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

sr1200 said:

Why would you be afraid of calibrating the 48v?  Is it worth cutting a corner to damage an expensive studio mic?  put the voltmeter on it and adjust as needed...

Click to expand...

Am on it right now actually! 

The one thing I'm not really sure on how to do is to calibrate the output. I googled on how to measure voltage but am not sure where to connect the 0V reference for the multimeter...
Once calibrated, is it supposed to cut the signal when the trim is completely down?

Thanks in advance guys!

1] 48v calibration: To measure and adjust the 48v you should put your voltmeter probes as shown in Rob Gould's drawing.... before you have made any adjustment you will typically read about 46.5v anyway.... so condenser mics will work fine without any adjustment at all.... you will certainly not damage a microphone with undervoltage.

[The voltage which the microphone gets will actually be significantly less than 48v anyway because of the 6k81 resistors in the 48v feeds.... for example, a U87 takes about 0.8mA.... when this is drawn through the 6k8 resistors they will drop the voltage by about 6 volts... so the U87 only actually gets 42v..... none of that is relevent to this issue I just thought it interesting to point out].

2] 24v regulator: I expect that any of the 7824 (1 or 1.5A) TO220 style regulators would be fine.... the one supplied is an ST electronics L7824CV.... (Farnell part number 975-6213, Mouser part number 511-L7824CV ... I presume)

3] Output trim control:  The output trim pot only drops the output level by about 9.5dBu... if you wanted it to cut the signal off completely you would need to change some resistor values. (it is not affected by the Output Bias Trimmer... that sets the output transistoir bias).

4] Smoked regulator; If the 24v regulator has smoked then there must be a short circuit somewhere (or you have it in backwards).... check all your diodes are in the correct way round, check that the body of the 2N3055 is not shorted to the Agnd (screws are a bit big for the pads really so they can cause a short to the ground plane).... when you have removed the regulator to replace it just measure the resistance between the 24v tab and the Agnd tab.... if you get a very low resistance (say 1 or 2 ohms) then you have a short circuit somewhere..... maybe a solder splash.

Colin
www.audiomaintenance.com

Thank you for the reply.  I guess the EZ1073 isn't easy for some people (pointing finger at myself).  I finished the second unit that i have and turned it on.  I put my probes on the +48v and the Agnd and get 56V!!  I tried to adjust the R10 Trimmer and it doesn't do anything.  Can anyone explain how to measure across the R26 resister for measuring the output?  I know someone else had the same question. 

Thanks again Collin, I appreciate you chiming in. 

Dan

If adjusting the 48v trimmer does nothing then it suggests you have made a mistake.... check every single component is in the correct place and you have soldered every pin and there are no solder shorts.

"How do you measure the voltage across a resistor" ??? ... you put the red probe on one end and the black probe at the other.... is that what you are really asking ?

You are not measuring the "output" by measuring across R26.... you are measuring the amount of current that the unit is taking.... by doing that you can get a good approximation of the adjustment required for the output transistor bias trimmer R20...... bvecause R26 is a 1 Ohm resistor, the voltage across it (in mV) will be equal to the value of current through it (in mA).....

Before adjusting R20 you will probably read about 80mV across R26.... adjust R20 until you read 130mV.... that will do.

[You should in fact be measureing THD+N on something like an AP to make the adjustment but that is too much for DIY.... adjusting the current will be fine].

Colin
www.audiomaintenance.com

Collin, thanks again for chiming in.  The whole Voltage regulator burning out has me second guessing everything I am doing.  I just want to make sure I am doing it correctly.  Thanks again. 

Dan

New guy here.  I decided to get 2 EZ1073 kits after I had done a couple of guitar pedal mods and builds, mic mods and recapped an Yamaha PM1000.  After I got my rack cases from ddt, I put everything together at the end of last week.  I double checked everything before powering up but I'm having a couple of issues that I can't get sorted out:

EZ1073 A:
Makes crackley/static noises
R10 and R20 doesn't seem to do much
No +48V at the XLR when switch is engaged
Q4 gets hot and smells

EZ1073 B:
Also makes the crackley/static noises, but mostly only after I've flipped either the +48V or impedance switches
Line Input doesn't work
Very low level when EQ is engaged.  (Initially I actually thought it didn't pass any signal when engaged but it does, just at an extremely low level.)

