GSSL HELP THREAD!!!

[ptron]

I think its missing a jumper on that vca circuit... And that 1m res going to distortion trimmer should be also there (other value cus of calibration.) off the top of my head i think its 680k for 2181A... I guess if u using 2180 u could leave these out..


Cheers!

 

[Harpo]

The issue of distortion is eliminated when bypassing the VCA's by linking pins 1-8 with the VCA's taken out..  what does that suggest?

Opamps in the audio chain are working properly. Audio-VCAs might be blown or distorting because of too much mV at the VCAs Ec- port pin3.
Verify the 120Rs in the upper right corner of the substitution circuits are 120Rs for real (lift one side for measuring), not 10Ks read backwards.

 

[wthrelfall]

I think its missing a jumper on that vca circuit... And that 1m res going to distortion trimmer should be also there (other value cus of calibration.) off the top of my head i think its 680k for 2181A... I guess if u using 2180 u could leave these out..


Cheers!

yes, i'm using 2180's.  where should the jumper go?

 

[wthrelfall]

The issue of distortion is eliminated when bypassing the VCA's by linking pins 1-8 with the VCA's taken out..  what does that suggest?

Opamps in the audio chain are working properly. Audio-VCAs might be blown or distorting because of too much mV at the VCAs Ec- port pin3.
Verify the 120Rs in the upper right corner of the substitution circuits are 120Rs for real (lift one side for measuring), not 10Ks read backwards.

Verified, these are definately 120R's.

 

[Looksharp]

http://homepage.mac.com/marten.thielges/gssl/calibration.html (also depends if you use 2181A, B or C grade.)

u should read this thread (GSSL HELP) thru.. even if you read the last 50 pages, u will find links to answer most of the current revision`s problems and questions regarding calibration & errors on BOM...
there are some bits u have to make notes before u start stuffing for it to work on first start.. also if you are adding any mods like turbo or ssc.. there are more bits that need to be noted

i hope this helps!

it helped a lot! thanks PTRON !

 

[guze]

Hi,
Wich resistor should i put before a behringer meter for the led? and where can i take the power for it?
Thanks

 

[wthrelfall]

So, it looks like I'm not going to get to the bottom of this, I think the best thing to do is strip out components and replace with new ones. 
Harpo, would you say there are components which I should NOT remove, ie. ones which we can say are definitely not causing the problems?  (we established op-amps are working properly for example).

thx.

The issue of distortion is eliminated when bypassing the VCA's by linking pins 1-8 with the VCA's taken out..  what does that suggest?

Opamps in the audio chain are working properly. Audio-VCAs might be blown or distorting because of too much mV at the VCAs Ec- port pin3.
Verify the 120Rs in the upper right corner of the substitution circuits are 120Rs for real (lift one side for measuring), not 10Ks read backwards.

Verified, these are definately 120R's.

 

[ptron]

If my eyes dont trick me i see your 47k pair are joined by a big smudge of solder? EDIT (i guess its fine since down the traces theyre connected)

I hope u can find the problemo soon man
About jumper missing  only for 2181's i think u not missing any

 

[wthrelfall]

Yeah, they are rather unattractively blobbed together because the contact on the bottom of the pcb came off..
thanks for the encouragement! 

If my eyes dont trick me i see your 47k pair are joined by a big smudge of solder? EDIT (i guess its fine since down the traces theyre connected)

I hope u can find the problemo soon man
About jumper missing  only for 2181's i think u not missing any

 

[ptron]

After a long break I finally got my Gssl compressing with all controls working. Unfortunately, I now have a very low (maybe -40db) hum that sounds like a high frequency hiss. The hum persists whether the VCAs, including the sidechain, are in or out. It persists in bypass in and out mode and in all various placements of the threshold and make up gain pots. My grounding scheme is as follows: ground from pcb input connected to right xlr ground, jumpered to left xlr ground and then jumped to a common ground, which is a metal screw in the base of the chassis. The output ground follows the same scheme terminating at the same common ground. I also have the ground from my power ICE input connecting to the common ground in the chassis.

Anyone have any ideas on the hum?

I also think that my ratio switch is some how reversed. I get the most intense compression with the switch to the left position and the least compression with switch to the right. When I connect my turbo pcb sound I reverse the 10:1 and 2:1 connectors?

Thanks for all your help.

Jeff

I had some similar hum problem... In the end my meter wasnt making proper contact on ground and i had to go direct to the star ground ... Made all hum disapear.  I had audio passing when unit was off but connected (still lot of hum)
Ratio thing.. I asume u are looking at the right ratios, only the knee changes on them. I found out 2:1 seems to compress more with threshold not so engaged.. 10:1 not so much but as you engage more u can notice the ratio rather than the knee

I hope this helps!

