GSSL HELP THREAD!!!

[sociald02]

I removed the 68,3K9,10K,10K and 1M around each VCA and replaced 3K9 for a 5k2.
This solved the -15v on pin 3 problem.  Should I be able to look at a sine wave on pin 8 with the VCA in? Currently I can scope a normal wave on the input and on the output it appears U shaped on the bottom and square on the top. If I jump pin 1 to 8 with wire I can pick up the sine wave at the 5532 socket.  Problems happen when I insert the 2180 and or the output 5532.

I have the rev7 board from chef.

I would really love to know what I have done wrong.

 

[ctechdx]

I´m also building the compressor with the REV7 board. I´m following the schematics of newer versions  like #9 that has changes for the VCA´s resistors as you did. I´m still building it... will take a bit more to start the tests... but hope everything will work fine. Hope to get some more tips to build the project with the REV7 without problems... and I will be looking for your posts coz maybe I will have similar problems.

Best wishes bro,

 

[Harpo]

I removed the 68,3K9,10K,10K and 1M around each VCA and replaced 3K9 for a 5k2.

5K1 connecting to 218x-pin5 for the audio-VCAs. Keep the 3K9, connecting to 218x-pin5 for the sidechain-VCA.

This solved the -15v on pin 3 problem.

Without the 218x VCA populated, -15VDC @pin3 with (ineffective and intended for a different type of VCA) 10K resistor between VCA-pins3/5 fitted is expected value.
With 218x VCA populated and without prementioned 10K resistor, a measurement of -15VDC @pin3 exceeds the abs.max.1V differential between VCA-pins2/3 by factor 15, so expect the VCA to be destroyed.

Should I be able to look at a sine wave on pin 8 with the VCA in?

Measuring voltage at VCA pin1 and/or pin8 doesn't make much sense. Both pins are current nodes (not voltage). With a healthy VCA following NE5532 populated (yours is not, for whatever reason) for the current to voltage conversion, the opamp will try its best to hold its inverting (-)input at same potential as its non-inverting (+)input and as the latter doesn't move, the inverting input (and VCA-pin8) will be @0VDC.

If I jump pin 1 to 8 with wire I can pick up the sine wave at the 5532 socket.

I read it as 'socket of NE5532-pin6 without the opamp populated'.

Problems happen when I insert the 2180 and or the output 5532.

NE5532 populated with correct orientation and no unintended shorts/solderblobs at opamp-pins or connected parts? Replace broken opamp.
Good luck.

 

[ctechdx]

I gonna share here the way I´m building the REV7 Board to have some feedback if I´m doing this right for the 2180 VCA. The image is attached.

I did changed 5 resistors value and omited 9, based on newer versions. Please if someone can take a look and give me a feedback I would really apreciate.

Thanks,

 

[sociald02]

Making some progress but not really...
Attached is a pic of what I am seeing on my scope.

with the VCA in socket
i see
At output 5532 pin 7 I see the top half of a sine wave with tons of gain
At output 5532 pin 6 i see the bottom half of a squared off wave

when i remove THAT 2180 and jump wire from pin 1 to 8
I see a normal wave on pin 7 of the output 5532
I have replaced THAT 2180 with new ones. no change

I have made sure the 5523 in the vca circuit was good by swapping it with an output 5532 and I can scope a sine wave on pin 7



Thank you in advance for any help and the help I have received thus far.

 

[turk sanchez]

quick (stupid) question:

regarding the (three) "relay and light power" pads, which one is "negative"?  Is it the "0v" pad, or the "nc" pad?

This is for wiring the VU meter light.

I'd appreciate the help if anybody is willing.

***sociald02 already answered this below. I thought I would say "thank you" by updating here, rather than making another post and making this thread too long. Thanks a lot, sociald02!!!

 

[sociald02]

negative would go to the 0v
n/c stands for no connection

 

[Harpo]

I have made sure the 5523 in the vca circuit was good by swapping it with an output 5532

you swapped a single opamp (NE5534) with a dual opamp (NE5532)? No idea if these opamps survived this swap because of their different pinout.

 

[sociald02]

Harpo,
I meant the input 5534. I swapped 5534's. Sorry I it's my first gssl build. Have you looked at the images of what I am seeing on my scope?  Any help?

 

[sociald02]

A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

I fall into the complete fool category

 

[jibiss]

Hello,  I just built a micandmod Gssl and have power and seem to have correct voltages +15 and -15 to the points I can trace from the Diagram.  I an getting 11 volts to the sidechain.  I have inspected all wiring and solder points over and over.  I have put the ohm meter on the switches and they seem to be functioning properly.  I have no output at all and the meter will not move at all.  Does anyone have suggestions where to start from here?  i have uploaded a diagram of my voltage readings.  i only know enough to get into trouble.  It is my second build behind a Marshall 18W 1974 head.  Thanks!

 

[sociald02]

If you have a scope can you trace signal to the 27k resistor before the vca?
I am kind of in the same boat.
I can't seem to get signal out of the vca.
In suspicion that I may have blown up the tl074 I have ordered all new ic's

 

[jibiss]

Thanks for the reply.  Sadly I do not have a scope yet.  Also these were readings with the chips out.  would it benefit if I read the voltages after the IC chips were in?

 

[sociald02]

Does any one know if the TL074 and TL072 are needed in circuit for there to be a control voltage on the L and R VCA's?
I cant seem to figure that out from looking at the schematic.
I have been trying to trouble shoot with them out.
Maybe this is why I cant get signal out of the VCA?

 

[jibiss]

Hello,  I still have no signal flow trough my MicandMod gssl.  I also discovered that occasionally when I turn on the unit the light does not come on and I do not get correct voltage.  I read through the forum and it has been suggested to replace the 78 and 79 regulators which I have ordered.  when the lights do come on i have measured voltages this time with the ic chips in.  could somebody possibly take a look at this and offer any suggestions? any help would be much appreciated!  Thanks

 

[turk sanchez]

...how do you guys keep from having a large bolt sticking out from the bottom of the single space rack enclosure (the bolt that mounts the power transformer)? Are you guys drilling a counter-sunk hole and not using the washer?

Any tips on this would be appreciated.

 

[sociald02]

I used some grade 8 hardware a socket and a piece of wood with a bigger hole than the socket and some washers. Drawing the socket tight betweent the wood and the panel,I was able to create enough negative space for the head of the bolt for the torroidiol. Heating with a torch helps.

 

[ctechdx]

I would like to know if the pcb transformer is a good choice for the the REV7 pcb. It may cause any noise? If it´s a good idea I would like to have suggestions for which transformer to use. I didn´t find those suggested by jackob at the pcb layout. (farnell 976-635 or RS 209-538)

thanks,

 

[weiss]

...how do you guys keep from having a large bolt sticking out from the bottom of the single space rack enclosure (the bolt that mounts the power transformer)? Are you guys drilling a counter-sunk hole and not using the washer?

Any tips on this would be appreciated.

how about using a flat hat?

 

[sociald02]

I would like to know if the pcb transformer is a good choice for the the REV7 pcb. It may cause any noise? If it´s a good idea I would like to have suggestions for which transformer to use. I didn´t find those suggested by jackob at the pcb layout. (farnell 976-635 or RS 209-538)

thanks,

I purchased this one

http://www.mouser.com/ProductDetail/Triad-Magnetics/VPT36-690/?qs=%2fha2pyFadugTQsUfP%2fAMLog1DwuRFP1YssENnXs72gk%3d