GSSL HELP THREAD!!!

[zebite]

Also the machine seems to be constantly in bypass mode: although the meter reads gain reduction and I can see that all the controls change the meters reactions I can not hear any of this in the audio path, when I bypass the meter stops working but the audio doesn't change.
I've checked and double checked all solder points (which I also did when soldering all components) and I can't seem to find anything wrong (obviously there is), I seem to have the correct voltages, I've also tried changing VCA's and op amps...
If some one has encountered the same problems it would be great to hear from you.
Thanks in advance.

Hey all ! I've been out of action for the last couple of months and not been able to touch my clone...I've tried everything suggested to me about the bypass problem and still no luck, audio works fine, meter appears to work fine (with threshold,ratio, attack and release knobs), nothing on the make up ?!
If any one has any ideas.
For information I'm building the rev 9 version using THAT 2180 vca's with pin 4 bent off on main vca's

 

[Harpo]

...I've tried everything suggested to me about the bypass problem and still no luck, audio works fine, meter appears to work fine (with threshold,ratio, attack and release knobs), nothing on the make up ?!

Feedback resistor between TL072-pins6/7 fitted 100 ohms instead of needed 100K ?
Resistor between TL072-pin7/DBX202C-substitution circuits fitted 100K instead of 100 ohms ?
Missing jumpers between prementioned resistor and 1K/120R attenuators in front of DBX202C-substitution circuits ?

 

[Jamie1234]

So I've nearly finished my gssl and I've run into a little problem. I have everything hooked up and it looks like my transformer (which says it has 18v secondaries) seems to be putting out 21v??? I am still getting +/- 15v dc on the 2 jumpers in the middle of the board, is it possible it will work like this? I'm assuming it will damage the circuit if I try to run it for too long off 21v, just thought I would check if anyone knows before I buy another transformer. Thanks

 

[gyraf]

21V is alright for a 18V transformer - no-load or low-load voltage is always higher than voltage at full-rated-load

Jakob E.

 

[zebite]

Hail Harpo !
Thanks to you I found that I had actually used 1M resistors instead of the 1K in front of the substitution circuits ! So now the left channel is compressing correctly but the make up distorts after roughly 6db gain ( any ideas ?).
And unfortunately no change in the right channel, compression can be seen on the meter but nothing on the audio ?!

Any ideas will be more than appreciated

 

[Harpo]

So now the left channel is compressing correctly but the make up distorts after roughly 6db gain ( any ideas ?).

Most likely either flipped wires at the bypass switch, shorting out the +12V rail (Lorlin type bypass-switch pole 'A' goes to 620K resistor and throw positions either go to makeup pot wiper '2' or 0V reference voltage '1') or you feed the unit with a too high input signal level (this is analog gear with levels limited by rail voltages, not digital DBFS at whatever level this might translate to the analog world gear and adding +6dB on top might exceed limits).

And unfortunately no change in the right channel, compression can be seen on the meter but nothing on the audio ?!

Compare (at least) parts values and solder connections between the 100R at TL072-pin7 and the audio-VCAs control ports pin3. Right and left side control (milli)voltage is/should be identical between these spots with the DBX202C substitution circuits in between.

 

[zebite]

Hey Harpo, thanks for the reply. Bingo I found the problem; a faulty 1K resistor in the right channel vca substitute card. Every thing works fine now no distortion and compression as to be expected, not quite the same glue as on the original ssl console but I'm well chuffed I managed ( with your help ) to build this thing.
Thanks again
Zebite

 

[Jamie1234]

I am officially a complete idiot. I put the chips in my gssl last night, fired it up and all I get is a big cloud of smoke. Found the problem, I had inserted one of the ne5532 chips backwards. Obviously that chip is completely fried. Everything else looks ok though, just wondered if my little cock up is likely to have damaged anything else, or is that anyone's guess? 

 

[gyraf]

..smoked 5532 (output circuit) rarely damages anything else. Although there is a small chance it could have killed the VCA in that channel, if you're very unlucky.

Just pop in a new 5532, and try it. If one channel misbehaves, switch the two VCA's, and you'll know if you were that unlucky.

Jakob E.

 

[Jamie1234]

Thanks

 

[ilfungo]

Sorry for a stupid question...
It's possible to use Lundahl 1539 as output transformer?
I have two left...
Thanks

 

[drj88]

Greetings fellow elctro-nerds. I just built a GSSL and I have a strange issue with it. Often (but not always) when I switch it on, the +15v will drop in power, gradually down to around 4v where it settles. (-15v rail seems fine though) What I first noticed was that the led starts at full brightness and as the power drops, it gradually dims until it gives off no light at all. What's weird is that the problem seems to come and go. I've managed to pass audio through successfully and everything seems to work, unless the power drops to 4v in which case it does nothing. What is likely to be wrong here, damaged regulator or capacitor maybe? Also, a couple of times I thought I noticed a slight burning smell, so I switched the unit off each time, to be safe.

I should perhaps also note that I previously made what I think is the 78L12 smoke (but may be something else in that area of the pcb), after carelessly poking around with multimeter probes. So that may or may not be the issue here. Would appreciate some input, because I don't want to make things worse by poking around the pcb again. :-[

 

[gyraf]

A power line dropping out is nearly always because of regulator overheating. Try with a heatsink, mount regulator isolated.

But remember to check WHERE this excess current drain comes from, and if it's problematic. could it be e.g. a relay or a lamp?

Jakob E.

 

[drj88]

I measured the voltage for the 7915 by measuring from the metal plate on the back of it (is there a name for that plate?). Anyway, I got about 39 volts. I looked at the specs for the part online and it says max voltage is 35, so is this the problem? If so, is it likely to be the 7915 at fault, or is it something in the circuit that comes before the 7915? Additionally, I measured the plates of the 7815 and 7812 and they were apparently both 0 volts. What are they supposed to read?

