Roland D-50 - invalid sounds (noise, creaking, cracking)

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Jeeper73
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Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Thu Jan 01, 2015 7:40 pm

Good day !

I have a faulty Roland D-50 - instead of sounds gives some noise, creaking, cracking. Some patches can be identified, but if you really-really listen.
As MIDI-keyboard synthesizer works perfectly.
All self-diagnosis tests (according service manual) are OK, without any errors. But the "wrong" sound available at the DAC output (IC10) - contact 25 (or 23). DAC is OK.
According to all tests, PROM (IC22), WORK RAM (IC23) and TONE RAM (IC24) - also are OK.
I'm checked all resistor arrays - resistance corresponds to par, no breaks and short circuits.
I'm checked all resistors - resistance corresponds to par, no breaks and short circuits.

I'm checked VR1 (100 kOhm) - 86 kOhm when measured full impedance and 90 kOhm if the measure through the midpoint.
Voltage on power board: "+12.1", "-12.4" and "+5".

What else to look?
That is service manual I using - Roland_D-50__SERVICE_NOTES
Last edited by Jeeper73 on Tue Feb 17, 2015 11:13 pm, edited 2 times in total.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by db0451 » Thu Jan 01, 2015 7:43 pm

Post some recordings.

Something obvious you did not mention: Check the digital connections between all the synth, reverb, and DAC chips.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Thu Jan 01, 2015 7:54 pm

Unfortunately, I can't attach some recordings.
I can only clarify: on the background of all this "chaos", you can learn some patches, for example - "13", "28" and a some else.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Thu Jan 01, 2015 7:58 pm

The "wrong" sound begins at the DAC output (IC10) - contact 23 (and 25). May be
DAC can corrupt?

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by db0451 » Thu Jan 01, 2015 8:07 pm

Is this “chaos” a form of harmonic distortion, random white noise, or something else? i.e. does it appear to be at all related to the main pitch of the intended sound?

What are 23 and 25’s functions? (I do not have the service manual at hand right now.)

Possibly the DAC is at fault, although more likely it is something caused by subsequent analogue circuitry, e.g. electrolytic capacitor(s) or muting transistor(s). but it is difficult to guess without more details on the sound or hearing it ourselves.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Sat Jan 03, 2015 11:29 pm

Happy New Year and Marry Christmas !
;)

Answer for year question: Yes, may be. The structure of "chaos" is tipical, the same for all patches,
I will try, on occasion, to record and attach examples of sound.

Did you mean the service manual for the DAC or a synthesizer ?
This is datasheet for DAC PCM54HP - PCM54/PCM55_datasheet
And this is service manual for Roland D-50 - Roland_D-50__SERVICE_NOTES

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Sun Jan 04, 2015 3:23 pm

There is good news. :)

I will soon have to bring a rack version of the synthesizer - Roland D-550, in excellent working condition.

QUESTION: Is it possible to localize the fault is gradually moving in the circuit with the tester and the oscilloscope, comparing both MAIN boards ?

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by db0451 » Sun Jan 04, 2015 3:33 pm

Probably but seems difficult. Seems easier to provide some clips for analysis, and replace capacitors/transistors ;) especially any around the DAC as they can significantly affect its output. Also, later caps and muting transistors are usually worth replacing while you have it open. The DAC itself could be replaced for about £20. Might save a lot of difficult investigation.

Although, again, first thing to check next are all traces among the synth/reverb chips and DAC; if the DAC is being fed bad data, it would produce bad sound, even if it is fully functional.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Wed Jan 07, 2015 11:34 pm

Finally I recorded some samples of my sound synthesizer - 10 files. In the last file I was a bit overdone :oops: :)
But how I can attach my recordings ?

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by synthRodriguez » Fri Jan 09, 2015 4:09 pm

The solder terminal connections on the audio output jacks are not robust on the D-50 and poorly supported.

I have seen more than one with cracked solder joints on the circuit board-to-jack connection.

Check the jack board solder joints for integrity.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by pflosi » Fri Jan 09, 2015 4:49 pm

Jup, those fail easily. Did you check both outputs separately and also the headphone out to see whether the noise you get is the same on all outputs?

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Sat Jan 10, 2015 8:01 pm

Finally I recorded some samples of my sound synthesizer - 10 files. In the last file I was a bit overdone :oops: :)
I signed up on "SoundCloud" an attach them - Roland D-50 "wrong" sounds

JACK board ok, I think... I checked.

Yes, I checked both outputs separately and also the headphone - noise is the same on all outputs.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by mike the spike » Mon Jan 12, 2015 11:20 am

I had this exact problem, the sound is identical. I replaced the DAC and all was OK. I had bad solder joints on the PSU board and the voltage spikes may have fried the DAC.

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Jeeper73
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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Mon Jan 12, 2015 3:49 pm

Thank you very much, mike the spike.

I'm going to change almost all the cheap chips (decoders, flip-flops, inverters, keys, operational amplifiers, etc.) :)
mike the spike wrote:I replaced the DAC and all was OK.
The previous owner changed the DAC to a new, but probably got rejected.
Then check again DAC - I'll remove from Roland D-550.
mike the spike wrote: I had bad solder joints on the PSU board and the voltage spikes may have fried the DAC.
I check the voltage on the PSU board, but not ripple pacing (currently not oscilloscope) and quality soldering checked. So be sure now'll see more quality soldering.

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Re: Roland D-50 - invalid sounds (noise, creaking, cracking)

Post by Jeeper73 » Wed Jan 21, 2015 8:06 am

Hello everyone!

Nothing new.

For many holidays had except vypayat of Roland D-550 DAC and insert in its place the socket (for convenience).
Time and health are not always enough work after more than something to do :)

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