Feeler: an "Eee-Zzz" christmas present...ez1073 and ez1073-500

Managed to get them back up and running, OTs are fine. I bought a transistor mica for the 2N3055 and just cut the end off so as to maintain circuit continuity (bottom plate is still in contact with the screw hole that is part of the circuit). I think the original problem was a short at the 2N3055 transistor through a bolt touching the bottom of the chassis. I'm using a bolt with a lower profile head. I put a 2N3442 in instead of the 2N3055, seems good so far. Still trouble shooting one of the pres. I'm maintaining 130mV over the 1r resistor but it sounded like a component started failing somewhere when switching the eq in and out? Time to check my soldering and other components in the circuit.

Hello,

I've just finished two units.  One works perfectly and sounds great! The other, well...

When I power the unit on, all voltages are correct, but there is a large hum when I listen to the output of the preamp.  Then when I tap the the input transformer with my finger, I hear a huge huge sound, like the transformer was microphonic...?

Does anyone have any idea on where to start troubleshooting?

Best regards,
C_S

maybe one of the pad isn't well solder (the thermal pad are hard to solder sometimes with that big groundplane). did youtest all your ground point to check for continuity, etc?

Thanks deepdark!  I'll check now  ;D

Super happy, my pair are 100% from the first power-up. Thanks for offering this great kit (mine were from the partial kit era which meant for a bit of scavenging, the least fun part)

Andy

Andy,

Glad it worked first time..... partial kits were from years ago..... all the painful scavenging is no more...... we have gone one stage further with the ez2254 as it contains the chassis and everything else as well...

Colin

Colin,

I just wanted to thank you for making the ez1073 available to us.
Mine is in heavy use since I built it and I couldn't be happier.
Please check the link below for an example.
http://groupdiy.com/index.php?topic=59704.0

Regards,

Christian

HI there! Is there a build guide that's been consolidated to a single thread somewhere on GroupDiy? I'm searching, and I can't seem to find it.  My main concern is wiring.  The PDF colourbook download is pretty comprehensive, but I'm a little confused on wiring.  I haven't bought the kit yet, as I like to look over all the info/instructions that I can before I get in too deep! Thanks kindly - jack

Hi all - I'm almost through building this wonderful kit.  The colourbook was super helpful and logical.  Lots of thought went into making it a simple project for dummies like me.  I have a few questions:

My kit was missing the 510r resistor, so I linked a couple together to get 510r.  Is that going to be a huge issue? 

I lost a couple of the greyhill pins.  They are so freaking small...I just cut the leg off of some unused caps.  Is that going to be a problem?  They aren't made of titanium or anything, right?

I'm also slightly confused at how to wire the power transformer to the ground/IEC inlet.  Does anyone have a photo of theirs? I'm in the USA, btw. 

Thanks kindly and i'm really excited about this great project.

Jack 

Hi all - I'm having trouble with my z1073 kit.  Well, I assume there's trouble.  I'm through building it and wiring it and I'm in the "calibration" stage.  The very first thing the colourbook says to do is measure the V across J5 and J6 spades.  I'm supposed to get 24v.  I get like .587 something DC.  I'm pretty sure I wired the AC inlet correctly. (I'm in the US).  I get 120v on the money. 

Can anyone help me? I have no idea what the problem could be. 

Thanks!

Here are some photos:

Well, as it turns out I accidentally swapped the Voltage Regulators.  Now all is fine! The Mic Pre sounds good but I have an awful buzz when I flip the EQ channel on.  Any suggestions?  I read about folks grounding the XLR directly to the chassis, but the buzz is only when the EQ section is on.  Seems like it would be buzzing on just the mic pre as well. 
Any hints?

Just finished up my ez1073. A few problems!

-Midband freq selector is @ off, almost no audio passing
-Constant boost  when mid freq is choozen but whay higher freq's and nog
-Mid boost/cut pot acts way to extreme, when turned down audio is gone and does like tons of boost!

-HF Shelf /LF Shelf seems to be ok.

who knows where to start searching, i already  checked for bad soldering

Well that's fixed by now, a damaged path on the pcb by the mid gain pot.

but the output of the unit waaaay to hot!

even with the line in at -20 db gain, the output is still more then the original signal
same with mic inputs, way to hot and distorting the output even with gains all down.

all right, fixed it!

there was a short between analogue ground/mic/line switch and the 2nd gain stage R80
i've cut the traces and made a bypass, all fine! sounds amazing.

Hi everybody,
I'm pretty new to the forum and have just finished soldering a EZ1073.
Coming to the calibration process, I measured the right voltages for the 48 V supply and the 24 V power, but as I try to adjust R20 to get the 130 mV for the minimum output distortion I cannot get either than 50 mV, turning the screw to both ends...
Trying to feed the mic input with a dynamic mic yelded no result, no output at all even with high gain settings - no buzz or other noise, actually. I've checked the soldering with a magnifying glass and believe there are no evident shorts or misplaced components, but hard to be sure about it..
My electronics skill is quite basic, I've tried fo feed the input with a signal generator (about 1V p2p sine wave) and catching the signal with an oscilloscope, I have been able to follow it through the trafos and the gain switch until the beginning of the first gain stage (R67, I guessed) but then no more...
Anybody could give me some advice about where and what to check first?
Many thanks in advance for the help.

Pietro

Are you measuring from both sides of R26? I origanally measured from ground to one side, which will gov you different readings...

Hi all,
I've recently bought one of Colin's kits and love it. I've been thinking I would love to add a fader to the unit though to have more control over the output, ride levels ect... My thought would be to build a NEVE switching unit, minus the sends and busses to patch in after the pre. I've looked all over but haven't found what R value NEVE used for their faders, as it's not on any schematic. The other option would be to replace the trim knob with a fader before the output section, but again, need to find what value the fader would be. Does anyone have this info by chance? Working the math has never been my strong point!
Many thanks!

Hi Glazer,
Thanks for the hint. I'll do a check as soon as possible.

Pietro

Hi,
I did the check suggested by Glazer, the reading from both sides of R26 to ground gives 23,6 V (being a 1 Ohm resistor I guess it is correct, from the schematic I believe it is a resistor placed there to have a point to measure the current flowing towards the amplifier stages): the same value I get reading across the 24V "spade" terminal to ground.
The voltage drop across R26 is more or less always 39,6 mV, either turning the R20 trimmer.
The only thing I'm able to think is that there is a short somewhere in the signal path, I'll do a triple check..
Any other hint?
Many thanks,
Pietro

Bit of a random question, but does anyone know if the Neve 8816 knobs would fit on the ez1073-500?
Thanks!