[bobtheninja]

Thanks for the quick reply! I tried pulling the line transformer and now I definitely need a new one. Not easy to get off the board in one piece. Anyway, it has to be the transformer so I don't think there were any hope for it even without me prying it off. Will order a new one asap and will report back.

Thanks again!

So, I got a new line input transformer and installed it. Now I get some sound, but what I'm getting is some 30-35 dB quieter than it is going out from my converters. I also see when running a white noise signal generator out from my converters that the low end rolls off quite a bit steeper than the digital signal I'm sending out from my converters. I'm a bit stumped for where to go with my troubleshooting. Does anyone have any tips? I'm getting the same frequency plot when using the mic input, so I'm guessing the problem lies elsewhere than the line input transformer, maybe? Hmmmm.

(In the photo I've compensated for the level loss by using the trim plugin in Pro Tools)

[Potato Cakes]

First,  use pink noise and not white noise. There is a big difference.

Second, try injecting signal after the transformer and see if you get similar results. If the mic preamp is working then number of possibilities for the issue are extremely limited. Inject signal after the transformer and see what happens.

Thanks!

Paul

[bobtheninja]

Thanks, Paul. I will do so Monday in a week. Left the studio for today and going on tour tomorrow.

Will report back, thanks again!

[babaorum]

Hello,

Unfortunately my ez1073 doesn't work, no sound.
I generate a 1 kHz signal into the line input and  do I have to see on all the PL11 points the same sinusoidal (oscilloscope) as the input XLR or just some of them (which) ?
Thanks for help

[hazer-drum]

Hi, just trying to understand the differences between 600Ohms terminated and unterminated on SW1 of the ez1073. Could somebody explain the reasoning behind?

[leadpoisoning]

HOPING someone can give me a hand with this (??)

well i finished my builds (2) god - at least a year and a half ago now but ever since then i've been having troubles with the 'power good' light and circuit - never had a light turn on on my one unit and although it's not totally necessary - it would be concerting to know it's turned on etc since my rack is all but inaccessible from the rear or if there are any power issues with it.

so anyway i have it on the bench now - and here's the odd thing .... there is nearly 24V being fed directly to the LED post transistor .... the 24v and 48v power are FINE and within spec - resistors are FINE and within spec - but SOMEHOW i'm just NOT getting the voltage drop across the 10K resistor that i should be (it's not doing ANYTHING seemingly - but I dont' think that's the problem. Swapped out the 550BC transistor for a new one and NOPE - SAME problem!! Checked both the circuit board in fine detail for possible bridges and checked the schematic - and there's just NO WAY for 24V to feed into  the collector - it's driving me crazy - the transistor SEEMS to be working since the 23 point something voltage at the collector seems to be coming straight out of the emitter to the LED.

Can anyone give me a fresh pair of eyes on this?? It's driving me a bit nuts ... is there ANYTHING that could cause this condition??
thanks

[Slenderchap]

If there is no volt drop.. there is no current flowing...  is the LED in the correct way round ?.. or open circuit ?

[leadpoisoning]

If there is no volt drop.. there is no current flowing...  is the LED in the correct way round ?.. or open circuit ?

thank you for the reply Colin - will get back to you on that tomorrow when i'm back and can check - having the realization that maybe i'm maybe having a premature 'senior moment' - the original LED never worked in either orientation (tried reversing) but i measured 23.XX volts at the anode so i assumed it burnt out from an overvoltage but if I'm understanding you correctly once the circuit is complete and i just have one in there I SHOULD see it drop to something in the range of 2-2.5 v?  Sorry if that seems daft to ask but it doesn't make so much sense to me ... to see that happen

[leadpoisoning]

If there is no volt drop.. there is no current flowing...  is the LED in the correct way round ?.. or open circuit ?

ALRIGHT! THANK YOU!! it was just what i needed to hear!! sorry for the needless trouble (though i'm feeling more sorry to myself for having had the units de-racked for close to a year for something so stupid!). It's quite surprising the amount of time I waste on false assumptions about the way circuits work - it's something only experience and not theory can teach you apparently. For a good thirty years I'd had load of problems with capacitors based on the assumption they unload their charge explosively as soon as they got full (based on a demonstration my dad showed me when i was little with a large capacitor attached to two electrodes going into a cup with a poor hapless housefly inside!!) ...

as for what was going on the first time with the LED -hard to say what was happening. Could have been reversed though I doubt it - or it just could have been a bad LED - who knows ... anyway - i learned something new so thanks

edit: WOW - i just found the answer to that too! turns out the 1U enclosure i was using has a tab on the bottom that magically coincides with the underside of the solder pads and one or both of them were (it seems) grounding the bottom of the LED to the case! 

[hazer-drum]

Could anyone confirm that the toggle switches are all in the engaged position when in the down position? For instance, phantom and EQ are on when down and signal is in phase when down, is that correct?

