GSSL HELP THREAD!!!

[phancak]

Hi. For settings THD  has be input signal 1kHz sine and voltage 0dBu (0.775Vrms) or +4dBu (1.228Vrms)
Thanks

 

[Logic Leopard]

Check all of your voltages with the ICs removed. You also probably have something missing/soldered incorrectly on the ratio board.

Thanks!

Paul

Thank you for the reply! I'll check.

 

[angelo2979]

Hi,

I have a working gssl with thurbo board here... just one problem with the ratios.. maybe someone can help.

It looks like the compressor is behaving correctly at 2:1 and 10:1, but with 4:1 I have a lot more compression (both I can hear that and see it on the meter). If I had to guess I'd say that 4:1 and 10:1 are inverted but that doesn't make sense, nor I see how I can have soldered the rotary switch in the wrong position (even then, 4:1 is at the middle, not a lot of possibilities here).

I've searched through this thread and found some similar faults, but still not a clear solution. I've also seen another thread about ratio measurements, but it relates to a problem mostly solved with 2180s (which I'm using) and slightly different symptoms.. plus I've followed the correct schematic for this VCA so I'm not sure that changing resistors is the solution.

I think my next move will be measuring ratio and gain reduction as suggested there and TL074 voltages both on the main board and on the turbo pcb... but, maybe you have some more suggestions? where would you look at?

Please let me know, thank you!

P.S. forgot to mention... if I'm not wrong 4:1 position on the control PCB is linked to two resistors, a 510k and 1M8. These look and measure correct

 

[Potato Cakes]

Does this work correctly without the Turbo board? If the answer is yes then this something that should be asked on the GSSL add on thread.

Thanks!

Paul

 

[angelo2979]

just checked... no, same behavior with and without Turbo connected

 

[Potato Cakes]

Go the GSSL page on Gyraf's website. Check all the components for the ratio switch, which aren't many. If 2:1 and 10:1 are working then it should be narrowed down pretty good which part to check. Bad solder joint, misplaced part, or something is oriented wrong. One of those guys.

Thanks!

Paul

 

[angelo2979]

Many thanks to you!
Can you help me spot these components? if there's anything else to look at other then those 1M8 and 510K resistors... I've checked these and they do look good, I may just try to reheat the joints.. also resistors around the TL074 look correct.

.. just to be sure I get it correctly.. The fact that I'm having more compression on 4:1 should mean I have more then desired resistance to the amp? Also, even just by looking at the switch and component position, am I right assuming there's no possible way that 10:1 and 4:1 are inverted, right?

Thank you again

 

[Gustav]

Many thanks to you!
Can you help me spot these components? if there's anything else to look at other then those 1M8 and 510K resistors... I've checked these and they do look good, I may just try to reheat the joints.. also resistors around the TL074 look correct.

.. just to be sure I get it correctly.. The fact that I'm having more compression on 4:1 should mean I have more then desired resistance to the amp? Also, even just by looking at the switch and component position, am I right assuming there's no possible way that 10:1 and 4:1 are inverted, right?

Thank you again

Your problem (unless theres some quirk in the symptoms I am not getting) is isolated to step two of the switch.

So check if you're even making contact from the  2nd position to the center of the switch, then move outwards.

Gustav

 

[angelo2979]

Yep, continuity check shows there is contact between 2nd position and A pole of the ratio switch.
I've re-heated some joints, but with no luck. Then I've measured ratios as suggested by SSL tech here:
https://groupdiy.com/index.php?topic=944.0

that is, for each ratio position: 1.  set the treshold so that the meter shows 8db of GR    2. check how the output increases after a 10db increase of the source  (400Hz test tone.)

So, for a 10db increase, I've got:
2:1  - output increases by 6 db (should be 5db)
4:1 - like before, output still increases by 6db  (should be 2.5db)
10:1 - output increases by 1 db (on spot)

So it looks like the 4:1 switch position isn't affecting ratio, but if I do not interfere with the treshold  the thing does compress more...why?? 

...Also one thing to notice:  in 4:1 and no audio passing the meter never really falls back at zero, it rather stays put around 2

 

[angelo2979]

Well, just tested with the treshold set at maximum so that there should be no compression.
Again, 2:1 and 10:1 all fine - but 4:1 gives me obvious compression and the meter jumps between 4 and 8 !!

 

[Gustav]

Well, just tested with the treshold set at maximum so that there should be no compression.
Again, 2:1 and 10:1 all fine - but 4:1 gives me obvious compression and the meter jumps between 4 and 8 !!

Look for shorts on the traces and components for the two first settings from the supply.

