GSSL CRC Board from Expat Audio

[Greg S.]

I took out the 22uF Elcos behind the 7x15 and it works..

+-15V at the Revision 7 GSSL Board

YES!!!

No 1N4001 and no 100nF Poly Condensators

 

[Greg S.]

Update:

It really depends at the brand of Regulators you have.

TS7815CZ  -->  no Elcos needed 
    Reichelt.de
L7815ST  (ST Microelectronics) works fine with 22uF Elcos!
    Segor.de

I really Love DIY Gear    :

THX to Harpo and all the others posted here, see ja

 

[SSLtech]

Yes indeed, some regulator brands/types are more or less sensitive to their environment causing them to latch up.

hopefully you now have a smooth, silent, hum-free limiter... -Enjoy!

Keef

 

[Greg S.]

It's that silent, simply graet!

:

 

[salomonander]

hey
i was about to fit this in. im afraid im getting about +-22V DC. it should be +-15v DC right? i did check all values and they are right. any idea what im doing wrong?

 

[Rochey]

actually, that sounds about right. bear in mind, there are no regulators on the CRC, so your getting a smoothed and rectified version of your transformer rating.
This is typically 1.4* your AC voltage output. so if your AC transformer is rated for 15V, that's ~21V or so...

Your regulators, on the GSSL etc should regulate down to the voltage you want.

 

[Greg S.]

Rochery is right about the 1,4 

It is precise Sqrt(2)  ;D

You always should be 2-3 V above the 7815's +15V out Voltage, but don't forget to add great Coolings

You may also take a look into the papers
+35V is the absolute max as far as I know for 7815

 

[salomonander]

great
so ill just wire it up then i felt double checking might be better than burning something. thx!

 

[Greg S.]

Cheers man! 

 

[salomonander]

...does its job just perfect. finally i can put the lid on! 

 

[Rochey]

pictures or it never happened

 

[Potato Cakes]

Here's a picture. Now it happened!

I too was confounded as I was getting +24V on the output of the CRC, thinking I screwed this up as I had built this a while ago and just now am using it. So thinking I was having some sort of short with the ground plane and the input pads, I just soldered directly to the legs of the rectifier, and when I still had the same voltage, I checked here and saw that I was to expect 1.4X the input to the output.

Thanks!

Paul

 

[salomonander]

could someone be so nice as to upload the schematic again? cheers

 

[Gertius]

Hi guys,
today I´ve tried to install an expat CRC board in my GSSL and encountered some problems.
First of all here is what I did:
- built CRC board
- measured CRC resistances to correctly read 20 Ohms as Keith described in reply 72 https://groupdiy.com/index.php?topic=35641.msg718238#msg718238
- connected CRC to secondary trafo winding (center tap to center pin, the others to AC input left and right), measured DC 22V and -22V on the output pins of the CRC.
So far so good.

Then when I connect the CRC output to the GSSL power input (center to center, output at C5 to plus, output at C6 to minus, rectifier left in on GSSL board) after turning on, the needle of the GR meter pegs at the very left (negative -10 dB or so).
But when I  connect a multimeter to measure DC between center and - pin, the needle goes back to 0 dB GR.
Turning around the outputs of the CRC into the GSSL board left the GR meter dark (background LEDs stayed off), and the meter climbed to a constant 12 dB GR. All this without any audio connections.

Fortunately, after removing the CRC board I could restore normal operation of the GSSL.

Does someone have an idea what could be wrong?
Do I maybe have a different version of the GSSL? My GSSL board looks a bit different as the one on the CRC promo shots (see pic attached).
Should I try with the rectifier on the mainboard removed? Of course then I would not switch around + and - to try, but connect + to + and - to -.

Thanks in advance,
Christian

 

[Potato Cakes]

Confirm that you are getting +/-24 or so DC after the CRC. Then pull the rectifier off of the GSSL board. Put jumpers where the rectifier was. Pull the four 1000uF caps from the GSSL board. Before power up, pull all of your chips and confirm voltages on the board.

Thanks!

Paul

 

[Potato Cakes]

Jumpers

 

[Gertius]

Ok, thanks! I´ll give that a try.

 

[Gertius]

Alright, I did the changes today and it worked!
I have a fully functioning GSSL with a CRC board now.
Thanks for the tips!

I have a follow up question though, because the hum unfortunately hasn´t completely gone away.
I have a noise floor (hum & noise) at around -70 dB. I haven´t measured before the CRC but my feeling is it has gotten a bit better.
Would you say that number is normal, or do you have any other ideas what I could try to improve the noise floor?

 

[Potato Cakes]

Alright, I did the changes today and it worked!
I have a fully functioning GSSL with a CRC board now.
Thanks for the tips!




I have a follow up question though, because the hum unfortunately hasn´t completely gone away.
I have a noise floor (hum & noise) at around -70 dB. I haven´t measured before the CRC but my feeling is it has gotten a bit better.
Would you say that number is normal, or do you have any other ideas what I could try to improve the noise floor?

Take the 0V connection from CRC to the star ground. Only the Ground connection to main PCB should be the Input XLR. All XLR have pin one directly connected to chassis.

Look up Ian's Grounding 101 to reference.

Thanks!

Paul

 

[erquere]

Hi ! what kind of toroidal do you use for the Gssl project ? Mine is a Triad 15 V / 25 VA one (european input) but the resistors (MOS1/2CT52R100J) are frying when power one ! Or the value of resistors ir wrong due to the power transformer ?

Please light me up !