Fixing my good old XP-50

[Maxx2206]

Hi,

i just started trying to fix my good old XP-50 which was my very first Synth/Workstation ever (bought 1994'ish from one of my first pays back in the days ;) ) and raises a lot of fond memories so I can gift it to one of my nephews. Its has a full set of expansions installed and was still a very fine instrument when it was still functioning properly.

What are the problems? Well, mostly the known issues, but with a twist it seems...

1. It has cold boot issues... When its been off for a while and I turn it on, it usually starts almost normal, just with a blank display (not the usual contrast issue, hold on...).
If I happen to press any key at this stage it usually just freezes.. no more heartbeat blinking play led...
However, if I turn it on and don't touch it for like 10 minutes or so and just leave... it usually shows display text and does not freeze on any press.

At this stage I suspected a bad power supply as the caps were already kinda bloated. I replaced all elcos on the PSU pcb but it didnt help. I tried to replace the regulators but couldn't get the original 5V regulator so I tried a different apporach... I removed the transformer as well as the bridge rectifier and regulators, placed a modern +5V /+15V / -15V PSU and wired it up to the GND/+5/+15/-15 path of the PSU pcb.

Unfortunately all this had no effect.
It still freezes when cold, and runs seemingly ok when its warmed up for at least 5-10 minutes :(

2. Very low Volume.
This problem occured just lately... it wasn't apparent when the PSU/cold freeze issues started and even after the PSU replacement. Now it is and I found a lot of posts about replacing the caps near the jacks and in the audio path... I actually replaced most of the caps in the area on the main pcb with original smd ones, cleaned the whole pcb with isopropanol and checked tracks for obvious corrosion etc. but couldn't spot anything too suspicious.
The cathode of the cap right next to JK1 had a defective pad so I wired it up directly to the nearby via it was connected to.

I found a few more references to checking the DAC output with my oscilloscope and checking various other caps and parts inthe muting circuit which I am going to do later today.

I would try to find a refurbished main pcb and maybe original PSU for it if it would help revive it.. I really want it to be operational again so my nephew can enjoy it like I used to when I was younger.

After all these years I still enjoy Roland instruments... I still have an FA-06 and got myself a Fantom 6 a while ago which is a wonderful device.

Maybe someone had similar issues and can help narrowing down the causes.
Any help is highly appreciated.

Regards

PS. I will try to add some pictures when I get home later...

[Maxx2206]

Hi,

oh.. and 3. the incremental knob/turnwheel is acting up all the time. Using some contact spray helps for a short while, but it reverts to missing signals again. Guess I will have to fully replace it soon... any idea which incremental swtich would be a direct replacement?

[Maxx2206]

Hi,

small update... unfortunately not very promising.
I ended up replacing every singe electrolytic cap on the main board, including those around the DAC, but the quiet sound hasn't improved at all.
I found a few damaged pads/tracks near 3 caps, 2 of them pfro mthe contrast circuit. I fixed the single one with a small wire and removed C63/C83 from the contrast circuit and wired pin 3 of CN14 to GND instead.

While at it, I also removed the incrementalk knob and washed it excessively with a contact/anti oxide solvent which seemed to fix it.

I'm not sure what to try next to fix the quiet sound though... I will start with checking the voltages and analogue ground connection from the replacement PSU tomorrow but I doubt thats the reason.

[Maxx2206]

Hi,

another update... and I am stuck now it seems.
I noticed the FFC cable connecting the expansion board to the mainboard was very worn and caused sporadic issues like not detecting expansions properly or showinbg expansions but not being able to access them.
I couldn't find an original replacement (35pin, type b, 1.25mm pitch) so I ordered 2 30pin cables (10cm) and carefully cut a 5pion piece out of one, adjusted the pitch of the connecting side and used that instead.
Worked like a charm...

Status now is, the XP50 boots perfectly now. No more freezing issues even on cold boots. Expansions work perfectly all the time.
Since I had to disable/bypass the dimming circuit due to bad solder pads on the old caps the display now works stable as well.

The only thing I still wasn't able to fix is the very quiet sound output... which really sucks... The synth is simply not usable with such a low output. Kinda sad considering that all other issues could be solved.

[MatrixRat]

Is the low output evident in the Left, Right and Headphone outputs? Buffer problem perhaps? Do you have a schematic?

[Maumajamma]

I’m interested in your progress because I have an XP-50 that needs work. Also wonder if you take on projects for others… Cheers!

[Maumajamma]

viewtopic.php?f=4&t=61034&p=327333#p327333

[Maxx2206]

Is the low output evident in the Left, Right and Headphone outputs? Buffer problem perhaps? Do you have a schematic?

Hi,

this is the odd thing...
It seems the separate left/right jacks have no output at all.
The very low output is on the stereo AKA headphone jack.

With a standard headphone sound is almost not hearable at all with the volume slider full up.
But what is hearable (headphone or a stereo speaker set with preamp built in) is, that there does not seems to be any distortion or similar.. all smaples seem to sound right, just very low volume.

