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AMS DMX 1580S problem
Old 17th May 2010
  #1
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AMS DMX 1580S problem

Hi Folks,

Having an intermittent problem with my DMX. The -15v rail keeps on blowing the 1.6A fuse when I switch on. When this happened first time I replaced the fuse, took some cards out and put them back in one at a time until it worked. I was unable to identify any problem card with this method as the unit worked OK with all of the cards in!!

It happened again today and I went through the process of taking out a couple of cards, restarting and sure enough it worked and is still working with all of the cards in.

I believe the fault lies with the -15v rail. I measured it at -15.8v so I think that perhaps when the unit is switched on with all the cards in it sometimes overloads. Having said that it has blown a 3A fuse so this might not be the case.

Does anyone have any ideas? How do I trim the -15V rail? Anyone have a bit of service information? Dave Kulka or anyone else with experience of these units please help me!!!!
Old 17th May 2010
  #2
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Radardoug's Avatar
 

The first thing to do is replace all the tantalum decoupling caps. This is probably your problem. I have had tantalums that work, then heat slightly and go short, then cool down and work again! But those caps are always a problem in old gear. Usually they just go short and are easy to find. replace with new tantalums or the solid aluminium types.
Old 18th May 2010
  #3
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Doug has given you good advice and it probably is one of the tantalums, as he suggests.

Also, you could try pulling all the audio cards, which are in the first 5 slots, counting from the left. (Be 100% certain that you note the location of each card and which way it faces.)

Try powering up with all those cards out. If the fuse doesn't blow, plug the cards in one by one (powering down each time!) until you find the bad guy.

It *might* be an opamp on one of the audio cards. There are also some caps and opamps on the motherboard, the problem might be there. Or it could be the PSU itself. But again, it's probably a tantalum cap.
Old 22nd May 2010
  #4
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Thanks for the advice guys. I'll get to work on those tantalum caps. I can actually see that a couple of them are slightly blackened so I'm hopeful that we're on the right track.
Old 7th July 2010
  #5
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Hi guys the AMS is currently working and has not acted strangely for a while now. I haven't worked on the tantalum caps yet but that is in the long list of things to do!!

Now I've had a chance to play around with the unit I have noticed that the B channel delay is not responding.

My box has 3.2s on A (with 2 x 1.6s cards) and 409ms on B.

The A delay works fine. The only way I can get B to respond is to shift the cards around or switch a few on the DIP switches on the memory controller.

I don't know what the correct DIP switch settings are for this combination of cards - can you enlighten me?
Old 8th July 2010
  #6
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Do you have the manual? There is a header on the processor card which needs to be set also. The instructions for board position and processor header are in the manual.
Old 9th July 2010
  #7
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Yes, I've got the manual. I have studied the DIP configurations for the number of cards and for number of pitch changers - all these switches are on the same board (MCB8 I think?).

I don't recall seeing anything about setting any other switches - perhaps I am missing a page? Could you enlighten me on this?
Old 9th July 2010
  #8
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Space Station's Avatar
RAM card configuration rests on the type of MCB board(8 or 4), DIP switches and jumpers on the MCB board, jumpers on the Motherboard, RAM card locations, version of the SCHIP Eprom, and jumpers on the processor board...add into that different types on RAM IC's (like 4116 that require +12 and -5) loaded on all the various different types of RAM cards that were shipped...and you have a nice mess to deal with..

3.2(or 6.4) seconds on A and 408ms on B was a common configuration so surely it was already set up that way?
Old 9th July 2010
  #9
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Radardoug's Avatar
 

Hi,
A file of the appropriate page is attached. Sorry for the dodgy quality.
David Kulka has new processor boards where this header is replaced with computer type links, much easier to set up.
Attached Thumbnails
AMS DMX 1580S problem-dmx_procheader.jpg  
Old 11th July 2010
  #10
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brianroth's Avatar
 

I hate to ask this simple question, BUT....was the original fuse a "slow blow", and is the replacement a "fast blow"?