Gustav

 

[angelo2979]

Thanks Gustav, I'm doing as you suggested, checking bad connections to the 4:1 joint... and I've come accross "C" point in the control PCB...

my "technique" essentially is playing around while the unit is powered on and set on 4:1.. and trying not to get elettrical shock  ;D
with this kind of rough approach, I've seen that whenever I touch "C" point with a cold solder iron the meter gets back to zero and compression seems to behave correctly too. 
Can somebody explain me why?

 

[angelo2979]

sorry ...thinking about it, I was probably just taking "C" to ground, so kind of bypassing compression. I was so concerned about any change that could get the meter back to zero in normal (non-compressing) operation at 4:1 that I did not consider bypass.

I'm tired. . components look good.. I've checked resistors around the ratio switch and all correspond to the schematics. Whatever it is I cannot see it.

 

[angelo2979]

I should report that finally I've fixed this problem.. thank you all!
It turned out it was a bad contact between the 4:1 switch position and the first resistor it connects to. So easy.
It was so difficult to spot it because the joints looked good, and I had actually re-soldered them while searching for bad contacts.
Maybe the trace was damaged and I couldn't see it, or maybe those pads, I don't know. I've just put a jumper there and it looks like it behaves correctly now... My only concerns now are two...

1. ratio measurements (they've changed after the fix, and the 10:1 worries me the most):

2:1 - 10db increment results in a 4,4db increase (should be 5)
4:1 - 10db increment results in a 2,4db increase (should be 2,5)
10:1 - 10db increment results in a 0,2db increase (should be 1db !)

2. Metering. The meter shows like double the actual gain reduction. I have a 1mA meter and the suggested 2k resistor on PCB (for 20db scale). And the meter's own adjust screw doesn't seem to help - looks like it can't cover that range.  Maybe it's just a broken meter.

Anyways I'm happy this main ratio problem got finally sorted out.. I should do further testing though!

 

[Potato Cakes]

Excellent! Nice work finding it! Now prepare yourself for a lifetime of hide and seek with the simplest of solutions during troubleshooting.

Thanks!

Paul

 

[Gustav]

2. Metering. The meter shows like double the actual gain reduction. I have a 1mA meter and the suggested 2k resistor on PCB (for 20db scale). And the meter's own adjust screw doesn't seem to help - looks like it can't cover that range.  Maybe it's just a broken meter.

Meters own adjust screw?

Sounds like you have a turbo mod installed. This will influence metering - replace the 2K resistor with a 5K trimmer and adjust.

Gustav

 

[innercityman]

Does this work correctly without the Turbo board? If the answer is yes then this something that should be asked on the GSSL add on thread.

The GSSL add on thread seems to have a sadly lack of interest unfortunately. I posted a lot about my problem and I'm pretty sure a that a lot of experienced diyers would have been able to help me figure out the issue I got with the turbo mod, but only one gave me some precious help (and I'm thankful for that) and then stoped posting. You can try, maybe you'll be luckiest than me.

 

[spreadspell]

Alright, I had time to flip the wiring and it has the same behavior.

LEDs turn on in the push buttons when switched

Audio gets passed through, both channels work great and have ZERO noise

Turning on the compression (deactivating the bypass) still does nothing, also it might be good to mention the makeup gain does nothing. Probing the voltage of the makeup pot, it goes from 0V-12V just fine, so I'm not sure what's going on.  Anyways, something that might be going on, I'm assuming there should be a voltage coming to "ON" and "OFF" and coming from "COM" so it can be managed by the switch. Well, there isn't a voltage coming from "COM" or going to "ON" or "OFF" . Looking at the schematic, COM goes to the ATTACK rotary, for some reason. Does this mean the switch isn't working?

- - -

Hi Newbie here..

yesterday i finished my GSSL. Thanks to Group DIY. Too much infos for a poor mind like mine. So i've made it, and sounds as should be. Nice PCB and components parts from Gustav and Don's Audio (case, meter, knbs ect), Also all other infos from this forum appreciated too..

Everything sounds and looks almost fine, except that i' looking a B.O.M. for my Super Sidechain PCB (Gustav's) and why my Bypass British style Button remains ON when button is not pushed. (bypass on) I follow this conection ...


Buttons Wiring


Thank you!

 

[Potato Cakes]

You are sending power to both LEDs when the unit is on in that wiring scheme. You need either a separate power source for the compressor in LED or use the relay diagram that was posted somewhere earlier in this thread.

Thanks!

Paul

 

[spreadspell]

You are sending power to both LEDs when the unit is on in that wiring scheme. You need either a separate power source for the compressor in LED or use the relay diagram that was posted somewhere earlier in this thread.

Thanks!

Paul

Hi Paul thanks for the reply!

yes now I'm looking for this relay diagram, but the thread is toooo big. I think that  keith starts talking (2008 thread) about that , but I can't find the diagram. If you remember any detail on that or you might have it , it would be great..if you can share it . Thanks again for your help.
I'm grateful!