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

[sr1200]

no I grounded the pins of the XLR to the board and grounded the separate chassis pin on the XLR to chassis.

 

[Aaronrash]

no I grounded the pins of the XLR to the board and grounded the separate chassis pin on the XLR to chassis.

Oh ok that makes sense! And you say yours is whisper quiet right? No issues whatsoever

 

[sr1200]

If you start cranking the gain to +60 theres noise on it, but the neve desk i used years ago had about the same "hiss" to it when it was cranked.

 

[Aaronrash]

If you start cranking the gain to +60 theres noise on it, but the neve desk i used years ago had about the same "hiss" to it when it was cranked.

I've worked on a few neve consoles too but never noticed any hiss. My AMS Neve 1084s I sold a few months back could be cranked up to 80 and I would start hearing room noise and outside traffic at that point! but still never noticed any hiss.

Hopefully the noise specs are similar on the ez1073

 

[sr1200]

Hiss was probably more mic self noise than the pre.

 

[Aaronrash]

When I get to that stage of my build I will do a measurement with only pin 1(ground) of the XLRs wired to the PCB ground and then additionally wire the XLR grounds to the chassis and make another measurent and see what I come up with.

Maybe it will make a difference maybe not but I'll post all my findings here to help future builders. I'll measure with and without a mic.

 

[Ninuz]

Hi,
I just finished my first of 4 channels of EZ1073.
Im having problems with my unit blowing fuses. I use 220-240vv and 100mA Slow blow fuses.

Just to get it clarified.
I connect the brown transformer cable to my Live and the blue to the Neutral and the Violet and Grey are only connected to each other.
The green yellow is connected to the star ground on the case and to this point is also connected the ground from the IEC socket and the Earth from the PCB connection.

Are these connections right?

I also tried to unsolder the 2 white and 2 red secundary cables and when that is done the fuse doesnt blow. With that I suppose the power transformer is working as it should and is wired as it should or am I wrong?

Really appreciate some expert help so I can get all the units upp and running



 

 

[mulletchuck]

Ninuz, draw a schematic of how you have it wired on a piece of paper and post it. 

 

[Ninuz]

Ninuz, draw a schematic of how you have it wired on a piece of paper and post it. 

Thanks for youre answer. Ill get a drawing as soon as possible but here is a picture also....
On the picture there are no heat sinks mounted but there was when testing.

 

[Ninuz]

Ninuz, draw a schematic of how you have it wired on a piece of paper and post it. 

Here is a picture of the drawing.

 

[Slenderchap]

That is correct for 220/240v operation..... it should only take about 15mA from the mains so a 100mA Slow Blow should be OK

Do you have a bench power supply with current limiting outputs ?

If you can.... power up your unit using the DC feed spade terminals and limit the bench power suply to about 400mA at 24v..... see if it power up OK..... this way you will know if the fault is in the audio circuit or power supply circuit.

Also check that the case of teh 2N3055 isn't shorted to the analogue ground plane..... the screw pad is only just big enough for the shakeproof washer.

Colin Adshead
www.audiomaintenance.com

 

[Ninuz]

That is correct for 220/240v operation..... it should only take about 15mA from the mains so a 100mA Slow Blow should be OK

Do you have a bench power supply with current limiting outputs ?

If you can.... power up your unit using the DC feed spade terminals and limit the bench power suply to about 400mA at 24v..... see if it power up OK..... this way you will know if the fault is in the audio circuit or power supply circuit.

Also check that the case of teh 2N3055 isn't shorted to the analogue ground plane..... the screw pad is only just big enough for the shakeproof washer.

Colin Adshead
www.audiomaintenance.com

I been putting some time aside to try and get 2 of my units to work but still get blown 100mA fuses.
The 48v rail works fine with the rail connected to the secondary wires from the main trafo as long as I don't have the white 24v cables connected to the PCB.
I got a bench power supply to Feed the 24v tab limiting to 400mA as Colin recommended and then I get the power led glowing.
Feeding the 24v rail I get a current draw of around 100mA without adjusting the BIAS Output.
Yesterday I tried connecting Line audio through both units one att a time and both units seems like they work as they should including the EQ section. This was done taking 48v from the main trafo and 24v from the bench supply.
I measured the white cables ( sec trafo ) and get around 27v AC
From this I suppose the problem is somewhere between the main trafo and the 24v tab. Looked for shorts and components placed facing the wrong side but can't find anything wrong there.
Any suggestions anybody? Places to measure or other tips?
Would really like to get them racked up so I can start using them.

