Rhodes Chroma Polaris

Hello polarized guys,

I'm trying to understand why my CP is acting strange.
At startup, sometimes about 90 % of all leds are on, but is not 
possible to change any parameter. Sometimes, after a couple of secs 
goes ok.
But when the startup is ok and also after doing the complete reset 
(and related adjustmetns), I'm getting strange results from, for 
example attack and releases. Or I'm getting unwanted modulations in 
the sounds...

I'm suspecting that the DC OK signal sometimes is not up: I'm getting 
a maximum DIGITAL DC +4.2 (maximazing the trimmer, 4.01 at minimum 
position). I have the second type board (so no trimmer for the DIG OK 
signal)

Do you think is the LM350k or is the power coming in that is too low ?
and what would be the correct incoming voltage from the transformer?
Can be the low voltage caused by old lytics caps ?
What could be a substitute for the DAC ?
thank you for your expertize
at

> ... At startup, sometimes about 90 % of all leds are on,
> but is not  possible to change any parameter. Sometimes,
> after a couple of secs goes ok.
...
> I'm suspecting that the DC OK signal sometimes is not up
...
> I'm getting
> a maximum DIGITAL DC +4.2 (maximazing the trimmer, 4.01 at minimum
> position). I have the second type board (so no trimmer for the DIG OK
> signal)

If this is actually the output of the 5V digital line that you're reporting,
then that would seem to be the source of the problem (i.e., 4.2v is .6 or .7
volts too low for good operation - and per the docs, you should be up at 5.0v).

The solid-on LED indication would indeed likely be due to the DC OK signal
never getting up there (since the power supply is struggling to get to a point
where the 5V is "ok."

If the voltage is really that low too - then other system operation would also
be questionable.

> Do you think is the LM350k or is the power coming in that is too low ?
> and what would be the correct incoming voltage from the transformer?
> Can be the low voltage caused by old lytics caps ?

I wouldn't immediately expect the electrolytics, but I would certainly look at
the input voltage to the LM350 to see what sort of levels you are seeing.  If
you can, it would probably be good to look at this with a 'scope.

While the circuitry between the old and new PSUs are different, I would still
expect to see the same order of magnitude of voltage going into the voltage
regulator - so that'd be about 13V coming in, with a ripple frequency of 120Hz.

Hello polarized friends, Hi David,

Ok I changed all the caps and no result,

at the end I changed the lm305k (the incoming voltage was correct) and 
bingo!

now the DIG voltage is stable a +5.00 and the DIG OK signal is "OK"..

The polaris starts

but!!

AAAHAHAHAHAHAHHAHA

is saying all the voice are defective ?
If I turn on all the channels no audio is coming out!

Let's clarify, that I worked on the voltages correction detaching the 
jp4 and jp3 connectors!

the tune all function is blinking just one time, and after all the 
voices are shut down.

I have an xpander, and I tested (just one) cem and is working!

so must be something else.

Another strange behaviour: the click for the metronome is missing, and 
so the click for pressing button and "honk" for the error:
I dont think the sound effects are generated using the 3374 (???)

Any idea help help help

Ciao
Antonio Tuzzi

On Giovedì, feb 17, 2005, at 02:57 Europe/Rome, David Clarke wrote:

> > ... At startup, sometimes about 90 % of all leds are on,
> > but is not  possible to change any parameter. Sometimes,
> > after a couple of secs goes ok.
> ...
> > I'm suspecting that the DC OK signal sometimes is not up
> ...
> > I'm getting
> > a maximum DIGITAL DC +4.2 (maximazing the trimmer, 4.01 at minimum
> > position). I have the second type board (so no trimmer for the DIG OK
> > signal)
>
> If this is actually the output of the 5V digital line that you're 
> reporting,
> then that would seem to be the source of the problem (i.e., 4.2v is .6 
> or .7
> volts too low for good operation - and per the docs, you should be up 
> at 5.0v).
>
> The solid-on LED indication would indeed likely be due to the DC OK 
> signal
> never getting up there (since the power supply is struggling to get to 
> a point
> where the 5V is "ok."
>
> If the voltage is really that low too - then other system operation 
> would also
> be questionable.
>
> > Do you think is the LM350k or is the power coming in that is too low 
> ?
> > and what would be the correct incoming voltage from the transformer?
> > Can be the low voltage caused by old lytics caps ?
>
> I wouldn't immediately expect the electrolytics, but I would certainly 
> look at
> the input voltage to the LM350 to see what sort of levels you are 
> seeing.  If
> you can, it would probably be good to look at this with a 'scope.
>
> While the circuitry between the old and new PSUs are different, I 
> would still
> expect to see the same order of magnitude of voltage going into the 
> voltage
> regulator - so that'd be about 13V coming in, with a ripple frequency 
> of 120Hz.
>
>

> ... at the end I changed the lm305k (the incoming voltage
> was correct) and bingo!  now the DIG voltage is stable
> a +5.00 and the DIG OK signal is "OK"..

