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EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by JPK on November 15, 2025, 05:07:11 PM »

It looks like the relay coil is disconnected.
Check that the relay is in the correct direction (white line on the left).
Can you measure the coil resistance across the diode?
Did you have to desolder and remove the relay during assembly?
The relay may be damaged, try to replace it.

72

EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by Colindsv on November 14, 2025, 07:33:34 PM »

When I measure DC voltage across D1 putting a meter probe on either side of the diode, I get 32V when the EQ is is in XLR 

Both switched Off and PRE give me a DC voltage across D1 very low 0.02V

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EQ573 Equaliser / Re: First three frequencies on the mid band not working

« Last post by JPK on November 14, 2025, 05:13:29 PM »

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EQ573 Equaliser / Re: First three frequencies on the mid band not working

« Last post by distortionplus on November 13, 2025, 07:08:32 PM »

Check the solder joints of inductor L1, in particular the bottom left pad, near R35.

Fixed!!!!! Thank you so much for the fast response and very helpful advice!

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EQ573 Equaliser / Re: First three frequencies on the mid band not working

« Last post by distortionplus on November 13, 2025, 06:34:54 PM »

On it - thank you!

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EQ573 Equaliser / Re: First three frequencies on the mid band not working

« Last post by JPK on November 13, 2025, 04:55:25 PM »

Check the solder joints of inductor L1, in particular the bottom left pad, near R35.

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EQ573 Equaliser / First three frequencies on the mid band not working

« Last post by distortionplus on November 13, 2025, 03:37:45 PM »

Hi,

I bought a pair of earlier 573s on Reverb, not fully working. I've ironed out many of the issues with relative ease but just come down to one last problem that I thought might be good to get some help on.

It's an EQ573-REV1.4

The first three frequencies on the mid band do nothing - the signal is unaffected by boost/cut, the EQ starts working as you would expect at 0.7 onwards.

0.27, 0.36 & 0.5 selections do nothing.

Any clues?

Thanks so much, the EQs sound really good and I'm looking forward to hopefully having them working 100%!  

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EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by JPK on November 12, 2025, 03:01:35 PM »

You should get 0.68VAC on TP1.
Except if the EQ stays in bypassed mode.
Can you check the DC voltage across D1 which also is the coil of relay RLY1. It should be above 20V when the EQ is activated.

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EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by Colindsv on November 10, 2025, 11:11:47 PM »

Ok all of the voltages without running signal were good.  All points A-N tested very close to the target measurement.

The next step was to send a sine wave and test.  Here is where I’ve run into issues.  I don’t know if it’s the way I’m testing though

I have a battery powered behringer cable tester that is also a tone generator.  It has a 1000hz sine wave at +4dbu.  I measured AC voltage at the pins of the XLR and got 1.4v

Plugged this into the unit and measured tp1 and 0v and I get a reading of 0.0 AC voltage on the meter.  

Is this because my sine wave is 1000hz and measuring 1.4VAC from the source?  Or should I be getting a reading?

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SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by JPK on November 10, 2025, 07:57:12 AM »

Yes, this cable will work if the two ground wires are independent and not connected together in one of the XLR connectors.