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 Forum index » DIY Hardware and Software » Thomas Henry designs
The GM Voice
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richard s



Joined: Jan 28, 2005
Posts: 76
Location: uk

PostPosted: Sat Mar 08, 2008 12:09 pm    Post subject: AVM duaghter boards?
Subject description: for busted buchla
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Hi

I have a Buchla Lightning 2 which features a AVM GM daughter board with a Kurzweil soundset - the output of the board dropped by 80% so I am looking for a replacement in the hpe it will fix the problem - anybody have a clue where to look for such a thing? The only info I have is that the board says AVM General Midi rev 3 - I guess it must be 10-12 years old as that is when this unit was manufactured.


do all the daughter boards you are discussing here have the same connectors and specifications? Are they interchangeable? I am wondering if I may take this opportunity to upgrade or try out some different boards - of course I don't know if the Buchla software would be very happy about it - the unit does have an extra midi input intended for computer editing of the soundset so in theory I could do that too

excuse my vagueness I only realised that such things as daughter boards existed today when I had a look in my Buchla because it stopped working

grateful for any pointers

Richard
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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Sat Mar 08, 2008 3:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Richard:

Can you post pictures of the board, (particularly if it has a 26 pin connector)? We might be able to take a quasi-educated guess if this daughterboard is compatible with the GM Voice boards.
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richard s



Joined: Jan 28, 2005
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PostPosted: Sun Mar 09, 2008 4:47 am    Post subject: Reply with quote  Mark this post and the followings unread

ok here is one side


P1020923.JPG
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P1020923.JPG



Last edited by richard s on Sun Mar 09, 2008 4:50 am; edited 1 time in total
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richard s



Joined: Jan 28, 2005
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PostPosted: Sun Mar 09, 2008 4:48 am    Post subject: Reply with quote  Mark this post and the followings unread

and here's the other


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P1020924.JPG


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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Sun Mar 09, 2008 5:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Richard,

It seems the connector is identical to a GM Voice connector. If I were a betting man, I would bet that it is compatible. It is probably worth a try to get a GM Voice daughterboard and try it out.
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richard s



Joined: Jan 28, 2005
Posts: 76
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PostPosted: Sun Mar 09, 2008 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks antman,

and the sources for these things? ebay and thrift stores I guess, but anywhere else?

Richard
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Dan Lavin



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PostPosted: Sun Mar 09, 2008 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Richard.

one more thing before you spend cash on a new daughterboard, try putting line level signals into the Lightning's mating connector, pins 20 and 24 to make sure it is not the output stage of the Lightning that is the problem....although it is doubtful if both channels are out at the same time ...unless they share a common op amp....then that would be the first place to look, I guess!
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richard s



Joined: Jan 28, 2005
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PostPosted: Sun Mar 09, 2008 6:03 am    Post subject: Reply with quote  Mark this post and the followings unread

ok that was my next question,

is there any way of telling what is 20 and 24? I have no numbering on the mainboard or daughterboard.... I do have J13 at one end of 26 pin the mainboard

typically would the entire D/A path going out to line level be on a GM daughterboard? Or would there likely there be some kind of op amp circuit on the mainboard? obviously the buchla is not typical of anything but it would be useful to know if I am probably on the right path.

I can ask Mr Buchla for the exact answers - but its much better if I know what I am asking, and from experience its sometimes its quicker to try and sort these kinds of things out myself

Richard
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State Machine
Janitor
Janitor


Joined: Apr 17, 2006
Posts: 2747
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Audio files: 24

PostPosted: Sun Mar 09, 2008 7:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
is there any way of telling what is 20 and 24? I have no numbering on the mainboard or daughterboard.... I do have J13 at one end of 26 pin the mainboard


If you take a peek on the solder side of the board, the square pad is pin 1, the one below that is pin 2. Just keep counting in that way .. The pin next to 1 is 3. This, that row gets all the odd pins. Hope that helps

Also, I see a number of transistors over near the end where pin 26 is. Do a diode check on all those transistor junctions to see if they have not been damaged ........

Bill
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richard s



Joined: Jan 28, 2005
Posts: 76
Location: uk

PostPosted: Sun Mar 09, 2008 8:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I really appreciate this guys, as you can no doubt tell I have no idea what I'm doing. But blowing up the Buchla would not be good at this point so I need to be super clear.

If I want to test the mainboard audio left I touch a line level wire to 24 and the other wire to what else - 23?

and to test the left one wire to to 20 and the other to 19?

Richard
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Dan Lavin



Joined: Nov 09, 2006
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PostPosted: Sun Mar 09, 2008 6:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Richard:

Yes 19 and 23 both connect to the same analog ground, so they would be your ground connection. Pls do go thru this whole thread from the beginning as a number of your questions have been addressed already.
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richard s



Joined: Jan 28, 2005
Posts: 76
Location: uk

PostPosted: Tue Mar 11, 2008 2:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay, it was a bit confusing. almost inevitabley the buchla is wrong way around so the relevant pins were different. But I did it without killing myself or the buchla

The level coming from the buchla is much lower than if I touch the line to the jack plugs... so i think I can safely assume my daughterboard is okay and it is the op amp/s on the buchla that have gone down - bummer.

However I am happy to discover the daughterboard and will be very interested to try some others in there to see if they work and how they sound

thanks for the thread, which has such great information in it, and for your help
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Dan Lavin



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PostPosted: Wed May 21, 2008 8:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Has anyone had any luck with the db50XG equivalent boards from the Shanghai ebay guy? I see he's reduced his price to US$25 each.
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fonik



Joined: Jun 07, 2006
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PostPosted: Wed May 21, 2008 10:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

antman49443 wrote:
Has anyone had any luck with the db50XG equivalent boards from the Shanghai ebay guy? I see he's reduced his price to US$25 each.

i bought two from him. they are definetely not in mint condition but they are working.

