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Newbie here Needs help with Simmons SDS-9 Repair
Old 20th April 2013
  #1
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Newbie here Needs help with Simmons SDS-9 Repair

Hello everyone, first time poster here and need some help from someone who knows the internal workings of a vintage Simmons SDS-9 drum synth controller/brain very well.

First the issue of what it is doing, but not supposed to:
It powers up normally and runs its self-test as it should and then goes to normal startup mode. The display shows "1" as it should and the kit number and mode selector led's light up as normal. Now, this is the part where things get strange. The trigger input LED for the third "tom" channel starts to flash and generates sounds on its own without a pad hooked up to the channel and without the autorun function turned on. Then gradually ALL the channels start to do this randomly until finally all the channel's trigger input led's are on and it pretty much generates a buzzing noice from the headphone output.

I have opened the case and found that the memory battery had leaked and failed. I purchased a new one of the same type and have fitted that to the board and now the issue seems worse and more consistant than before the battery was replaced. The other thing I found was the insulator pad that is bonded to the top of the power transformer coil had broken loose from the coil and was floating around inside. I have reattached that to the coil, but it seems to make no difference. I'm thinking that the processor chip may have shorted when this happened, but can't confirm this. There is no visual evidence of anything burned out or and scorch marks on the PC board.

I have tried "dumping" the memory and reloading the factory settings, but it also does not seem to change anything as far as what the machine does.

There is a fourth EPROM inside the machine that is NOT for the snare sound generator that is marked "SDS-9 4.0" Is this for the bass drum channel or is it an "operating system" program chip of sorts? I am concerned that it may be this chip or the processor chips, but am not positive. If this chip is the culprit and has some kind of "OS" on it, does anyone have a working one that they could read into a .BIN file for me so I can blow a new one? I don't want to take a chance with reading what is on the one in my machine as it could be corrupt, but again, not sure.

Anyone ever heard of this issue before with an SDS-9? I paid good money for this unit and need to get it working no matter what at this point. (I have no recourse with the seller unfortunately.)

I have tried contacting Michael Buchner via email, as I hear he is the man to talk to in Europe about these (besides Dave Simmons himself) but have not had a reply yet.

Basically, HELP!
Old 11th October 2013
  #2
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Castor's Avatar
 

I'm working on an SDS9 myself with a similar problem so it's likely located in the same part of the electronics. Your problem is probably not the CPU, but a problem in the de-multiplexing of the microprocessor signals. The triggers for the instruments are de-multiplexed by IC64, and that one is controlled by a combination of address decoders IC61, IC58, IC63. There's also a Digital to Analog converter that could cause the problem but in your case its unlikely the culprit. If it's only the trigger signals (random sounding of the instruments) and experience no other problems (like changing the position of the pots not having any effect on the sound) I would advice to start your debugging on IC64, if you're not really into electronics you could try to simply replace it. It's a cheap and still available analog switch chip of the type 4051 (CD4051).
Although the problems of my unit are not the same as yours I wonder if the dead battery has anything to do with it, 'cause mine also had a dead battery that I replaced myself. My debugging attempts did not reveal any problems in the de-mux part itself nor in the analog switches, and the analog output of the D/A converter looks fine on an oscilloscope so i suspect my problem is on the digital side of the D/A converter. Maybe a faulty memory chip? Address decoder? Data latch or anything else on the address or databus of the CPU. I didn't have any luck on repairing mine and consider blindly replacing parts that are related to the de-mux part. If you have any luck in having your unit repaired please let me know 'cause this could also be the solution for my units problem.

The fourth Eprom you refer to is indeed the OS. Mine is marked 6.0 or 0.9 (depends how you look at it) so I guess that's the OS-version.
Since you do not experience any other problems with the unit I'm quite confident that the program in the Eprom is not corrupt.

I hope this helps you in any way, success!
Luc
Old 11th October 2013
  #3
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Castor's Avatar
 

Oh I forgot to mention what the problem on my SDS9 was, you could check if you have similar issues on your machine.
On my SDS9 only about half of the sound control pots seems to have effect on the sound. When I check the signals of the affected channels they are always stuck at max (about 5VDC).
The effect is obvious on the RIMA PROM A/B LED at the bottom of the RIM channel. When you switch to PROGRAM mode and select the RIM channel for editing, the second pot from the bottom controls RIM PROM A/B SELECT. When you turn the pot from left to right the LED should turn on when you're on the clockwise end and off on the CCW end. My LED remains on all the time, it only dims a little when turned to the CCW side. Also some controls of the other voices are stuck at max and rotating the pot has no effect.
Looking at the circuit diagrams it's always the odd-channels of the demux that have the problem while the even channels are ok.
Old 28th October 2013
  #4
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Hello.
I had a SDS9 with almost the same problem as "LudwigDrumFan", when i select a mid tom or so for editing with knobs, the tom seem to be triggered by the led blinking.
Thump-thump-thump....
This happen on only one tom channel.
The snare channel also seem to trigger itself from time to time.
Another problem: i was unable to switch via pots the rimA/rimB: the led is always lit, i think this mean rimB selection.