 

[kante1603]

Hi wthrelfall,

I haven´t read all of your posts related to this topic.
Member ptron wrote something about a "big smudge of solder" at the 47k´s.
So I searched the pics in your posts to have a look if I can find more issues.
I´m sorry and really (!!!) don´t want to bother you,but looking at your solder joints I must say that there seem to be a lot of them where the solder didn´t really flow,some of them look like blobs.Cannot proof it because the pic´s resolution is not really high.
Also way too much flux everywhere all over the pcb.
This all can cause a lot of troubles.
Maybe you have a general issue with your soldering techniques;can be that your soldering iron has the wrong temperature (looks like it is too low) or cheap solder or a both.
Again:Let the solder "flow",soldering times should be short.I have attached a small graphic to this post (left is good,right is bad!).
And keep your pcb clean.
Another little hint (if I may):Your audio wires (flat cable) to the xlr´s on the back are not twisted or shielded.This can pick up noise later on.A good way to wire this is-as said-twisting them and keep them short.In this build ths can be achieved by just turning the main pcb 90 degrees clockwise so the audio connections are much closer to the xlr`s.

I know,it´s a hard way to learn,but we all had to go this way (at least I did ),but some day you´ll end up in a working unit:This is a big satisfaction-believe me!
After that point you can not stop diy anymore.

Don´t give up,I´m sure you´ll manage this;worst case is doing all of it again (maybe with a new and clean pcb).

I hope to have helped,

best regards from germany,

Udo.

 

[wthrelfall]

Hey Udo

Fair point, was my first build and learning all the time..  However I suspect my soldering isn't as bad as you think    The vast majority of my joints look like the 'good' one in your diagram..  and so far i've been unable to detect any short circuits caused by bad soldering, and believe me I check about 3 times a day!!  I did wonder if flux could cause a short circuit but couldn't find any supporting evidence, but if you have information to the contrary..?
I will definitely try the twisting wiring technique, great information and hugely appreciate ANYONE trying to help me through this difficult time! 

w.

Hi wthrelfall,

I haven´t read all of your posts related to this topic.
Member ptron wrote something about a "big smudge of solder" at the 47k´s.
So I searched the pics in your posts to have a look if I can find more issues.
I´m sorry and really (!!!) don´t want to bother you,but looking at your solder joints I must say that there seem to be a lot of them where the solder didn´t really flow,some of them look like blobs.Cannot proof it because the pic´s resolution is not really high.
Also way too much flux everywhere all over the pcb.
This all can cause a lot of troubles.
Maybe you have a general issue with your soldering techniques;can be that your soldering iron has the wrong temperature (looks like it is too low) or cheap solder or a both.
Again:Let the solder "flow",soldering times should be short.I have attached a small graphic to this post (left is good,right is bad!).
And keep your pcb clean.
Another little hint (if I may):Your audio wires (flat cable) to the xlr´s on the back are not twisted or shielded.This can pick up noise later on.A good way to wire this is-as said-twisting them and keep them short.In this build ths can be achieved by just turning the main pcb 90 degrees clockwise so the audio connections are much closer to the xlr`s.

I know,it´s a hard way to learn,but we all had to go this way (at least I did ),but some day you´ll end up in a working unit:This is a big satisfaction-believe me!
After that point you can not stop diy anymore.

Don´t give up,I´m sure you´ll manage this;worst case is doing all of it again (maybe with a new and clean pcb).

I hope to have helped,

best regards from germany,

Udo.

 

[kante1603]

You´re welcome!

Concerning flux:I wanted to give you this as a general advice.Normally flux has a pretty high resistance,so doesn´t hurt in most cases.But some day you might start building a cool microphone or an other high impedance circuit.Then one single blob of flux will drive you mad,hahahaha......

Concerning twisting:Yes,doing this on audio wires helps a lot.And you mustn´t twist the flat cable between the main board and the control pcb in the front as this part only carries dc (just control voltages,no audio).

Good luck and have a nice weekend,

Udo .

 

[ptron]

Btw all ctrl board wiring also pukka? Just trying to rule out your problemo. What is happening today with your compressor? Still not passing audio when compressor circuit engaged?
I see what udo means with the soldering and flux.. Couple of scratches there trying to check if joint was shorted i can see also.

Btw other thing your inputs and outputs .. The neutral on gssl pcb(0v)is going to ground on your XLR's.. Common practice (i believe) if these xlr arent insulated from case, is to link chasis pin (no number pin) to pin number 1 or ground. Then u make only one contact to case from xlr.
If xlr is insulated your scheeme is good!

