Sound Skulptor forums

Build help and troubleshooting => EQ573 Equaliser => Topic started by: andrixb on February 15, 2026, 02:40:08 PM

Title: EQ573-II doesn't play sound
Post by: andrixb on February 15, 2026, 02:40:08 PM

I would need help with this module, please.
The module doesn't play any sound when in both pre and XLR mode.

V values match what is reported here: https://www.soundskulptor.com/forum/index.php?topic=25.0

I checked the tension, and I measured 16V.
Also,  I followed this thread too and around diod D2 I measure -15V / 7V (it goes 7V / -15V when I select XLR) https://www.soundskulptor.com/forum/index.php?topic=362.0
I checked all the solder joints around what is suggested, but the value around D2 measured doesn't change at all.

Thank you

Title: Re: EQ573-II doesn't play sound
Post by: JPK on February 16, 2026, 05:32:44 PM

Do you get a sound in bypass?
You must try to follow the signal on TP1, TP3, TP4, TP2, as described here (https://www.soundskulptor.com/forum/index.php?topic=25.msg41#msg41).
It will tell you where the signal stops.

Title: Re: EQ573-II doesn't play sound
Post by: andrixb on February 18, 2026, 11:45:53 AM

Hi

Thanks for the suggestion.

I get a sound in bypass if it is connected to the MP573; nothing gets through otherwise.
On TP1, I get 0VAC. The board is REV2.3B, and the C8 is oriented as in the picture (negative facing the back of the launchbox)

Title: Re: EQ573-II doesn't play sound
Post by: JPK on February 18, 2026, 04:48:29 PM

Check the value and solder joints of R1...R4, C4, C5, U1, RLY1.
Check the direction of U1, RLY1.
Try swapping U1 with one that you are sure of.

Title: Re: EQ573-II doesn't play sound
Post by: andrixb on February 19, 2026, 01:02:07 PM

Thanks. 
I can get 1VAC on TP1, but now it is 0VAC on TP2. Soldier joints look fine. Could it be an issue with the U2 THAT1646?

Title: Re: EQ573-II doesn't play sound
Post by: JPK on February 20, 2026, 11:36:28 AM

Also check TP3 and TP4 (the audio goes through them before TP2).

Title: Re: EQ573-II doesn't play sound
Post by: andrixb on February 21, 2026, 01:43:23 PM

Checked. On TP3 is 0.9VAC and TP4 0.8VAC

Title: Re: EQ573-II doesn't play sound
Post by: JPK on February 22, 2026, 10:09:45 AM

Check if you get the signal on U1 pin 5.
- If not, the issue is around the high pass filter. Check the solder joints on rotary switch SW1, connectors J5a-b and J6a-b.
- If true, the issue is in the relay RLY1 or in U2. Check the solder joints. Try replacing.