Building the WHAT compressor

[Kir_For_Pleasure]

No signal passes through :shock:
troubleshooting the signalpath, here are some pictures.
What do you think ?

In sine signal 2000hz

After transfomer CC cap

U1 Out

U6 Out

U7 Out

 

[Kir_For_Pleasure]

I use all the controls and the switch not april

Schematic
http://www.thediypill.phx.com.br/forumfiles/what_sch_rev2.pdf

 

[Kir_For_Pleasure]

I have tryed for a couple of days to find whats wrong but havent found anything, swapped opamps, taking out the pcb time after time and holding it in bright light to see any short in the circuit.

im stucked in that something is wrong around U7, first i thought it must be the opamp then maybe a short under the dip socket, took out c14 c15 r29 and replaced them with mesured new ones, but no sound and nothing coming out from U7 ?? how should i proceed with tracing ?

Help me guys !

 

[3nity]

I'd put signal by stages...i mean try the output amp first. :thumb:

 

[Kir_For_Pleasure]

did you look at my pictures ?

if i cut J1 and just tracing the U1 U6 U7 would i have signal all the way then ?

 

[AnalogPackrat]

1) How large of a signal are you feeding into the thing?
2) Have you verified that your DOAs work properly (not using the WHAT circuit)?
3) How are the controls set during your test?

Have you tried swapping your DOAs around? If not, swap the first and third and see if the problem follows the third amp module.

Good luck,
A P

 

[Kir_For_Pleasure]

[quote author="AnalogPackrat"]1) How large of a signal are you feeding into the thing?
2) Have you verified that your DOAs work properly (not using the WHAT circuit)?
3) How are the controls set during your test?

Have you tried swapping your DOAs around? If not, swap the first and third and see if the problem follows the third amp module.

Good luck,
A P[/quote]

1) The signal 2000 hz is as strong as possible without clipping +2db maybe

2) For the U1 U6 U7 i use ne5534 and i have tried many diffrent, but if they works i cant tell for 100% but they are all new. i have swapped them around.

3) I cut J1 but set all the controls to 12 o clock to be sure audio should pass if something was wrong, i also move the controls up and down to see if that affect the signal.

Cant see why i have audio into U7 but not out ???
how is that possible if the amp is ok ??

 

[AnalogPackrat]

Well, if you've used ICs and swapped them around and the problem stayed the same, then its something on the board (including the PSU section). Looking more carefully (counting reticule lines on your scope shots), it appears you do not have the proper voltage on one of your rails. You've only got one half of the waveform coming out of U1.

Did you verify that the power supply section is operating correctly? With no power on and no op amp chips in place have you checked for a short between each rail and ground? It also would be a good idea to probe for shorts on the IC sockets for U1 and U7.

A P

 

[Kir_For_Pleasure]

Thank you Analog for your time :grin:

 

[Kir_For_Pleasure]

i didnt found any shorts :roll: i used my multimerter and the sum
function, sometimes when i hit a spot i get a very very short signal and i have a value on the meter, what am i measuring then :?

 

[flintan]

[quote author="Kir_For_Pleasure"]i used my multimerter and the sum
function, sometimes when i hit a spot i get a very very short signal and i have a value on the meter, what am i measuring then :?[/quote]

That's probably beacause those spots have a capacitor in parallell.. Then it will beeep for as long as the cap holds voltage to feed your instrument, the bigger cap=the longer beep. The resistance metering will add a voltage on to where you are measuring and if there is already a voltage there, it will beep...

 

[Kir_For_Pleasure]

here are some new shots, this time with batteries as power +16,2 -16,2


first with amp

After C1

in U1

Out U1

Without amp in socket

U1 in

U1 out

 

[Kir_For_Pleasure]

someone with ideas and knowledge in reading schematic
http://www.thediypill.phx.com.br/forumfiles/what_sch_rev2.pdf

 

[Kir_For_Pleasure]

I have signal  8) But no compression ???
Ratio affect the signal but not threshold,attack,release, when i was measuring with my scope suddenly when i point the u4b in+ the sidechain starting to work  ??? ??? every time i spot that point sidechain working and when i take the probe away sidechain dies ??
Can someone explain what is going on ?

 

[peterc]

Sounds like the sidechain needs a load? Just a guess.

Make sure your earthing is correct.

Peter

 

[Kir_For_Pleasure]

I found what was wrong i forgot to mount RR1 ?? Really nice sounding but not what im use with, not smashing at all so smooth and gentel. next step will be a meter

Thank you all for your help and your time THIS FORUM RULES !!! 

 

[Kir_For_Pleasure]

Someone got a working meter for the what ?
Im playing with a LM3914 but have problem with the signal feeding the LM3914.
Taking the dc from the yellow comp led but since the 3914 just reading positiv dc and the dc at comp led just have dc negative i must come up with a solution inverting dc negative to dc positive. I cannot find that good solution, surley very basic op amp operation, someone into op amps with a idea ? 

 

[Luny Tune]

You should of course do what you want but in my opinion the What comp doesn't need a meter at all. It's so gentle and so quickly dialed in that you won't even have time to focus on a needle. Besides when you hit it hard and you think that it's hard to determine if it's doing more at all when you twist the knob further yet, then it's because it just doesn't do any more no matter how far you turn the knob. It can "only" compress to a certain point. After that it just turns the volume down.

Save the effort for something that actually makes a difference.

Just my advice of course! You may have other preferences!

PS: I'm the happy owner of eight of those babies and use them all the time as a little extra level control/attack shaping when mixing. Like them a lot on acoustic guitar and often on distortion guitars too. Love the sound of opto comps and have built the LA-4. If you like your What but miss the ability to squeeze the hell out of something with it, build the LA-4. I'll be offering a handful of boards for sale sometime soon...

 

[Kir_For_Pleasure]

The meter thing is mostly for learning. Thinking of building 3 more of whats into a 2U. Uses all the controls so more than four i dont think i have space for. La4 sounds intresting. Love the sound of opto comp too !

Thanks for your opinion !

 

[Luny Tune]

Hey, just noticed you're from good old sweden! Where's Hallstahammer at?

I'm in Helsingør. Maybe the LA-4 boards wouldn't have to travel far...

My 8 Whats are in a 2U case.

I'm actually considering leaving out the meter on my LA-4, and actually replacing my What comps for LA-4s instead. Not in one 2U case though...

We have a Danish forum too, by the way. It's even called groupdiy.dk
Feel free to drop by, but if you can't get passed the clever question to keep spambots out, drop me a mail and I'll either tell you what to write or create the profile for you. We often have these "builder weekends" where 10-12 of us meet and build nice gear. Great fun and an amazing way to learn a lot! If you're not too far up in Sweden maybe you'd want to join in. You'd be most welcome!