Roland XP50 LCD Display Problems

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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 18:58, 31 May 2015

Working...removing the caps.

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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 19:01, 31 May 2015

Can you tell me the value of R82? It's next to the CR2032 battery. And R940. It's on the back of the PCB right along the short edge of the copper plate.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 22:22, 31 May 2015

R82 and R940 is not phisicaly mounted on PCB.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 22:52, 31 May 2015

Valentine, also please check the electrict conductivity of all pcb cooper traces around the replaced caps, specially that very thin bus traces. One can be opened by the corrotion. The negative side of C175 goes to R186 and R85. It is the path of Left output of DAC.
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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 07:53, 1 June 2015

Hi Cesarsound,

So R82 and R940 contain no components? I wasn't sure about R940 but the pads for R82 looked burned like the resistor exploded :-) Can you make a photo of R82 on your board so I can compare them? I'll try to continue repairs tomorrow evening.

grtz! Valentine.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 16:36, 1 June 2015

Hi Valentine, R82 and R940 contain no components on board. I will post a photo tonight.

Cheers,
Julio.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 00:11, 2 June 2015

Here we are.

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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 08:55, 2 June 2015

Tnx Julio. I'll continue repairs this evening. Does your XP-50 work again?

edit: the brown stuff visible on the first picture. Isn't that leaked electrolite? I removed alot of that stuff from were the old caps sat.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 13:21, 2 June 2015

Hi Valentine, I have not finished my caps replacement yet. This is a delicate and time consuming task. I have only Sundays mornings to work with it, I’ve already replaced half of caps so I am thinking to finish it on next weekend and then test it.

That brown stuff is the flux paste used to easy the soldering process. You may remove it with alcohol.

tks.
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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 13:32, 2 June 2015

A photo of my handywork using regular caps:

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Hmm.. just click on this link :-)

https://synthsandkeyboards.files.wordpress.com/2015/05/xp50-medium.jpg
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 18:22, 2 June 2015

Good work! if I had not found the smd caps to buy I would have done the same.
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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 18:39, 2 June 2015

Hi Julio,

Quick question: I put my multimeter in diode test mode. If I touch the same pad with both leads off course I hear a loud beep from my multimeter. If I touch both pads with one lead where a cap should be on some pads nothings happens (good I think) but on some others I see a number on my multimeter (not a beep) indicating that there is some current flowing (?). When I test this there is no cap soldered in place.. Is this a problem?

I've soldered on the cap where I broke the negative pad of C175 and tested if it connected to R186 and R85 and it does :-) so that problem is solved I think.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 22:00, 2 June 2015

Valentine, this is normal, your multimeter actually reads the resistance of others components connected to that pads, for example, the internal resistance of ICs, resistors. No problem here.

But the important is to check if copper wires (traces) must have almost zero OHMS (or the beep ringing), specially that ones near the replaced caps, where you find a black spot resulted of leakage of electrolytic on board. If one data bus trace was opened by corrosion, you may have the problems you related. So you can re-make this electric circuit, repairing the trace with a thin wire.
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Re: Roland XP50 LCD Display Problems

Postby CesarsoundOne » 15:15, 6 June 2015

Repair finished.

After the replacement of 24 electrolytic SMD capacitors, a meticulous cleaning of PCB on corrosion points and the rewire of an opened trace (analog output of DAC converter), the 20 years old XP50 is back to live, invigorated with a clean and punch audio, specially in low and high frequencies, with the same sound when I bought it in 1995.

Attached is a sound example after the repair.
Julio - Cesarsarsound.

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ROLAND XP50 RENEWED.MP3
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Re: Roland XP50 LCD Display Problems

Postby Valentine10 » 20:43, 6 June 2015

Very good Julio :-)

I've removed half the newly installed caps to check for leakage of the old caps and I'm considering removing the rest of the new caps too just to be sure everything is clean. I also allows me to better check all the traces. I'll try to continue tomorrow..

grtz, Valentine.
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