Neve 1290 build completed!!

[stitch-o]

Don't you after some point just want to throw the whole thing out or start back from scratch.

No freakin way!!! I'll figure it out eventually.
I think 3nity has the key...I've been putting off measuring all the fets and such.
The crackle returned for a second so I guess that will be my next stop on the troubleshooting express....

 

[mitsos]

FETS? what FETS? Damn it! I knew I did something wrong!   

just kidding, I know what you meant... ;D

 

[stitch-o]

FETS? what FETS? Damn it! I knew I did something wrong!   

just kidding, I know what you meant... ;D

ooops, transistors...yesyes, touche'. 

 

[snipsnip]

my voltages have always been fine.

The wierd thing is, when I first completed the pres, and did not have my scope, I used the trimpot and set it up so it was as close as pos to the voltage chart.

When I was setting the BIAS with the scope, my voltages did not seem to change when I was adjusting the trimmer.

odd.

 

[stitch-o]

hmmmm....well, I am still on the fence as to taking the time right now to measure volts as
I am exceedingly busy.
I had a brief spike of crackle yesterday after I had the pres on for quite a few hours.
I powered them down for 5 minutes, and when I fired them back up: no crackle.

What I don't get is if something is going thermal, wouldn't it happen sooner as peak operating temperature
(Im sure) is established in 20 minutes or under....

 

[3nity]

did you guys checked for cold joints?
checked resistor values?
If you use a FET DI just might try to get rid of it for the moment!
high resolution pix always help.

thanks.

 

[stitch-o]

did you guys checked for cold joints?
checked resistor values?
If you use a FET DI just might try to get rid of it for the moment!
high resolution pix always help.

thanks.

I did a survey for cold solder points and touched up a few connections.
I'm about 99% the resistor values are correct-> I have a habit of testing part values before I
install them.
No DI on mine...

I had the crackle pop up again this morning: shut down the pres, waited a few minutes and (again) the crackle is gone.
BUT I did record a few seconds of it before it disappeared...below is a link to the mysterious crackle.

CRACKLE.AIF

Any suggestions would be great!

 

[3nity]

Transformers wiring 100% good?
Grounding scheme what kind its?
2N3055 and heatsink is tight to the PCB? do they make contact?

Now does that cracklings happens with mic connected or not?
Thanks

 

[mitsos]

hmmmm....well, I am still on the fence as to taking the time right now to measure volts

You a pothead focker?

 

[stitch-o]

Transformers wiring 100% good?
Grounding scheme what kind its?
2N3055 and heatsink is tight to the PCB? do they make contact?

Now does that cracklings happens with mic connected or not?
Thanks

Been through the transformer connections a few times: they are good

The chassis grd point has connections to each standoff mount in the corner by the trimmer for each board.
Also connected the hanging shield of the LO1066 to board (used shielded mic cable) to chassis ground.

The 2N3055s are def in there good and solid.

The crackle happens with mic attached or not...

weird thing is it is VERY sporadic. I've had the pres fired up since 7am and the crackle happened that one time
that I recorded and posted above. They have been noise free since I powered down and powered back up around 8am.
???

Intermittent problems are the worst...I'll track this down tho.  ;D


EDIT: Mitsos, yer a crackup yo.

 

[snipsnip]

CRACKLE.AIF

Thats the same crackle as me!

Weve got to beat it 

 

[stitch-o]

CRACKLE.AIF

Thats the same crackle as me!

Weve got to beat it  

absolutely!

Still fired up from 8am...still no crackle here...thats 7hours on, noise free.
Perhaps they need time to burn in a bit? This I don't know.

EDIT: I've got 24 hours fired ON now: no crackle...

EDIT2: 48 Hours on: no crackle...

 

[gerardmanvuca]

Is it really a must to seperate the input and output tranny from each other?  i noticed on the chandler they dont bother. Anyone had problems putting them 2 close?

 

[mitsos]

There was someone who had an issue. There are pics either here or in the other thread. He had a very compact case and the trafos very closer (I think even closer than the chandler).

 

[snipsnip]

If you look at martins 8 channel version, hes got them quite close.

I guess it just increases the risk of oscillation.

 

[madriaanse]

Hey guys,

Good work on the troubleshooting! Wanted to chime in here re: the crackle. For good measure, also try swapping in a new LM317 on the +24V PSU and make sure you put a fat (and I mean P-H-A-T) heatsink on it - something like:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=HS276-ND
or even
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=HS117-ND

A diecast aluminum case also makes for a great heatsink (used in my instructions), but you have to make sure you're not shorting Vregs to case.

Also, you *HAVE TO* keep 10468 away from LO1166. And keep input wires away from output wires - use shielded cable for all audio. You will get oscillation at high gain guaranteed if you don't. For my two 8 ch units I moved the transformers around with the EZ1290 gain maxed until I didn't get oscillation; then I bolted them down. There's a reason Neve mounts the iron like this: http://www.highprofileaudio.com/1073inside.jpg

All the best,

M.

 

[mitsos]

Don't remember seeing any man. I think most people like the simplicity of these. They'll clip anything that comes after them WAY before they clip. 

 

[desol]

Also, you *HAVE TO* keep 10468 away from LO1166. And keep input wires away from output wires - use shielded cable for all audio. You will get oscillation at high gain guaranteed if you don't. For my two 8 ch units I moved the transformers around with the EZ1290 gain maxed until I didn't get oscillation; then I bolted them down. There's a reason Neve mounts the iron like this: http://www.highprofileaudio.com/1073inside.jpg

All the best,

M.

What about trim placement on the frontpanel? Can having the output trim too close to the input gain switch(section) pose a problem?

 

[madriaanse]

Hi Desol,

You'll probably be ok (just don't run the wires close to each other). I would do a cardboard mockup frontpanel to test before committing to aluminum.

M.

 

[gerardmanvuca]

i have a question about the JLM AC/DC PS. On the JLM website it sais to do this:

But in ez1290 pics of the power supply i see that people are leaving in caps that the pic sais to take out.  Basically i'm a bit confused as how to wire this. Do i just wire everything in and leave out the LM337 reg or leave caps out like in the jlm pic? I have version 2 board ACDC. In the 220v ACDC wiring PDF Madriaanse sais to wire the right pad to the centre pad but in the jlm pic it sais to 'strap T to the centre pad' which is the left pad to centre pad?? i'm confused...... any help wud be appreciated. cheers