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Chroma Polaris, RIP


ElectricPuppy

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I think my poor Polaris may have a fatal wound. I've been having trouble with one row of buttons on the left side of the panel up until recently. Now, ALL of the buttons are unresponsive. Sliders are fine. So, I thought it was due for a little TLC.

 

Here's the beast on the bench, powered-up. Still plays, although I'm stuck with one patch and can't alter a lot of parameters due to the non-functional buttons.

 

polaris_1.jpg

 

 

Inside, behold the glory of early 80's technology! (I screwed-up the img resize, sorry) Here the front panel is behind the main chassis, standing on it's rear edge.

 

polaris_4.jpg

 

 

Here's the bottom view of the front panel. The controls are split between 2 boards, which are jumpered together via the colorfull loom you can see bridging them. The conventional ribbon cable carries all the control signals to the CPU board. Now, keep in mind that the Polaris uses those god-awful membrane-style buttons, can you see what the problem is? Take a close look.

 

polaris_3.jpg

 

 

Let me point it out: The membrane switch ribon "cable" has gotten brittle and snapped in two. There are 4 of these ribbons, 2 that you can see here, and 2 more from the other board, which you might see between the two boards in the previous photo.

 

polaris_2.jpg

 

Unfortunately, only one ribbon is still somewhat intact, the three others have all broken where the ribbon was bent to meet the board socket. The bends where not creases, but gentle bends. But, apparently the plastic was aging and they just broke under the stress.

 

Here's the fatal problem:

- The breaks leave no exposed conductive fingers to insert in the sockets. I tried gently scraping the green insulator off the bottom to expose the fingers, to no avail. Sandpaper didn't work either. The amount of scraping/sanding is either not enough to expose the conductor, or too much and the conductor is compromised as well.

- With the ribbons now being shorter, there's no good way to get them back into the sockets, there's precious little slack left. I considered removing the sockets from the board and jumpering them with short leads to take the strain off the ribbons, but if I can't expose the ribbon conductors reliably, this is a futile exercise.

 

I sincerely doubt anyone has Polaris front panel membranes lying around I could just replace them with. My alternatives:

- Hold a wake and say goodbye, and then send it to the recycler

- Find another busted Polaris to salvage and pray that its front panel hasn't suffered the same fate

- Make a new front panel. Yes, I'm seriously considering this, if for no other reason than it'd be a cool, one-of-a-kind synth then.

 

So: What say you, KSS? Bury it, fix it, or customize it?

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...same thing happened to me a while back. Worked perfect until I opened it up to check the batteries. Closed it....and 2 rows of buttons were out. I sold it and bought an an A6. I love how the Polaris sounds though....super cool synth. I'd fix it...what the hell. I would have had mine fixed, but I had just spent $500 fixing my Chroma's power supply. Flippin' Chromas

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i have one. same thing. BOTH ribbons are out on mine.

 

i found out that you can patch the solder points together on the back if you want to activate the buttons - use a wire of somekind, preferably while drunk so the sparks don't scare you too much.

 

the way those ribbons are just epoxied in there doesn't leave much flexibilty for repair! if you figure something out, be sure to let me know.

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Have you searched for a replacement ribbon cable? I'm sure Fender sourced (not manufactured) them from somewhere, and who knows... maybe they're still available.

 

Even if a replacement cable isn't available, why not just solder in some different connectors that use a cable that IS available?

 

:idea: If you decide upon the "bury it" option, I'd really like to help. Just let me know, and I'll send you the cash to ship it to me. I'll do all the hard work with the uhh... shovel for a proper burial; I promise!

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the problem isn't really the cable, that could be sourced. the way the cable connects to the panel is the problem - it's literally sandwhiched in between plastic panels with epoxy, and i don't see a reliable way of getting it out.

 

the connection to the actual PCB is a connector, thank god - but mine are broken _right at_ the membrane panel and there isn't a way to fix that without melting off the epoxy somehow.

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Burn the plastic, metal conductor should remain intact, LOL. Seriously, that is just one wild idea from someone who knows nothing abouth fixing synths ;-)

 

Don't know that I'd burn the plastic, but you're on the right track actually... Maybe look at rubbing the broken ends of the ribbon cable with acetone or something to expose a small (but large enough) area of the leads on each end of the broken ribbons. Just be sure to use small amounts of that acetone and work slow and careful. You don't want to slop it all over and potentially cause more problems. Maybe use a q-tip...

 

After that, find a way to connect the two broken ends...direct solder the 10 leads using new ribbon cable, put new socket "ends" on each of the broken sides and connect with a longer ribbon to give you more working room, etc. However you repair it, make sure that you keep all 10 leads separated so they don't short together. Poor man's solution - hot glue...solder them slightly spread apart, then dip the whole thing in the glue and let dry with them spread apart. Not the cleanest way, but if you aren't putting new socket ends on those ribbons that would be another way to go that would protect and insulate it electrically speaking.

