So Jakob I think my explanation might not been the best, so just to make it clear for me: Everytime I switch the unit off, I get a delayed and loud "squeeking" sound, even with no input connected. So did you say this is normal or did you get me wrong?
GSSL HELP THREAD!!!
- Thread starter hairyandy
- Start date
Help Support GroupDIY Audio Forum:
..misunderstood you, sorry: Yes, this is normal - opamps loosing supply voltage will behave weirdly for a sec. Nothing to be alarmed about..
/Jakob E.
/Jakob E.
jsilverstream
New member
Just a FYI, I successfully built a GSSL (no mods) and all knobs/functions/buttons work as expected.
Initially had an issue where the right channel was distorted and extremely quiet (but the input meter was still reading and compressing correctly)
I followed the output right channel signal backwards until I located some bad solder connections touching near the output 5532 and also the right channel VCA and 5534. I attempted to remove solder and try to tidy up (magnifying glass inspecting each solder connection)..I then "fixed" the bad soldering. Then no sound on right channel!
I then used contact cleaner on the board where I did my bad soldering mess, and it seems to wash away very fine bits of solder (looking in magnifying glass) then tried again and the sound was prefect in the right channel, and everything fine.
So my advice if anyone has an issue with one channel being distorted or quiet, mine was bad solder connection of some type, not sure if this helps anyone!
I have no electronic experience and this was my first unit I ever built. I did read hours of info on this thread, and studied the PCB diagrams in depth, and triple checked everything when putting it together, and found approx 5 issuers in my triple checking (e.g I used 15K for unity gain instead of 27K...).....so it could have been really bad if I didn't triple check even when I "thought" it was right.
Sorry for the rant but might help someone one day!
Thanks to anyone who contributed on here as I probably read your comments at some point and to Mr Erland for taking a massive amount of time back in the early 2000's to do the PCB/schemtaic and doco and get this all happening initially
Initially had an issue where the right channel was distorted and extremely quiet (but the input meter was still reading and compressing correctly)
I followed the output right channel signal backwards until I located some bad solder connections touching near the output 5532 and also the right channel VCA and 5534. I attempted to remove solder and try to tidy up (magnifying glass inspecting each solder connection)..I then "fixed" the bad soldering. Then no sound on right channel!
I then used contact cleaner on the board where I did my bad soldering mess, and it seems to wash away very fine bits of solder (looking in magnifying glass) then tried again and the sound was prefect in the right channel, and everything fine.
So my advice if anyone has an issue with one channel being distorted or quiet, mine was bad solder connection of some type, not sure if this helps anyone!
I have no electronic experience and this was my first unit I ever built. I did read hours of info on this thread, and studied the PCB diagrams in depth, and triple checked everything when putting it together, and found approx 5 issuers in my triple checking (e.g I used 15K for unity gain instead of 27K...).....so it could have been really bad if I didn't triple check even when I "thought" it was right.Sorry for the rant but might help someone one day!
Thanks to anyone who contributed on here as I probably read your comments at some point
and to Mr Erland for taking a massive amount of time back in the early 2000's to do the PCB/schemtaic and doco and get this all happening initially Attachments
I need help with debugging few problems:
1. No compression - signal going throught unit - doesnt change depends on bypass
2. Make up gain doesnt work like expected (after resoldering) it doesnt volume up until meet 90% of way, in that point it 'jump up' volume so much and max vu meter scale - it looks like faulty potentiometer (but could be something else?)
Actions made:
- replaced 78L12 - there was 11,9V ,but during other measurment -0,78V (strange..) , but after replace component = 12,09V
- faulty diode on mainboard - "A" connector pin (don't know how/way it happened)
- removed opamps and VCA and tested supply voltage - looks correct (55... opamps has +-15V , VCA about 8V , tl074 +-12,08V)
- checked connections between control and mainboard
- voltages on make up and treshold potentiometers = about 12V
- TL074 with signal .. pins 1 and 14 , values changes from - 1,5v to +1v depends on signal type (dynamic signal on input or constant sinewave)
I run that unit last week , and it was full working (except little 50Hz hum) - so I components are correct placed
Unit stopped working after first connection of meter and LED diode (diode were connected to 7812 relay) , resoldering MakeUp potentiometer
What next should I check/do?
1. No compression - signal going throught unit - doesnt change depends on bypass
2. Make up gain doesnt work like expected (after resoldering) it doesnt volume up until meet 90% of way, in that point it 'jump up' volume so much and max vu meter scale - it looks like faulty potentiometer (but could be something else?)
Actions made:
- replaced 78L12 - there was 11,9V ,but during other measurment -0,78V (strange..) , but after replace component = 12,09V
- faulty diode on mainboard - "A" connector pin (don't know how/way it happened)
- removed opamps and VCA and tested supply voltage - looks correct (55... opamps has +-15V , VCA about 8V , tl074 +-12,08V)
- checked connections between control and mainboard
- voltages on make up and treshold potentiometers = about 12V
- TL074 with signal .. pins 1 and 14 , values changes from - 1,5v to +1v depends on signal type (dynamic signal on input or constant sinewave)
I run that unit last week , and it was full working (except little 50Hz hum) - so I components are correct placed
Unit stopped working after first connection of meter and LED diode (diode were connected to 7812 relay) , resoldering MakeUp potentiometer
What next should I check/do?
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ho-fi
Member
I've build the basic GssL on a Revison 7 Board from Pusherman. Checked voltages without IC's and all is good. But after putting the NEs/TLs in, without the VCAs, bridged L-R VCA Pin 1 to Pin 8 (input to output) and Signal passed undistorted from XLR to XLR. After inserting the VCA's the positive rail measured -0.8V while the negative still was -15V.