 

[Harpo]

I measured the voltage for the 7915 by measuring from the metal plate on the back of it (is there a name for that plate?). Anyway, I got about 39 volts. I looked at the specs for the part online and it says max voltage is 35, so is this the problem? If so, is it likely to be the 7915 at fault, or is it something in the circuit that comes before the 7915?

What are your mains transformer secondary voltages? (..and updating your profile with your location data might give us a clue if you accidently might have the transformer primary winding(s) hooked up wrong, causing this overvoltage). Expect the 7915 to be blown from exceeding parts max.max limits. The 7815 will blow up next from this same overvoltage, assuming your multimeters battery isn't low and give you nonsense readouts.

 

[tcrane]

Hi, first build going nicely.
Just wondering if in the UK this toroid would be fine:

http://uk.farnell.com/multicomp/vtx-146-030-115/transformer-30va-2x-15v/dp/1675052

The reason I'm confused is it says it's 1A but I'm sure the recommended amps was 10A, or am I mis-understanding.

Cheers

 

[Engels]

Hi there,
I'm almost done with my gssl clone 
I would like to know how to wire a single led when turning on the bypass function;
I'm using a rotary switch for the bypass as in the diagram.

I'm pretty sure it's pretty silly thing to do, I just haven't understood well how poles and traces are linked in a rotary switch 
I bet I can just use two spare pins, one connected to the 12v and the other to the ground, in between there's the led with proper Resistor, or am I wrong?
I just don't want to risk and prefer to ask to you!

Byebye

 

[drj88]

What are your mains transformer secondary voltages? (..and updating your profile with your location data might give us a clue if you accidently might have the transformer primary winding(s) hooked up wrong, causing this overvoltage). Expect the 7915 to be blown from exceeding parts max.max limits. The 7815 will blow up next from this same overvoltage, assuming your multimeters battery isn't low and give you nonsense readouts.

I'm in the UK (profile updated.) I tried to test the secondaries, voltage was around 17 volts as far as I can tell. I only tested one of the secondaries though, because the other is inaccessible at the moment (can't really reach it while the pcb is mounted.) Something interesting happened while I was doing this however. I knocked one of the wires on the transformer secondaries while testing it and the led light came back on at full brightness and stayed there (after having done its normal routine of dimming after a few seconds of power). I retested the 7915 and it read about 21 volts. Is that what it's supposed to be, or is that still too high? Anyway, I guess my transformer is connected incorrectly, (or just shoddily) to the pcb. So I think I've now found the source of the problem, but I'm not sure precisely what is wrong.
My transformer has 4 secondary wires, red black yellow and orange in that order. The label lists them in a different order though, black red orange yellow. There is a little dot next to the black and the orange, which I assume denotes the 0v wires. There are 5 holes on my pcb and I have the yellow connected to the first, nothing on the second, orange and red in the middle, nothing on 4th and the black is on the 5th one. Does that all sound ok?
The red/orange does seem a bit loose, so I will resolder that one and see if it makes a difference.

 

[drj88]

OK, another update. I resoldered those wires and switched the GSSL back on. The led lit and stayed on, the 7915 measured around -15v. After a minute or so I started to smell burning again, so I switched it off. I then touched all the regulators and chips, none of which seemed very warm. So I then turned the GSSL back on, this time the led wouldn't light at all. The led was receiving under 2v. After a few minutes I switched it back on again and the led lit just fine, but I started to smell burning again. After sniffing around a bit (literally) I discovered that the smell of burning seems to be coming from the toroidal transformer, and not the pcb. The toroid is also getting rather hot, after being powered for only a minute or so. Is it meant to get hot that quickly? Any thoughts?

EDIT: ok, so now I'm wondering if my primaries are wired incorrectly, or if I have a faulty toroid. So I will explain how I wired the primaries. It's a 2x115v (Noratel TA015/15) 4 wires on the primaries, one pair is gray & blue, other is purple & brown. I wired the gray and purple together. Brown and blue go to the power switch. Label has a dot next to the blue and the purple. Toroid gets very hot, very fast. Smells of burning. Did I wire is incorrectly?

 

[MeToo2]

OK, another update. I resoldered those wires and switched the GSSL back on. The led lit and stayed on, the 7915 measured around -15v. After a minute or so I started to smell burning again, so I switched it off. I then touched all the regulators and chips, none of which seemed very warm. So I then turned the GSSL back on, this time the led wouldn't light at all. The led was receiving under 2v. After a few minutes I switched it back on again and the led lit just fine, but I started to smell burning again. After sniffing around a bit (literally) I discovered that the smell of burning seems to be coming from the toroidal transformer, and not the pcb. The toroid is also getting rather hot, after being powered for only a minute or so. Is it meant to get hot that quickly? Any thoughts?

EDIT: ok, so now I'm wondering if my primaries are wired incorrectly, or if I have a faulty toroid. So I will explain how I wired the primaries. It's a 2x115v (Noratel TA015/15) 4 wires on the primaries, one pair is gray & blue, other is purple & brown. I wired the gray and purple together. Brown and blue go to the power switch. Label has a dot next to the blue and the purple. Toroid gets very hot, very fast. Smells of burning. Did I wire is incorrectly?

NO it most certainly is not meant to get hot. Transformer Grey to transformer violet, then Blue to mains AC neutral, Brown to mains AC live is correct for the UK for this transformer http://www.farnell.com/datasheets/90564.pdf. Looks like excessive current draw (short circuit somewhere). Does the mounting bolt touch the top of your case? That can cause a single short magnetic winding via the case. Is your earthing correct? Is your bridge rectifier built properly (diode orientation)?