Hello to forum and I need some help with a Drum Machine build

[Psqwall]

Hello All,

I have been a big fan of Dave's youtube channel and I decided today that I should join the forum. It seems like the perfect community of people to ask my questions about a drum machine build I have been trying to do for a few years. I am a novice beginner at electronics and I just rebuilt my lab scarily to the specs of Dave's lab. I actually soon will be posting on my youtube channel a video of the new lab and the workbench builds. Anyhow enough of my yappin' on with my request for some help. I am gonna post a link to the tape op forum here which has photos and an explanation of my project. I hope it's not against the rules to point folks to another forum but I have had minimal help there and I figure this is a better place for the advice I seek. Basically I took apart a Viscount Bahia combo organ. I have had it in pieces for almost 3 years now and my goal is to re house it and modify it into a stand alone drum machine/ 1 octave keyboard sideman type unit. It is an old 60s organ and I am hoping to do something cool with it. This project is a bit ambitious but I think eventually I can come up with what I want and I think it will teach me a lot.
Here is the link
http://messageboard.tapeop.com/viewtopic.php?t=58508&highlight=

Where I am at now with the project is:
I pulled the boards out from my attic where I was storing them (I know not a smart move) dusted them off and plan to try and re connect all the boards
to retest that the unit still works as it was intended. However I am doing this with out a schematic and the only pictures I have of the boards all connected to each other are the ones pictured on the tape op forum post. I do think the connections should be obvious being that they are all molex and size referenced.
I plan to make a youtube video of that attempt should provide some laughs if nothing else. I will post it in this thread when I have it up.

I would love to hear what you all think of this project.

Bit of a long winded first post but I thought it was a good way to say hello to all

Thanks
P

[IanJ]

Hi,

I think you are quite correct in your next move.....i.e. re-build the organ and start documenting.
First stop a basic wiring diagram, including all the pcb's even if you don't think you'll need them later.
Then get your meter/scope out and start understanding how it works, focus'ing on the DM section. Start putting signal names to wires.

Over the years I've re-packaged all sorts of gear, including some audio stuff...........great fun!

Ian.

[PA0PBZ]

Looking at the number of connectors on the drum pcb it looks like this is not a standalone drum computer, there are just too many connectors... Ideally you'd want a power connector, a control connector and an audio out, but it looks like there are at least 5 connectors on that board. I hope you saved the cables, that would make putting it together again a lot easier, and then, as above, start measuring and documenting.

[Psqwall]

Wow thanks guys
very useful advice already! I knew this was the right place for this dialog. I do have all the wiring and all the parts pictured. All the wiring is coming off the main piano keyboard and yes is all connects to the main PCB. I am going to need a lot of help once I get this on the bench to take my measurements. I am a new proud owner of an analog oscilloscope and I am about to purchase the haiko iron Dave recommended along with the multi meter in that video he did about tools for beginners. So I am trying to use this project and a few others that are less involved than this one as my starting point to learning my new test gear.

I will post a video when I get the unit onto the bench for its first power up after being in pieces for so long.
 

[Psqwall]

Ok guys
I got the organ back on the bench and all molex connectors connected but I am stuck on which place to connect the power supply. I made a video showing what part I am stuck on now. I have 4 connectors that goto the power supply and I do not which ones go where? Once I can figure that out I can power this up and see if it still works and then the real challenge begins. Anyone have any idea where these connectors plug in on this board?

http://youtu.be/xjQESGKbc04

[PA0PBZ]

Hi,

Please post a picture of the front and back of the power supply board, and while you are making pictures do also one of the 4 connectors.

[Psqwall]

Here is 2 pics of the power supply board and the two sets of connectors in question. My guess is that the yellow and brown connectors go on the posts closest to the power transformer and the multi colored ones go on the posts further away from it on the end of the pcb. Let me know what you all think?

[PA0PBZ]

Hi,

Unfortunately you didn't post a picture of the back of the power supply, but at least something is clear now.
You are right, the 3 brown cables must be the -15 volt, the black one is ground and the 2 yellow ones are +12.
It would be a good gamble to connect the other cable the same way, but since there is nothing written on the pcb on that side it would still be just a guess. If you want to be sure post a picture of the back of the pcb.

[Psqwall]

ok when I get home I wil flip the pcb and take a picture.
My guess still is to place the yellow and black closest to the transformer and the multi colored furthest away. What is the worst thing that can happen if they are hooked up wrong and power button is turnned on ? Blown fuse? or worse?

[PA0PBZ]

My guess still is to place the yellow and black closest to the transformer and the multi colored furthest away.

Yes, that is what I tried to say in my last post. See what is printed on the pcb.

What is the worst thing that can happen if they are hooked up wrong and power button is turnned on ? Blown fuse? or worse?

Worse... FUBAR! Or if you are not familiar with that, you could destroy it beyond repair. Think about what that unobtainable component that is supposed to run on 5 volts would do on 12 volts?

[Psqwall]

Ok I did a little trial and error and got the thing to power on again. You were right about the position of the connnections however now I have a new problem. I am only getting sound from the bottom keyboard the top row produces no sound. Also the drum machine appears to have a short in the tempo fader no drum sounds play until I hold a finder under on of the solder points under the pcb under the tempo fader. I will do a video and post it so you can see what I am talking about.

[Psqwall]

further help required
two videos one showing the thing sorta working and then after tinkering
a video showing it not getting sound

http://youtu.be/4GFf8s3MrCk

http://youtu.be/AKzYkiPMj5c

[Psqwall]

Oh no
I have scared my friend from the Netherlands away with my bad videos and lack of electronics skills

[Rerouter]

for starters, a front and back image of each board, with connectors in, and a diagram showing how the plugs connect all the pieces

now that you somewhat have it working, document the wiring, (give boards there apparent functions for names, give plugs designators and what colour wire goes to where in what size plug)
and take plenty of pictures of the rest of it, without a clear idea of how it connects it will be a little hard for us to walk you through it,

for the drum machine, it may have a damaged component, or a bad solder joint, either way get a nice in focus well lit image of both sides of the problem area,

thepower supply board with +12 and -15V board is your main power in, with the board next to it likely being your secondary voltages, (any connection between the +12 or -15 and the second board?)

[Psqwall]

thanks for the reply and advice. Working on a detailed video that will show all you requested and be clear clean and fully descriptive. Currently hit a wall as to why the sound is now not coming out the speaker and the TRS outs turn the speaker into a big mic?
Something is routed wrong. I will make diagrams and take pics but please excuse my lack of technical describing words. This is a learning experience and I'm thrilled to gain the knowledge from this blog and look forward to being talked through making this a cool unique drum machine/mini organ and perhaps midi sound bank. Dreams!

[Rerouter]

due to its age, the traces and various parts should give a nice strong hint as to what might be connected wrong,

[T4P]

You probably reversed the outputs into an input and vice versa for the input to output