LED lights up and apart from Q4 it doesn't seem like anything else is running hot or smoking.  I made very sure that all polarity-sensitive components were the right way around.  I also checked every component on both boards against the colourbook again today and I can't find anything I did wrong.  Also went over the boards with a magnifying glass to check for shorts.

When measuring at +48V and Agnd, both boards measured around 46V.
When measuring at +24V and Agnd, both measured around 23.5V.

I would appreciate any advice immensely.

Hi Colin,

Seems that you've stopped proposing the ez 1073 full kit on your website.
Are you out of stock or is it finished ?

Cheers

Domi

would like to know as well.
thanks!

Just built a pair of these, one sounds fine, the other has a bit of hum when the EQ is engaged but I don't have all the metal standoffs fitted to it's case at present. I'm waiting for those to come, probably needs all those fitted for proper grounding anyway!!! 

I using the finished one with Guitar & Bass  through my trusty DI / Reamp unit, a Little Labs Red Eye, tried the Line input at first but I think it sounds even better through the Mic input, the Red Eye sends a Mic level signal so that's the probably best match.

My very old knackered Gretsch Country Gent sounds fantastic, plenty of warmth & sparkle & that's without even micing a amp, the Fender Jazz Bass sounds great, a real recorded DI sound without much effort at all.

It even makes my cheapo mics sound good, I really need a decent mic now!!!!

Thanks Colin for the great kit!!!!!  8)

domi62 said:

Seems that you've stopped proposing the ez 1073 full kit on your website.
Are you out of stock or is it finished ?

Click to expand...

We don't have the time at the moment to do these full kits... it just takes too much time to kit.

There are still a handful of PCB's left so it may become a "partial" kit consisting of PCB, wound components, pots and switches etc....  that would not take so long to do....

Colin
www.audiomaintenance.com

That's a good news !!!
I would be in for 2 or 4 partial kits depending on price...
Does the partial kit includes the front plate+bracket or only PCBs + a few components ?

I will take 2-4 pcbs depend on the price )) i want to have them home ))

yes how much for a pcb?

I would also like to put my flag in the ground for 2 pcb/partial kits for the 1RU version, I was quite to see the kit has disappeared from the website.

I would be interested in 2-4 pcbs or 2partial kits.

Interested in 1-2 partial kits.

It is now back on as a "Partial kit" (until the PCB's are all gone)..... contents are listed if you click on its photo.

Colin
www.audiomaintenance.com

Oh the sales pressure... ACT NOW!!!!  yeah... i bought in

me too, major case of the "snooze you lose" as now the parts hunts begins.....

Couple of questions Colin;

1) is there a substitute for the BC184C? it's showing obsolete/discontinued at all the usual suspects including Farnell. Can one rely on the info here http://www.groupdiy.com/index.php?topic=48279.msg609709#msg609709 ?

2) some parts, like the heatsink, once one finds the substitute, newark numbers are cheaper in USA/Canada, but not stocked....is Newark and Farnell the same outfit or are they parallel businesses, I'd hate to have to order some parts from the UK and others from NJ?

3) the BOM notes many electrolytics pitch as .1 while the ones on the audiomaintence store are .25 pitch.... if this could be verified please

TIA Andy

BC184C's can be got easily from Ebay.... Farnell do list an alternative.

The heatsink is pretty standard (lots of different manufacturers/suppliers)... just get the drawing from the Farnell website and pick an alternative brand.... Farnell owns Newark (and CPC).

BOM list is in Inches... Store is in mm.... 0.1inches = 2.5mm

Colin
www.audiomaintenance.com