Nightpro preQ3

[digitall2000]

hi all
i just got handed a preQ3 with switching PSU
it blows the first fuse (mains one) even when the PSU is not in the unit
i'm thinkin' it's the mosfets
does anyone have one of these puppies and could tell what the voltages on the PSU pins are
what is on the board is kinda strange for audio attached a pic of the connector
oh yeah IPD no longer sells this unit and has no info on it

so dasnevestheo

Quote from: dasnevestheo on February 11, 2020, 05:02:39 AM

    Here's everything I have on this project : https://we.tl/t-6iQaqbnDkN

could you please re-post a link to the project docs
the link is dead

thank you muchly
lance

 

[electrog]

I have one where the switching supply died. I had no luck finding any direct replacement. Since I have a unit with only two preamps, there's plenty of space left on the other side of the chassis to replace it with a linear supply - one of these days I'll get around to that.

I would think the voltages should match the labeling on the board, as shown in your photo +28v -28v +52v.  That was the assumption I was going on in finding and/or building a substitute.   

Unfortunately there is very little info around on these, unlike the NiteEq, which is well documented here.  Maybe write Maag audio?

 

[Whoops]

Wel you if you are able to get the schematic, or through forum or Maag then you  try to fix the PSU.
Did you pm dasnevestheo on the docs?

Without the schematic maybe it would be easier like electrog said to build a linear PSU to replace the original one.

 

[peterc]

As was said, a linear PSU with the correct voltages would probably be the best replacement, if the original cannot be repaired. A voltage doubler on the AC supply would take care of the 52v, which is probably regulated to 48v for the Phantom supply.

Peter

 

[electrog]

Yes, my assumption was always that the +52v is filtered/regulated to 48v on the board for phantom, and +-28v down to +-24 for audio...that makes the "kinda strange for audio" voltages make sense. As I recall, a glance at the board also bears out that there is a section for psu filtering. 

 

[Khron]

Since this isn't a power amp or anything of the sort, it's a pretty safe bet the power supply is just your bog-standard flyback design, with 2-3 secondary windings.

Primary will either be a UC384x and a MOSFET, or perhaps even an all-in-one solution (controller and MOSFET in the same multi-legged TO220 package).

 

[peterc]

+ and - 24v would mean some special high voltage opamps or DOAs.......

 

[electrog]

...nothing quite that esoteric. 11 NE5534ANs per channel (labels mostly rubbed off, but I can make out a couple). One is for the Aiband Eq, I assume.  Jensen JT-16-A input transformers. Maybe the +-28 was a result of using an available switching supply and is regulated even further down to +-18v? 

 

[digitall2000]

thanks guys
have tried maag, but haven't heard anything back yet

peace lance