WEIRD DCX ISSUES HELP!!!!!! - diyAudio
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Old 4th February 2013, 08:44 PM   #1
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Default WEIRD DCX ISSUES HELP!!!!!!

O's here goes.. no one has been able to help so far...so PLEASE??? Suggestions??

I have 3 DCX 2496"s ranging from date codes 1105, 0303, 0308, the newest one being the 1105

2 stock, 1 modded (1105) with all the goodies from Pilgham (Didden active I/O , clock, and regs)

my didden kit is the REV2 board, I see the rev 3 board has a groundstrap!!!!
and direct digital input to mainboard via neutric aes xlr/canare da206 cable and neutric aes spec plugs. The ground /shield is left open in the dcx since it don't have a grounding schem and I use a Vlink196 (transformer output) to send the digital signal to the dcx.

the stock unit exhibit none of these problems!!!!!!!! C input for digital on stk dcx

problems listed below pertain to the MODDED DCX only
unit is set to LLMMHH

1) ANALOG INPUT passes thru the DCX with NO POWER ON>>!!!
ALSO, I can mute the dcx with power on and it passes signal to the amps at about the - 24 db level. It will not completely mute nor will it drop the output below about the -30 db level. IF I POWER OFF the dcx the signal still passes thru to amp. This occurs with any analog input, single ended or balanced, but the balanced is much higher level output obviously.

2) the dcx boot up with BUZZING on analog input B. When I first power one the DCX the Input B channel shows an input level signal at appx 3 leds lit up. and output on channels 4 and 6 respectively. If i turn on amp(s) the buzz come through loud n clear.. sound like a ps ground but other weird higher order harmonics or signals too. I'll try to scope it n take picture it would help. Only in channel B does this and only if its left on analog input..once I switch input to aes/ebu then back to analog the noise goes away. then the unit seems to function fine.

3) DCX just goes Whacko, for lack of better term.
screen goes blank, output start popping thru speakers and led's on INPUT A and OUTPUT 1 start blinking at full scale.. power reboot or a good whack clear it up ..sometimes.. sometimes I have to let it sit a while to power it up. THIS IS A BIG PROBLEM

4) grounding issues with analog inputs
depending on source or input to the analog I get severe buzz , hum or noise thru the outputs.
single ended or balanced. Since I have no idea how the Didden board is grounded or how his pseudo balanced circuit is implemented I have no way to chase down ground loops or other such nonsense. this is the one reason to use balanced inputs, it cuts out this crap if done correctly. this may have sumin to do with issue1, but I don't think is related to issue 2


I have been thru the schems on the dcx but have no clue as to why the modded dcx has these problems and the stock does not!!!!!! If i knew some potential causes I could do some more in depth trouble shooting. I can tell you I have swapped power supplies and also the main screen board,(with led n pushbuttons) all to no avail.


HELP ANYONE??
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Old 4th February 2013, 10:34 PM   #2
tomtom is offline tomtom  Slovakia
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disconnect and reconnect all internal connectors, especialy power. Or better with unit on try to gentle shake each one and look what is goin on. I has very very strange behavior from bad power connector. There was cold joint on some pins.

But no power passthrue is very hard to explain with this.
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Old 5th February 2013, 01:40 AM   #3
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MAN THAT'S WHY I AM ASKING..i've wiggled n jiggled n shook n banged n arghhh

SHORT OF RESOLDERING EVERY JOINT I HAVE WIGGLED N JIGGLED everything..

that analog pass thru is really bugging me.. with no power on..

i wish i could find single pin connector to solder cable to too those ribbon cables suck!!!!!!
Im leaning toward ps issue i think the DIDDEN mod way over taxes the stock POS PS but when i check voltages they are with a few 0.th's of spec.
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Old 5th February 2013, 03:27 AM   #4
Pano is offline Pano  United States
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Ditto the ribbon cable. I've heard reports of that before. Bad power or ground can cause wacky problems. No idea on the pass thru - leakage via power rails?

BTW, the stock digital input is A. C is the switchable line/mic. Unless there have been some changes I haven't seen.
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Old 5th February 2013, 06:37 AM   #5
Davey is offline Davey  United States
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Quote:
Originally Posted by IMSTOOPID View Post
Im leaning toward ps issue i think the DIDDEN mod way over taxes the stock POS PS but when i check voltages they are with a few 0.th's of spec.
Complete speculation.

Clearly, you have a malfunctioning unit that needs troubleshooting. You don't appear to have the necessary skills to accomplish this, so best to find a good technician in your area and let him/her take a crack at it. I believe all the schematics for the Didden modifications are available on his site, so it should be straightforward.

Cheers,

Dave.
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Old 5th February 2013, 05:36 PM   #6
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I would say you should keep in mind that this is a *Behringer* unit, meaning every place a corner can be cut, it will be cut. Biggest problem is that the metal cladding of the circuit board is as thin as it can possibly be, so it is extremely easy for foils to crack, not just near connection points, but anywhere that there is the smallest bit of mechanical or heat stress on the board. And anywhere that anything has been soldered more than once is likely to start peeling off the board and crack foils. Other point is that Behringer just loves to use cheap relays run at over their voltage rating, causing the coils to fail. As for supply stress, you need to measure for increased AC on those dc lines to see if there is overstress, as it won't show until it's severe on dc. Then there's all those hundreds of cheapest possible caps, chips, etc., so you basically have to suspect everything. If you try to hotrod a Ford Fiesta, don't be surprised when it collapses in upon itself.
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Old 5th February 2013, 05:55 PM   #7
Davey is offline Davey  United States
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For a Didden modified unit, much of the original Behringer circuitry is removed. (The entire rear assembly with all op-amps, etc, etc.) Only the DSP board remains. The alternative circuit board is then installed.

I'm not sure, but I suspect the modified unit probably places less load on the stock power supply relative to the original configuration. Jan could no doubt answer, but I suspect he will probably (smartly) avoid this thread.

Cheers,

Dave.
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Old 5th February 2013, 07:33 PM   #8
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DIDDEN DOESNT HAVE A SCHEMATIC..#1

#2 I AM am quite capable of trouble shooting and I own a scope( tek 2225) and know how to use it. schematics help I don't want to reverse engineer his board..

#3 yea duh behringer sux duh..I'm just looking for suggestion or to see if anyone has has similar problems before I check every damn connection and component on the board..I've checked all the major stuff

I have 3 stkc dcx PS and they all load test differently.. I can't see any significant ac on any of them when load tested on a 100 ohm resistor..

problems 1 and 2 are biggest issues.

the reason i bring up power supply is the voltage drop in use of the PS is greater on the modded unit vs stock unit.( same setting .. swap PS between units)
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Old 7th February 2013, 02:48 PM   #9
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UPDATE.. 1 AND 2 NOT FIXED

3 AND 4 WAS POWER SUPPLY ISSUE
THE STOCK SP SUCK..ESP THE NEWER ONES.
WONT GO INTO DETAIL BUT .....IHAVE (2) PS IN MY UNIT NOW.

NOW TO FIGURE OUT PROBLEMS 1 N 2
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Old 27th February 2013, 01:38 AM   #10
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OK #2 FIXED

bad connector on the PS cable...

ok now to # 1 and the biggest problem...
and I know that is not a PS issue.. because I can disconnect all the
PS and circuity from the board and it still passe signal..and I got huge amounts of buzz when using my preamp..so its definitely a grounding issue.
anybody got schems or any idea of whats going on with the didden board?
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