Neve 1290 questions

Still haven’t found the right setup for this yet!!
It’s sounding nearly there just a little hum still present.
I’m going to move the Psu out of the enclosure as another test as everything is pretty close!!!
And I will get round to changing the input txf for one which i know is ok to eliminate that as the problem.

Also I need some advice on how to test for ripple as I’ve forgotten!!! Or I’ve never done it!!

Spencerleehorton said:

Also I need some advice on how to test for ripple as I’ve forgotten!!! Or I’ve never done it!!

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I have a scope put it on power rails at quite a sensitive setting.  If you don't use your multimeter on a sensitive a.c setting.

I’ve had success before with wrapping the toroidal with M6 laminations so May try this as well.

Rob could you explain the ripple a little more please, I don’t really understand what you’ve put.

I have a scope and a MM just don’t know exactly what I’m looking for regards ripple

You are checking the power rails to see if they have an a.c component.  If they do this will be to some extent be superimposed on the audio.  This is because any circuit is basically controlling current between the power rails, so if the PSU is noisy or has ripple it will happen on the audio.

I also want to make sure I’m not under powering as my toroidal is a 2 x 12v 0.83vac which I’ve put to 24v.
1.6A should be enough I hope to run one Neve 1290  and the phantom power right?

Spencerleehorton said:

I also want to make sure I’m not under powering as my toroidal is a 2 x 12v 0.83vac which I’ve put to 24v.
1.6A should be enough I hope to run one Neve 1290  and the phantom power right?

Click to expand...

Easily.

As it turns out they are 1.2A per coil so 2.4A on toroidal, so I can take that out of the problem pile.
I’m replacing the gain switch for this Russian 3 pole 11 position rotary switch as I’m not happy with this 24 position one, I only end up turning it halfway!
So I’m going to loose the 75db position from the ez1290.

Done the switch now and routed the connections correctly, doubled checked this time!!!
Getting a nice waveform and I’ve tuned the circuit now so getting perfect bias.

Fingers crossed now that there is no hum!!!!

The ez1290 and NV73(don classics) both use 3x12 switches and have schematics showing the gain switch resistor values. The ez1290 goes 20-75(or 80, I can't remember) and the NV73 goes 0-66. They also show connections to the appropriate boards as it pertains to the 1073 schematic. You should be able to easily apply this to the boards you have. I can dig the schematics  up if you have trouble finding them.

Thanks!

Paul

Hi Paul,

I’ve found the don classic version but to be honest my version seems to be working ok.

Just need to plug it in and hope there is no hum!!!

Comparing the EZ1290 and the don classics version I’ve hit a couple of questions as I need to loose a position as they have 12 positions and the don classics seems to add values after the positions.

Position 1 would have the most attenuation, so in my case it would be 60db, would I add the 3.3k and then the 3.9k after the B gang?
Also I need to check that these pcbs have included the 15k at S to U hand A and the 18k S to U gang B.

Even though everything is looking really good I do want to really fine tune this circuit so I can then look at all my others and do the same.

The 15k resistor is in the same place isolated from the switch mechanics on the original schematic with the EK20033 switch, so that would probably need to stay where it is on regarding your specific setup.

From what I can tell, you would loose the 3k9 and use the 3k3 to connect P to the 60dB switch position. Again, this is based off of looking at the original schematic. As always, I would double check to verify if this is indeed correct.

Thanks!

Paul

Ok Paul,  thank you, I’ll do a bit of experimenting and see.

Ran out of time again before another night shift, but the rewire temporarily had worked and I had a silent preamp, now there is something wrong with the Psu on the 24v side as it’s jumping around and not stable!
The Psu is heavily modded so I will rebuild and find out what’s wrong.

But at least I have a no hum preamp now!! 

New Psu built and getting good solid voltages so far, going to do a bit more tomorrow after some chill time and a little beer!!

Have tested new Psu and getting solid 24v and 48v.
As soon as I connected to pcb 24v I get voltages all over the place?

Could it be the 3055?

I’ve got another adjustable Psu which is 30A I can test it on but I’m having a nightmare with this, any ideas?

Do you have any other +24V circuits to test your PSU? Does it still have issues with just the NV board connected?

I had a similar issue when I tried to use the +48V rail on a JLM Powerstation trimmed down to +24V so that both cards in a stereo compressor would have their own rail, but the voltages would go steadily increase and decrease, so I wound up just sharing the +24V rail and all was fine.

If you have another PSU to try that first. Also try with the NV and AV boards connected separately.

Thanks!

Paul

Yeah I need to break it all down and test individually.
Got another couple of days off soon, so will continue to investigate!!

I’ve got the 553 eq going now and need to connect this to the 1290.
Hopefully it will connect ok?
I can see K and C connect to the low frequency, and I can see it connects to P.
Would like a bit of advice to connect it to the 1290 if anyone can help please.
I’m going by the original 1073 and the EZ1290 schematic.

If you are using a 553 style EQ, wouldn't you just connect the TX Hi/Lo connections to the Hi/Lo connections on the 553 and go to a LO1166 that is wired 1:3? This of course depends if you plan on using the 553 as the original with -6dB going in and being made up for that on the output.

The LF/HF and the MF each got their own makeup gain circuit that is the same as your NV board as you see on the original 1073 schematic. You'll also notice that the LF and MF sections both have an OFF position, which is probably the reason why those bands have their own amp card. This of course is not need on the 553 as it just using a make up gain circuit at the end. Is the circuit you have like the original or do you have a modded scheme are you using?

Thanks!

Paul