73 Fender Rhodes Mark I Tone Pot Help

[mydeadblues]

So I recently picked up this 1971 Fender Rhodes suitcase piano.  I noticed the tone pot was not working, so I opened it up hoping to just spray some contact cleaner in it and I realized that it is not connected to anything.  I'd like to get this working again, does anyone know what to connect?  I am fine using a soldering gun, I just need to know what to attach  .  Also, does this look like the original capacitor?  If I need to replace it, what size cap should I use?
Thank you!

[David Aubke]

[paulb]

Try this link towards the bottom.  There is a photo and schematic showing the connections as well as the 47nF (.047) capacitor.  I assume this was the same for your 1971 stage model as with the later stage model pianos from the mid and later 70's?

http://ep-forum.com/smf/index.php?topic=7002.msg36555#msg36555

[mydeadblues]

Thanks for the info guys! So the later models should have the same schematic correct? Should I go ahead and change the capacitor while I'm at it? If it's blown will it affect anything after I rewire it?
Thanks!

[David Aubke]

I'm pretty sure I've seen several different wiring schemes on the various Stage pianos I've worked on. There is more than one way to wire up a volume and tone pot to achieve the same final result. I plan on documenting future pianos that come through my shop.

I don't really know what a defective capacitor will do. I'd say the absolute worst that would happen is that it would somehow bleed all of your signal off to ground.

[Tine-E]

I don' think that my order for a reverse (anti-log) 50k-ohm pot was correctly supplied. I received a normal linear pot.
Would this still be useful by reversing the terminal connections?

[sean]

You will probably not be happy using the linear pot.  You will not get the gradual adjustment that the anti-logarithmic (reverse audio taper) pot provides.

You want the "reverse audio" taper so that when you twist the knob all the way to the right, you get a smooth swelling change to maximum bass, and it functionally matches with the silk-screened label on the name rail... Bass Boost.

If you use any other pot taper, you will get a drastic sudden change in tone with very small movement of the knob, or you will get nearly no change in tone with large movement of the knob.

Sean

[Tine-E]

You're right Sean.

The reason I ordered the linear was that Antique Radio (tubeasandmore) did not have  the log type. I ordered several other parts from them so I would save on ship costs.

Do you have a source for this?

[David Aubke]

http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV16AF-10-15K-C50K-3/?qs=EusSljnoWfidM8xZPc9jbw%3d%3d

[sean]

and...

http://www.tubesandmore.com/products/R-V38-50K-RA


If you google for "50K reverse audio pot" you will  find lots of folks selling the right animal.   (Of course, you will also find heaps of almost-the-right-thing too, but that's google for ya.)  I am surprised that the ebay paid links are on top.

sean

[sean]

AAAACK!

Wait! 

David's link is the right one, mine is wrong.

You want the splined shaft so your knobs just push on and pull off. 

(My link shows a smooth shaft that would require knobs with a set screw.)

Sean

[David Aubke]

(Of course, you will also find heaps of almost-the-right-thing too, but that's google for ya.)

http://www.xkcd.com/1334/

[sean]

I love xkcd.

When I did the google search for "50K reverse audio pot," I was hoping to find a few links discussing the Dark Side of The Moon and marijuana....

[David Aubke]

The munchkins dancing to Money is the best part.

[Tine-E]

I need to review my Antique Radio invoice to check that pot model. They told me that it was a reverse but I had some doubts when I received it so I checked the resistance while turning the shaft and it was reading like a regular pot!

Thanks Sean and Dave.

Luis

[paulb]

AAAACK!

Wait! 

David's link is the right one, mine is wrong.

You want the splined shaft so your knobs just push on and pull off. 

(My link shows a smooth shaft that would require knobs with a set screw.)

Sean

I think his older style Fender knobs do have set screws.

Paul