Neve 1290 build completed!!

[snipsnip]

haha - wicked. Glad I could help.  ;D

I got a lot of help from martin & others with my oscillation issues, so the beers should be for him / them really!

Cheers
Jake

 

[stitch-o]

haha - wicked. Glad I could help.  ;D

I got a lot of help from martin & others with my oscillation issues, so the beers should be for him / them really!

Cheers
Jake

at least a keg for Martin

I think the crackle has something to do with the power supply...something is going thermal, that's for sure.

 

[snipsnip]

Absolutely! 3 cheers for martin! 

Interesting update on the crackle... do let me know when you have more!

Jake

 

[stitch-o]

Absolutely! 3 cheers for martin! 

Interesting update on the crackle... do let me know when you have more!

Jake

Im still kinda pulling at straws as I haven't had the pres on the bench for volt messures and the like,
but my boss had an interesting suggestion:
He said if the 2N3055 isn't properly bias (ergo: wildly off) that it could be loading the FETs and transistors causing
power spikes kinda like what I described.
I hadn't taken the time to do the biasing so that will be first today.
Snip: did you bias your 2N3055's? Could this issue cause the described cracklefizz?

more to come...

Cheers!

 

[snipsnip]

interesting!

No, I never set the bias correctly as I lent my scope out to a mate.

I'll take a look today if I get a sec. Thanks a lot!

 

[snipsnip]

Hi... I just tried this and for some reason the 1/2 watt 47r started smoking.

Any reason why this might happen?

Cheers
Jake

 

[stitch-o]

uh-oh

while you were trying to bias without a scope?
what pos is the 1/2w that burned?



on a dif note: what happened to my beer toasting emoticons?  ???

 

[snipsnip]

NO, I had a scope on it, but was finding it hard to get anything looking that close to the diagrams in the guide.

The 47r is up by the 5k trimmer, under the heatsink.

 

[stitch-o]

NO, I had a scope on it, but was finding it hard to get anything looking that close to the diagrams in the guide.

The 47r is up by the 5k trimmer, under the heatsink.

If I can confirm with a schematic that that resistor is tied into the biasing circuit, we might have the culprit.
If its a 10turn 5k trimmer, turn it all the way til it clicks, then turn it 5 turns the other direction before firing up to bias.

This is all speculation on my part, btw...

hoping someone more knowledgeable can weigh in.

 

[mitsos]

The 47R is tied to both the TR3 emitter and the 5K trimmer.

here are the schemos for the 1073... check page 6

http://technicalaudio.com/neve/neve_pdf/1073-fullpak.pdf

 

[snipsnip]

I replaced the 47r and checked my bias again.

This is what shows on my scope. It also doesnt seem to change when i turn the trimmer.

 

[stitch-o]

Hey snip, did you start at the lowest gain setting of your tone generator and preamp gain and then work it up?
What is the volume of the sinewave being shown there?

Also, is the crackle problem in both of the channels (assuming you are building a stereo pair)?
With mine its in both...

 

[snipsnip]

I dont have a tone generator, I was just using a tone downloaded from the following site in Cubase..... all settings left at default.

http://www.gearwire.com/gearwire-reaches-1000-1k-tone.html

When I was experiencing crackle, I think it was just in one channel. Although I dont appear to be having any today. I did reheat all my transformer joints, thats the only thing Ive done though.

 

[mitsos]

About biasing: I got this suggestion from a member here who has built a bunch of neve stuff: (maybe Martin can clarify, but it's probably been posted before). This worked for me, at least I think so

To adjust the bias, you have to futz around with the input level (run the
preamp at high gain) and gain to get it to just clip, and adjust for equal
clipping on top & bottom of the waveform. The 47 ohm resistor should run
cool.

 

[snipsnip]

Hi Mitsos,

Thanks for the tip, I just cant seem to register any change to the waveform by adjusting the trimmer, no matter what volume the clipped input is set at.

And sticho - my crackle issues were almost certainly related to the transformer joints. They looked fine, but were under pressure where there is slight tension from the stiffish mic cable . Maybe give them a waggle when you hear the crackle and see if you hear anything?

Jake

 

[mitsos]

For some reason I think I may have had the same issue as you at first, but I don't remember what fixed it, so maybe I'm imagining things. It's happened before...  How are you getting the signal from your DAW to the preamp?  Are you using a mic level signal? I had to use the PT sig generator going out a line output, into a passive DI in reverse(doh!), and into the preamp.  That seemed to work ok.

 

[snipsnip]

Hi Mitsos,

Im using a line level signal, but Ive got it padded down to mic level with one of these.

http://www.kmraudio.com/dw-fearn-lp1.html

 

[gerardmanvuca]

just soldered all parts to the pcb now...but i am confused as to where the 10ohm 1watt resister is supposed to go!?
theres no where on the board for it.  Also the 47 ohm resistor in the bom is 1/2 watt whilst on the pcb it sais 1watt? i assume it is fine to use the half watt since it is on the bom but just wanted to double check. any help is much appreciated.cheers

 

[snipsnip]

From memory, I dont think there is a 1w 10r is there? Is it on the BOM? Dont have a schematic to hand to check at the moment.

1/2 watt is fine for the 47r.

jake

 

[gerardmanvuca]

From memory, I dont think there is a 1w 10r is there? Is it on the BOM?

It is on the BOM. its R98 under the EH10023-2 part:

R98  Digikey PPC10W-1CT-ND

But not on the board? que pasa