CLX-VU Build Thread (DBX 160VU ) UPDATE: REV 3

[Spencerleehorton]

Hi,

Have cured oscillation by changing c80 from 5pf to 10pf on the rms unit.
When turning ratio pot it cuts out all sound now? Also led is always on and doesn't change?
One step forward 2 back!!
Any ideas anyone?

Regards

Spence.

 

[Bowie]

Hi,

This is a picture of my pcbs, have put in C39 since this picture was taken but not tested.
If you spot anything please let me know!!!

Regards

Spence.

I took some time to compare this to mine and, without checking the actual resistor values, everything looks ok, save for the missing C32.  Are you sure that there's no solder blobs shorting underneath?

 

[sage]

Hi Abe

here we have both boards populated and ready to wire... I see thru the posts that R30 is sometimes installed and sometimes it is not.... from your pictures in the manual Rev3 it is installed but it's not on the BOM.... so here is the question that you have probably answered before .... IS R30 SUPPOSED TO BE IN or NOT ? And if yes is it 1 k ?

THANK YOU

Sage

 

[Bowie]

Hi Abe

here we have both boards populated and ready to wire... I see thru the posts that R30 is sometimes installed and sometimes it is not.... from your pictures in the manual Rev3 it is installed but it's not on the BOM.... so here is the question that you have probably answered before .... IS R30 SUPPOSED TO BE IN or NOT ? And if yes is it 1 k ?

THANK YOU

Sage

I found this, posted a few years ago;  "the reason I was getting hardly any compression was that I had  R30 installed.  In the pdf coloured overlay it indicates to install it, but it difficult to read that it says omit it for that's builds on the overlay."
So, if you're using THAT then I would say to try it without.  Hopefully Abe will check the thread soon as I'm still awaiting an answer about where to jump my dead trace.

 

[sage]

Thank you Bowie I had seen that post but it is so old that it might be referring to REV 1 or REV 2... my boards are REV 3 so I just wanted to confirm that -
Every thing else in the PCB seems pretty clear...

THANK YOU

Sage

 

[Dr Gris]

Checking my boards, you can jump AC Centertap to C2 minus(-). From there it goes to C3 plus(+).

Do you have continuity between C2(-) and ground (where you check power-rails)?

At first I was going to give an answer just reading the schematic but there it seems to be the other way around?? As far as I can read polarized caps the symbol for C2 shows + to ground. No???

I hope that wasn't confusing...

Best
//M

 

[Bowie]

Checking my boards, you can jump AC Centertap to C2 minus(-). From there it goes to C3 plus(+).

Do you have continuity between C2(-) and ground (where you check power-rails)?

At first I was going to give an answer just reading the schematic but there it seems to be the other way around?? As far as I can read polarized caps the symbol for C2 shows + to ground. No???

I hope that wasn't confusing...

Best
//M

Thanks, I was thinking the same thing, based on the schematic.  Just wasn't confident enough to go ahead w/ it w/o some confirmation.

 

[Spencerleehorton]

Hi,

Have put in c24 and c32 1nf and gonna check all ic's working as ratio pot when turned clockwise cuts all audio?
Brew baca had the same problem but can't exactly remember the fix, anyone else remember ?

Regards

Spence.

 

[sage]

Hello there

almost completed the build - just double checking on a couple of things....

PARALLEL WIRING FOR TRIAD VPT 36-1390 115VAC :

INPUT : BLUE AND VIOLET TIED TOGETHER - GREY AND BROWN TIED TOGETHER

OUTPUT TO THE BOARDS: BLACK AND ORAGE TOGETHER - YELLOW AND RED TOGETHER

THEN YELLOW/RED and ORANGE/BLACK GO TO BOTH INPUTS ON PCBs AT THE SAME TIME INDIVIDUALLY


ALSO DOES ANYONE HAS  PICTURE ON HOW TO WIRE THE LINK BOTTON ?

THANK YOU

Sage

 

[Bowie]

Hello there

almost completed the build - just double checking on a couple of things....

PARALLEL WIRING FOR TRIAD VPT 36-1390 115VAC :

INPUT : BLUE AND VIOLET TIED TOGETHER - GREY AND BROWN TIED TOGETHER

OUTPUT TO THE BOARDS: BLACK AND ORAGE TOGETHER - YELLOW AND RED TOGETHER

THEN YELLOW/RED and ORANGE/BLACK GO TO BOTH INPUTS ON PCBs AT THE SAME TIME INDIVIDUALLY


ALSO DOES ANYONE HAS  PICTURE ON HOW TO WIRE THE LINK BOTTON ?

THANK YOU

Sage

I used the Allied PT so I can't help there but for the link, just check continuity on the terminals when engaged and disengaged and wire accordingly.  1 page back there is a mention of where you can find the stereo link diagram.

 

[Dr Gris]

Hello there

almost completed the build - just double checking on a couple of things....

PARALLEL WIRING FOR TRIAD VPT 36-1390 115VAC :

INPUT : BLUE AND VIOLET TIED TOGETHER - GREY AND BROWN TIED TOGETHER

OUTPUT TO THE BOARDS: BLACK AND ORAGE TOGETHER - YELLOW AND RED TOGETHER

THEN YELLOW/RED and ORANGE/BLACK GO TO BOTH INPUTS ON PCBs AT THE SAME TIME INDIVIDUALLY


ALSO DOES ANYONE HAS  PICTURE ON HOW TO WIRE THE LINK BOTTON ?