 

 

 

If that doesn't work, have you tried an Xacto knife or scalpel to carefully cut between the leads and see if you can "peel" the plastic sandwich of the ribbon open leaving the leads exposed? Might be another way to go...

 

 

@scenic - unfortunately it sounds like you're screwed unless you could find a way to remove that epoxy and desolder the ribbon sockets. In your case, I'd really *not* suggest acetone :)

 

Thanks!

bax

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Thanks, everyone, for the sympathies and ideas! :thu:

 

I did a bit of Googling last night to see what else I can do. Apparently this is a common problem with the Polaris; The plastic ribbon just gets brittle and breaks. I saw another possible solution using conductive silver ink. If I can figure out how to expose the fingers on the ribbon that remains, I have an idea on how to make a good, permanent fix. I have acetone, I'll try a little of that.

 

Scenic: I think yours is screwed, bud. :( I believe the ribbon is actually an extension of the switch membrane itself, not a separate thing that's sandwiched between the membranes. It IS the membrane, it's one piece. Well, two, actually, the lower switch membrane and the upper switch membrane. If there's not enough ribbon left to work with.... :cry:

 

I suppose that eh very least I could salvage the CEM chips and sell 'em. Or, if I REALLY had to keep it, stick the guts in a box and remote the controls via MIDI.... I dont' know if the MIDI is extensive enought o allow this though.

 

Poop. I hate broken equipement.

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Scenic: I think yours is screwed, bud.
:(
I believe the ribbon is actually an extension of the switch membrane itself, not a separate thing that's sandwiched between the membranes. It IS the membrane, it's one piece. Well, two, actually, the lower switch membrane and the upper switch membrane. If there's not enough ribbon left to work with....
:cry:

 

Now I understand. OMG, what an... "unfortunate" design. :eek::freak: My sincere condolences.

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I would maybe use a scalpel to scrape of the plastic coating from the ribbon, then applly some solder paste (NOT solder wire) to the exposed metal. Then prepare some regular ribbon cable of suitable lead pitch, ie expose and wet the ends with solder. Then use a tiny tip soldering iron on about 330C to very quickly fuse the solder paste into the exposed ribbon cores.

 

Using paste and a tiny tip iron should allow the paste to melt and fuse very quickly and prevnt melting the rest of the platic ribbon if your lucky.

 

 

While you are at it, may be worth replacing the existing wire ribbon as well - old ones seem to degreade as well - common problem with some large format mixers after a while.

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Thanks, guys. Don, I think there' light at the end of the tunnel, thanks for the offer though. Khazul, that's essentially what I think I'll do, but I don't plan to attempt to solder anything to the ribbon itself, even quickly I think the plastic would be damaged.

 

The good news is that lacquer thinner removes the green insulating coating easily, but more importantly, it leaves the conductive traces and plastic unharmed! Huzzah!

 

What I plan to do is glue the ribbon down, conductive-side up, to a small "landing" sheet of blank PCB. Then, I'll extend the ribbon's traces to the PCB via conductive silver ink. From there I can solder leads from the landing to the original PCB (having removed the ribbon socket).

 

I need to order supplies, but once I get everything, I'll post more shots as I go.

 

Wheee, I might save this thing yet!

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The good news is that lacquer thinner removes the green insulating coating easily, but more importantly, it leaves the conductive traces and plastic unharmed! Huzzah!

 

SWEET!!!! Sounds like it should be clear sailing from that point...definitely show us some pics when you're done! :thu:

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I recommend Good Guys Audio Repair in Minneapolis...they are certified Chroma repair techs.

 

Seconded. They worked on my Polaris when I had one. It probably won't be cheap and they're usually pretty backed up, but they do good work.

 

If any of you are guitar players, they're also great with tube amps. I've had more than one amp modded by Quint (their tube guy)...

 

ew

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can you bypass the ribbon by drilling holes into the traces on the pcb itself, and soldering from there? i can't tell from the pic if this would be possible.

 

The switch membranes basically lie on the face of the front panel. They're sandwiched between the very heavy steel of the panel and the plastic graphic overlay. There's no PCB involved, and the steel would be a bear to drill through.

 

Proof of concept pics:

 

Here's a piece of the ribbon that used to plug into the socket on the PCB. Note the green overcoat, and the black conductive fingers. Because of the break, the remaining ribbon no longer has exposed condutors.

 

ribbon_sample.jpg

 

 

Our savior, Lacquer Thinner!

 

ribbon_solvent.jpg

 

 

Apply lacquer thinner and voila! No more green! Note the exposed traces, silver not black. I wonder what the black is and what purpose it served? Maybe to prevent the traces from oxidizing?

 

ribbon_exposed.jpg

 

 

Are the exposed traces actually conductive, or did I wipw away the traces, too, and these are just "ghosts"? Whip out the DVM and see:

 

ribbon_ohm.jpg

 

Success! :thu:

 

I'm about to place a Mouser order for the necessary supplies. Stay tuned for further developments!

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