weiss

Re: 3D "AIR" EQ - "Night EQ" PCB's Complete!
« Reply #1200 on: February 11, 2019, 10:02:01 AM »
HI Weiss,
LM317 and LM337 are adjustable voltage regulators.

Check their datasheet on how to install a trimpot

check also the implementation of these regulator in the JLM PSU:

http://www.jlmaudio.com/ACDCVer2sch.pdf


I think in mine I just replaced R1 and R5 for a 5K Multiturn Trimpot

thank you!


jrasia

Re: 3D "AIR" EQ - "Night EQ" PCB's Complete!
« Reply #1201 on: April 15, 2019, 07:06:48 PM »
I'm using a DIY Racked PCB of this EQ, and have a particular question about 60hz hum I'm getting.

Ch1 is very quiet. 
Ch2 is fine so long as I have the 'Air' switch on.  When its in 'Off' position, I'm getting the 60hz noise. 

I have Mumetal around the transformer, tried rotating it with no change.  Audio cabling is all shielded.  All wiring is nicely twisted and moved away as far as possible from the psu.

Any ideas?

« Last Edit: April 15, 2019, 08:06:47 PM by jrasia »

lukas

Re: 3D "AIR" EQ - "Night EQ" PCB's Complete!
« Reply #1202 on: April 16, 2019, 04:55:47 AM »
Yeah...bad power supply.

Harpo

Re: 3D "AIR" EQ - "Night EQ" PCB's Complete!
« Reply #1203 on: April 16, 2019, 07:06:08 AM »
I'm using a DIY Racked PCB of this EQ
assume your schematic and pcb to differ from this topics schematic and pcb.

Quote
Ch2 is fine so long as I have the 'Air' switch on.  When its in 'Off' position, I'm getting the 60hz noise.
So this seems pre psu related. (Post psu would be dominant 120Hz from rectification).
Double check traceside of pcb. There might be a wire not clipped off that now connects to your case ground.
Other possibility might be a device inducing mains frequency into your eq with lid open. (halogen spot, ...)
Good luck
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

jrasia

Re: 3D "AIR" EQ - "Night EQ" PCB's Complete!
« Reply #1204 on: April 16, 2019, 08:32:00 PM »
Thanks guys!  I'll have to measure what frequency I'm getting,  but it may indeed be 120hz.   


 

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