Best,

Bri
Old 23rd July 2010
  #11
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Hi everyone,

The fuses were all slow blow.

Haven't had time to mess around with the DIP switches but I'll update as soon as I do.

Thanks for the advice so far.
Old 12th October 2010
  #12
Gear Head
 

I'm back

Hi Folks,

I'm back with a new studio and now I've the time to look into the AMS problem once again.

Today I took it out of the rack and took the lid off. Despite the fuse blowing not having occured for a long time now the problem with channel B still exists.

In dual mono operation Channel A works fine with 3.2s memory. Channel B's input registers on the meters but there is nothing at the output unless you switch to mixed output. I have swapped the input cards and this had no effect.

I also swapped the DMX9.8 pitch shifter board. One of these is different from the other in that although identical in layout and components it is called harmonizer board (the other is pitch shifter board). When I swapped these around I got some digital glitching and the unit didn't seem to function properly so I put the cards back to how they were and it was like it was before.

I cleaned all the ribbon connection points and edge connectors whilst I was at it.

I assumed the problem may lie one one of the boards where there are pairs such as the input boards and the pitch shifter boards. However, I have swapped the inputs, 12.2 DAC cards and the pitchshifting cards as described above.

I have also traced the signal as far as I can with a probe. All I can say here is that there is nothing analogue getting to the 12.2 DAC for channel B unless I activate the mix channels. Channel A's DAC does have audio when I probe at the same points.

Does anyone have any suggestions? Dave - ever experienced an issue like this before? I have attached some pictures of the switches on the 65.5 card in the hope that it might simply be these that are wrongly set.

Old 12th October 2010
  #13
Gear Head
 

Whilst I'm on the subject of AMS I thought I'd post these scans which I found when going through old manuals during the studio move:



Old 12th October 2010
  #14
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Space Station's Avatar
Seen it a couple of times could be a fault on the motherboard, that's where all the circuitry for the channel mixing is..also have you checked all the wiring underneath the motherboard?
Old 12th October 2010
  #15
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waveterm's Avatar
 

And this is exactly why I´m not dropping 2000 Euros on a DMX. Unless it comes with a warranty and service-record.

WT
Old 12th October 2010
  #16
Gear Head
 

Thought I'd also ask if my memory boards are in the right slots.

13.3 in EC14
69.1 in EC15
69.1 in EC16

Quote:
Seen it a couple of times could be a fault on the motherboard, that's where all the circuitry for the channel mixing is..also have you checked all the wiring underneath the motherboard?
Quick on the draw Space Station!

I had a probe around underneath. All I can say is the TL071 associated with Channel B doesn't seem to have anything coming or going unless output is mixed. It's very difficult to see where all of the wires go. This might be the next step.....tracing all of them.
Old 12th October 2010
  #17
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It sounds like the memory cards are in the right positions. The last slot is the microprocessor board and then the 5 slots to its left are for memory boards.

Your B Channel problem might be the pitch shifter, deglitch or a RAM board.

The pitch shifter boards need to be jumpered for left or right. If you didn't reset those jumpers when you swapped the boards, that's why things got worse. I'm out of town now but I believe the links are just to the right of the big micro processor chip. Some order DMX9 boards don't have solder pads for the links; instead you cut foils and install jumpers in a certain way.

AMS repair is tough and there are countless ways to get mixed up or make things worse! Good luck with it.
Old 12th October 2010
  #18
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Space Station's Avatar
Quote:
Originally Posted by David Kulka View Post
AMS repair is tough and there are countless ways to get mixed up or make things worse! Good luck with it.
Too true!
Old 12th October 2010
  #19
Gear Head
 

On further inspection I have both 9.6 and 9.8 pitch shifter boards.

It appears the 9.6 board for channel B has the mods as described by Howard Jones in his fax above.

