GSSL HELP THREAD!!!
- Thread starter hairyandy
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Help Support GroupDIY Audio Forum:
Ok, so I started testing chips and they're all ok. Then I started testing voltages and found that the Vin on my 7915 was varying between -22V and -24V, and the thing is scorching hot, while the 7815 is good at +14.87V and barely warm. I'm pretty sure that's not good, so I'm replacing the 7915, but will that likely solve my problem, or is the problem somewhere before the 7915 and putting another one in will just get it fried, too?
Any ideas are greatly appreciated.
Any ideas are greatly appreciated.
Ok. 7915 replaced, same result. Comparing values with my other SSL that works, I see it's supposed to be around -22V on the Vin, but the Vout should be my -15V, and it's not. It's measuring -33mV. Milivolts! And this is a brand new regulator. Where is my problem? Bad cap before it? Diode? Beuller? Beuller?......
dufo
Well-known member
[quote author="RemcoV"]Andre:
I found the SSL to be very sensitive as standard, and kicking in quickly aswell.
I solved this with adding an extra resistor with the bottom threshold line (the one that goes to the potmeter from the board) i used i think 56k and that limits the threshold range a bit, but it makes it way more usefull (to my opinion atleast)
hope it helps!
Remco[/quote]
AHHH!!! VERY interesting Remcov. Is this to counteract the meter banging over at full scale as soon as you start the threshold CCW?? I may have to try this today. Can you be any more specific exactly where you put the resistor and if indeed it was 56 K? Thanks alot . :grin:
I found the SSL to be very sensitive as standard, and kicking in quickly aswell.
I solved this with adding an extra resistor with the bottom threshold line (the one that goes to the potmeter from the board) i used i think 56k and that limits the threshold range a bit, but it makes it way more usefull (to my opinion atleast)
hope it helps!
Remco[/quote]
AHHH!!! VERY interesting Remcov. Is this to counteract the meter banging over at full scale as soon as you start the threshold CCW?? I may have to try this today. Can you be any more specific exactly where you put the resistor and if indeed it was 56 K? Thanks alot . :grin:
> I'm replacing the 7915, but...
You do remember that a 79xx has a different pinout from a 78xx? And that the tab is the center leg, and on 79xx usually can't touch Ground?
> It's measuring -33mV. Millivolts!
There is a short on the output.
Study the circuit board (I'm not going to go looking for the plan) and figure out how you can disconnect the output of the 7915 from everything it feeds. Put a 1K resistor from Out to Gnd and check the voltage: should be 15V and not-hot.
If it works with the 1K dummy load, but not when connected to all the -15V loads on the PCB, you have to find your solder-bridge, reversed chip or electrolytic-cap, or other mistake.
> there's a pop when I connect or disconnect a cable from the left input, but not from the right or either output.
If it was just bad -15V, it would be the same on both channels. It isn't, so that's a clue. Unfortunately it may be "normal" to pop when -15V is -0.033V (with full +15V) so we can't be sure if this points to the left or right channel.
> the (+) and (-) leads from the trafo to the IEC were backwards.
Does not matter one bit.
You do remember that a 79xx has a different pinout from a 78xx? And that the tab is the center leg, and on 79xx usually can't touch Ground?
> It's measuring -33mV. Millivolts!
There is a short on the output.
Study the circuit board (I'm not going to go looking for the plan) and figure out how you can disconnect the output of the 7915 from everything it feeds. Put a 1K resistor from Out to Gnd and check the voltage: should be 15V and not-hot.
If it works with the 1K dummy load, but not when connected to all the -15V loads on the PCB, you have to find your solder-bridge, reversed chip or electrolytic-cap, or other mistake.
> there's a pop when I connect or disconnect a cable from the left input, but not from the right or either output.
If it was just bad -15V, it would be the same on both channels. It isn't, so that's a clue. Unfortunately it may be "normal" to pop when -15V is -0.033V (with full +15V) so we can't be sure if this points to the left or right channel.
> the (+) and (-) leads from the trafo to the IEC were backwards.
Does not matter one bit.
PRR,
Thanks for the help. I didn't remember the pinout difference at first, but then saw it laid out on the packaging and remembered. That's when I measured the -33mV.
In the meantime, I've since removed the rectifier and swapped it into the working comp. It was fine, but the other rectifier I took out got broke in the process, so I have to go get another one tomorrow before I can try the 1K resistor test.
Thanks for the help. I didn't remember the pinout difference at first, but then saw it laid out on the packaging and remembered. That's when I measured the -33mV.
In the meantime, I've since removed the rectifier and swapped it into the working comp. It was fine, but the other rectifier I took out got broke in the process, so I have to go get another one tomorrow before I can try the 1K resistor test.
