3D "AIR" EQ - "Night EQ" PCB's Complete!

[peterc]

I'd say 2dB steps might be fine, owing to the wide Q of the bands.

I have very rarely done huge cut or boost settings on mine.

Peter

 

[fazeka]

Thanks Pete!

 

[frazzman]

Hey Guys,
I just finished building a pair of these.. great sounding units and my first self-etch project... nice design for first time etch as well...

Anyhow - has anyone experienced a 'squealing' sound when maxing out the 2500k band or the HI-SHELF band ?

As soon as I wind the pots back a tiny bit on either of these pots the 'squealing' stops. Both bands sound like they are working fine though and the problem immediately disappears if you turn back the pots a little...

I don't have this issue on any of the other bands.

I was thinking maybe something to do with the inductors, but I can't see any issues there. Its more of an annoyance than anything and in my limited testing it doesn't appear to cause any other issues.

Interested to hear if anyone else experienced this?

 

[dribro]

hi

thank you all, especially to Peter for this great project. Got it up and running from first try. Sweet sounding unit, very good indeed! Now it's time to finish the second one!

best,
Adriano

 

[bieckmusic]

Hi frazzman, congrats.    I didn't have squealing on my unit, is it on both channels?  On my self-etch I reinforced some traces with solid core wire, because eq bands were cutting in and out.  A few hours with the continuity checker and I figured it out.  Self-etching was a blessing and a curse... 

I had squealing come up on the optical desser I built, only when I cranked the threshold all the way up, some high frequency oscillation...  I too wonder what causes high frequency oscillation?

 

[frazzman]

Hi frazzman, congrats.    I didn't have squealing on my unit, is it on both channels?  On my self-etch I reinforced some traces with solid core wire, because eq bands were cutting in and out.  A few hours with the continuity checker and I figured it out.  Self-etching was a blessing and a curse... 

I had squealing come up on the optical desser I built, only when I cranked the threshold all the way up, some high frequency oscillation...  I too wonder what causes high frequency oscillation?

Hi Bieck, thats for the reply! Channel 2 isn't finished yet so I can only confirm on channel 1 for now. I do have a couple of tracks that aren't as thick as I'd have liked (when compared to a commercially produced PCB). I did use a DMM to measure continuity across and 'suspicious' areas to make sure that the circuit wasn't broken anywhere due to thin tracks, but everything checked out.

As I said, its only on the 2500k and Air band, with either pot maxed out that I get the squealing... soon as I turn the pots back a notch it goes away, the boosts on both bands seem to be working fine though... I can hear the obvious high end boost.
Anyway... its really odd, I thought maybe it was due to the inductors, I removed them and bridged the gaps with resistor legs, it didn't really make a difference for better or worse.
I suppose I could live with the issue as it doesn't have that much of an impact but it is damn annoying. I went through this entire thread but no one else mentioned it. I'll see what happens with channel 2.

 

[bieckmusic]

You know, maybe, it could be the end of a cap on the 2500k part of the circuit.  If you trace it from the pot back and check all the caps???  I read somewhere that un-grounded filter caps can cause this, ...  anyway good luck, I love my nite eq!  trouble shooting has been helping me understand these circuits.  Also you could try and relocate the torroid or the power supply wires away from the board??

I think it's totally worth it to get all the bugs out, otherwise it just drives me nuts 

best,
greg

 

[frazzman]

You know, maybe, it could be the end of a cap on the 2500k part of the circuit.  If you trace it from the pot back and check all the caps???  I read somewhere that un-grounded filter caps can cause this, ...  anyway good luck, I love my nite eq!  trouble shooting has been helping me understand these circuits.  Also you could try and relocate the torroid or the power supply wires away from the board??

I think it's totally worth it to get all the bugs out, otherwise it just drives me nuts 

best,
greg

Hi Greg,
Thanks for that, sounds like a good place to start. I'll have a look around C51 and C3 as per the schematic these are the caps in the 2500k boost section. I understand that the air band and the 2.5k band are interrelated so one could therefore impact the other.
I haven't properly grounded everything yet as the unit is still out on the test bench before I finally rack it, so its therefore possible that the filter caps aren't grounded properly... So far its a great sounding EQ

 

[frazzman]

  I read somewhere that un-grounded filter caps can cause this, ...

You're the man Greg! This is exactly what the issue was. Now with proper grounding, there is no noise or squealing at all on the 2.5k and AIR bands.

This is an awesome sounding unit!

Thanks for your help.

 

[bieckmusic]

No problem,  way to go, so glad it works!!   

I love my eq too, I think I'm going to add a pair of these meters.  More colored flashing lights!! 

http://fivefishstudios.com/component/content/article/56

 

[frazzman]

No problem,  way to go, so glad it works!!   

I love my eq too, I think I'm going to add a pair of these meters.  More colored flashing lights!! 

http://fivefishstudios.com/component/content/article/56

Cheers mate! First self etch too... Worked a treat

I reakon you could etch up a few of those vu boards , not much to them, they would sure look cool but $19 for a few led's and a meter driver ic ain't that cheap!! Good luck with your additions

 

[Bonsaimaster]

Ok I built one of these NITE EQ 500 Series. But don't know how to calibrate it. Also do not know where pin 1 is on the 26 way upper deck. Also there are test points and a variable trim but no reference for testing. Any help appreciated.