The 9.8 board does not have any traces cut but does have a link from pin9 IC17 to the hole below pins 5 & 6 of IC22.

Does anyone know whether the 9.8 boards require this mod when used in conjunction with 9.6 boards?
Old 13th October 2010
  #20
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The mods Howard described are only for the 9.6 boards. I'm out of town and can't check my docs but as I recall, the 9.8's won't need any mods -- you just set the jumper for channel A or B.

I don't think the problem will be on the motherboard.
Old 13th October 2010
  #21
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Space Station's Avatar
Also check the wires running up to the switches and pots..if you haven't already..
Old 13th October 2010
  #22
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I wish mine would bloody work properly. One channel drops out, sent for repair a while back, worked for a few weeks and now its the same...
Old 13th October 2010
  #23
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Space Station's Avatar
Quote:
Originally Posted by RobJB06 View Post
I wish mine would bloody work properly. One channel drops out, sent for repair a while back, worked for a few weeks and now its the same...
You need a new repair guy
Old 13th October 2010
  #24
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Yes.... one that works for minimum wage and is damn fast.. you know anyone good heh
Quote:
Originally Posted by Space Station View Post
You need a new repair guy
Old 14th October 2010
  #25
Gear Head
 

Quote:
I had a probe around underneath. All I can say is the TL071 associated with Channel B doesn't seem to have anything coming or going unless output is mixed. It's very difficult to see where all of the wires go. This might be the next step.....tracing all of them.
Well, I've traced most of the wires. From the B input card the signal goes to the input pot and input select switch and comes back to the input card. It is difficult to trace it after it goes digital. I believe the output of channel B's DAC is fine because the card receives signal of the TL071 when the output is mixed.

Probing around there seems to be a voltage of 0.64V coming off the DAC card that goes off to the 'Regen' pot. There is no audio present at any of the regen pot terminals or at this pin on the DAC card. On the other card on the same pin there is a voltage of 0.03v and audio present. Swapping the cards around has no effect so I believe the cards must be OK.

Any ideas?

Old 6th April 2017
  #26
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Please can someone help. My 1580s has started flashing "H" on the left hand side of the display. Has anyone any idea what this means.
The unit does seem very hot on the rear end which is the heat sink. It has also stopped putting out sound now so am rather concerned.

Thanks in advance
Old 6th April 2017
  #27
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Space Station's Avatar
Quote:
Originally Posted by matsab View Post
Please can someone help. My 1580s has started flashing "H" on the left hand side of the display. Has anyone any idea what this means.
The unit does seem very hot on the rear end which is the heat sink. It has also stopped putting out sound now so am rather concerned.

Thanks in advance
It means you are just changing the pitch. Set the pitch to 1.000 and it will stop flashing. It's a normal function. Try pushing D then 0 to reset the parameters quickly..

It's worth reading the manual.
Old 6th April 2017
  #28
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waveterm's Avatar
 

It is broken. I can buy it from you for 200 euros

No seriously, read the manual. You have entered pitch mode.

Wat
Old 6th April 2017
  #29
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Thanks so much. Silly me.

I still however have no sound passing through. Upon turning the output to maximum I can hear the noise floor looping and repeated delay like sound but I have no signal passing through the unit now. Are there any procedures I can follow to find the offending board or possible reason. There are no other units to swop boards with unfortunately in my region .
Could replacing the battery have anything to do with this as it was just replaced.
Old 6th April 2017
  #30
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Radardoug's Avatar
 

DMXes are very hard to work on. David and I do a lot of work on them. Its not uncommon to have multiple faults. If you have the A channel working, one way is to strip the unit down to one channel and then substitute cards from the faulty channel. This will require you to reset jumpers on some cards. You can check memory cards by shuffling them round. If you have different length cards then the 1.6 second in the 408mS slot will still work. The 408 in the 1.6s will have a holes in the audio possibly or glitches every 408 ms.
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