So I took out the ICs one after the other, measuring voltages each time i removed one.
When I leave only the TL074, TL072 and the left input 5534 in, all is good. But as soon I insert any other IC NE553X, the positive supply rail goes negativ (around -0.7V.)
Any Ideas?
Edit:
I tried with a new IC on input R. all good at first, but after turning the unit off and on a few times, the issue was there again.
So I took out the ICs one after the other, measuring voltages each time i removed one.
When I leave only the TL074, TL072 and the left input 5534 in, all is good. But as soon I insert any other IC NE553X, the positive supply rail goes negativ (around -0.7V.)
Any Ideas?
Edit:
I tried with a new IC on input R. all good at first, but after turning the unit off and on a few times, the issue was there again.
Last edited:
ho-fi
Member
Thanks Script!
I had the meter LED connected, although the polarity was right, I disconnected it for now.
There's no short on the IC sockets, checked it.
But there's a lot of DC on the VCA-buffer 5534-socket IN- (Pin 2). I measure -14.85V on both sockets and also -14.87V on both outs (Pin 6) obviously also on pin3 (input) of the VCAs. As far as I can see from the schematic, there should be some DC, but isn't it a bit too much?
Maybe there's something wrong in the "DIST NUL"? Is it correct to have the 1Meg resistors installed there? I'm using 2181 VCAs.
I also noticed some DC on Pin 8 of the VCA socket, when powering on it's about +1.5v, very slowly decreasing, maybe through the voltmeter?
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Harpo
Well-known member
You might have mistakenly fitted NE5534s (single opamp) in the NE5532s (dual opamp, different pinout) sockets. If so, expect the wrongly fitted opamp to be faulty.
Expect each VCA faulty in this circuit, that had -14.85V applied to their control port with their corresponding port held at 0V. (THAT2181 Abs.max is +/-1V between EC+/EC-).
Good luck
Expect each VCA faulty in this circuit, that had -14.85V applied to their control port with their corresponding port held at 0V. (THAT2181 Abs.max is +/-1V between EC+/EC-).
Good luck
ho-fi
Member
I’m pretty sure I didn’t fit the wrong opamps but you’re probably right, the ICs I’ve had in are fried now. Anyway, the measured voltages are without any ICs, just the empty sockets.
Painful, but we have all done that at some point. You need to fix that short on the empty socket before frying more ICs. Then better check all pin holes again (maybe even of all empty sockets again, doesn't take long, I do), before inserting anything anywhere. DC in the sidechain (if present and other than +/-15VDC rail) is in the mV.
For VCA (2181 A/B/C) distortion trim and 1M resistor etc, consult Matt Fisher's list.
For VCA (2181 A/B/C) distortion trim and 1M resistor etc, consult Matt Fisher's list.
ho-fi
Member
yes, we’ve all been there
I’ll dig into it again, maybe a faulty cap, who knows…
concerning the Matt Fisher list: does anyone have a link? all I found was a link to Account Suspended but it says the account is suspended.
Implementing different VCAs in the GSSL.
Matt Fischer's list.
THAT2180
THAT2181
VCA 2155
---- And as it says, better also consult the respective datasheets. ---
https://web.archive.org/web/20190915041735/http://diy.fischerworks.com/gssl_vca.shtml
Matt Fischer's list.
THAT2180
THAT2181
VCA 2155
---- And as it says, better also consult the respective datasheets. ---
https://web.archive.org/web/20190915041735/http://diy.fischerworks.com/gssl_vca.shtml
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Harpo
Well-known member
Symptoms of the positive voltage regulator hanging on startup. Most often a diode across regulator output and 0V fixes this latching behavior.
ho-fi
Member
or just replace the regulator?
Harpo
Well-known member
... or click on the Search button in the upper right corner and search for '7815' by user 'Harpo' ... just for examples sake. It's been answered lots of times, just read the thread ...
ho-fi
Member
sorry, I didn’t want to step on your toes. and sorry I haven’t read all the 431 pages of this thread. but no need to freak out…
I just wanted to understand if it’s a design/layout issue or something that happens with certain regulators/regulator brands and not with others. but I’ll do as you say and maybe figure it out.
If you modify the design by soldering in the diode proposed, you can be 100% sure to fix the latching issue with any regulator used.
If you solder out the 3 pin regulator and replace it with another, it will depend on how the the specific regulator behaves.
Someone may have a list of suspected brands and types of regulators, prone to behave in this manner.
Gustav
Hy guys
Hope you are having a great weekend...
I'm building the gssl and i am on a great point... I read most of this thread and i'm not sure if i found the right solution for the meter connection...I know that this is surely been asked before and i'm sorry to be repetitive
I choose to put the pushbuttons and this meter (SSL dB Meter (8027), 32,50 €)
I follow this scheme...Can you tell me if this is correct?
Sorry for my incompetence...
Hope you are having a great weekend...
I'm building the gssl and i am on a great point... I read most of this thread and i'm not sure if i found the right solution for the meter connection...I know that this is surely been asked before and i'm sorry to be repetitive
I choose to put the pushbuttons and this meter (SSL dB Meter (8027), 32,50 €)
I follow this scheme...Can you tell me if this is correct?
Sorry for my incompetence...
Attachments
Harpo
Well-known member
Don't connect external wires to the +12V rail connection in the yellow circled spot, use the Aux.12V connection on main pcb instead.
Switches illumination is set for 10mA per switch by the 3x 1K resistors. Use a maybe 620 ohm current limiting resistor for comparable brightness in series to your meter illumination terminals (small pins). Don't operate the LEDs inside the meter without current limiting resistor, else these LEDs won't survive.
The meters M+/M- connection to show the amount of gain reduction is above the 10-pin connector at the control pcb, not at the yellow circled spot.
