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

[scott2000]

Well thru troubleshooting the entire PSU signal flow, the only thing that stands out as wrong/not working is the fact that the AC ground did not have continuity to the AC Ground.

Yes I got that. Normally I'd try to find out why instead of venturing off the path of others.

Any ideas why that may have happened?

I see there's an errata section for one of the board revisions. Is this relevant to yours and, if so, did you make the changes?

 

[djmiggymigz]

If you're referncing the correction re: the diode orientation, then yes I did see that and account for that as I was building. As well as the additinal link that needed to happen. Just to be safe tho I will double double check that I put those in properly.

 

[peterc]

Before inserting the ICs, do a couple of quick measurements to check for shorts and continuity.

With power disconnected, measure the resistance from where the pos power rail comes into the board, and each IC socket pin 8. Do the same for the negative rail.
Then measure from each IC socket pins 4 and 8 (for dual ICs) to ground, checking for shorts.

Only then insert the ICs and switch on.

 

[djmiggymigz]

Okay I've tested all the sockets and IC's and there aren't any shorts or connections that shouldn't be happening. Checked the +- DCV coming into the IC's and all seems well there too. Checked all the resistor values near/around the DC Input and IC's: all seems well.

Now what I did find: On the L channel PCB with the smoking RPSU (connected to -DCV) resistor; if I simply take out the 5534 IC at U5, voila no smoke. With it in, the same RPSU resistor is smoking within a minute of being on. With it out, no smoke after being left on for upwards of 5 minutes. With this knowledge, I placed the 5534 IC from the right channel (which seems fine) onto the L channel and all was fine. Again, unit was powered on for a good while (5-10 minutes) and no smoke, all the voltages looked good, LED's work, etc.

Could it simply be a bad chip? I.e if replacing the chip eliminates the issue, is the chip itself the issue? Or could it be something deeper? (like maybe when the chip is in, it's making a connection and sending signal elsewhere where the real root of the problem is)

I think I'm really close! Can't wait!! Got a heat gun today and a bunch of shrink wrapping and went crazy cleaning up all my wiring all over the place. Also getting switches (lorlins) in next week sometime. figuring that out should be fun!

 

[peterc]

Sounds like a bad chip.

What you could try is to put the 'bad' chip into the other channel, and with your finger on the corresponding resistor that burns up, turn on the power.

If the resistor under your finger gets hot, turn off immediately to save the resistor from smoking. Then it is definitely a bad chip.

 

[djmiggymigz]

Sounds like a bad chip.

What you could try is to put the 'bad' chip into the other channel, and with your finger on the corresponding resistor that burns up, turn on the power.

If the resistor under your finger gets hot, turn off immediately to save the resistor from smoking. Then it is definitely a bad chip.

Okay I'll give that a shot today. Ordered the chip last night and since I was paying for shipping anyway, bought a few extras as well. Hopefully never use em but just in case! THANK YOU GUYS... seriously can't wait to plug this is and boost that air band!

 

[djmiggymigz]

Okay another question regarding switches that I just want to clarify. So I have (I believe harpo's) excel sheet to calculate the resistor values for using switches. On the excel sheet it specifically says at the top to use Non-Shorting (BBM) however others are saying that I should use shorting (MBB) switches?? I'm inclined to follow the guidance of the excel sheet and Harpo. (in fact I already ordered non-shorting lorlins). Just wanted to see if someone could confirm that.

Here's the other thread I started for reference.

https://groupdiy.com/threads/diy-stepped-pots-w-rotary-switches-resistors.87811/

 

[Bobby Baird]

Typically active circuits like this will emit a small DC offset voltage from the op-amps. This offset DC voltage can cause pots to sound scratchy. Better to use conductive plastic in this case. Switches on the other hand will cause a popping sound from your speakers with a BBM switch if DC is present. So, with an active circuit, I recommend to use MBB switch if there is a measurable offset.

 

[djmiggymigz]

Okay new problem alert! Update first: Got the new chips in and replaced the seemingly bad 5534 chip which was successful. Got the new chip popped in and no smoke from any resistors! I check all the DCV at the chips and everything seems good across both channels.

However, when I plug it into my interface (via balanced xlr in and out) the L channel when engaged is absolutely flooded with a low noise. I got a little RTA of what the noise looks like. Everything seems to be just fine in bypass; signal is passing thru and I can't hear/see any problems with the bypass. But, again when I engage the Left channel. NOISE.

Could this be related to the bad chip? I.e when I maybe burned the chip out while figuring out the PSU, could some other component also burned out? It's definitely important to note that the noise is only present when the 5534 chip is installed. I took all the chips out and when placing them back in the noise only appeared when I installed the 5534. (Also tried several different (brand-new) 5534's and it was all the same.

Any guidance/ideas on what I should check? I confirmed ground continuity to everything that should be grounded. I checked all the resistor values around the 5534 and all seems fine.

 

[Brian Roth]

Silly question from me....I ASSume you had the power off (for maybe 30 seconds to allow the power supply voltages to bleed off) before swapping the chip(s).....

Bri

 

[djmiggymigz]

Yeah I did! Got myself with a little shock earlier in the project lol so I e being extra careful about letting this drain

 

[djmiggymigz]

What were you thinking tho? Even if it wasn’t the case I’m curious what your train of thought is!

 

[Brian Roth]

I haven't closely followed this project so I don't have a copy of the schematic. My guess is the noise problem comes from "upstream" of that 5534 you replaced. IOW, when that chip was removed from the signal path it "interrupted" the crappy noise source from the path.

Just guessing...

Bri

​

 

[peterc]

Swap the inputs on your interface. Plug eq left channel out into interface input 2 and eq right channel out into interface input 1.
See if the problem moves channels in your software.

 

[djmiggymigz]

Will do! Don’t think it’s an interface/software issue tho. Was just running test on a reel to reel today with the same out/inputs and all was fine,, of course worth a test tho!

 

[Script]

You can swap (same-type) ICs around until you find the offender. -- unless it's a problem with the circuit. Should have tested all empty IC sockets for shorts etc

 

[fragletrollet]

Someone should make a 500-series version of this (yeah I know of the retail module, or even of the EQ2

 

[Whoops]

Someone should make a 500-series version of this (yeah I know of the retail module, or even of the EQ2

I'm not very good at designing PCB's neither I have the time.

But for someone that knows how to design PCB's and is experienced, designing the Night EQ for the 500 series format would not be not difficult

 

[lukas]

Someone should make a 500-series version of this (yeah I know of the retail module, or even of the EQ2

...maybe you should drawing this board.

 

[fragletrollet]

Yes maybe I should. Probably wouldn't work, tough