Neve 1290 questions

[Spencerleehorton]

Yeah my 553 is as per original, I’m happy to try it before output txf and parallel up output txf primary.

 

[Spencerleehorton]

I’ve tried the 553 before the 1166 and get a cut off bottom half of waveform!!!?

Any ideas how to improve the output waveform please?

 

[Potato Cakes]

Was the circuit biased before you put the in the 553?

Thanks!

Paul

 

[Spencerleehorton]

Yes, both channels were biased perfectly.

Pic of waveform with eq in

 

[Spencerleehorton]

When I run the 1k 0.775vac signal through just the 553, the waveform looks good and it bypasses good.

 

[Potato Cakes]

Make sure the output of the 3055 transistor is connected to the HI input of the 553. Keep in mind the LO connection of 553 goes to the audio ground so this may cause complications with the TX connections on your BA283AV boards.

You may just need to pick off after the transformer or add some other buffer between the preamp and EQ. The other option is to go out of the Preamp out of the AV board to the 553 HI input then to the stage three input of the AV board.

One of those methods should work. I hope.

Thanks!

Paul

 

[Spencerleehorton]

With the preamp put are we saying that the preamp our is P and then use K for the input back in?

 

[Potato Cakes]

I don't remember exactly how the labels translate. This is how I connect the EQ circuit for the 1073s I build with the boards you have.

Thanks!

Paul

 

[Potato Cakes]

P is Preamp Out and L is Stage 3 Input.

Thanks!

Paul

 

[Spencerleehorton]

Yep I with ya now, I’ll reconnect that way and see what I get!!
Thanks again Paul.

 

[Spencerleehorton]

yes finally success!!! connected to P and L and get lovely waveform HF, MF and LF work fine, my only question now is i have used 5k pots rather than 10k, would it make a big difference?

Next stage is to wire in some switchable frequencies!!

 

[Potato Cakes]

You should be getting about +/-15dB of gain on each band. If you are and it sounds good to you then you're probably fine.

Thanks!

Paul

 

[Spencerleehorton]

So am I correct I thinking 15db = 5.62vac ?

 

[Potato Cakes]

It should be about 4.35VAC at that bands frequency. The stock frequencies are low shelf at 100, MF peak at 2k5, and high shelf at 10k. So you would set the generator for those frequencies and then measure.

Thanks,

Paul

 

[Spencerleehorton]

Thanks again Paul, I
Waiting on some switches for bypass then I can re jig everything in the case and rework the face plate.
Once done I’ll check everything and put some sounds through it!!!

 

[Spencerleehorton]

I tested the Psu today and circuit was dodgy even with a good Psu?
So I fiddled with the 5k trimmer and I think it was a bad solder joint as now all voltages seem solid and current wise it seems to pull 0.12A at full gain and 0.08A at no gain.
I seem to remember this was about right, more testing on the way but will need to go to Germany to do a gig first!!!

 

[Spencerleehorton]

Another question for you, the 180pf cap on the input txf.
What frequencies is this cutting out?
I’m assuming it’s 22khz and above?

I can see that using 300pf for the eq selects the 12khz frequency.

Just wondered how to work this out?

 

[Potato Cakes]

That seems to make sense, but I don't know exactly. I'm not smart enough to know what precisely is happening with the components. I just guess and then test.

Thanks!

Paul