Did u check the "gssl calibration" link ?

Btw.. U started off with turbo installed didnt you? Is it still attatched?

Just trying to stir it up a bit hope it helps

 

[guze]

Hi,
Wich resistor should i put before a behringer meter for the led? and where can i take the power for it?
Thanks

 

[wthrelfall]

Hi Ptron

Control board has been checked several times so AFAIK it's all correct.  wiring between control board and main board is correct, no shorts.

With the bypass switch set clockwise (turned to the right) position, no audio passes and compressor is silent (no hum).  With bypass set to the anti-clockwise position (left), I get very distorted audio.  Meter does nothing, and no other knobs work.  Strangely, the attack knob, when set to the last 2 positions in a clockwise direction, kills the audio signal.
(which bypass knob position IS bypass anyway?!)

I'm (temporarily) using a plastic case, so xlr's are insulated, no?

Which calibration link are you referring to?

Turbo has been temporarily taken out so that I can troubleshoot easier.  it's not connected at all.

thoughts?
thx.

Btw all ctrl board wiring also pukka? Just trying to rule out your problemo. What is happening today with your compressor? Still not passing audio when compressor circuit engaged?
I see what udo means with the soldering and flux.. Couple of scratches there trying to check if joint was shorted i can see also.

Btw other thing your inputs and outputs .. The neutral on gssl pcb(0v)is going to ground on your XLR's.. Common practice (i believe) if these xlr arent insulated from case, is to link chasis pin (no number pin) to pin number 1 or ground. Then u make only one contact to case from xlr.
If xlr is insulated your scheeme is good!

Did u check the "gssl calibration" link ?

Btw.. U started off with turbo installed didnt you? Is it still attatched?

Just trying to stir it up a bit hope it helps

 

[ptron]

Mm dam weird man...
Yeah if is plastic its insulated from xlr's just keep it in mind when changing to metal for ground loops..

http://homepage.mac.com/marten.thielges/gssl/calibration.html this is the calibration link i meant.. I think  some resistors need to be swapped for precise functioning of the comp.

Sorry i cant help more man! Im a total noob myself but trying hard to figure it out.. Meter not working.. Is +leg of the meter having continuity with the ground? Made big difference to me.

 

[kante1603]

Hi,
Wich resistor should i put before a behringer meter for the led? and where can i take the power for it?
Thanks

Hello guze,

depends on the supplied voltage and the values of the led.
As far as I can remember the led in that meter is white?
I know that it was just a single one,so let´s use Ohm´s law.
Given it´s a classic white led it will need arround 2vdc at 10 to 20 mA.
You´re right:we need a pre-resistor because the supplied voltage must be brought down to 2vdc.
Say we take 10mA (=0.01A) the formula is:

(Supplied voltage -led voltage / 0.01Ampere) = pre-resistor in Ohms

Take the resistor that is the next to it and you´re done.
If you want it a bit brighter then simply insert 0.02A instead of 0.01A.

Concerning where to pick the supply voltage:I remember the 12v regs are working close to the edge...
I don´t know how your psu is set up but I wouldn´t take it from there.Do you have a voltage rail left?
Otherwise a possible way is to pick the rough dc after the rectifier and filter caps which is a non-regulated dc (should work).
This voltage is roughly 1,4 times higher than the ac voltage coming in from the transformer.
You can measure it there with your multimeter set to dc,the black probe at a 0v point.
Then use the formula and you´re done!

Now have fun with Mr.Ohm!

Cheers,

Udo .

 

[guze]

Thank you so much for this, the best answer i could get.
Always learning

 

[jjaskuna]

Hooked up my expat audio turbo board and now my gain reduction meter shows 1db GR on two of the three ratio settings with no input signal. There is also no output detected when this -1db GR is showing (with no input signal present). The reading is present when the ratio switch is turned right and in the middle, but disappears when the switch is turned left. Additionally, when I touch(with my finger) the solder blobs of the Pole and 2:1 on the turbo board at the same time, the mysterious reading disappears and the meter reads 0.

Any idea on whats going on with these two ratio settings and the meter?

A few other pieces of potentially useful info: I now have a gain imbalance with the left channel ~5db louder than the right. All ratio switch positions worked fine before I added the turbo board. I vaguely remember reading about the gain imbalance previously and will reread for solutions. But, any help with the meter is greatly appreciated.

Thanks for the help ptron, I was able to get rid of the hum and had the unit working fine before I attempted the turbo addition.

Cheers,

Jeff