Teisco Nomad Dual - newbie DIY repair

[mintmissiles]

Hi.

Just acquired a Teisco Nomad Dual in pretty bad shape, despite a claim of perfect functionality on a popular auction site. I don't know much about electronics but I have soldered a few synth kits together, so I'm not completely clueless when it comes to soldering capacitors and such. I just don't know the language of components. There are no reliable repair places in my area, so I was looking to do a DIY repair for experience and necessity.

Here's the rundown:

1) The rear panel is not attached to the back of the unit and is completely loose, missing 3 screws, and I'm unable to plug the power cord (which seems to have been created using a knife to a regular plug) into the rear panel without holding the one screw with a pair of pliers and pulling hard enough to plug it in.

2) The bass section is completely unplayable. The E and A key are at an angle to the keyboard and unplayable. The D key sticks and the F key doesn't sound on most lower manual voices.

3) The gray F key in the lower manual doesn't sound on any voice

4) The Horn 8' voice on the upper manual doesn't make a sound on any key

5) The Oboe 8' voice on the lower manual doesn't make a sound on any key

6) Every voice is just a little scratchy and most voices don't sound on the lower manual

7) The Brush percussion key makes an almost inaudible sound when pressed. Not sure if this is the actually sound or if it needs cleaning.

However, the Vibrato, Octave, Fuzz, Reverb, and Tremolo circuits seem to work fine, just a little scratchy/poppy when selected.

I'm not even sure how to open it to investigate what's wrong.

If you can provide some guidelines on how to open this unit, and other repair tips, please post it.

thanks so much

-mint

[karl]

Hello there,

If you can't find a plug/receptacle to replace that power cord
problem, you might just want to replace the whole thing. It sounds kinda dangerous the way it is. As far as the other problems you describe, most can be fixed by simply cleaning it up. Inside and out. Clean the key contacts real good and any switches that are giving you trouble. then check all the wiring for loose connections. Then look closely at the circuit boards for loose solder connections.
Re solder as necessary.
This will probably fix 80% of what you describe.
Also read the key contact cleaning post in the technical area.
Good Luck
- Karl

[mintmissiles]

Karl-

Thanks for the suggestions!!

Hopefully a good cleaning and checking the connections will resolve most of the issues.

The main issue now is getting the unit open--I'm not quite sure how to open it to get inside to clean it. I'm not able to just lift off the shell like I can on my Teisco Checkmate C, and I don't know where to start unscrewing things, or if that's even necessary.

Any advice?

[blair]

Aug 17, 2009 6:13:16 GMT -5 mintmissiles said:

Karl-

Thanks for the suggestions!!

Hopefully a good cleaning and checking the connections will resolve most of the issues.

The main issue now is getting the unit open--I'm not quite sure how to open it to get inside to clean it. I'm not able to just lift off the shell like I can on my Teisco Checkmate C, and I don't know where to start unscrewing things, or if that's even necessary.

Any advice?

Can you post pics of the organ from all angles? My first guess would be that the screws are underneath, but I've never had a Nomad Dual.

[mintmissiles]

Here is a link to some photos of the Nomad Dual. Hopefully these will help identify possible entry points so I can open this beast.

www.flickr.com/photos/67048066@N00/sets/72157621960267341/

I'm thinking either the silver plate over the voices is the best possible place to start, except that the volume knobs would have to be taken off to remove the face plate, or the top 2 screws on either side of the organ (side view_R, side view_L).

The bottom of the organ contains the legs.

Let me know if you have any ideas on where to start unscrewing so I can open it up and start cleaning it!

-aaron

[blair]

<grin> Well, I'm the type of guy that just starts unscrewing screws to see what they're there for. Really, not a bad method.

Have you checked what the ones on the right side do? How about the ones that are just below the upper keyboard (but above the lower one)?

[karl]

Hi,
Just looked at the pics. I would think the screws on top are a good place to start. Also the ones on the ends.

Blair Said:

Well, I'm the type of guy that just starts unscrewing screws to see what they're there for. Really, not a bad method.

Blair has a good point here. some experimentation may be in order. I find it helps to draw a rough drawing of it and mark it, to show where different kinds of screw go. This keeps me from mixing them up when I put it back together.

- Karl

[mintmissiles]

Hi

So I took the advice of Karl and Blair and started unscrewing things and was able to finally get the unit open and inspect the guts. The top screws were in fact the place to start.

Once the top screws were removed, the shell came right off. The outer shell--which has the tone switches attached--had to be lifted straight up in order to get inside because of the location of the tone circuit box.

The hardest part was figuring out what to unscrew to access the keys. Each manual was attached by four screws. The top manual was easy to access: I removed the front two screws and used the back two screws as hinges . The bottom manual was real challenge. Due to the location of the screws and the design of the organ, the screws required an Allen wrench with a philips head on one end to bend around the edge of the manual. It was almost impossible to get enough leverage and pressure to get the screws moving. It took me many hours and many different approaches to get the bottom manual unscrewed. Once unscrewed, the lower manual could be angled enough to access under the keys. I was able to fix the action on a couple keys.

I inspected all the contacts for the upper and lower manuals and none of the contacts were touching or missing, but I did notice a visible difference in the coating of the contact wire for the lower "F" key where the contact meets the wire. The part of the wire under the "F" key looks like the copper coating has been worn off--it looks like it was rubbed off. Could this have any effect on the behavior of the sound?

After putting it back together and testing it, I found that there are still some problems that need fixing. I've noticed that the "F" keys on both the lower (including bass) and upper manual only work when the 4' voices are engaged. And even on some of the 4' voices, not all the harmonics sound.
Is this a problem with the tone circuit board or something else?

Thanks for all the helpful suggestions
-aaron

[Rod MPS]

I think your next step is to look for anything visably charred or burnt. If you find nothing, that is good. Then look for loose wires.

I use Karl's "poke it with a stick" method. Turn it on, turn the volume way down so you don't blow a speaker, and cautiously probe your wire connections to your oscillators and filter circuits with a pencil or a plastic stick. Something NOT METAL cuase... you know... you can get killed.

Loose connections will be most of the rest of your problems.
Rod