BTW i will breadboard my motherboards circuit soon to get it fixed. i am currently trying to close all open projects before starting a new one!

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matthias
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Dan Lavin



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PostPosted: Sat May 24, 2008 10:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Mathias,

Thanks for the feedback, but I see out Shanghai friend has now increased his price to US$40!?!

Anyway. Here's a cheap one from a guy in the UK:
http://cgi.ebay.com/YAMAHA-DB50XG-DB50-MIDI-XG-Daughter-Board-Sound-Card_W0QQitemZ170221579249QQihZ007QQcategoryZ3701QQrdZ1QQssPageNameZWD2VQQcmdZViewItemQQ_trksidZp1638Q2em122
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Silas



Joined: Apr 27, 2008
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PostPosted: Sun May 25, 2008 7:20 am    Post subject:   Reply with quote  Mark this post and the followings unread

Just a heads up since I'm not going to bid on it anyways..

There's a DB50XG on ebay UK for around 4 $ ATM.. Auction ends 1/7..

Includes box, instructions and original package that had Cakewalk Express 3.01 for Windows (on floppy with instruction booklet) and a "Bonus CD" with Midi clips and a demo version of visual arranger.
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fonik



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PostPosted: Fri Jun 27, 2008 3:25 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik Posted: Thu May 22, 2008 5:51 am wrote:
BTW i will breadboard my motherboards circuit soon to get it fixed. i am currently trying to close all open projects before starting a new one!
Laughing
dan, i just wanted to let you know, since you took care of it and kindly tried hard to help me with it. very appreciated.
i am not quite sure if you remember the problem, though - long time ago. however:

yesterday i bypassed the regulators on my motherboard and i still got the voltage drop to about 7V on the 12V rail as soon as i plugged in the DB50XG.
that led me to the conclusion that my power regulating circuitry on the motherboard was not causing the problem (at least not alone).
i then finally managed to breadboard the circuit according my redrawn schematic, leaving off the power regulating circuitry (and the midi thru circuitry). everything worked fine.
so i eventually come to the conclusion that the motherboard itself is faulty. there may be a short or bad connection somewhere i still have not detected? that would explain the protecting 22R resistor on the 15V input running hot and finally smoking and burning.
however i will rework the PCB and try again... at least all my three (3!) DB50XG boards are fine.

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Dan Lavin



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PostPosted: Fri Jun 27, 2008 5:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Matthias,

Thanks for the update. Yes, I remember this well as it was quite a "head scratcher!" Also, I just bought one of the boards from our friend in Shanghai. If I were smart, I would have had it shipped to my company's office in Shanghai, but I didn't think of it until this morning. He did drop his price back down to US$25 each at least.

I do periodically peruse the soundcard section of ebay looking for more daughterboards for other E-M Forum members, but we seem to have hit a long dry spell (except for our friend in Shanghai).
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fonik



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PostPosted: Mon Jun 30, 2008 2:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

i still don't get it.

i breadboarded the GMvoice using a laboratory PSU for the 5V rail. everything worked fine.

i then powered the GMvoice from +/-15V instead of +/-12V, since the db50xg regulates it down onboard to +/-5V anyways (+/-12V is just what you get inside PCs). everything worked fine.

as soon as i replace the laboratory PSU by a LM7805 regulator, the voltage on the positive rail (12 or 15V) drops by approx. 20% and the LM7805 gets hot.

the power consumption is about 120mA on the 5V rail and about 270mA on the 12V rail, which seems reasonable to me.

are both LM7805 i tried faulty? i will order new ones tomorrow.

any additional comments on my private waterloo?

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Uncle Krunkus
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PostPosted: Mon Jun 30, 2008 3:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

This may be the solution, it may not, I'm not 100% sure I know this stuff, but,......

You're using an LM7805 on a +15V rail right?
That means there is about 10V across the LM7805.
You said the current draw on the 5V rail is about 120mA.
That means the LM7805 is dissipating 10*.12 or 1.2W
According to the data sheet, with no heatsink, max power dissipation at 0C is less than 2.5W.
So if your +ve rail is a little up or if it draws just a bit over 120mA, and the ambient temperature is not 0C then you'll be getting close to problems. Yeah?
So I'd check the current draw, and put a little heatsink on it.

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Uncle Krunkus
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PostPosted: Mon Jun 30, 2008 3:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just realised the same argument applies to the DB50xg except that, being a piece of PC hardware, it's probably even more sensitive to being run on 15V as compared to 12V, as it might use SMD regulators, less heatsinks, and fly closer to the limits.
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fonik



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PostPosted: Wed Jul 02, 2008 10:30 am    Post subject: Reply with quote  Mark this post and the followings unread

good points, absolutely.
OTH the regulator even gets hot when powered from 12V, and i mean it gets really hot within seconds. even the protection resistor (22R) on the positive rail gets hot. we will see what happens with the new regulators tomorrow... i will keep you posted.
thank you very much, my friends.

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Dan Lavin



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PostPosted: Thu Jul 03, 2008 12:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

My life is now complete:
This project has been posted at the "Make" website:
http://blog.makezine.com/archive/2008/03/diy_general_midi_synth.htmll[/url]
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Blue Hell
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PostPosted: Thu Jul 03, 2008 12:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

antman49443 wrote:
My life is now complete:


Nope, one URL left to fix here Wink

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richardc64



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PostPosted: Thu Jul 03, 2008 3:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Nope, one URL left to fix here Wink


Simple. One too many l's.
http://blog.makezine.com/archive/2008/03/diy_general_midi_synth.html

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