8 Channel, 3U NEVE 1073 completed

[Whoops]

-What is the EH10023-2  and EK20032    that is on the BOM?

It's not a component not worry about it
it's clearly a section, like "a) Pre Stage 1 (N-V)" and "b) Pre Stage 2 (N-V)" and "c) Driver Stage (A-M)"

 

[Chrome Heart]

Hi, guys   

I planning to make a 2ch 1290 mic pre, but first i want to ask you somethings:

-What is the EH10023-2  and EK20032    that is on the BOM?

-If I want the phantom power, i need to take a JLM kit "go between",  and a PSU that give 48v and 24v, right?

for phantom power you need a PSU with a 48V rail output and a 24V rail output for the circuit but you dont need the Go Between.

Just read the Assembly documentation on this project all the info you need is there , Martin explains how to connect the phamtom power On/off with led indicator, you need 1 switch, 3  resistors and 1 LED

I dont know what those two items are on the BOM, one thing is certain, they're not in any of my builds. I would just ignore those entries as I think they are not "parts". As far as the go between from JLM, I would suggest using one. The pad and phase reverse are indispensable as far as Im concerned.  And while your at it, buy your PSU kit from him, its great.

 

[-nemo-]

When do you think PCBs will be back in store?

http://www.diyrecordingequipment.com/products/ez1290-preamp-pcb

 

[MicDaddy]

Who knew these would pass audio at barely over 3V  :

Fun discovery  8)  what is the negatives of running something low V?

 

[Whoops]

Who knew these would pass audio at barely over 3V  :

Fun discovery  8)  what is the negatives of running something low V?

Low headroom? Distortion? low gain? narrow frequency response?

 

[MicDaddy]

From the sounds, probably all of those things.

Breakup seemingly increases with decreasing voltage.

 

[-nemo-]

Hi everyone!
Can somebody tell me what is the grid/dimensions between all the pins of the grayhill switchs?
Or at least, how long there is between the most distant pins. (the line of 12 and the three row)

Many thanks!

 

[madriaanse]

-What is the EH10023-2  and EK20032    that is on the BOM?

-If I want the phantom power, i need to take a JLM kit "go between",  and a PSU that give 48v and 24v, right?

Hello,

EH10023-2 is simply a part designator for the support circuitry surrounding the amp stages.

EK20032 is the gain switch

Boards should be back in stock in 3-4 weeks.

If you only need 48V (no pad/phase) you'll need a PSU with 24/48 and just follow the build manual on how to wire it to the mic input.

M.

 

[tomas1808]

Is anyone selling the Grayhill switch in the US?  I need a bunch.

 

[madriaanse]

You can special order them from Mouser.com but it's just as easy and usually a bit faster to order from audiomaintenance.com

 

[tepachsekach]

I decided to draw this EZ1290 schematic in multisim software for circuit simulation.  Link: https://s3.amazonaws.com/EZ1290/assembly6.pdf

What results can i expect?


Are there any specifications for EZ1290.
In wich class works ba283am output amp.
What do you think of this results  and why.

I really what to build one, but i have to be sure they work. thx

 

[Potato Cakes]

Is anyone selling the Grayhill switch in the US?  I need a bunch.

I thought that I had bought mine from Mouser and they had them in stock, but that was over a year ago. It seems any US supplier that I know of is currently out and there is a 6-8 week lead time. Even a couple of the Asian market suppliers are also out of stock.

I'd be curious if Colin had some currently available.

If you're in a pinch, you could use this:

http://www.mouser.com/ProductDetail/Grayhill/71BD30-03-1-AJN/?qs=ls7QRyWmRk6%2FTCx8BJ2R6g%3D%3D&gclid=COr-jZe46swCFVQ2gQodTs8D5w

BUT, as you can see, you have to solder wire from the lugs to the board, which will affect how you place and mount stuff. But you could at least proceed with your build.

 

[TDRS]

I've been a long time fan of this site and have built a couple of Jim's EZ1084s and bought 12 of Martin's EZ1290 and built 8 so far and have really enjoyed the process. I have read this whole thread several times and really marvel at the knowledgeable contributors here.

My 2 EZ1084's and 6 of my EZ1290's went with no problems. Only minor things that with the help here I was able to solve. However I'm having a problem with two of the EZ1290s.
All of them were build using the BOM and by the book.  As I said 6 of them are working perfectly but two have the same problem. As I click up the attenuator and pass the 50db to the 55db gain into the next gain stage, 2 N-V, they actually go down 5db then go up.  So if I'm clicking up, it's 45db, 50db, 45db, 50db, 55db and so on.

I thought I must have made the same build mistake twice and started looking at the resistors in the second gain stage after the switch and looking for solder bridges. I touched up all the solder pads, Then I checked all the voltages of both stages and the Tant's for DC on the ground. All the transistors voltages check out as do the Tant's and my resistors in the whole switch section are fine. I basically followed the troubleshooting guidelines expressed here several times. I assumed  I should be looking around the switch and the second gain stage but also have read that odd things can be caused by problems with TR3 ( loose screws )and or the output transformers though they seem fine. I'm really stumped and could use a clue of where to concentrate on troubleshooting. Odd that it's the same problem on 2 different modules. Has anyone had an experience with this and can you point me in the direction to look.?

Thanks.

