Synth-DIY Yahoo! Groups Archives

Quick question help from Polaris Users

2019-02-25 by conor.strachan@...

Hi there

My tech has got my Polaris at the moment.

He asked a question I can't remember the answer to.

What happens when the Polaris is switched on?

Do all the lights flash and then it turns to the initial patch?

Mine could have a problem with a relay if there is one.

If anyone can shout out if they know let me know.

Many thanks

Conor

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-26 by Paul D. DeRocco

> From: Conor
>
> My tech has got my Polaris at the moment.
> He asked a question I can't remember the answer to.
> What happens when the Polaris is switched on?
> Do all the lights flash and then it turns to the initial patch?
> Mine could have a problem with a relay if there is one.

There are no relays in the Polaris. On startup, the LEDs initially come up in a random state, and less than a second later the CPU initializes them to the correct state. If the CPU never starts, or crashes before that point, the LEDs will be in that initial random state, which will usually be invalid (e.g., more than one letter or digit on).

--

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

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-26 by conor.strachan@...

Hi Paul

Thanks for reply.

Mine seems to be turning on and not getting past the phase where lights all come on.

Would this happen if the EPROMS were corrupt or not present? or would it only be an issue with the processor to not get past that stage. The voltages are all fine going from power board to logic board apparently.

Many thanks

Conor

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-26 by Bob Grieb

In order to initialize the LEDs and other chips, the CPU needs to be running properly,
which requires a good CPU, clock, and CPU reset, plus the EPROMs that hold the
CPU code need to have the correct data and be connected properly to the address
and data buses. Also, the SRAM chips need to be working and connected properly
as well. So a lot of chips are involved in having the CPU execute code properly,
including some small support logic chips.

Bob

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-28 by Paul D. DeRocco

> From: Conor
>
> Thanks for reply.
>
> Mine seems to be turning on and not getting past the phase
> where lights all come on.
>
> Would this happen if the EPROMS were corrupt or not present?
> or would it only be an issue with the processor to not get
> past that stage. The voltages are all fine going from power
> board to logic board apparently.

If you have the old power supply with the LED on it, make sure the LED is turning on. If it doesn't, the CPU is being held in reset, and the DC OK trimpot needs to be adjusted. But if that's okay, yes, it could be faded EPROMs. Fortunately, faded EPROMs just need to be reprogrammed, not replaced.

--

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

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-28 by conor.strachan@...

Hi

Thanks Bob and Paul for replying.

I have the newer board without the LED.

The tech who has my board says there is an Omron LAB2 5v relay that lets the power through the logic board.

He tested it and the relay is not switching when it has voltage on it.

At the moment he is under the impression that the Reed relay is broken.

I am trying to find a replacement for this part but it does not exist anymore, has anyone ever found an alternative or know about this and if it makes sense.

Many thanks

Conor

RE: [chromapolaris] Quick question help from Polaris Users

2019-02-28 by Lou Champagne

Hi Conor,

Please give this a try. I had the same problem. After much testing with no results I found the jumper for memory size selection was open. It was in place but slightly corroded and not making contact. After cleaning and replacing the jumper on the pins the Polaris got past the boot. I tried everything RAM, power supply caps and adjustment, CPU, some of the glue logic , latest ROM etc. and it would occasionally work for a while. When I discovered this it was a solid fix.

It’s worth a go as it’s so easy to try. Just take the jumper off and clean up the pins, try with a ‘fresh’ jumper if you have one (0.1”). Do them all. Make sure you note where they were before you take them off!

Worked for me, now mine is fine – no problems since. Good Luck!

Lou

From: chromapolaris@yahoogroups.com [mailto:chromapolaris@yahoogroups.com]
Sent: February-27-19 11:42 PM
To: chromapolaris@yahoogroups.com
Subject: RE: [chromapolaris] Quick question help from Polaris Users

> From: Conor

>
> Thanks for reply.
>
> Mine seems to be turning on and not getting past the phase
> where lights all come on.
>
> Would this happen if the EPROMS were corrupt or not present?
> or would it only be an issue with the processor to not get
> past that stage. The voltages are all fine going from power
> board to logic board apparently.

If you have the old power supply with the LED on it, make sure the LED is turning on. If it doesn't, the CPU is being held in reset, and the DC OK trimpot needs to be adjusted. But if that's okay, yes, it could be faded EPROMs. Fortunately, faded EPROMs just need to be reprogrammed, not replaced.

--

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

RE: [chromapolaris] Quick question help from Polaris Users

2019-03-01 by Paul D. DeRocco

> From: Conor
>
> Thanks Bob and Paul for replying.
>
> I have the newer board without the LED.
>
> The tech who has my board says there is an Omron LAB2 5v
> relay that lets the power through the logic board.
> He tested it and the relay is not switching when it has voltage on it.
> At the moment he is under the impression that the Reed relay
> is broken.
> I am trying to find a replacement for this part but it does
> not exist anymore, has anyone ever found an alternative or
> know about this and if it makes sense.

I forgot about that relay. But all it does is turn an external Radio Shack cassette recorder on and off when you use the cassette functions. It has nothing to do with the internal operation of the instrument.

If your tech has an EPROM programmer and eraser, it would be a good idea to try reprogramming the EPROMs. Use the latest version from the rhodeschroma.com web site.

--

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

RE: [chromapolaris] Quick question help from Polaris Users

2019-03-01 by conor.strachan@...

Hi There

Thanks Lou for the tip on the RAM jumpers will make sure to give it a try..

Paul are you sure on the second board the OMRON LAB2 5v is just for the cassette?

The trace goes to the cassette but also goes to the whole +5v power rail which I think powers all the chips?

Cheers

Conor

RE: [chromapolaris] Quick question help from Polaris Users

2019-03-01 by Bob Grieb

There is no way all of the TTL chips would be powered by a small reed relay.
That doesn't make any sense.

The K1 (Motor control) Relay coil is connected to +5VD on one end,
and an active low MOTOR signal on the other end (which drives the relay coil).

The relay contacts connect to the cassette jack.

If your tech thinks all of the TTL logic on the main board is being powered
through a small reed relay, you may want to find someone else to work on the synth.

Just sayin'

Bob

RE: [chromapolaris] Quick question help from Polaris Users

2019-03-02 by Paul D. DeRocco

> From: Conor
>
> Thanks Lou for the tip on the RAM jumpers will make sure to
> give it a try..
>
> Paul are you sure on the second board the OMRON LAB2 5v is
> just for the cassette?
> The trace goes to the cassette but also goes to the whole +5v
> power rail which I think powers all the chips?

Sure. It's powered from +5V too. Look at the schematic. It's at the bottom center of page 4 of the 11 page schematic PDF, the page labeled "interface, timer, keyboard & chan. control, misc."

--

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