Roland XP-50 repair

[Jose EB5AGV]

I am working an an XP-50 I bought with a known fault: it generates lots of noise along the sound it should produce, which is barely audible.

 

I have uploaded a video with some samples:

 

 

 

[Jose EB5AGV]

Here you have some pictures of the unit on my workbench:

 

 

Once bottom cover is out, you can see the innards of the synth. I noticed that someone had been already here, as some cabling is not routed properly:

 

 

And this is the offending PCB, which usually has problems with leaking SMD capacitors:

 

 

 

[Jose EB5AGV]

So I have taken out the MAINBOARD to work on it. Note that this one has an M3 marking on it. I have seen M1, M2, M3 and M4 so far. These are small evolutions of the PCB

 

 

I will replace all the SMD electrolytic caps (although they seem replaced, there was not a proper cleaning when that was done, and also some caps measure high ESR (*)), clean carefully the PCB, look for any leakage damaged trace / via and check the PCB on the unit.

 

(*) ESR = Equivalent Series Resistance. This value tells a lot on quality and condition of the caps. I use a PEAK ESR70 to measure them on-circuit

 

PS: I will update this thread as work continues. Now I am waiting for some spares to arrive

 

 

 

 

[Jim Alfredson]

Shotgunning repairs can lead to other problems. By ”shotgunning”, I mean that just replacing a bunch of components without properly tracing the problem. 

 

In this particular case, I would try to find where the noise is entering the signal by looking at the output of the DAC before the output opamps on an oscilloscope and then follow it through the various components until I see the noise. This assumes the problem isn’t the DAC itself. Or before it, which is a whole different can of worms. 
 

Anyway, just my two cents. 

[Jose EB5AGV]

4 minutes ago, Jim Alfredson said:

Shotgunning repairs can lead to other problems. By ”shotgunning”, I mean that just replacing a bunch of components without properly tracing the problem. 

 

In this particular case, I would try to find where the noise is entering the signal by looking at the output of the DAC before the output opamps on an oscilloscope and then follow it through the various components until I see the noise. This assumes the problem isn’t the DAC itself. Or before it, which is a whole different can of worms. 
 

Anyway, just my two cents. 

 

Hello JIm,

 

I would have done it that way, but the problem is that someone had already replced ALL the caps, and done that poorly: the leakage from older caps was not removed, the soldering was not very good... So I decided to carefully remove them, one by one, clean and check the area around each, and replace with good Panasonic SMD caps. Most of them are 10uF caps. Well, with the ESR meter, the measurement was about 8 Ohm on the ones installed. A good 10uF/35V Panasonic cap is less than 2 Ohm ESR. So, as the 10uF accounted for 80% of the caps, and been so poorly replaced, my best bet was to get all out.

 

So I will then troubleshoot with a good starting point. Is like trying to fix a car engine where someone has done some messy work... You don't trust the oil and filter, right?

 

Thanks for your advice, I understand why you make it and am 100% with you when an instrument / accessory just fails and nobody has messed with it. Then I would, for example, measure caps with the ESR meter, and replace only the bad ones. But in this case, trust me, it was the way to go.

[Jim Alfredson]

21 minutes ago, Jose EB5AGV said:

 

Hello JIm,

 

I would have done it that way, but the problem is that someone had already replced ALL the caps, and done that poorly: the leakage from older caps was not removed, the soldering was not very good...

Ah, that makes sense! Good call!

[Jose EB5AGV]

Well, I have got my ailing Roland XP-50 working !!! (BTW, it was bought as non working, for about 173€ shipped. Given its external condition, I thought it was a good one to try)

 

Finally I removed all the (already replaced, but not well done) SMD capacitors. Then I carefully cleaned the PCB and installed new Panasonic ones (mostly 35Vdc). Then, as it was previously resoldered and looked suspicious, I replaced also the 18 bit DAC. And here you have the results:

 

 

[AUSSIEKEYS]

Hey Jose thanks for this thread.

 

I just returned from a 12 hour drive with my old XP50 which had been stored at my brothers place for 9 years after almost leaving it behind when we moved interstate. Luckily he took it home for me.

 

In those years the battery died and upon startup the display is low contrast and no sound emanates from the phones or outputs. 

 

I replaced the battery and did a reset so now its normal other than the no sound.

 

i hear mostly XP50s usually have a very faint sound or crackling when caps go. Mine is totally silent.

 

Its in almost new cosmetic condition which brings me to a wish to get it going again although i have 2 XP80s in storage with the red goo problem. But after 9 years storage these may also now need caping

 

My question is before i look at capping can you think of other reason for zero sound not even crackling

[Jose EB5AGV]

Well difficult to say from the distance, but it could be a bad DAC, as it is close to, most probably, leaking caps and, if it just stops working, maybe a reason for the silence.

 

All in all, I would replace all SMD electrolytic capacitors, taking special care of cleaning any residue they may leave and checking for nearby damage. Then, measure voltage rails from the power supply, and work from that point.

 

Please, let us know what you find!

[AUSSIEKEYS]

Thanks Jose. Will look into that when workshop is setup. 

 

I just did a quick battery change on the new music room floor incase that was a lucky fix.

 

Hopefully I'll have room for a few keyboards to be open so i may do the XP80s at the same time when my workshop is ready as there is enough bench space

 

Ill keep you notified down the track It may be a while yet