Synth-DIY Yahoo! Groups Archives

frozen

2015-02-11 by lou@...

Hi everyone,

My Chroma Polaris has developed a problem.

On power up it freezes. LEDs light up as though it remembers the program but there is no response to button pressing or keys played. After power down and up again the exact same pattern appears.

Any suggestions?

Lou

Re: [chromapolaris] frozen

2015-02-11 by Bob Grieb

Sounds like the CPU is not running. It may not be getting reset properly,

or maybe is held in reset. Your code EPROM's may have lost some bits due

to bit rot, but it's probably something else. You could try re-seating the RAM

and EPROM chips. If you have a scope, check the reset and clock signals to the CPU,

and the chip select to the code EPROMs. If you don't have a scope, re-seating the

memory chips (carefully) and checking the 5V logic supply might be worth doing. Also,

you could verify that the CPU reset signal is not asserted. There are a number of chips

that could stop the CPU from executing code properly. Trying to troubleshoot it without

a scope will be challenging...

I guess it's possible that the CPU is writing that pattern out to the LED's before it stops

running, but it may also simply be how the chips that drive the LED's power up. It's

possible that they don't get reset at power up, and the outputs are in a sort of random state.

Random, but repeatable for a particular chip.

A friend of mine had a Polaris that was in a similar state to yours. We fixed it by swapping

out the CPU with one from a parts unit that he had. Not saying your CPU is definitely bad.

That's just one reason the CPU may not be executing code properly.

Bob

From: "lou@... [chromapolaris]" <chromapolaris@yahoogroups.com>
To: chromapolaris@yahoogroups.com
Sent: Tuesday, February 10, 2015 9:50 PM
Subject: [chromapolaris] frozen

Hi everyone,

My Chroma Polaris has developed a problem.

On power up it freezes. LEDs light up as though it remembers the program but there is no response to button pressing or keys played. After power down and up again the exact same pattern appears.

Any suggestions?

Lou

Re: [chromapolaris] frozen

2015-02-11 by David Clarke

> ... My Chroma Polaris has developed a problem.
> On power up it freezes. ...

While there certainly would be many possible causes - this behaviour can
also occur because of the 'reset level' adjustment ("DC OK Threshhold")
on the power supply being incorrect (and this setting can change over
time, as the components in the power supply age).

Specifically, it could be a little low, causing the CPU to wake up
before it should. If this is the source of the problem, then it is
something easy to address (and is covered in the Service Manual, ref:
Section 6 - Adjustments and Checkout) [The service manual is available
in PDF form at http://www.rhodeschroma.com/?id=polaris . The section of
interest can be found at
http://www.rhodeschroma.com/?id=polarisserviceadjustmentscheckout#dcokthreshold ]

David Clarke

RE: [chromapolaris] frozen

2015-02-11 by Paul D. DeRocco

> From: David Clarke
>
> While there certainly would be many possible causes - this
> behaviour can
> also occur because of the 'reset level' adjustment ("DC OK
> Threshhold")
> on the power supply being incorrect (and this setting can change over
> time, as the components in the power supply age).
>
> Specifically, it could be a little low, causing the CPU to wake up
> before it should. If this is the source of the problem, then it is
> something easy to address (and is covered in the Service Manual, ref:
> Section 6 - Adjustments and Checkout)

Or, it could be a little high, causing it to remain held in the reset
state. Although in my experience, the initial LED pattern tends to be more
random when that happens. But you're right, that's always the first thing
to check if you have the old PS board with the three trimmers, because it
is trivial to fix if that's what it turns out to be.

--

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

Re: frozen

2015-02-17 by lou@...

I have a scope and Service Manual. I've done some work on this unit in the past. Years ago I replaced pots, fixed the damn ribbons, increased the RAM and upgraded the firmware to the last version.

I was checking out the original Chroma website and saw a great troubleshooting resource. Many mods and improvements. Lots of changes and attention paid to the power supply, a major overhaul really. Is such a thing available for the Chroma Polaris? Are there mods to be done to improve or add features?

Is it worthwhile to upgrade the 12Mhz CPU to 16Mhz? I gather that is possible from the service manual. Just change the CPU IC and the crystal to 16Mhz? Has anyone done this?

So I'll open it up and have a look, maybe next week. Thanks for your advice!

Lou

Re: [chromapolaris] Re: frozen

2015-02-18 by Bob Grieb

I asked Paul D about upgrading the CPU speed about a year ago, when I got my Polaris. IIRC, he said that the synth may get a little more responsive with the faster CPU, but I had the impression he didnt think it was a compelling upgrade. I did not upgrade my CPU as a result, although there were some faster parts on ebay for around $20 I think. I did upgrade to the latest OS, and maxed out the RAM.

Bob Grieb

From: lou@... [chromapolaris] <chromapolaris@yahoogroups.com>;
To: <chromapolaris@yahoogroups.com>;
Subject: [chromapolaris] Re: frozen
Sent: Tue, Feb 17, 2015 12:30:42 AM

I have a scope and Service Manual. I've done some work on this unit in the past. Years ago I replaced pots, fixed the damn ribbons, increased the RAM and upgraded the firmware to the last version.

I was checking out the original Chroma website and saw a great troubleshooting resource. Many mods and improvements. Lots of changes and attention paid to the power supply, a major overhaul really. Is such a thing available for the Chroma Polaris? Are there mods to be done to improve or add features?

Is it worthwhile to upgrade the 12Mhz CPU to 16Mhz? I gather that is possible from the service manual. Just change the CPU IC and the crystal to 16Mhz? Has anyone done this?

So I'll open it up and have a look, maybe next week. Thanks for your advice!

Lou

RE: [chromapolaris] Re: frozen

2015-02-23 by Paul D. DeRocco

> From: Lou
>
> Is it worthwhile to upgrade the 12Mhz CPU to 16Mhz? I gather
> that is possible from the service manual. Just change the CPU
> IC and the crystal to 16Mhz? Has anyone done this?

The main thing is that the analog inputs (e.g., pitch bend lever) have a
slight lag to them at 12MHz, which pretty much goes away at 16MHz.

If you make the change, you also have to move two jumpers, as described on
page 7-3 of the service manual.

--

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