Roland XP50 LCD Display Problems

Forum for JD, JV, XP and XV synthesizers from 1990's
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

The value of C83 and C63 will not impact on the LCD brigtness, believe me. So you may use the 1uF or 0.47uF to replace the original 0.1uF.

In mine I have not replaced the power supply caps yet, normally these are more robust than SMD caps and last more. Unless you find some traces of leakage or some ripple (60 / 120Hz) on sound.
These caps don't necessarely need to be high quality, because this is not a switching power supply, it is a convencional power supply that operates with 60Hz.
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Thanks very much, Cesarsound. I'll continue working on this and get back here if I still have questions.
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Hi Cesarsound, I was able to get a Service Manual for the XP-50 and it has the schematic. On the schematic I am seeing the value "50CVR1" for C83 and C63, but I'm not familiar with this notation. Does it mean "50V 0.1uF"? If so, the schematic that you have must be different since you said those caps are 1uF in your schematic. Would you like to have a copy of my Service Manual for comparison? I can email it to you if you want. Just give me your email address.

Also, the Service Manual says that older batches of the XP-50, those with serial # below ZH33050, had a Sharp brand LCD display. In the later batches, those with serial # ZH33050 or higher, the LCD display was changed to OPTLX brand. The serial # of my XP-50 is ZH47673. What's the serial # of yours?
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

Hi mtl777,
I'm not familiar with this notation because this is an internal Roland notation. The fact is that physically the cap value present on my XP was 1uF x 50v (see pic take before the replacement, it is clearly 1uF x 50v).

Image

And also another pic posted by the guy Obsolet in this thread:
http://www.obsolet.de/gfx/XP50/IMG_1939.JPG

My XP s/n is AH64380 (purchased in 1995). I uses Hitachi LCD module.

Cesarsound.
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Hi Cesarsound, I'm thinking that the "R" in "50CVR1" means a decimal point because I sometimes see resistor values like 4R7 Ohms which means 4.7 Ohms in some schematics (I am just making an analogy here). I guess then that the XP-50 schematic may have different versions. Either that, or it doesn't accurately represent what the actual values are on some components because there may have been several changes made already that were not updated on the schematic. Another example of a difference is C902. It is 10uF 16V on the schematic but it is 330uF 6V in my actual synth. Now that's a big difference!

According to the schematic, there should be a connection from left side of R74 to pin 7 of IC17B. I have confirmed this to be true in my actual PCB as I see that there is indeed a connection. However, what I am not sure of is the connection from right side of R73 to left side of R74. According to the schematic, there should be a connection. But in my actual PCB, there is a trace that goes from right side of R73 to left side of R74 but the trace is cut short before it reaches R74. The thing is, the cut looks very clean. It does not look like the cut is due to corrosion from a leaking capacitor. It looks like the cut is intentional as part of the PCB design. And now I'm wondering if my PCB version is different and has been changed by Roland to cut off the connection between R73 and R74. Do you think this is highly possible, or is the cut really due to a leaking capacitor and am I just not seeing it clearly (it's so small even with a magnifying glass)?

Sorry for my uncertainty, which is due to my seeing those differences in some component values between the schematic and the actual board. I just want to be sure that there really should be a connection between R73 and R74 in my particular PCB version and that I will not damage anything by putting a connection between these two resistors. I would be more than happy to hear from you that there really should be a connection and that it is very unlikely that Roland would intentionally cut off the connection in my board's version. It would free me of my worries. :-)
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

It will always have differences between hardware and schematics in all areas, I saw it several times, so it is not recomended to trust 100% on it. But according to electronic topology, the R73 must be connected to pin 7 and consequently to R74, as R74 is the looping gain (negative feedback of opamp). The R73 is the current path that sends the signal of -0.5v to +0.9v to the pin 3 of LCD, to adjust the contrast of it. In my XP it is exactly this way and contrats adj is working perfect.

CS.
Attachments
LCD_CONTROL.jpg
LCD_CONTROL.jpg (41.22 KiB) Viewed 5796 times
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Thanks very much, Cesarsound! I am now confident and will do the rewiring between R73 and R74.

One last thing. It was previously mentioned several posts back that someone "wired pin #2 of IC17 with R74 left and R73 with R74 (right to left)". This was a typo error, right? I think it should be pin #7, not pin #2, that should be wired with R74 left. Anyway, I see in my board that there is continuity between R74 left and pin #7 of IC17B -- the trace is not damaged so I do not have to do this rewiring. I only need to do the rewiring between R73 and R74.
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

It was a typo error, because the pin 2 is related to the battery voltage checker circuit.
Attachments
V_BATTERY_CHK.jpg
V_BATTERY_CHK.jpg (58.92 KiB) Viewed 5788 times
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Hi Cesarsound, you are a God-send, thank you so much!!! I rewired R73 to R74, replaced C83 and C63, and it worked! Woo-hoo!!! You can't believe how happy I am that the problem is fixed and my XP-50 is back in business!

When I powered it on I saw a horizontal bar for a moment on the top line of the display but then it disappeared. Then the display was very faint, I had to turn off the lights in my room to see anything on the display. But at least I could see something even if it was hardly readable, unlike before the fix when I could not see anything at all. I knew it was a good sign. Then I performed the factory reset procedure and voila! The display became very clear and everything went back to normal. I played some patches and they sounded great! I think my XP-50 sounds better now, the sound is more punchy and robust after replacing all those caps in the audio signal path.