And yes, I have the XP50 service manual with the schematics. These were helpful but not as much as I was hoping Especially since many of the parts are very uncommon in my area and I have to search for replacements or alternatives all the time during my attempt to understand the sound path.
Next thing I will try is checking if I can find a relationship between left/right not outputting anything at all and stereo being so quiet. Luckily I got a oscilloscope what might be useful finding audio signal path components.

I really want this synth to be working again after all the work i put into it.
Even the USB floppy emulator seems to work a like a charm.

[Maxx2206]

I’m interested in your progress because I have an XP-50 that needs work. Also wonder if you take on projects for others… Cheers!

Hi,

replacing the caps was a bit of a challenge tbh.
But it was doable with some soldering experience (haven't done much lately but I am into electronics and used to solder and even create my own circuits/pcbs including SMD parts back then).
Since the mainboard was really very old (1994 model) and the caps worn, a few of them caused a bit trouble, but nothing that couldn't be fixed. In fact, the solder pads lifted of with two caps... I used a small wire to fix one, and the other one was from the contrast circuit so I just removed them and applied the contrast fix (grounding pin3 of CN14).

Experience returned/grew quickly once I started soldering... In fact, this small repair had me improve my smd replacement skills significantly.

I'd do it any time again... pity I'm a bit far from you though (Germany ;) )... I would have offered you assistance otherwise.

PS. If I had been more successful with the volume issue i would have created sshort youtube video showing the parts I replaced and the technique I used in the end...

[Foksadure]

Kuddos for the recapping work.

Since the mainboard was really very old (1994 model) and the caps worn, a few of them caused a bit trouble, but nothing that couldn't be fixed.

Must be from one of the first batches since the XP-50 was released in ealy 1995:
https://en.wikipedia.org/wiki/Roland_XP-50

Decoding the serial number should give the month and year of production :
https://serial-number-decoder.co.uk/roland/roland.htm
https://bossarea.com/sndecoder/

As Saxifraga already pointed out in another thread, there's a video on youtube that shows the recapping process.

https://www.youtube.com/watch?v=19y6_QMpAqQ

Seems easy, but I would'nt try myself, before doing a few SR-JV80 first. Congrats again for doing it yourself.

My 1995 XP-50 was serviced by a Roland registrered center twice: firmware ugrade at first, and - much later - worn switches replacement, mostly.
It's still not quite fixed yet, with an occasional crackling noise in the audio.
Yet, it was getting too expensive to have it fully serviced given the 2nd hand price, and the fact that I have a JV-2080 it can control and sequence perfectly.

[MatrixRat]

That corrosive goo that leaks out of caps can have hidden consequences like migrating underneath other SMD components and if it has not yet eaten tracks or vias away can create some leaky (= noisy) pathways. I'd be following the signal path with a CRO from the DAC to the outputs to see if the buffers are introducing the noise.

Mine had substantial goo and signs of corrosion around what looks like some ICs that may be audio buffers. Only fault is distorted crackling audio. From the looks, we have a split rail supply for the audio out buffers so their output (pins) should sit at 0V or within a few millivolts and stay there under no-signal condition. Have not seen a schematic yet.

Corrosive stuff can damage ICs by eating the plating offa the pins and finding it's way into the package.

[stansteph]

hi,

got the same kind of issues..
- a noisy sound but noise which seems to be gated
- strange too much modulation on some sounds
- C1 cursor which cut the sound
- fdd out of order

comments and ideas much appreciated

I will interested in the service manual if by chance you may have an electronic copy

big thanks beforehand

[Maxx2206]

Hi,

small update... more like work in progress/planning...

Since I wasn't able to find any service center that would at least try to fix my main board, and since there don't seem to be any repaired/reqorked mainboards available at the usual sources for ages already, I just ordered a pair of the uPC4570G2 opamp which I hope is the most logical common part to explain my extremely low volume.

Replacing the SOP8 ic shouldn't be much of a problem.. and I'll keep you updated if that finally fixes my good old XP-50

I will interested in the service manual if by chance you may have an electronic copy

You mean a PDF of the service manual including the schematics?

[Some-E]

Hi.

I've just looked at the schematics, helping to fix a friend's XP-50.

Very low volume: you have MUTE on for some reason. Line outs are muted after the line op amp -> headphone amp connection. Headphone amp is muted before the op amp, but the mute transistors don't go all the way down to zero ohm so some signal can pass through. That's how I see it.

Can verify by disconnecting/cutting the mute control signal.

[Fixer]

Hi, thanks for sharing your experience. Any updates on this? Especially regarding the opamp? Did you have this kind of issue with high frequency noise like in this video?

https://www.youtube.com/watch?v=902wtaz1c-4

This is not mine, but I have the same problem. I have done the capacitor changing for the main board but it did not help with this issue. Any ideas what might cause that?

Thanks in advance!