Rhodes Chroma Polaris

I seem to have an issue with the envelope depth slider. It is not responsive. The only one on the keyboard that is. However it is working through the editor in midi quest so it works so this seems like a mechanical problem or something on the panel board(it hasn't new panels). Does this sound like it needs a new potentiometer?

Thanks

Conor

> From: conorstrachan@...
>
> I seem to have an issue with the envelope depth slider. It is
> not responsive. The only one on the keyboard that is. However
> it is working through the editor in midi quest so it works so
> this seems like a mechanical problem or something on the
> panel board(it hasn't new panels). Does this sound like it
> needs a new potentiometer?

Most likely the wiper or elements are dirty, or the wiper contacts are bent. If you remove the slider from the board, you can pry back the tabs that hold it together, then clean the inside with alcohol and a Q-tip. If it appears the wiper contacts are bent, you you should be able to bend them back with sharp tweezers if you're very careful. If the contacts are broken, then you're SOL and will have to find a new slider. I've repaired quite a few sliders this way.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...

Thanks Paul

It got the board off and it appears that the slider does not have very much resistance compared to the rest. I guess as it's unresponsive it must be disconnected on its contact that's why it feels loose on the track. Would bending the pins sort this out? Might have to be looking at finding a new slider

For what it's worth I have had great results opening up the Polaris sliders, giving them a decent cleaning, and re-bending the contacts back to where they should be ... and then closing them back up again. Personally I have found the easiest way to bend the bottom clips open is to use a small set of wirecutters and to get the edge of one blade positioned under the clip and then just gently pry it up.

Sent from my iPhone

> From: conorstrachan@...
>
> It got the board off and it appears that the slider does not
> have very much resistance compared to the rest. I guess as
> it's unresponsive it must be disconnected on its contact
> that's why it feels loose on the track. Would bending the
> pins sort this out? Might have to be looking at finding a new slider

If by "pins" you mean the things attaching it to the circuit board, then no. It sounds like the wiper contacts on the movable shaft assembly, which bridge between the resistive track and a parallel conductive track, are bent so they are no longer touching the tracks, or possibly broken. As James and I said, these things can be taken apart to clean them and unbend the wiper contacts.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...

I just took it off the board cleaned it, dexoxited it and put the pins back. No luck, still nothing. I'm going to swap the keyboard tracking slider and then will see if it just needs a new slider or the problem is somewhere else.

I swapped them around and the fader is fine. Any ideas of where to head next to, So the envelope depth control is not responding. It's now definitely not the fader. It works through controlling externally through midi so it mušt be working at some point.

> From: conorstrachan@...
>
> I swapped them around and the fader is fine. Any ideas of
> where to head next to, So the envelope depth control is not
> responding. It's now definitely not the fader. It works
> through controlling externally through midi so it mušt be
> working at some point.

Since you've already ruled out a cold solder joint on the slider by resoldering it, it's almost certainly the 4051 that the slider connects to. The only other possibility I can think of is a bad trace on the board, which can happen if the board suffered water damage and the resulting copper oxidation.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...

Paul you were right with the 4051, I swapped Z4 into Z3 and now the envelope depth is working! Many thanks!

Just one question what uses The 4051 in Z4?

> From: conorstrachan@...
>
> Paul you were right with the 4051, I swapped Z4 into Z3 and
> now the envelope depth is working! Many thanks!
>
> Just one question what uses The 4051 in Z4?

You can find the schematics on the rhodeschroma.com site. Here are all the assignments, sorted by slider position, left to right, with the non-slider inputs at the end:

pin in source
------------------
Z3-12 3 Master
Z3-13 0 Osc 1 Pulse Width
Z3-14 1 Osc 1 Pulse Width Mod
Z3-15 2 Osc 2 Pulse Width
Z4-1 4 Osc 2 Pulse Width Mod
Z4-2 6 Sweep Rate
Z4-4 7 Filter Cutoff
Z4-5 5 Filter Resonance
Z4-15 2 Filter Sweep Depth
Z4-14 1 Filter Env Depth
Z4-13 0 Filter Kybd Track
Z4-12 3 Envelope Attack
Z5-1 4 Envelope Decay
Z5-2 6 Envelope Sustain
Z5-4 7 Envelope Sustain Decay
Z5-5 5 Envelope Release
Z5-12 3 Volume Envelope Attack
Z5-13 0 Volume Envelope Decay
Z5-14 1 Volume Envelope Release
Z5-15 2 Assignable
Z3-5 5 Lever 1
Z3-1 4 Lever 2
Z3-2 6 Pedal
Z3-4 7 Battery

Z5 is on the right board. Here's the same list, sorted by input number.

pin in source
------------------
Z3-13 0 Osc 1 Pulse Width
Z3-14 1 Osc 1 Pulse Width Mod
Z3-15 2 Osc 2 Pulse Width
Z3-12 3 Master
Z3-1 4 Lever 2
Z3-5 5 Lever 1
Z3-2 6 Pedal
Z3-4 7 Battery
Z4-13 0 Filter Kybd Track
Z4-14 1 Filter Env Depth
Z4-15 2 Filter Sweep Depth
Z4-12 3 Envelope Attack
Z4-1 4 Osc 2 Pulse Width Mod
Z4-5 5 Filter Resonance
Z4-2 6 Sweep Rate
Z4-4 7 Filter Cutoff
Z5-13 0 Volume Envelope Decay
Z5-14 1 Volume Envelope Release
Z5-15 2 Assignable
Z5-12 3 Volume Envelope Attack
Z5-1 4 Envelope Decay
Z5-5 5 Envelope Release
Z5-2 6 Envelope Sustain
Z5-4 7 Envelope Sustain Decay

So now, Osc 1 Pulse Width Mod shouldn't work, since pin 14 on the 4051 is blown out.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...

Hi thanks

That's good to know.
Slider was not the problem in this case. It was the 4051. The sliders on mine are really big and chunky they seem pretty solid.