Terrific!  That's great news.

> ... is saying all the voice are defective ?
> If I turn on all the channels no audio is coming
> out!

As the power supply had been worked on, it would probably also be good to
double-check the other voltages coming from the supply (to make sure they're
OK).

Assuming everything looks OK there, (and if you have not already done so), I'd
suggest that it would be good to go through the Adjustments and Checkout
section of the service manual, which will confirm such items as the DAC null -
and will also ensure that the volume leves are set up and memory is restored
(the most common reason for loosing all of the audio, especially if the error
honk is missing, would be that the memory data has been lost and has to be
recalibrated - although that should not explain why the voices will not
auto-tune.)

Perhaps, you might have disconnected the battery backup power during your
repair?

If you did, you should reset and recalibrate everything, and also reload
all the voices. If you do all that, you should also install fresh backup
batteries while you're at it.

take care,
McLilith

Hello CPs!

I've still no luch with my polaris.

I've completely redone the power supply, Voltages are correct and
precise. And I started againg and again resettingg everything, but
voices are missing.
But the click and honk too are missing.

I tried to measure variation in voltages arriving to the Voices. But
the voltages are unchanged for any operation in the panel.

If for example I change the volume, I can't see a volume change in pin
7 of teh ZX03 IC

But I see variation entering in the ADC (from the 374).

I'm suspecting, at this point a blown DAC:

A)
What I can do to be sure that DAC is working (or not working) ?

B) 
Do you know of any DAC HS3140C reseller ?

thank you for your time

AT

You need to scope the output of the DAC / input to the S/H buffers to 
check if the DAC is working.  You should see a waveform that looks 
like a strange-bargraph (or S/H LFO).

My HS3140C blew and I searched-- the only replacement was from a 
military supplier and cost something like $150 or $175.  I think I 
blew it by messing up the power supply sequence while troubleshooting 
the power supply which is similar to what you did...

I ended up using the analog devices AN7538 DAC ($15) which has the 
similar specifications but a different pinout.  It wasn't hard to 
make an adapter using a stack of DIP sockets.  Datasheets for both 
parts are online.  You will also need to set the null-offset per the 
service manual when you are finished.

If that seems beyond your technical abilities, send me an email-- I 
can have a AN7538->HS3140C socket adapter PCB built for you for $75 
(including all parts) or $40 for just a PCB.

Thanks,
Ben

> I'm suspecting, at this point a blown DAC:
> 
> A)
> What I can do to be sure that DAC is working (or not working) ?
> 
> B) 
> Do you know of any DAC HS3140C reseller ?
> 
> thank you for your time
> 
> AT

Hi Polariser,

On Sabato, feb 26, 2005, at 23:38 Europe/Rome, bkuris wrote:

> You need to scope the output of the DAC / input to the S/H buffers to
> check if the DAC is working.  You should see a waveform that looks
> like a strange-bargraph (or S/H LFO).

I can see the bargraph in input to the ADC (pin 6), but flat at the DAC 
output.
Do you think I should do other tests ? Is any Capacitors in the loop I 
should test or exchange ?


regards

at

At 12:07 PM 2/26/2005 , atuzzi wrote: 


>
> I've completely redone the power supply, Voltages are correct and
> precise. And I started againg and again resettingg everything, but
> voices are missing.


Are *all* the voices missing, or just some of them? It might help, if we knew
that.


take care,
McLilith

all voices missing, and the metronome click and the "error honk" too...

at

On Lunedì, feb 28, 2005, at 20:55 Europe/Rome, spamtemp@... 
wrote:

> At 12:07 PM 2/26/2005 , atuzzi wrote:
>
>
> >
> > I've completely redone the power supply, Voltages are correct and
> > precise. And I started againg and again resettingg everything, but
> > voices are missing.
>
>
> Are *all* the voices missing, or just some of them? It might help, if 
> we knew
> that.
>
>
> take care,
> McLilith
>
>
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>
>
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Hello Polarised friends,

this is for the archives:

Ok finally I have the CP back from the dead!

As I suspected from the start (ok not from the start but since I've 
redone the power supply, so probably my fault).

Thanks to Ben I was able to find a replacement for the DAC

Great list

Thank you

at