Question: According to the Service Manual, if you removed the battery or disassembled the main board (both of which I did) you need to perform the bender adjustment that's accessible in Test Mode. Do I still need to do that even if I had already performed the factory reset?

Lastly, if the cause of the LCD display problem is the leaking caps C83 and C63 with their corrosive electrolyte damaging the traces, what could have caused C83 and C63 to leak? And why were so many people having the same problem? Is it a faulty design or "bug" of the XP-50 circuit that makes these caps prone to failure and leaking? What could be done to prevent this from happening again? Use higher temperature rated caps perhaps? Use higher voltage rated caps? Is 50V rating enough for these caps?

Thanks again!
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

Hi mtl777, good to know that your XP is working now.

The correct is to proceed with the bender adjustment. I did it on mine.

What could have caused C83 and C63 to leak?
In my understand 2 factors: the age of it and the fact that these 2 caps work with high frequency (above 30kHz) due to the PWM operation principle. Caps that operates constantly with high frequency will fail early.

Yes, it is a XP bug, becasue it is a too much sophisticated and complex circuit to adjust the LCD contrast. Even the Fanton X uses a simple potentiomenter to do this task.

I think these 2 caps are simple ordinary cheap elect caps, the correct should be use the high freq. caps or ceramic multi-layers caps or polyester caps (non polarized).

CS.
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Cesarsound wrote: I think these 2 caps are simple ordinary cheap elect caps, the correct should be use the high freq. caps or ceramic multi-layers caps or polyester caps (non polarized).
So that circuit can work with either polarized or non-polarized caps for C83 and C63? I happen to have a few Wima 0.1uF 63V polyester caps. Can I simply replace C83 and C63 with these non-polarized polyester caps without changing anything else in the circuit? Is this perfectly safe to do? And is 0.1uF still the correct value if using non-polarized?

By the way, why did Roland use polarized caps for C83 and C63 then? Is it simply because they are cheaper and not because the circuit requires polarized caps?
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

Yes, non polarized will work perfectly too, without changing anything else in the circuit. The only problem is that usually are bigger, what may difficult the assembling.

Roland use elctrol. because they are smaller and cheaper.
mtl777
Posts: 20
Joined: 23:45, 1 December 2010

Re: Roland XP50 LCD Display Problems

Post by mtl777 »

Thanks again, Cesarsound! I have replaced C83 and C63 with Wima 0.1uF 63V non-polarized polyester caps. It's working great! And in addition to replacing the many audio signal path related caps, I have also replaced all the electrolytic caps in the power supply. My XP-50 has been reborn and all these high quality caps I used have made it even better now! I have noticed a certain fullness and smoothness in some patches that used to sound digitally thin or harsh before. Something's telling me I will continue to enjoy my XP-50 for a very long time! Thanks to you and this excellent site!!!
Cesarsound
Posts: 369
Joined: 04:50, 24 December 2005
Location: SP - Brazil

Re: Roland XP50 LCD Display Problems

Post by Cesarsound »

mtl777 wrote:Thanks again, Cesarsound! I have replaced C83 and C63 with Wima 0.1uF 63V non-polarized polyester caps. It's working great! And in addition to replacing the many audio signal path related caps, I have also replaced all the electrolytic caps in the power supply. My XP-50 has been reborn and all these high quality caps I used have made it even better now! I have noticed a certain fullness and smoothness in some patches that used to sound digitally thin or harsh before. Something's telling me I will continue to enjoy my XP-50 for a very long time! Thanks to you and this excellent site!!!
Hi mtl777,
Yes, good caps on adio path make the difference. I know this well, becase I have assembled pre-amplifiiers and power amplifiers using polyester caps instead of electrolytics, and the results are really terrific. The problem of common electrolytic is that they are not linear for AC signals.

I wish good luck to you and your XP. And I will be here to help folks when it is possible.

Cesarsound.
User avatar
Remodulator
Posts: 2
Joined: 08:08, 26 April 2012

Re: Roland XP50 LCD Display Problems

Post by Remodulator »

Hello Roland folks,

I wanted to thank Caesar sound for providing this helpful thread.

I repaired my XP-50 on the weekend by replacing the two troublesome capacitors C63 and C83 and then installing a short link between R73 and R74. In my case, the circuit track between R73 and pin 7 of IC17 had gone open which I confirmed with a multimeter. Although replacing two components seems like a trivial task they are tiny and a lot of care is needed. A soldering iron suited to SMD work is a must as are tweezers and a magnifying lamp. I could only get 0.1 uF 35v Tantalum SMD capacitors, which are technically under rated but they seem to be working fine. I hope the voltage won't be a problem.

A photo of my handy work....

http://s14.postimage.org/pim6r6wep/Rola ... paired.jpg

A couple of notes;

I cut the old electrolytic caps off the board and then desoldered the leads to reduce the amount of heat applied to the PCB. The electrolytics are soft metal and easy cut with a good set of sidecutters. Cleaned the spilled dielctric with isopropanol and tinned the PCB pads with lead free solder.
Even with a magnifier I could not find any evidence of a damaged track between R73 and pin 7 of IC17. Without the circuit and multimeter to check I would have never suspected the damage.

Anyhoo. Everything is working as it should and I can get back to playing music without having to guess what patch I'm playing. Happy days...!
Post Reply