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Kurzweil PC361 display and lights problem


szurcio

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I haven't played my Kurzweil (PC361) for a while and when I turned it on, I noticed that the display is dark. It stays bright for the first 30 seconds after booting but then (especially when I hit the keys and start playing) it's gradually dimming until it becomes unreadable. It's completely dark on the left side and lit only a little on the right side. Also, none of the buttons lights up - for example, when I changed to the KB3 mode, I remember most of the buttons above the sliders did light up in the past - now it's no longer the case. The synth itself still plays and when I used it with a computer editor, I didn't notice any problems. First I thought it's only a display problem but since the button lights don't work either, I'm not sure what it could be.
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With lights not working also, possibly one of the voltages that feeds both the display and button lights. There are some IC power regulators on a couple of the boards, would have to be traced out with schematics to find out if the above is even likely.

At least more promise than if just display went out - the original display module is no longer available, and the replacement kit (I understand from posts) is rather expensive, enough to make it questionable whether worth repair.

 

A good tech with access to Kurzweil's service information needs to look at it to really be able to diagnose.

 

My PC3 (also have 361 and X) lost all analog audio a couple of years ago, After failing to component level troubleshoot, and figuring the cost of replacing the two boards that are likely suspects, I've been using it at church (since I don't have to move it often) with the SPDIF Digital Audio connected to a small external DAC. If anything else goes out on it, I would be likely to either sell as-is or part it out (or keep parts for my other two).

 

Howard Grand|Hamm SK1-73|Kurz PC2|PC2X|PC3|PC3X|PC361; QSC K10's

HP DAW|Epi Les Paul & LP 5-str bass|iPad mini2

"Now faith is the substance of things hoped for, the evidence of things not seen."

Jim

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They may be separate issues. The dying display is pretty common -- I had mine in the shop a few years ago for that as well. There are even third party sellers of replacement backlights or whole displays, if you're into do-it-yourself.

-Tom Williams

{First Name} {at} AirNetworking {dot} com

PC4-7, PX-5S, AX-Edge, PC361

 

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Yes, they may be 2 separate issues - but the display stays bright as new for about the first 30 seconds so I was hoping it's some (hopefully less expensive) electrical problem not a dying display. I just love the sounds of a PC3 so much and pre-owned Kurzweil keyboards are more than $1,000 on EBay so with my teacher salary I think I'll just keep fixing the old one. I also have a Motif keyboard from 2003 and it never gave me such problems. My Kurzweil was already once in a shop (digital output not working). Does Yamaha have more reliable components?
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Just a thought - I presume that you have turned the pot on the back of the PC3 that varies the brightness, but it might not have come to mind.

 

Reliability: I've been in electronic work for close to 60 years. There has been a significant loss of reliability since a decade or so ago when the EU passed a law that nothing (except military, medical, or aeronautic electronics, where reliability is supreme) containing lead could be imported. Solder was made with about 60% lead. The newer stuff without lead just plain doesn't do as good a job for reliability over time as the old lead core solder. This affects all manufacturers, not just Kurzweil.

My firm was an Authorized Yamaha Service Center for musical products for a decade or so, I can assure you that (although generally well-built) there were service calls there also. We don't do music electronics now, focus is on computers and networks.

 

 

Howard Grand|Hamm SK1-73|Kurz PC2|PC2X|PC3|PC3X|PC361; QSC K10's

HP DAW|Epi Les Paul & LP 5-str bass|iPad mini2

"Now faith is the substance of things hoped for, the evidence of things not seen."

Jim

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Just a thought - I presume that you have turned the pot on the back of the PC3 that varies the brightness, but it might not have come to mind.

 

It´s also possible this pot now has contact problems after being unused for a longer period of time.

 

Anyway,- for the display there´s a much better replacement available.

 

 

There has been a significant loss of reliability since a decade or so ago when the EU passed a law that nothing (except military, medical, or aeronautic electronics, where reliability is supreme) containing lead could be imported. Solder was made with about 60% lead. The newer stuff without lead just plain doesn't do as good a job for reliability over time as the old lead core solder. This affects all manufacturers, not just Kurzweil.

 

True.

Ironically, the old solder is available for repairs in europe.

That´s what I use when gear is out of warranty and starts introducing issues.

Resolder everything possible.

 

A.C.

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Interesting! However, I'm really bad at repairing anything, especially if soldering is required.

EDIT: I noticed the seller says no soldering is needed - that's good!

 

Yes, no soldering anymore. The ribbon is attached already.

But you have to learn how to open the PC361, how to remove the old display and replace.

There are some youtube vids about disassembly of a PC3 somewhere ...

 

Would it also fix any backlight problems?

 

Replacing a display fixes the display issues.

It doesn´t fix nonfunctional button-LEDs like you described for the KB3 button in your 1st post.

Can be everything like contact problems (plug/ socket), soldering joint(s), single LED failure, other LED controlling component failure or supply power issue.

 

A.C.

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OK, it's worse than I thought - the front panel board with the transformer is bad. That has been causing the voltage issues. They want $800 for repair. I always had it plugged into a Furman surge protector - what could have happened?
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Guessing my pc3 has a similar issue, though all the buttons work I think. Mine will "flicker" and once in a while stay dark, but fortunately a tap or two on it will make it come back. I had a guy check it, he's just someone I know that has owned and worked on a number of Kurzweils over the years, and he couldn't find anything wrong that he could fix (like a loose connection etc). His general thought was that "the screens on Kurzweils eventually all go bad and need replacing".

