KR-4500 Schematics

[J-Major]

Hi Guys n Gals

I was wondering if anyone had the electrical schematics for a Roland KR4500.

Mine has developed a ground fault. I took it to the local distributers which is not an easy task as the thing weighs in at about 65kg but their "repairs" actually made things worse.

Any help or directions would be greatly appreciated.

Thanks
J

[David Hodges]

i take it you are getting aloud buzz from speakers if it is like mine anew main board is required i was told it could be the capacitors as they break douwn in old age!have changed all these to no avail the next move is to buy a damaged piano with a working board i have complete wiring diagram and a copy can be obtained from a uk specialist can give name if required have you removed main board and done avisual check

[J-Major]

Hi David

Thanks for your reply. Good diagnosis, I would agree that it is probably the caps. Be careful with the type of capacitors that you replace them with.

With sound gear it is not only the capacitance that must be the same but also the dielectric material. If you replace a tantalum cap with an electrolytic you will change the characteristics of the circuit due to vast differences in the ESR (equivalent series resistance) that can occur between capacitor types. This effectively changes the characteristic of any filter causing it to let through frequencies that the designers were trying to remove like mains hum (100-120Hz buzz that you often hear in cheap mains driven kit).

Electrolytics are typically very leaky (good enough for smoothing power supplies where their leaky characteristics are sometimes favoured), but they suck for filters. I have often seen hobbyists replace some fancy super low ESR tantalum cap with a cheap electrolytic that really might as well not even be there because its characteristics are so bad. I mention electrolytic because they (along with ceramic caps) are the easiest to come by in hobby shops but neither are any good for audio filters

I am not sure how to access the main board. I removed all of the screws for the back panel but the panel remained firmly attached. I did not want to risk breaking anything so just put everything back. I was hoping that if someone had schematics then they probably had some form of disassembly instructions as well. There are probably screws on the underside that need to be removed as well, I don't know, but I will need to get someone to help me turn the piano upside down if that is how one needs to get access.

The reason that I went for a ground fault is that certain columns of buttons do not work whereas others do. This is only since I sent it in, so I am sure that it is some bad soldering or cracked tracks or something in that league.

Best regards
Jeremy

[David Hodges]

with ref to your comments thanks
if you look up under the keyboard you need to take out 4 screws2 left 2right then you can lift the key board up 90degrees then it is held on 2 wire stays exposing all the innards looking from front on left power supply and audio amp
in middle main pc assembly board connected to this by variousplugs all of different size so they cannot be mixed up
is sound out to amp ,2 leads to key board ,,lead to floppy drive,led to screen,,lead to all buttons on console about 15 scrwes attach a metal screen/cover over the main board undo these,remove plugs carefully and you can now remove
the main board that controls everthing turning digital to anlogue and hence sound from speakers hope this helps otherwse ring me uk 0044 1934 712706
regards david hodges ps disconnect any leads on rear ,move forward from any wall at back so as to let keyboard become vertical

[J-Major]

Hi David

Thanks. This is exactly the info that I need. I guess that takes care of this weekend.

Best regards
Jeremy

[Andrej]

Hi there,

i have the same, obviously common problem with my 4500.
Mainboard caps leaking and destroying the copper leads.

Any experience which caps are commonly broken and/or if repairs will restore the piano? Will other parts of the main board be severly damaged even if they look o.k?

Some look very good others are corroding the soldering points.

Will SMD aluminum electrolyte caps that look the same from the outside be o.k. or can i use others that might be more resistant to leaking?

Could anyone send me the schematics? Most of the leaking capacitors are in the d/a-converter section.

thank you lots.

Euer Andrej

[stig]

Contact

spares@roland.co.uk

for service notes and spares

[Foosy]

Hi all,
I have a KR 4500 that started behaving strangely:
The notes are sounding an octave lower than they should be.
Also some of the settings seem to be stuck so that you can't change them.
Finally, when you turn the unit on - it displays a message: "No memory backup>press write"

I do not have the hum or crackling sound that others referred to as the common issue with this piano.

Any help would be greatly appreciated!

[Foosy]

I wanted to add these additional details:
1. Doing a factory reset (Load + save + Write) reloads factory defaults, but does not solve the problem.
2. The "Tune" and "Oct shift" buttons are always lit and can not be turned off.
3. Pressing the "Tune" button shows: Master Tune 4y3.5Hz. This is not a 'y' but a garbled character.
4. Pressing "Oct shift" shows: Octave Shift
B:_ 11_-2_11_2_11. Some of these are gibberish and pressing the inc/dec buttons do not change anything.

Hope this helps...

[Foosy]

Have been trying to fix this 4500 but could not get it open. David posted instructions above that got me in the right directions.
Here are the full directions:
1. Remove the note holder from the top and push the piano far from the wall.

2. Underneath the keyboard there is a horizontal metal with many screws. Do NOT unscrew these.
Also , do not unscrew any screws in the back panel.

3. Locate and unscrew 3 screws on the right, 3 on the left and one in the center - all underneath the keyboard. The one in the rear right and rear left may be a little difficult to get to, as they are just above the backboard.

4. Hold the right and left sides of the kr4500 and lift up. Note that the keyboard should stay down.

5. Inside are the boards in the order that David described.
The main board has a metal cover. I suggest you take a picture before removing all its screws, especially due to the back screws that have a spring metal attached to them.

Now, I do not see blown or damaged capacitors.
Anyone know if there is something I could look for the problem of the octave shifted and buttons not responding (see my previous post)?

[Helen]

Hi, I'm afraid my main processor has also died. I'm really annoyed as I only bought it 6 months ago (second hand). But it had the common problem of crackling and buzzing. Could you direct me to where I can get a copy of the circuit diagram. My next task is to find someone to replace the capacitors, as so far nobody want to touch it.
Cheers Helen

[Shadow52]

Hi Helen,

Doyou havealready the diagrams of the KR4500?
If not let me know and send them to you by email.
I had the same problem en i changed all capacitors by standard electrolytic types.
The KR is working as new. Total cost was 21 €

CU

Anton
anton.pauwels@telenet.be

[Helen]

Hi thanks for that. I managed to find someone to replace all the capacitors for me and clean up the board. It is much better now. It still crackles a bit when
I first turn it on if the brilliance is on high, so crossing my fingers that it won't get any worse.

Thanks

Helen

[Sharon_]

I've been searching to find any way to start to fix the problems with KR-4500. Would you send me the diagram, too.

[Sharon_]

Thanks Anton for the diagram. Now I need to find someone to work on my KR4500. Wish me goold luck.