THANK YOU

Sage

Looking at the data for your Triad transormer you are correct about the primary connection.
On the secondary you need to create a center tap by connecting red and orange.
So now you will have three wires to your board insted of two. BLACK, RED+ORANGE, YELLOW.
There should be 18V AC between your center tap(red+orange) and black wire.
The same goes for center tap - yellow wire.

Then you connect the two boards in parallel. That means you split your secondary AC wiring so
both boards get the same power. I use some kind of screw terminals to do this in the back of the case.

Don't forget to trim down your voltage to +/- 15V DC before you insert any IC's.

Link button: if you search this thread you will know where to connect the cables to the PCB.
Connect the two cables to the link button, one in the middle and one to the "engaged" (closest to PCB).
"Not engaged" (closest to front panel) left alone.
You have to press both link button and one of the other buttons (IN/GR/OUT) on that channel
to get a reading from the VU.
Set controls on both channels to the same.


Good luck!
//Magnus

 

[Bowie]

I decided to cross my fingers and jump CTR to C2-.  Surprisingly, it worked great on start-up.  I was very concerned about this build because I used a DBX black can VCA and I haven't seen much success among those who tried it.  The black can gives that classic smack or "knock" to the attack, which is exactly what I was after.  The only obvious problem I've encountered so far is that the "above" light is constantly lit.  When I started up w/o the VCA installed, the "below" light was on.  So, I know the below light can work, I just need to figure out why the above is constantly lit.  Any ideas would be greatly appreciated!  Until then, I'm too to start populating the 2nd board.

 

[sage]

THANK YOU Dr GRIS - MAGNUM

that is very detailed and I will follow this am.... gonna try to post a clear picture for future users of the same trafo - this is a step that is essential NOT to make mistakes and even if we have done a dozen projects when it gets to the POWER I am always nervous....

Sage

 

[Spencerleehorton]

Hi,

Bowie I get the same thing going on with led light, if you find out what it is let me know!!!
And if I do I will let you know.

Regards

Spence.

 

[shot]

Regarding the LEDs lit, did you try to calibrate the unit? Maybe the treshold is not calibrated yet?

 

[Bowie]

Regarding the LEDs lit, did you try to calibrate the unit? Maybe the treshold is not calibrated yet?

Thanks for the suggestion.  I haven't calibrated in the proper way yet but I have tinkered with the pots enough that it's functioning close to normal and full CW gives no compression.  The Above light is on even when no signal is present.  Looking through the thread, this has been a problem for several people but I can't find a resolution.

 

[shot]

Thanks for the suggestion.  I haven't calibrated in the proper way yet but I have tinkered with the pots enough that it's functioning close to normal and full CW gives no compression.  The Above light is on even when no signal is present.  Looking through the thread, this has been a problem for several people but I can't find a resolution.

My unit also behaves that way, but I don't see a problem with that. Above LED is lit identifying that the gain reduction is not happening. If it is not having any signal or the signal is not loud enough is the same - the treshold has not yet been crossed. When you have your LEDs both off that is when the compression starts kicking in. That's the treshold level.
As long as it switches to below LED correctly everything is ok!
I don't know if it is different from the original unit, but I believe this is how LEDs should perform.

When I re-read your post i noticed that you say that "full CW gives no compression".
If your talking about the treshold potentiometer than this behavior is WRONG! Both LEDs should be off then your at aprox. 2 o'clock when calibrating with specified sine tone. And every different signal that you put into your unit will have a different treshold pot position where LEDs go off since it depends on the input signal's level or density.

Go through the calibration procedure. It is tricky and maybe you won't be able to get it first time (I didn't!), but it is very important. And if you get stuck, don't forget to check the procedure written in the original manual, not only Abe's. It might give you some ideas.
My unit is still not calibrated completely (it's showing real output level lower than it is) but I don't care since I allways use only GR meter. And it took me few days to calibrate it!

 

[Spencerleehorton]

Hi,

Well I'm gonna try and go through the setup procedure again and try and sort this ratio pot problem.
The unit passes audio with the ratio pot full CcW but if turned CW about 9-10 o'clock it cuts all audio.
I think the rms unit is working corrects now without oscillation, but I couldn't get 0.011v on r79.
Not 100% sure what all the trims do so maybe a simple fix.

Regards

Spence.

 

[Spencerleehorton]

Hi,

By looking at the schematic looks as though I should be tweaking r43 to adjust ratio, and also to adjust meter better r59 and r56. I have no idea how these are set so will spend some time tweaking these.

Regards

Spence.

 

[shot]

I also had problems with R79. Couldn't get even close to -0.011V. I was due to the fact that the unit varied voltage on this spot dependant on the position of the pots (and it's not supposed to do that). My fix was to remove the lorlin switch and go with pushbutton array. Even though there's a diagram how to use lorlin rotary somewhere in this thread, that didn't perform well.
After I got the correct voltage on R79 it all started performing better.

When you say that it cuts your audio on the ratio pot, does it really cut it entirely off or it lowers the volume but still passes a small bit? If it passes small amount of audio that would indicate that the ratio amount is huge, bigger than it's supposed to be. Or that the treshold point is very low.