 

Might or might not be related, but I had the thing not boot during a gig and it refused to do so (loading into various error and garbled screens) until I went into their "safe mode" (or whatever it is called) and initiated a boot. Ever since, it has booted fine, though the screen flicker is still there. At that gig, I plugged directly into stage power, they had outlets all over the place. Normally I use our bass players Furman rack, which is just one of the <$100 deals and not one of the fancy ones. Nevertheless, it did make me wonder if the power at the place had something to do with the problem.

 

Unfortunately I can't really sell it like this--I'd have to take a huge loss since I'd disclose these things--and I expect the repair cost (as you found) would be the worth of the keyboard (I paid 875 used about 4 years ago). I'm just going to ride it until it drops, it's been a great gigging keyboard (other than "the incident") and it makes a great controller for my home studio. It does make me very leery about buying another Kurzweil though.

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OK, it's worse than I thought - the front panel board with the transformer is bad. That has been causing the voltage issues. They want $800 for repair. I always had it plugged into a Furman surge protector - what could have happened?

Too bad there isn't a Louis Rossmann for the synth world. Mac folk might know who I'm talking about.

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I think I'll just keep using it until it dies - I'm not going to pay $800 for a keyboard I got new (old stock) for about $900 a couple of years ago. I wish I had known more about technical stuff - maybe I would try to do it myself for less money.
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I am also on "Hail Mary, Cross Fingers" mode with regard to my PC3's display backlight. About 6 months ago the flicker thingie started happening, so I would just tap the brightness knob with my finger... that did the trick. (Loose wiring or bad solder?)

 

Over the past 4 or so months, the problem hasn't come back. Ticking time bomb, I suppose. But I'll deal with it when it happens. I have a backup synth when the time arrives.

Kurzweil PC3, Yamaha MOX8, Alesis Ion, Kawai K3M
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I'm going by PC3 info here but I assume the PC361 is similar - still something to be aware of.

 

That's the power supply transformer - wrong part! There's a separate transformer (5Volt) that powers the LED/Backlight which is mounted to the front panel board. If you're thinking about replacing the front panel board there are a couple of concerns: 1) Does that replacement board from instrumentalparts.com come populated with the LED transformer? 2) There seems to be 2 versions of this board and I'm not sure which LED it's compatible with. May not be an issue but something to check up on. Also

 

OK, it's worse than I thought - the front panel board with the transformer is bad. That has been causing the voltage issues.

 

There are a number of other components in this circuit. It's easy to determine that the output is not providing any or the wrong voltage/current. But did your tech isolate it down to the power transformer itself? Could just be a 50 cent part that needs replacing. I just wouldn't want you to replace the transformer assuming you can find the right part only to find out it wasn't the culprit. Kurzweil has the approach of replacing whole boards - even at their own service department and they do not provide part numbers or parts for individual components.

 

If it were me (and it might be one of these days with my PC3x) I would try to check if that replacement front panel board has the LED transformer. If it does you might run that by your tech and see what he'd charge to install it.

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Thanks! Do you think the LED transformer can cause voltage problems for the whole unit? I'm mostly using this keyboard now in my studio so I don't necessarily have to have a working display and lit-up buttons. I could use it with a PC editor instead.
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Thanks! Do you think the LED transformer can cause voltage problems for the whole unit?

 

Well without doing extensive analysis I'd say no. The front end of that circuit is driven by secondary voltages that look to be well isolated with fairly high value resistors. And I think that side is drawing pretty low power. Btw one of those secondaries provides a divide down voltage adjustable with a potentiometer. I wonder if your tech thought to adjust that and see if it made a difference. :idk

 

 

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Instrumentalparts says I would have to buy both of these if I have an older PC361:

Its a two part thing if you have the older unit - https://www.instrumentalparts.com/ams-101040064002.html and https://www.instrumentalparts.com/ams-101090023002.html

[About $600 together]

 

That would explain the $800 estimate you received. Sadly not worth it imo.

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I get you there. At a certain point it's not worth selling, or someone buying it if it's non-functional in a major way.

 

I'm using mine as a home studio controller so assuming it can send midi I don't even need to see the screen (I only use the keys and mod/pitch wheels, I haven't set up anything fancy with the other controls). It makes an excellent controller, love the action.

 

I'll keep gigging it until either the screen completely fails or it has a constant boot issue again. Every gig helps pay for a replacement!

 

 

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I had similar problem with my Korg CX-3. Mother Board went south and only worked as a controller. New MB cost $600. Some things just aren't worth fixing even if you have the know how. I'm not sure if the Kurzweils are anymore susceptible to failures than any other manufacturer. Yes there's been a history of the display/backlight itself failing but this is the first time I've heard of the display and LEDs failing with the xformer being the cause. Sometimes things just fail with no apparent cause. We call that random part failure and it can happen to anything.

 

It sucks. If you're in the DC area and would like me to take a look at it let me know. As always no guarantees, but no charge.

 

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Thank you but I'm in Birmingham, AL unfortunately - not exactly the best place for synth repair services but I'll take it to another technician (not directly affiliated with Kurzweil) to get a second opinion. Maybe they'll have a closer look at the individual components instead of suggesting a whole panel replacement.
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Update: I took it to a local keyboard repair guy. He replaced 3 shorted capacitors on the right panel that were killing the 5v power supply. Parts: $11 + Labor: $100 = $111 (instead of the $800 that an authorized Kurzweil repair center wanted to charge me for replacing the whole front control panel and the display because apparently that was supposed to be the only way to have it fixed). It's working perfectly now.
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