"What" Compressor Issue (Fabio V2 Boards)

Hello guys,

I actually working on an old project, the what compressor fabio's version (V2 boards).

Actually i run it unbalanced and with ic opamps for testing. If i'm satisfied by the way this compressor work i will upgraded it with input transfo and DOA in place of ics. I only use the treshold and gain pot and the sidechain filter switch.

The problem is compression dont work. Gain stage work well but treshold stage seems to be inactive. And the yellow compression led dont light up.

I run it +18v -18v. I check the voltage and adjust the trimmers. Everything is ok. I have the good voltage for each opamp. J1 and sc filter switch are in place.

When i look the compression section on the fabio shematic, the biggest difference with original shematics from Deet's is the option for attack and release pots. I dont use these but i mount RR1 that not figure in the Deet's shematic. Maybe it's the cuz of my problem.

Edited with the good fabio shematic
Fabio shematic here : http://www.fileshost.com/download.php?id=D7E517F71
Deet's shematic here : http://dt.prohosting.com/hacks/what1.gif


I will try to work on this when i'll back home (at the moment i compare shematics at job place...) but if anybody have the solution to my problem, your welcome !!

Cheers,
Guillaume

Have built the what but with the transformer. the first thing i was thinking about was the jumper RR1 but that was mount so...have to take a closer look at the schematic...i write back if i find something to add

Damned !! The fabio's shematic i post in my precedent post is not the one i have print some years ago when i bought the boards ! The shematic i own is really close to my boards with attack and release option. So my first post seems to be a little confused for you guys. I update with the good shem.

Kir_For_Pleasure, thanks for your reply. I saw your post in the "building the what compressor thread". Your unit seems to have the same issue as mine right ? (no much compression or not at all and no compression led). Did you fix it.

Any chance to find fabio here ? He certainly got the key...

Folks,

here we are. I think i haven't got the knowledge to fix it alone.
I try to skip the att/release section wiring like  in the deet's schematic (jumpers on att/rel conrol on fabio board with a jumper in place of rr1).
I turn it on, pass signal play with control. Signal seems to be more distorted but no more compression control and no compression led working.... And a few minutes after turn it on something smells "hot"... And that's not my soldering iron... I turn it off and put a finger on ics. U3 and U4 were very hot !! Grrrr.

So i remove U3 and U4 and remove all jumpers and resolder rr1. And i check the voltage for U3 and U4. All ic's I use are NE5534. U3 and U4 are U3a U3b and U4a U4b on Fabio schematic. Here are the voltages :

u3 : 1=16,7v
      2=17v
      3=0v
      4=-18v
      5=0v
      6=17v
      7=17v
      8=18v

U4 : 1=-1,35v
      2=0v
      3=17v
      4=-18v
      5=0v
      6=17v
      7=0v
      8=18v

Looking to NE5534 datasheet and try to understand if something wrong with these voltages but my electronic abilities are really short  and i cant diagnostic anything...
Like my electronic abilities, my english language is not very good. I hope I describe the situation clearly enought to get a little help on this project.

And does anybody had done a fully functionnal fabio's what compressor ? I cant find someone talking about a fully functionnal unit on the forum.

bubble said:

... U3 and U4 were very hot !! Grrrr.

So i remove U3 and U4 and remove all jumpers and resolder rr1. And i check the voltage for U3 and U4. All ic's I use are NE5534. U3 and U4 are U3a U3b and U4a U4b on Fabio schematic....

Click to expand...

Didn't build it, but you noticed, a NE5534 is a single stage opamp, but the footprint on pbc calls for dual opamps coming with a different pinout for U2ab,U3ab,U4ab and U5ab, something like NE5532, OP275, OPA2604, ...? (using a TL072 might be close to the edge with your +/-18V supply, NE5534s will need a compensation cap between pin 5/8 to be unity gain stable if for whatever reason you want to use these chips with some artistic pin bending and flying leads)

Shame on me...
Replace U2 U3 U4 U5 by ne5532
Work great !!

Thanks guys for your help !

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