 

[TDRS]

Still struggling with 2 of my 8 ez1290's.  At first I suspected it was a resistor or solder bridge around the switches that caused my 55db position to be the same as my 45db position on the switch. After comparing a good module with these troublesome ones I see that I'm just not getting the gain I should be on the second gain  stage.  I have triple checked all the values of the resistors and caps. I've replaced the Tant's on the second BA183. The voltages are perfect on all the transistors, not sure if I should replace those next. I can follow a tone all the way through with a scope and the sine is clean. But as I move the attenuator past the 50db setting the 55db setting is more like 45 and the gain goes up from there but not anything like it does for a working module. I've swapped out to a known working output transformer and it's the same. It's so odd that these two modules have the same problem and the other 6 have blasting gains above the 55db setting. I was sure I had made the same build mistake twice but I'm not finding it.  Things I'm left thinking about is did I burn out a poly cap while building and would that have this effect? And very unlikely I did it twice.  Do I have a funky transistor despite the voltages being fine? But two of them in the same place on two different boards? I can't believe it's the switch and certainly not two of them. I just keep coming back to the resistors around the switch particularly R20,21,22,11,29 and 30, right? But all check out.

I could sure use a suggestion for the next troubleshooting move if this rings a bell for anyone.  Thanks.

 

[useme2305]

faulty grayhill switch? if you're good at desoldering, swap out the grayhill for one from a correctly functioning channel and see what happens.

 

[Whoops]

Do I have a funky transistor despite the voltages being fine? But two of them in the same place on two different boards?

If you have the correct voltages on all the transistors I dont think transistors are the problem at all.

Things I'm left thinking about is did I burn out a poly cap while building and would that have this effect?

How have you done that? I never burned a Poly Cap
Can you show pictures of your build?

I can't believe it's the switch and certainly not two of them. I just keep coming back to the resistors around the switch particularly R20,21,22,11,29 and 30, right? But all check out.

How much heat did you apply to the switch? normally the problem would not be the Grayhill switch,  but has you burned a Poly cap maybe the iron you are using might be too hot. For Grayhill switch pins I use a really thin tip 12w Soldering Iron.

- Print the schematic and follow continuity between all components from beginning to end
- Re Check everything for possible solder  bridges

 

[TDRS]

Thanks for your help,  I really appreciate it.  Since my last post I've had a chance to really give these a going over. To re-cap I have 2 out of 8 modules that when the attenuator is set to the number 8 position I have low gain.  In this position input is routed to the number 2 BA183 at "U" out at "P' through R20, R21, and R22 and onto "U" of the first BA183.

So I suspected a solder bridge around the switch and resistors,  a misplaced resistor or build mistake on the 2nd BA183.  I was also mindful that this exact problem is happening on two modules so what ever build mistake I made I did twice exactly the same.

First thing I did is look with a jewelers loop and all the solder joins for cold solder or bridges. I re-heated everything and confirmed visually and with continuity everything was OK. Next, even though I measured each resistor as I placed them I checked them over many times. I even replaced R22,11,21 and 20 at one point. All seems fine. Then I then looked at the 2nd BA183, and that when I posted last. I didn't burn any poly caps but know they are fragile thats why I asked.  Since, I've confirmed the voltages and all the component are fine.  Using a scope and tone I followed through both BA183s checking at every stage,  all fine.  I then injected tone into "U" (C8) and the amp is working great.

Last night just to be sure I lifted "P" at C15 of the 2nd BA183 and twisted  3k9, 3K3, and 2K7 resistors in series and alligator clipped them from "P" of the 2nd BA183 to "U" of the first one.  It worked as it should and by using the alligator clip I could move up and down my chain of resistors and increase and decrease my gain.

So, what does it mean?  The switch?  In fact 2 out of 8 switches?  What are the probabilities of that?  But I suspected it as well and wrote AML asking if he has had problems with switches like this.  Waiting to hear back.

I'm loath to try to de-solder a good switch to test as removing a multi pinned component has it's own risks and I don't want to have 3 non-working modules. So I could remove the switch and try to test it's continuity, or order a couple more and just replace it.

Or if I'm missing something here I could sure use any suggestions.

Thanks again for the help.

 

[Whoops]

I dont think it's the switch,
but you could replace the switch on one of the bad channels by the switch of one of the Good channels!

Easy enough

 

[TDRS]

Yes, I agree, it seems very unlikely. I bought and populated 12 of these for use with drums. Then I purchased 4 AML kits and racked 4 at a time. Then I bought 4 more and this is my second set of 4. The first set went flawlessly. This second set of 4,  of which two have a problem. That left me with 4 populated boards but no switches or transformers yet.  I ended up removing the switch from the bad module. I figured if it's good I'll put it on one of my last set of 4 populated boards. I did and the problem followed the switch, or the same problem exists on several boards. So, yes, I guess to conclusively eliminate the switch I'll move a known good one to one of the bad boards. If it's not the switch I need to find a problem in my build that is common to at least 3 boards so far. The probability of making the same build mistake 3 times that result in the exact same fault seems almost as low as a bad switch. I'm sure it's stupid human error, I'm just not seeing it……yet.

 

[Whoops]

Yes, I agree, it seems very unlikely. I bought and populated 12 of these for use with drums. Then I purchased 4 AML kits and racked 4 at a time. Then I bought 4 more and this is my second set of 4. The first set went flawlessly. This second set of 4,  of which two have a problem. That left me with 4 populated boards but no switches or transformers yet.  I ended up removing the switch from the bad module. I figured if it's good I'll put it on one of my last set of 4 populated boards. I did and the problem followed the switch, or the same problem exists on several boards. So, yes, I guess to conclusively eliminate the switch I'll move a known good one to one of the bad boards. If it's not the switch I need to find a problem in my build that is common to at least 3 boards so far. The probability of making the same build mistake 3 times that result in the exact same fault seems almost as low as a bad switch. I'm sure it's stupid human error, I'm just not seeing it……yet.

Yes I understand.
Do the Good switch swap, and them you will be sure.

At least if it's a switch problem it's easy enough to sort out