Put in the new rectifier, disconnected the 7915 output from everything, put a 1K resistor on it and I read -26mV. So, does that mean the new 7915 is bad, or maybe one of the 1000uF caps before it? There isn't much else I can think of. All the 12V stuff works and reads just fine, but I don't think that would affect the 15V anyway....maybe I'm wrong.
[quote author="bubba_b"]I've since removed the rectifier[/quote]
Since your +15V and your +/-12V supplies are working, and they're all fed from the same rectifier bridge, I doubt that has anything to do with the problem... I also doubt your regulators are bad. Check your solder joints, and after you make sure they're fine, check them again. Go through this process a few times.
Make sure you got the pinout right by downloading the datasheet to the regulator you're using from the manufacturer's website. You're not shorting the tab to ground or anthing, are you? With the regulator out, check for continuity/low resistance between ground and where the output pin of the regulator goes.
Peace,
Al.
Since your +15V and your +/-12V supplies are working, and they're all fed from the same rectifier bridge, I doubt that has anything to do with the problem... I also doubt your regulators are bad. Check your solder joints, and after you make sure they're fine, check them again. Go through this process a few times.
Make sure you got the pinout right by downloading the datasheet to the regulator you're using from the manufacturer's website. You're not shorting the tab to ground or anthing, are you? With the regulator out, check for continuity/low resistance between ground and where the output pin of the regulator goes.
Peace,
Al.
So I've pulled out the regulator twice, resoldered it, went over all the solder joints with a fine tooth comb and can not find a solder bridge or stray wire strand or anything of the sort. Looking at the schematic, it looks like the only things between the trafo and this regulator is: (1) 1000uF cap, the bridge rectifier and (1) 100nF cap. I haven't replaced the caps yet, but if either of those don't fix it, then it has to be something after the regulator, but I don't understand how that could be. But then again, I am a novice at this.
@ Dufo
If you look at the control board you have the 2 potmeters on either side of the board connected with wires.
If you take the threshold pot, and put the resistor in place of the bottom wire going from the pot to the controlboard.
That should numb you threshold sensitivity.
Hope it helps.
Remco
If you look at the control board you have the 2 potmeters on either side of the board connected with wires.
If you take the threshold pot, and put the resistor in place of the bottom wire going from the pot to the controlboard.
That should numb you threshold sensitivity.
Hope it helps.
Remco
Now it's really weird, but it may be a sign of what's exactly wrong. I've replaced both caps (1000uF and 100nF) in line with the 7915 and now when I measure the Vout pin on the 7915, it fluctuates between +.5mV and -150.00mV consistently. Any thoughts?
After many hours fiddling with this thing, I finally tracked down where the problem was coming from and found a solder bridge on the input side. Grounded itself out. So, I fix it, recheck my voltages and they're normal (about -15.2V on the 7915 Vout). So I'm stoked.....until I plug it in to see if it actually works. No. Won't pass signal and the control board does nothing.
Back to square one.
Back to square one.
bubba, did you already check the 12V/-12V rail aswell?
and best is to check first if all your opamps get their power as they should.
So for the 5532 there should be 30Volts between pins 4 and 8.
for the 5543 there should be 30 volts between pins 4 and 7.
the TL074 should have 24Volts between pins 4 and 11, and the TL072 should have 24Volts between pins 4 and 8.
If they are healthy you can check the audio going thru. Do you have access to a scoop? that would make the search allot easier.
hope it helps
Remco
and best is to check first if all your opamps get their power as they should.
So for the 5532 there should be 30Volts between pins 4 and 8.
for the 5543 there should be 30 volts between pins 4 and 7.
the TL074 should have 24Volts between pins 4 and 11, and the TL072 should have 24Volts between pins 4 and 8.
If they are healthy you can check the audio going thru. Do you have access to a scoop? that would make the search allot easier.
hope it helps
Remco
Checked voltages across all my chips and they're all ok, gettin' the right juice. Does that mean they're good, or could there still be something wrong with one of them? If they're good, then where should I look next?
No, I don't have a scope, but I have a friend who works at the Conservatory of Recording Arts and Sciences here in town who can take a look at it tonight and he's got one. I'll let you know what happens.
BTW, I appreciate the help, RemcoV. :grin:
On another note, the Conservatory has a 4056G series SSL. Is my compressor comparable to the one in that board? I'd like to A/B them, but if they're that much different, it really wouldn't matter.
No, I don't have a scope, but I have a friend who works at the Conservatory of Recording Arts and Sciences here in town who can take a look at it tonight and he's got one. I'll let you know what happens.
BTW, I appreciate the help, RemcoV. :grin:
On another note, the Conservatory has a 4056G series SSL. Is my compressor comparable to the one in that board? I'd like to A/B them, but if they're that much different, it really wouldn't matter.
right, so we need to check to see where the audio disapears.
