Access-312 Build Thread

[3nity]

Heres what the ground wiring shoud look like.
Thanks.

 

[3nity]

Heres one more thought.
Those boards are from this year batch.
They are double layer with pads on top .

Did you made sure to have the transformer shield non touching those pads??
Thanks.

 

[bieckmusic]

Thanks so much 3nity and Harpo!!

shorted input transformer to pcb pads, duh!!  Works so much better now, wow awesome!!

thanks for the help, and Merry Christmas!!

peace and love,

Greg

 

[3nity]

really that was it?
Was the transformer touching the pads?

LOL enjoy them now!

 

[bieckmusic]

yes, shorted out so the can of the input transformer to the pads on the PCB.  Fortunately I left the pins long enough I just raised the transformer a bit and it works and sounds awesome!!!  I used all cinemag transformers 2 channels with CMOQ-2S and 2 with the CM-3301.

Merry Christmas, and thanks for putting this project together!!

bless,
Greg

 

[3nity]

good to know its allright!
post some pix of your build!

 

[3nity]

Alright guys.
Make this fast.

4 x Access-312 boards left.

I cant tell if a new batch can happen!

 

[bieckmusic]

Anyone know why my pad switches don't work?  all 4 boards work and sound amazing, very clean.

But all 4 pads make a small click sound when pushed but don't reduce the gain.  My hunch is I have the wrong switches.

 

[emtee]

Anyone know why my pad switches don't work?  all 4 boards work and sound amazing, very clean.

But all 4 pads make a small click sound when pushed but don't reduce the gain.  My hunch is I have the wrong switches.

Solder bridges?

 

[3nity]

Bieckmusic.
Are you sure you got the right resistors?
If its the same switch as on the 48V and phase i dont think its the switch.

 

[Spencerleehorton]

Hi 3nity,

I'm up for a few more pcbs if you have any left?

Regards

Spence.

 

[3nity]

Sorry for the late response Spencer.
I dont have any left but im gonna send for another run next week.
New batch should be here around this day next month!

Thanks.

 

[Spencerleehorton]

Hi 3nity,

Ok great put me down for 2 possibly 4, how much are they again?
The four I've got off you before sound great with some Sowter transformers I managed to get, just gotta finish of my 16 mic pre section with more API and SSL pre's then my last build is some kind of summing mixer / monitor section.

Regards

Spence.

 

[soundsactive]

Hey all!

So a few years ago i bought 4 boards. i had to fight my way through PSU issues and seemingly everything in between (luckily with enough time to still make a bund of great records!). I'm revisiting this project to finish it up and start using it.

I have 2 pairs of press, one pair is stuffed with Classic API/Ed TXs and SSL Red Dot 2520s. Those work and are passing signal. Phantom works great.

The other pair is full of Cinemag TX and Gar-2520s. I'm not even getting the tiniest bit of signal through them and phantom is inconsistent. Here's some photos of where I'm at with them and let me step you through my trouble shooting thus far:

I made sure there is enough room under the transformer so pads aren't shorting it out.

Voltages at DOA pins are 15.7/-15.7 respectively.

Re heated and checked for cold solder joints.

2 of my pots were shot, so I have been shorting Gain 1&2 to eliminate another problem until I get new pots.

DOAs have all been swapped and tested on working channels and work fine.



The problems I'm having seem identical on both of the Cinemag boards, so I'm sure it's just some stupid **** up like "don't jumper this" or whatever. Any help would be great, it would be wonderful to get this off my bench and in the rack where it belongs!

 

[toneboner]

"the only reason you need to jumper C8 is when installing an 150K resistor on R6-R7.
But given the fact that RC is specific place for that resistor you dont need to jumper R6-R7 or C8."

...just guessing tho

 

[3nity]

@ Soundsactive.
2 things to watch out here: Make sure your transformers dont touch the top layer pads if they do you're screwed.
Id clean those boards with Alcohol and a brush...just to eliminate residues.

Good luck.

 

[Harpo]

The other pair is full of Cinemag TX and Gar-2520s. I'm not even getting the tiniest bit of signal through them

sure silence with the transformer secondary winding shorted out by your jumpers.

and phantom is inconsistent.

relates to the psu whos name you kept a secret and further don't tell what load is connected to this psu (maybe 1 or 2 or ... 4 preamps with or without phantom switch enabled and condensor mic connected...).

2 of my pots were shot, so I have been shorting Gain 1&2 to eliminate another problem until I get new pots.

setting the DOA to max.avail.gain, so be aware of a feedback/overload problem when the jumper shorts are removed. Usual min.gain setting would be a same value as feedback resistor (10K?) instead.

 

[soundsactive]

thanks for the pointers

I'll try removing the jumper at C8.

@3nity, if they touched for a short period would they be fried? i raised the transformers last night to see if that would help but no good. i'll clean it tonight for sure.

@harpo, I apologize for the lack of information. while sipping on coffee this morning I was trying to remember everything I had checked out over the past few days. the PSU is the DIYPartSupply PSUniversal. The PSU is only powering one of the troubling channels at a time, to isolate potential current draw issues. When I attach the PSU to the two working boards, 48+ is fine and consistent, however on the Cinemags boards it is not, which leads me to believe that it is a isolated issue to the individual boards. Voltages on PSU test fine, +/- 0.05V.
And I further apologize, but when you say i shorted the secondary wirings on the transformers, are you referring to the ratio jumpers or something else?

 

[Harpo]

the PSU is the DIYPartSupply PSUniversal. The PSU is only powering one of the troubling channels at a time, to isolate potential current draw issues. When I attach the PSU to the two working boards, 48+ is fine and consistent, however on the Cinemags boards it is not, which leads me to believe that it is a isolated issue to the individual boards.

R1, R2 (close matched) and R11 are rated for at least 0.5W and correct value ?
C5 has an at least 50V rating ?
When the PSUniversal has to supply 4 mics simultaniously, at least increase both caps values at the voltage doubler.

when you say i shorted the secondary wirings on the transformers, are you referring to the ratio jumpers or something else?

R6/7 in series with C8 is a provision for a zobel network across the input transformer secondary winding. Parts values depend on type of transformer and selected ratio setting. From your pic both parts are jumpered in your build, shorting out the transformer secondary. Just cut one of those jumpers in order to interrupt this short.

 

[soundsactive]

well i'll be. 3 years and that does it, thanks! i'm going to replace r1+2 and see if that will get it together. thanks for the help!