8 Channel, 3U NEVE 1073 completed
- Thread starter madriaanse
- Start date
Help Support GroupDIY Audio Forum:
sgenevay
Well-known member
At Least with color codes.... Are your 2 boards reacting the same ?
sgenevay
Well-known member
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.
All your transistor voltages are ok ?
Sylvain.
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.
Take some clear pictures and post them up here.
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?
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?Attachments
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
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
They are, as in M. adriaanse's pdf on page one of this thread.MicDaddy said:
MicDaddy said:
can it short circuit when it is touching the house of the capacitor (not the legs?)
MicDaddy said:
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?>
no shortsMicDaddy said:
confirmed, signal is coming in exactly as it is leaving the oscillatorMicDaddy said:
MicDaddy said:
working on that
attachedMicDaddy said:
Attachments
The same 22.6V is on the heatsink I believe, though it may not be your problem.
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?
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***
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
Well-known member
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
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
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... ***
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... ***
Attachments
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?
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?
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?
sgenevay
Well-known member
I WOOOOOONNNN
lol
Sylvain
lol
Sylvain
