It looks like tr 456 designations are used twice...

Rule out basic problems with visual inspection.

Did bending the heatsink leads cause them to short to a capacitor?

Are any of your tr legs shorting against anything or themselves?  Check the 2N3055 as well for any shorts between EBC.

On your picture on the previous page, at designation 7 and 10/shield you noted 'perfect sinus'.  Can you verify that you have a good looking waveform at this point? 

Compare the section of the preamp that is showing good/correct trVoltages with the section that is a mess.  Part by part verify they are correlating. 

Can you remove the bottom of the chassis for a visual inspection of the solderside of the pcb?


try a macro function or a photographer's loupe to bring the components into view more clearly

 

[erikb1971]

It looks like tr 456 designations are used twice...

They are, as in M. adriaanse's pdf on page one of this thread.

Rule out basic problems with visual inspection.

Did bending the heatsink leads cause them to short to a capacitor?

can it short circuit when it is touching the house of the capacitor (not the legs?)

Are any of your tr legs shorting against anything or themselves? 

They are not shortening against themselves, but eg both tr5's are touching the 22u/16v caps next to them.. where can i find out if they are supposed to be connected?>

Check the 2N3055 as well for any shorts between EBC.

no shorts

On your picture on the previous page, at designation 7 and 10/shield you noted 'perfect sinus'.  Can you verify that you have a good looking waveform at this point? 

confirmed, signal is coming in exactly as it is leaving the oscillator

Compare the section of the preamp that is showing good/correct trVoltages with the section that is a mess.  Part by part verify they are correlating. 

working on that

Can you remove the bottom of the chassis for a visual inspection of the solderside of the pcb?


try a macro function or a photographer's loupe to bring the components into view more clearly

attached

 

[erikb1971]

OhI finally understand the schematics in the building instructions, can check connections there...

 

[MicDaddy]

can it short circuit when it is touching the house of the capacitor (not the legs?)

The same 22.6V is on the heatsink I believe, though it may not be your problem.

confirmed, signal is coming in exactly as it is leaving the oscillator

With the same reference, follow the audio with your scope looking for where it goes funky.  The schematic should help with the path to follow.

Poke around visually on the solder side and reflow any joints that look cold or messy.  If you can't see solder coming up on the top/component side via, reflow until the via is at least 50% filled.

Too much heat may piss off the transistors, any chance you cooked them when populating? 

I'm curious do you see a happy sine wave at the input pads 7/10 on the channel that is totally dead?

 

[erikb1971]

I just  found out that my go between was the problem on the totally dead channel. I placed the working go between on the dead channel, and now it is working, but with exactly the same problems as the first channel. With exactly the same values on TR4-6. That would mean the error is either not on the pcb's or exactly the same on both pcb's. And that makes an accidental sloppy solderjoint less likely right? Iam going to bypass the go between alltogether on one channel and see what happens. My guess right now is that I have used a wrong value component somewhere on both boards... If anyone has a clue of where that might be accoding to the results described ealier, input is very welcome!

cheers!

Erik

***edit*** Bypassing the go-between results in exactly the same results: distortion in the pre amp and the wrong TR4-6 values ***edit***

 

[sgenevay]

So u clearly mistook somewhere on the board and made this mistake twice....
I don't think it's a dead part cause having 2 same part having same pb....
Are u sure of your resistor and cap polarity for ex ?
Sylvain

 

[erikb1971]

My thoughts exactly...

I checked all pol's (resistors don't have pol. right?) and that seems to be fine.

Iam working with my oscilloscope now... but maybe I do not know enough of it to do it right. What Iam doing is:

1. put 1k sinus on input.
2. measure 10-7 on board (green lines), result: fine sinus).
3. measure tant cap a (blue lines),  result: fine sinus).
4. measure tant cap b (pink lines), result: bad bad sinus!


So I fugured: somewhere in the middle BA138V is something wrong. So I checked for components that had a nice sinus one one side and a mess on the other and I found C16. So my idea would be: something wrong with C16 (white lines on pic), am I correct?

Cheers

***edit*** changed C16 with one from the other board and still no good... ***

 

[MicDaddy]

Don't hate me for this, but it may (or may not) prove beneficial to isolate the preamp section from the gobetween altogether.

Set it up so your XLR in hits the carnhill straight to the pcb back to the output carnhill and XLR out.

Take a quick listen for distortions, if distortion is present, we have ruled out the gobetween, if you have no distortions then the gobetween is suspect.

For the same problem to be shared between both boards, either there is a common error in the wiring configuration.  You ruled your dead pcb to actually be passing similar audio when you swapped gobetweens.  I would omit the gobetween altogether and go from there.  Look at it this way, if you ever need to service these pres in the future, you will be a master at assembly.

All of the jumpers are terminated to the correct pins on the in/out transformer, and the cap/series resistor are in the correct spots? 

 

[erikb1971]

I have disconnected the go between, and still distortion. All the connections to the transformers are as they should be. BUT.... I think I seem to remember that the input transformes should be connected to the case... so they would be grounded. Mine ae connected to the case, but because of the paint, they do not make contact with the metal of the case... could that be the souce of the poblems?

 

[erikb1971]

For me transformers has to be linked to the ground ... so to the case...

Sylvain

AHA!

***edit*** linked the input transformes to ground, but still distotion and still v measurements at tr3-6

 

[erikb1971]

****FIXED!!!!****

My dad is the Sherlock Holmes of PCB's! Turned out I mixed up the 51K and the 5k1 resistors.... Thank you for helping!

 

[sgenevay]

I WOOOOOONNNN 
lol

Sylvain

 

[erikb1971]

comon say it: I told you so... I deserve it!

 

[erikb1971]

There is just one word for the sound... SWEET...