When you've got access to a scoop check the folowing things(ofcourse you apply some audio to the inputs):
- check pin 6 of the 5534s, those are the de-balancers
- check pin 1 and 7 of the 5532s. those are the output balancing circuits.
Probably it wil have disappears at the outputs ( i recon)
then check the folowing things:
In the sidechain, there should be signal at TL074 pin7, variable with the threshold pot.
At 074 pin 14 there should be a rectified DC voltage following input signal level. At 074 pin8 there should be a replica of this signal, but now timed with attack and release time.
At TL072 pin2 you find this signal again, but added with a variable DC voltage from the "makeup gain" pot. So this voltage follows both input signal level AND position of the "makeup gain" pot. This signal in turn controls both the main VCA's.
At TL072 pin7 you find the signal from 074 pin8 again, but this time mixed in with a variable DC voltage from the "threshold" pot. So this voltage follows both input signal level AND position of the "threshold" pot. This signal in turn controls the sidechain VCA.
With this you can check if there is signal inthe sidechain.
Hope it helps!
Remco
When you've got access to a scoop check the folowing things(ofcourse you apply some audio to the inputs):
- check pin 6 of the 5534s, those are the de-balancers
- check pin 1 and 7 of the 5532s. those are the output balancing circuits.
Probably it wil have disappears at the outputs ( i recon)
then check the folowing things:
In the sidechain, there should be signal at TL074 pin7, variable with the threshold pot.
At 074 pin 14 there should be a rectified DC voltage following input signal level. At 074 pin8 there should be a replica of this signal, but now timed with attack and release time.
At TL072 pin2 you find this signal again, but added with a variable DC voltage from the "makeup gain" pot. So this voltage follows both input signal level AND position of the "makeup gain" pot. This signal in turn controls both the main VCA's.
At TL072 pin7 you find the signal from 074 pin8 again, but this time mixed in with a variable DC voltage from the "threshold" pot. So this voltage follows both input signal level AND position of the "threshold" pot. This signal in turn controls the sidechain VCA.
With this you can check if there is signal inthe sidechain.
Hope it helps!
Remco
I've just been measuring on my SSL trying to find out why it distorts the sound.
It seems the -15V rail and the -12V is ok, but the others (+12v and +15v) is far to low.
I measured on the WO4 bridge and found out I've got -17.8V on one side and only 5.4V on the other. Is the WO4 broken? Is there I way to measure this component with a multimeter?
/Rikard
It seems the -15V rail and the -12V is ok, but the others (+12v and +15v) is far to low.
I measured on the WO4 bridge and found out I've got -17.8V on one side and only 5.4V on the other. Is the WO4 broken? Is there I way to measure this component with a multimeter?
/Rikard
radiance
Well-known member
Wo4 bridge is basicly 4 diodes so a diode tester will do...
martthie_08
Well-known member
Hello, I am just finishing my GSSL and have two questions, though first of all: big thanks to Jacob for making all those ressources on the ssl comp available to the public, this is only my second diy project and I am really happy with how it's turning out to be...
1. I would like to use a 6 volt power indication lamp like on those old Fender guitar amps instead of the red diode on the control pcb, what is the best way of powering this? I also need to apply 12 volts to the lamp on the vu illumination - any hints? I have a really beefy PT (80 Watts - don't ask
so would it be best to hook up to the PT output and set up an extra little board that will give me the correct voltages? has this been answered before?
2. Is it possible to get the gain reduction on the vu set up reversed way, as on an 1176, for example? I got a Sifam AL29 I'd like to use for my Compressor...
I just "completed" the project this afternoon and have done a short listening test, which was very pleasing I will comment on sonics in detail later, as there are still some things to do, I want to change the threshold range, as all the action is happening on only about one-fifth of the pot range. Then I must adjust the ratios, and the frontpanel is still in work, and... there is a lot of work to do!
1. I would like to use a 6 volt power indication lamp like on those old Fender guitar amps instead of the red diode on the control pcb, what is the best way of powering this? I also need to apply 12 volts to the lamp on the vu illumination - any hints? I have a really beefy PT (80 Watts - don't ask
so would it be best to hook up to the PT output and set up an extra little board that will give me the correct voltages? has this been answered before?2. Is it possible to get the gain reduction on the vu set up reversed way, as on an 1176, for example? I got a Sifam AL29 I'd like to use for my Compressor...
I just "completed" the project this afternoon and have done a short listening test, which was very pleasing
I will comment on sonics in detail later, as there are still some things to do, I want to change the threshold range, as all the action is happening on only about one-fifth of the pot range. Then I must adjust the ratios, and the frontpanel is still in work, and... there is a lot of work to do!Similar threads