Thanks in advance!

 

[Sillen]

I don't get my preamp to work when putting in  a mic in it. No sound coming through it even with the mic trim maxed out) Allthough, if I send something out of my daw into the preamp sound is actually coming through it but with a heavy distorted sound.. The EQ section works fine and the power section too, so we probably know that there's problem in the audio section.. A tech had a quick visual inspection of it but couldn't see anything that looked wrong.
It does seem like 2 pins that shouldn't make continuity of the vtb9045 are actually making continuity. But not visually so they have to be connected in the circuit or something. Could this affect the whole gain stage though? Is the signal always passing the mic transformer first even if you connect to the line input? :O
Anyone have any idea?

 

[Aaronrash]

Hey Colin,

Do you remember the part number for the 100nf ceramic capacitors? Several of mine cracked during soldering.

 

[Aaronrash]

I replaced the ceramics.

I tested the mic input hot and cold for continuity and the fluke is beeping. This is happening on both units, is this normal? I'm not getting continuity between the cold and hot line inputs, only the mic inputs. Upon closer inspection I'm guessing that it's happening somewhere in the transformer windings.

Here's a update of my build. After studying the original 1073 schematic religiously, I've replaced all the caps in the audio path with vintage polystyrene caps, tantalums and NOS fairchild BC184C's. Thanks to everyone on this forum for the help. I can't wait to power these up!

 

[Sillen]

Okey I discovered that there's a problem with my output Bias now. I only measure 28.3 MV Dc across R26 and it doesen't change in value when turning R20 ( the output bias trimmer ). I may have damaged the semiconductor D3 with my dmm at some point could this be the problem? Edit: Wasn't the diode..

No one have any clue why the output is so low? The tech I left it to didn't leave it back for like 3 months and said he lost his wife and children and couldn't help me for a year at least. And there's no other technicians that want to help me for a fair price down here really.

/Isak

 

[Sillen]

.

 

[Ninuz]

Sorry

That is correct for 220/240v operation..... it should only take about 15mA from the mains so a 100mA Slow Blow should be OK

Do you have a bench power supply with current limiting outputs ?

If you can.... power up your unit using the DC feed spade terminals and limit the bench power suply to about 400mA at 24v..... see if it power up OK..... this way you will know if the fault is in the audio circuit or power supply circuit.

Also check that the case of teh 2N3055 isn't shorted to the analogue ground plane..... the screw pad is only just big enough for the shakeproof washer.

Colin Adshead
www.audiomaintenance.com

I been putting some time aside to try and get 2 of my units to work but still get blown 100mA fuses.
The 48v rail works fine with the rail connected to the secondary wires from the main trafo as long as I don't have the white 24v cables connected to the PCB.
I got a bench power supply to Feed the 24v tab limiting to 400mA as Colin recommended and then I get the power led glowing.
Feeding the 24v rail I get a current draw of around 100mA without adjusting the BIAS Output.
Yesterday I tried connecting Line audio through both units one att a time and both units seems like they work as they should including the EQ section. This was done taking 48v from the main trafo and 24v from the bench supply.
I measured the white cables ( sec trafo ) and get around 27v AC
From this I suppose the problem is somewhere between the main trafo and the 24v tab. Looked for shorts and components placed facing the wrong side but can't find anything wrong there.
Any suggestions anybody? Places to measure or other tips?
Would really like to get them racked up so I can start using them.

Thanks in advance!

Sorry for nagging all of you
Anybody with any thoughts on my problem?
Have all 4 units with the same problem so Im wondering if the problem is in the PSU Wire'ing. They are all blowing fuses immediatly when the main transformer is conected to the main power outlet ( 240v ). Fuses used 100mA slow blow. 
Att this point I even tried to feed current with my Lab Power Supply all the way back att the + point on the bridge rectifier on the 24 DC rail. I get the unit working powering this way with the 2 white transformer wires diskonekted. All the units are taking around 100mA in current. With the Lab power supply I get no indikations of problems.
Att the same time I do have the 2 red wires on the 48 rail connected to the main transformer and getting the "power ok LED" to light upp.
Any thoughts?

 

[Slenderchap]

If it is working all the way from the +ve of the bridge rectifier it would suggest that the problem was the bridge rectifiers.... if you have removed them then you could test them with a diode tester.

Colin
www.audiomaintenance.com

 

[Ninuz]

Thanks Colin. Ill try that on one of the units to see if thats the problem.