Sound Skulptor forums

Build help and troubleshooting => True-Grit Tube saturator => Topic started by: Oliv on December 09, 2024, 11:15:25 AM

Title: TRUE GRIT
Post by: Oliv on December 09, 2024, 11:15:25 AM

Hi,

My module doesn't work as expected...
Where do I find a test guide for this module ?
Thanks
Olivier

Title: Re: TRUE GRIT
Post by: JPK on December 10, 2024, 03:54:30 PM

First, check that you get the correct supply voltages on the V+ and V- pins against 0V. You should get a little above +/-15V.

I loose my AC signal between TP3 and TP4
This is the tube stage. Is the tube getting warm?
Check that you get the 12V heater voltage accross the 2 extreme pins of the tube PCB.

(https://i.imgur.com/qkKnvIk.png)

In the schematic R25 and R26 are supposed to be 56k. Wich one is right ?
56k. There is a mistake in the layout doc (corrected now).

Title: Re: TRUE GRIT
Post by: Oliv on December 10, 2024, 06:47:48 PM

You're right, The tube isn't getting warm and I have 0V accross the 2 extreme pins of the tube PCB.

Title: Re: TRUE GRIT
Post by: Oliv on December 11, 2024, 11:10:02 AM

Hi,

Accross the 2 extreme pins of the tube PCB I get -15V DC
Is it normal ?
Thanks

Title: Re: TRUE GRIT
Post by: JPK on December 11, 2024, 03:17:21 PM

Something is wrong here.
Check the components value, direction and solder joints of L1...L4, C37...C42, R39, R40, U6, Q1, D8.

Title: Re: TRUE GRIT
Post by: Oliv on December 11, 2024, 05:47:28 PM

I just double checked all the components value, direction and solder joints of L1...L4, C37...C42, R39, R40, U6, Q1, D8.
I always get 15V Accross the 2 extreme pins of the tube PCB I
Any ideas ?
Thank you

Title: Re: TRUE GRIT
Post by: JPK on December 12, 2024, 04:46:08 PM

And the tube still doesn't warm up, right?
Check the solders joints on the tube PCB to main PCB and on the tube socket.
Can you share a picture of your PCB in the U6 - Q1 area?
You can also check the tube heater with your ohmmeter, it should measure around 12 ohms beteen pin 4 & 5 (bottom view (https://www.jj-electronic.com/images/stories/product/preamplifying_tubes/pdf/ecc81.pdf))

Title: Re: TRUE GRIT
Post by: Oliv on December 13, 2024, 02:40:33 PM

Hi,

Yes the tube still doesn't warm up.
The tube heater between pin 4 & 5 is around 10.3 ohms.

(https://i.imgur.com/BNblEfb.jpeg)

Title: Re: TRUE GRIT
Post by: JPK on December 14, 2024, 09:18:16 AM

From the picture, I see that you have soldered the tube socket and the 2 connectors on the wrong side of the small PCB. Luckily, the True Grit PCB has 2 of them. You may need to replace the connectors if they get damaged during desoldering.

Title: Re: TRUE GRIT
Post by: Oliv on December 15, 2024, 03:48:52 PM

Thank you : (with a lot of patience) I replace the second small PCB (on the right side this time) !
It works like a charme ;D

Merci

Title: Re: TRUE GRIT
Post by: JPK on December 18, 2024, 06:08:14 PM

(https://fonts.gstatic.com/s/e/notoemoji/15.1/1f44d/32.png)