Newbie builds GroupDIY 51X rack

[mulletchuck]

Volker, those dsub thru-hole pins are definitely connected to the XLR jacks.  only the metal case doesn't have a DB25 hole cut into it.  Why no provision for that??

 

[bruce0]

What is the easiest way to add a DB25 pin out to this, so I can hook up at least 8 channels to a patch bay?

- It looks like there is a 50 pin connection to ribbon.

@piano... I did that, check out this http://www.groupdiy.com/index.php?topic=47653.0

If there is enough interest in the PCB I will do a group buy and get some more of them made.  I only had 4 made, and I could use 2 more myself now.

They work in one of two ways:  Either you can make 2 db25's have 8 connections, or you can spread all 11 connections over 4 DB25's.  Both input and output of each slot covered is on the "TASCAM" standard DB25 analog connection (see thread).

You do have to punch the case or drill and dremel it, but it is not too hard, and I have put an actual size PDF template up.

If you want me to start a group buy thread, PM me.

Bruce

 

[mulletchuck]

Brilliant, especially if using a patchbay that has dsubs on the back instead of TRS's

 

[piano]

Thank you Volker for the quick response!

I just found someone here who is selling a KIT for the 25 pin Tascam style in and out - for those who are looking as well.

There is no SubD25 connector option in this project.
Build it like it is.

Thanks
Volker

 

[bruce0]

Piano,
I think the original intention might have been to allow a DB25 connection alternative to all the XLR's.  I think the original design included one which was abandoned.  I made a PCB to DB25 connection on the GDIY Rack, and I am going to do another run of those, as a group buy (my cost plus postage) if there is interest post over in that thread http://www.groupdiy.com/index.php?topic=47653.0

There are other uses as well for the 50 pins:
  You could add a meter bridge to the top 3 slots to meter the bottom 8 slots (I did one of these)
  You could implement a mixer in the top 3 slots though it would be tight (radial did one in the workhorse rack).
  You could pretty simply create a little pushbutton passive "sum"er which could be interesting using those 50pin connections
  I think with a bit more work you could do some sort of routing (connect this input to that output, etc) to allow you to assemble virtual channel strips out of your modules.

So many projects... so little time.

 

[qmp audio]

  You could add a meter bridge to the top 3 slots to meter the bottom 8 slots (I did one of these)

Id love to see a photo of that.

 

[bruce0]

http://www.groupdiy.com/index.php?topic=47820.msg604198#msg604198
Pictures are early in that thread

 

[Timh]

Hey guys. I finished my rack today and I checked the levels with my DMM and I was getting weird stuff, then I realized I wired up the 7-pin jack totally wrong. So I just rewired it and I'm getting the same weird levels:

pin12(+16v)- I'm getting +34.9v
pin15 (+48v) getting 105.3v
pin17 (+24v) getting 52.7v

Weird that I'm only getting readings on the "+" pins. That's gotta mean something, but I'm new to this so does anyone have any idea what's goin on?

I should mention that I checked the levels of my PSU to do the trim pots when I finished it and everything seemed to be fine.

 

[gemini86]

If those voltage readings are for real, you just blew up a bunch of caps...

Disconnect everything, check everything again at the PSU board.

 

[bruce0]

I am with Rodney, but also I wonder if you don't have some sort of grounding problem, and you are maybe measuring some floating levels, (or you have some floating levels connected together so you are summing to the 105V with 48+32+24=104... pretty close).

Still, same advice as Rodney.

Check the PSU levels at the rack end of the PSU cable (checking continuity of ground to chassis, and chassis to chassis)

Then check the proper wiring of the 51x, 
1) continuity of each PSU connector pin to the proper pins on the backplane connector.
2) Make sure that there is NOT continuity between any DC voltage pin on the rack, and ANY other DC voltage pin or ground on the rack (they should all be unconnected  With the possible exception of the Chassis and Ground connector which may be connected depending upon how you have the ground chassis straps).

 

[bruce0]

By the way, if all you have done is "stack" the various voltages by your wiring, your caps are probably fine. But don't plug any modules in till you fix it!

 

[Timh]

Maybe I should have asked this before...

mhmmm....what exactly am I supposed to be touching the black pin of the DMM to when I'm checking levels on the rack? Sorry...just bought my first multimeter 2 days ago when I finished the PSU. I'm learning.

 

[Timh]

Hold on a second. I just turned the knob on my DMM the opposite way and everything is reading the correct numbers. I think I was just measuring all the pins wrong on my DMM. Holy shit. I SAID I'M STILL LEARNING. Well I'm glad everything's working right. I just completed my first real project with almost zero problems! YESSSSS. Cheers.

 

[bruce0]

Step by step:
Turn off the PSU.
Turn the multimeter to ohms and set it to beep when there is continuity.
Touch the cables connectors, be sure it beeps.

Touch the ground and chassis pins with the red and black probes.  It should beep, because ground and chassis should always be connected at the PSU.

With that verified, turn the multimeter to DC Volts (and if it is not auto-ranging to some level over 48 volts (probably 200 Volts)).  (On some older models you would use different plugs on the multimeter, but on modern one you just need to turn the dial to volts.)

Turn on the PSU.

Make double sure the multimeter is on volts

Touch the black to Ground or Chassis (they are connected) and the red to each terminal in turn +16, -16, +24, -24, +48 they should read those values.

 

[Timh]

It's definitely reading right. BUT how close should the readings be? I'm getting some .5 overs and stuff. Is that a problem?

 

[bruce0]

There are pots on the board for each voltage.  You can adjust the voltages and it is easy to get them closer than .5V.

The rack and most modules would run fine within .5 volts, but I always try to put it spot on.

 

[Timh]

Okay. On the build aid Jeff said he would run some .7 high. I was just wondering if I should calibrate them again.

 

[bruce0]

Oh, I did just look in the build thread (and I did see the suggestion that you run the rails .7V high.)

So, .7V on both rails gets dropped on the diodes that usually sit on the card to prevent them getting damaged if someone reverses the voltages on the rack.  So if you run .7V high, the card circuits run at 16 or 24.

Most circuits are not that sensitive to voltages, so even if the designer that dropped those diodes into the circuit didn't take them into account it probably works fine. 

There are cards that will operate slightly differently with the higher voltage, usually (but not always - think step up voltage converters) better.

 

[Timh]

That all kind of sounds likes Spanish. The little tenths of volts that are running high are alright....right?

 

[bruce0]

right.