GSSL HELP THREAD!!!

[Chrome Heart]

Hey all. Does anyone of a bench test for the THAT 2180LB?

 

[MeToo2]

Hey all. Does anyone of a bench test for the THAT 2180LB?

That 2180b is a current in / out device. Probably the easiest way to test one is to use a breadboard to build the sample circuit in figure 2 of the datasheet. Any old opamp will probably do for functional testing. Similarly the cap values shouldn't be critical. You can feed the control voltage Ec- from a pot + a voltage divider across the supplies. Figure 7 shows how the expected gain boost/ cut is controlled by varying Ec- between -180mV and +540mV. Since the 20K feedback resistor matches the 20K input resistor, nominal voltage gain will be 0dB.

www.thatcorp.com/datashts/THAT_2180-Series_Datasheet.pdf

 

[Chrome Heart]

Found it. The smallest bit of copper thread at the underside of the control pcb header connector between points C & B were keeping it in bypass. Man, a little tiny thing like that can ruin your week.
Thanks for all the replies.

 

[wthrelfall]

So, I have the compressor routed via desk inserts, and when in bypass mode the signal is distorted, really hot.  If I send via an Aux I can tame the signal but there's still a bit of distortion.  Also, when I change the Attack to the 2 fastest settings (in bypass), the signal disappears.
When comp is 'IN' there's no signal passing at all 

any suggestions?

Harpo, you are right - there was a short in chef's pcb, from the + to the ground just after the rectifier - a really tiny piece of copper (I took a photo in case others have this problem, it's about halfway between the rectifier and the capacitor).  So thankyou Harpo & Jakob for helping...
But!  I have correct voltages everywhere and I can pass signal when in bypass, but no sound when compressor is 'on'.. here we go again  :-[

You have a short somewhere in between the positive raw DC and 0V. There are only 3 parts in this area. The (maybe broken) 1000uF cap next to the rectifier, the (maybe broken) 7815 voltage regulator and the (maybe shorted) pcb trace linking these parts. Until you remove this short circuit, you will blow your rectifier again. Use a magnifying glas to spot a short between pcb traces, double check the regulator is a 7815 for real, not a 7915 or whatever else. Ohm it out for a higher ohm reading before soldering the next rectifier on pcb. A low/zero ohm reading will indicate, there is still a short.

 

[Harpo]

So, I have the compressor routed via desk inserts,

assuming unbalanced

and when in bypass mode the signal is distorted, really hot.

you left the cold/XLR-pin3 on GSSL output unconnected ? (you'd never be so evil to link cold/XLR-pin3+0V/XLR-pin1 on output and try to fry your NE5532)

 

[wthrelfall]

yes, unbalanced.
yes, cold/pin 3 disconnected. 

So, I have the compressor routed via desk inserts,

assuming unbalanced

and when in bypass mode the signal is distorted, really hot.

you left the cold/XLR-pin3 on GSSL output unconnected ? (you'd never be so evil to link cold/XLR-pin3+0V/XLR-pin1 on output and try to fry your NE5532)

 

[wthrelfall]

And still no signal with compressor in....

yes, unbalanced.
yes, cold/pin 3 disconnected. 

So, I have the compressor routed via desk inserts,

assuming unbalanced

and when in bypass mode the signal is distorted, really hot.

you left the cold/XLR-pin3 on GSSL output unconnected ? (you'd never be so evil to link cold/XLR-pin3+0V/XLR-pin1 on output and try to fry your NE5532)

 

[Harpo]

wthrelfall, did you already try to fix it step by step ?
http://www.groupdiy.com/index.php?topic=47.msg483540#msg483540

 

[wthrelfall]

Harpo, no, not done this procedure.  I will though.. 
In the meantime I measured voltages with chip's installed.  everything is normal, except ALL 2180 pin 5's are showing just under 3V..  Pin 7's are all correct voltage.

wthrelfall, did you already try to fix it step by step ?
http://www.groupdiy.com/index.php?topic=47.msg483540#msg483540

 

[Harpo]

.. except ALL 2180 pin 5's are showing just under 3V..

pin 5 set VCAs bias current with the 3K9 to the -12V rail or 5K1 to the -15V rail in between.

 

[wthrelfall]

Harpo. 
I found some bad readings using your checklist. 

TL074 pin1 will measure about 0.42VAC,  0.5VAC  about 0.1VAC at the junction 10K/20K/kathode 1N4148  0.8VAC, same maybe 400Hz frequency as at input, swinging positive. Case not, check for shorts, diode orientation ...
TL074 pin14 at varying ratio settings, double frequency from rectification, will measure at ratio 2:1 about 4.8VAC, 0.54VAC  swinging between -3.5...-5.5V, at ratio 4:1 0.83VAC, 1.07VAC swinging between 0.3V...-1.4V and at ratio 10:1 swinging between 0.3V...-0.2V  3.03VAC . This is a DC voltage with rectified audio riding on top. Case not, check lorlin endstop position by (in this order) removing the end stop washer, located below screw and sawtoothwasher, turn the switch full ccw and put the ring back in, set for position 3.
Set ratio back to 2:1. Set Bypass switch for compressor engaged.  Lorlin's endstops all correct

Checked again for shorts on both boards, none found.  Diode's all correctly oriented.

All readings up to this point appeared normal.