Bonsaimaster

 

[Bonsaimaster]

Ok got sound to go thru the unit but cannot get the EQ to kick in.

 

[Harpo]

@Bonsaimaster, wrong thread for different circuit (schematic and operating behaviour)
with unit powered (inside your 500 rack or using a cardslot extender), bypass switch pushed to 'In' (red LED is shining), Air switched to 'off' and all level pots centered,
feed unit with 1V rms signal at a frequency your multimeter can handle, maybe 100Hz (IE measuring AC voltage between TP4/5 will show 1.000VAC). Confirm readout at TP2 for 0.039VAC in respect to 0V reference voltage (TP11) after debalancing stage and voltage divider R36/R24. Adjust trimmer R41 for a 0.500VAC readout at TP3 in respect to 0V reference voltage (TP11). Confirm readout of 1.000VAC after balanced line driver between TP6/8. Done.

 

[Bonsaimaster]

I am getting .122V between TP4 and TP5 so something is wrong and nothing between TP2 and TP11.

 

[Harpo]

I am getting .122V between TP4 and TP5 so something is wrong and nothing between TP2 and TP11.

So you either didn't feed it with 1VAC between XLR-pins2/3 or something is wrong with your ribbon connection. Have a look at the schematic and just follow the traces to make sure you connected it correctly.
With 0.122VAC between TP4/5, TP2/11 should read 0.005VAC (or 0.004758V if your meter could do it and your attached measuring wires doubtfully don't pick up any garbage), not dead zero, so there might be more wrong. What are the supply voltages at NE5532-pins 4 and 8 in respect to TP11 ?
For your Bypass/active LED not showing up, you simply might have fitted the LED the wrong way round. The LED will still be alife. Other polarized parts might/will not be that forgiving, once powered with wrong orientation.

 

[shot]

Please help me out with this!

I've stuffed two Peter's pcbs. Also I made my PSU based on LM317/337 regulators, self etched it.
I've calibrated PSU to give +18V and -18V before connecting the EQ board.

On first EQ power up there was smoke from 22R resistors near the power rail connector. I immediately turned it off so I wasn't able to spot where exactly smoke came from. Then I took out all the ICs and measured DC resistance between +18V header and opamp socket pin 8 (or pin 7 if it's 5534). It's 22R as it should be.
I've checked for some solder blobs, cleaned all again with isopropylene and checked to see DC resistance between + and - headers (without PSU rail wires connected). It measured roughly around 1M6. That's supposed to be okay, I guess.

Then I applied power again.
There was no smoke this time.
But I noticed that bypass caps CPSUb1 and CPSUb2 are starting to grow on top. Ready to explode I guess. So I turned off the power.
I've checked again the DC resistance between + and - rails, but this time with screwed wires from my PSU board. Now I measure around 6K DC resistance! Is that normal? I've powered up the PSU again without it being connected on EQ board and DC voltages remain correct. But this seems as a fairly low resistance, am I correct? Could that be the reason for bypass caps (almost)blowing?

What is the next step I should do?
My noobish brain is left without ideas...

I've attached the psu schematic I used to build my psu, and my board layout (single layer) if that helps...

 

[Harpo]

On first EQ power up there was smoke from 22R resistors near the power rail connector...
...But I noticed that bypass caps CPSUb1 and CPSUb2 are starting to grow on top. Ready to explode I guess...
What is the next step I should do?

Unsolder and replace the blown from probably reversed orientation or insufficient voltage rating 47uF/35V caps CPSUb1 and CPSUb2. (if CPSUb3 and CPSUb4 are fitted with same reversed orientation as CPSUb1 and CPSUb2, unsolder and replace as well.) Caps positive leg goes in the rectangular shaped solder pad. Double check for 22R resistor values of all 4 RPSUs with PSU disconnected. They might be still alife or blown from excessive current demand of reversed fitted polarized caps.
Good luck

 

[shot]

I have replaced all PSU bypass caps. They were underrated (25V) but were oriented correctly, and I've replaced them with 35 volt rated ones.
Now when powered up without ICs, everything is ok. Voltages on the IC sockets are correct.
When ANY IC is inserted RPSU resistors start smoking! Now I'll replace those since they dropped in value and got a black burnt trail on them.
I can't imagine all of my ICs are faulty! That would statisticaly make no sense!
And I triple checked IC orientation - its good.

Is it possible 1/4W rating of RPSU resistors is underrated? If I replace them with 0.6W ones will that help?

Thank you Harpo for helping me with this! Please stay with me!

 

[shot]

:-[ SELF-PUNISH  :-[ SELF-PUNISH!!

Damn how emmbarrassed I am now...

I found out what was wrong!

I mislabeled + and - wires!
Wrote wrong designations on small tape labels!

DAMN!

Excuse my stupidity!