[EarthTone]

I built two ez1073 units about a year ago. They both work and sound amazing on their own, but one of them is about 5-6db quieter than it should be on mic input and 3db hotter than it should be on line input. When I run a sine wave a -20db through the 1st one's line input at "0", it measures the same on DAW input metering. When I run the same signal at -20db through the 2nd one, I get -16.9db.  Similar issues with the mic inputs, except the opposite (mic input quiter on 1st unit, hotter on 2nd unit).

I originally built two because I wanted to use them as a stereo pair for tracking and line level stereo mix warming, but I can't use them that way like this. I just wind up using them on mono sources, which is still cool, but not what I intended...

I think when I first built them I put the pins in the wrong place on the pots. I took the pins out though and was able to put them in all the right places according to the Colourbook. Could the original placement of the pins in the wrong place on one of the units have screwed up the pots? It seems like as long as the pins are now in the correct places, it should be working correctly...

I'm not an electronics wizard, I'm only a musician/engineer and just like to build stuff. Any ideas? Literally everything else about them works perfectly.

Thanks,
Matt

[Potato Cakes]

Sounds like you have some resistors mixed up at the gain switch positions or even possibly a misplaced stop pin.

Thanks!

Paul

[EarthTone]

Sounds like you have some resistors mixed up at the gain switch positions or even possibly a misplaced stop pin.

Thanks!

Paul

OK, thanks! That is very helpful. I don't think it could be the stop pin, I triple checked that those were in the right place, so maybe I messed up some resistors! It's workable as-is anyway but sure would be nice to have them both gain staged correctly.

Cheers,
Matt

[leadpoisoning]

Could anyone confirm that the toggle switches are all in the engaged position when in the down position? For instance, phantom and EQ are on when down and signal is in phase when down, is that correct?

up = off
down = on
for phantom power
for impedance IIRC down is 1200 vs up at 300

[leadpoisoning]

well if it isn't one bloody thing it's another - per an earlier post I managed to fix up my power good LED problem and managed to sew everything back up tight - though stupidly resoldered the board GND to the barrel GND pins on the mic and line inputs - I don't THINK this would have damaged anything (?) but now I can't seem to summon ANY phantom power ...

CAN SOMEONE HELP??

I have a great, strong 48V at my test pin/tab, all the way through the phantom power switch and back up to R2 and R3 (both 6K8 resistors) but on the other side of those i measure about 345mv and 0mv respectively ...  i cut both resistors out of circuit and tested and both read a very exact 6K8 ... can anyone guess what's going on here?? did i screw up my grounds somehow???

signed,
perplexed

[leadpoisoning]

also ... another semi general question - i'm using PVC standoffs and PVC screws for mounting the circuit board to the case ... I know that TECHNICALLY the drawings show a certain dependence on using conductive mounting screws to the case - will this cause me problems or undue noise? I'm not particularly noticing any ill effects but maybe it's because I have no reference to compare it to (?)

[leadpoisoning]

hmm - okay - looks like i somehow managed to short my VTB 9045 input transformer - anyone know where i can get a replacement? From Colin maybe?

[greyskull]

Hey all, apologies to resurrect this one, and I promise I have been through as many pages as I could... BUT!
Finished up my first 73 500, and, other than the phantom light which I'm fairly sure I killed removing it after fitting to wrong side of the board, It all seems to work perfectly!

Now the question is.... How does one calibrate it if the only tools you have are Pro tools signal generator and a Rapid Dmm.

Apologies for being massively thick here!

[TillM]

I build the ez1073 500-Kit for a friend.
Colin shipped fast as hell and the Kit is really, really nice.

Calibrating was a bit tricky, cause I don’t have the right equipment.
Tried it with 600ohm termination and without.
Decided to go with the 600ohm termination.
This preamp is a bang for the buck.

[realmozart]

Hi! I'm making this post as short as possible (no pun intended!)

------------------------------
Readings :
J3 - J5: 45.61V
J4 - J6: 23.98 (OK)
----------------------------------------

R6 is smoking. It smells like burnt toasts
14V is going through R6

----------------------------------------
Q2 is 0.70 from B to E
Q2 is not O.L (0.55v) in reverse polarity
The Q2 PCB screw nearest to the front is shorted with B & E
----------------------------------------

Q4 is 0.74V on the diode test mode. (between base & emitter)
Many transistors are 0.70 ish between base & emitter)
Q5 - Q8 - Q9 - Q10 - Q12 - Q13 - transistors are not O.L when polarity is switched between B&E / B&C

----------------------------------------

I suspect bad transistors and bad soldering
Here's my checklist :

• Verify solder joints
• Verify if Q2 heatsink/pads are causing short, if-else replace (seen in forum)
  
• Replace bad transistors

Is there something else I should be looking for?
Any clue/hint would be greatly appreciated

Cheers!

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