Someone had the schematic diagram for the SDS9 ?

Many thanks.
Old 29th October 2013
  #5
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Castor's Avatar
 

Hi SimmonsManiac, I have the schematic diagram. I can email it to you if you send me a private message with your email address.
Meanwhile I managed to solve the problem with my SDS9. I already suspected that the dead battery corrupted the RAM of the unit. Since the unit is designed in this way that a change of potentiometer values has no effect until you "pass" the setting previously stored in RAM it could happen that there was a value in RAM that is larger than the value coming out of the DA-converter that reads the pots. Since you can never pass that value the setting keeps stuck at maximum. The effect is that some controls stick at their highest setting (like the RIM A/B selection LED that stays on).
I kind of by accident solved this issue, after failing to find any hardware problems for days on end I was in the progress of resetting the unit to factory patches when I accidentally pushed a wrong button combination. This combinations seems to be some kind of a "general factory reset" so it sets everything to factory defaults rather than initializing only the voices. After that the unit worked just fine.
*Here's how to initialize the voices according to the manual: <<WARNING this procedure will destroy all your user sounds>>
Hold down 'load' while you turn the power on. You will see a 'L' on the display. If you then press 'bank' you will see it blink. If you press 'kit' all of the kits in user ram are initialized.
*Here's how to reset the whole unit to factory default (couldn't find this combination in any manual nor on the internet): <<WARNING this procedure will likely destroy all your user sounds>>
Hold down 'load' while you turn the power on. You will see a 'L' on the display. If you then press 'bank' you will see it blink, then press 'bank' again.
The SDS9 will now initialize and play the sequence "high tom"-"mid tom"-"low tom" repeatedly. Switch off the power, switch on again, ready!
Old 26th March 2015
  #6
I know this is an old thread but I'm keen to know if any of you solved the problem with the low Tom triggering?
Mine does exactly the same thinG.
Also, the mono output is quite noisey on mine.
Old 22nd April 2015
  #7
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Bump I'm also interested in any repair information as I'm looking to buy a ads 9 shortly. Anyone know where to buy knobs,schematic etc. Thanks in advance.
Old 4th July 2015
  #8
I have 4 or 5 spare knobs you could buy off me?

I had mine serviced a while back and it's fault less, He said he just cleaned everything out and it solved the triggering problem.
Old 28th January 2016 | Show parent
  #9
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Castor,please..can you help me.?.i need the schematics of [email protected]

[QUOTE=Castor;9548087]Hi SimmonsManiac, I have the schematic diagram. I can email it to you if you send me a private message with your email address.
Castor,can you help me ,please.?
I need the schematics of sds9.
My email:[email protected]
Thanks.
Old 25th March 2016
  #10
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Hi guys, I'm wondering if anyone can help me, I need the schematic of the sds-9 too. I just got one from eBay with a dead snare and dead noise circuits in the toms. It would be a great help to have the schematics.
I see the thread is a few years old so I don't want to PM anyone without prior permission. Warm regards... :-)
Old 16th April 2016
  #11
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Lui_s's Avatar
I have bought sds9 without pots the top row and the lower row (sensitivity and volume) and I want to learn face values to restore. Pots- 20kOm, 100kOm??? Tell please what will approach? Somebody has the scheme on sds9?
Not my English native language.
Old 16th April 2016 | Show parent
  #12
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Lui_s's Avatar
Quote:
Originally Posted by merryprankster View Post
Hi guys, I'm wondering if anyone can help me, I need the schematic of the sds-9 too. I just got one from eBay with a dead snare and dead noise circuits in the toms. It would be a great help to have the schematics.
I see the thread is a few years old so I don't want to PM anyone without prior permission. Warm regards... :-)
Try to make reset that it is described above (#5). toms and snare didn't work for me too, after reset everything was restored. And still it is necessary to replace the battery.
Old 4th March 2019
  #13
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Ok, so here I am years later posting on my original post. To answer one of the older posts about if I ever got the issue resolved, the answer was no. I replaced practically every component on the board eventually over a 6 month period and never got it to work properly. I gave up on it and sold it off for parts, moved on to an SDS-7 instead with much success.

Since then, I had sold all my vintage Simmons gear.

Recently though I got another SDS-9 brain that had the same issues that my original one had for cheap $$. Several years on I know a bit more about electronics repairs and this time I replaced ALL the electrolytic capacitors in this unit and to my surprise, it fixed all of its issues. Moral of the story.....replace all of those electrolytics and don't listen to any of the so called "experts" that I was listening to way back when I started this thread. Those "experts" had no clue as to what they were talking about. One of them told me to replace ALL of the capacitors on the boards, not just the electrolytics. They also told me that the issue was with certain IC chips in the mux/demux circuits. All of this was wrong/bad advice.

So here we are six years later, and my advice is replace the electrolytics on the main board and the power supply board. Clean all the pots, switches, and jacks, and replace the memory battery soldered to the main board with a new one and let it rip. As I said, this one did the same thing my original did, and this time, this is all I did and it works like its supposed to.

Hope this helps some that were in the same boat I was in a few years back.
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