Still looking for help...

wthrelfall, did you already try to fix it step by step ?
http://www.groupdiy.com/index.php?topic=47.msg483540#msg483540

 

[wthrelfall]

Any more ideas?  I'm going to start disassembling the boards and rebuild unless anyone has a suggestion..  :-[

Harpo. 
I found some bad readings using your checklist. 

TL074 pin1 will measure about 0.42VAC,  0.5VAC  about 0.1VAC at the junction 10K/20K/kathode 1N4148  0.8VAC, same maybe 400Hz frequency as at input, swinging positive. Case not, check for shorts, diode orientation ...
TL074 pin14 at varying ratio settings, double frequency from rectification, will measure at ratio 2:1 about 4.8VAC, 0.54VAC  swinging between -3.5...-5.5V, at ratio 4:1 0.83VAC, 1.07VAC swinging between 0.3V...-1.4V and at ratio 10:1 swinging between 0.3V...-0.2V  3.03VAC . This is a DC voltage with rectified audio riding on top. Case not, check lorlin endstop position by (in this order) removing the end stop washer, located below screw and sawtoothwasher, turn the switch full ccw and put the ring back in, set for position 3.
Set ratio back to 2:1. Set Bypass switch for compressor engaged.  Lorlin's endstops all correct

Checked again for shorts on both boards, none found.  Diode's all correctly oriented.

All readings up to this point appeared normal.


Still looking for help...

wthrelfall, did you already try to fix it step by step ?
http://www.groupdiy.com/index.php?topic=47.msg483540#msg483540

 

[MeToo2]

Any more ideas?  I'm going to start disassembling the boards and rebuild unless anyone has a suggestion..  :-[

You quoted AC measurements. What about DC? Looks like your hitting it real hard but not getting any compression. High AC voltages out of the rectification and ratio section should be causing high compression. Check further along pin 8 of the TL074 and pin 7 of the TL072.

 

[wthrelfall]

Any more ideas?  I'm going to start disassembling the boards and rebuild unless anyone has a suggestion..  :-[

You quoted AC measurements. What about DC? Looks like your hitting it real hard but not getting any compression. High AC voltages out of the rectification and ratio section should be causing high compression. Check further along pin 8 of the TL074 and pin 7 of the TL072.

I quoted AC because that's what Harpo's troubleshooting guide required.  I posted the DC earlier - up there ^.

 

[wthrelfall]

Any more ideas?  I'm going to start disassembling the boards and rebuild unless anyone has a suggestion..  :-[

You quoted AC measurements. What about DC? Looks like your hitting it real hard but not getting any compression. High AC voltages out of the rectification and ratio section should be causing high compression. Check further along pin 8 of the TL074 and pin 7 of the TL072.

MeToo2, I checked the traces and soldering along those pins and all looks ok. 
TBH I'm a total novice when it comes to electronics as I'm sure you have noticed?!  So I'm presuming when you say 'check', you mean check for shorts, cold joints or broken traces?
I'm well aware that the majority of problems are probably caused by incompetence, but in my own defence I have successfully built other compressors with no issues (and detected a tiny short on chef's pcb which was barely visible).  So is it possible that I have wired everything perfectly but there's a faulty chip installed, or other faulty component, or would this be obvious from the voltage checks being wrong?  In other words, could something be damaged despite having correct voltages, that would be impossible to diagnose by visual inspection and current metering?

Harpo, if you're reading this, did you read my post with AC readings (following your diagnostic test method)?  Does this give you any indication of where the problem might lie? 

Your patience and help are very well received!

 

[jjaskuna]

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

 

[Harpo]

TL074 pin1 will measure about 0.42VAC,  0.5VAC 

Sorry for late reply. Assuming, your measurements are with VCAs pulled out and their pcb sockets pins1/8 linked. The 0.08V off will be 33K/47Ks parts tolerances.

about 0.1VAC at the junction 10K/20K/kathode 1N4148  0.8VAC

factor 8 off looks like the reason for your faulty behaviour (the rest is probably only a follow up).
From your previous pics, parts values and orientation seem to fit, so the most likely fault might be a bad TL074 or a chips pin bent inwards, missing its connection to its socket.

Is your 'and when in bypass mode the signal is distorted, really hot' still an issue with audio-VCAs bypassed ?

 

[Looksharp]

hi again,
I've noticed that in the pcb there's written : 2150 circuit (or dbx etc..) so I think the pcb was intended for the 2150.. since I'm goin' to put a that 2181 the question is: do I have to change some components in the circuit in order to update it ?...
thanks!

 

[ptron]

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!

 

[wthrelfall]

TL074 pin1 will measure about 0.42VAC,  0.5VAC 

Sorry for late reply. Assuming, your measurements are with VCAs pulled out and their pcb sockets pins1/8 linked. The 0.08V off will be 33K/47Ks parts tolerances.

about 0.1VAC at the junction 10K/20K/kathode 1N4148  0.8VAC

factor 8 off looks like the reason for your faulty behaviour (the rest is probably only a follow up).
From your previous pics, parts values and orientation seem to fit, so the most likely fault might be a bad TL074 or a chips pin bent inwards, missing its connection to its socket.

Is your 'and when in bypass mode the signal is distorted, really hot' still an issue with audio-VCAs bypassed ?

Harpo. 
I swapped out the TL074, still the same results.  Checked the others for non connecting/bent pins, seems ok.

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?
thanks again.

PS. can you just check the photo for anything unusual, such as incorrect resistor placement or missing jumpers?  I'm still not 100% sure about the modifications for using 2180's...