Roland D50 Main Board Fault

[pp10050]

Hi everyone. Hope someone can help. I recently bought a faulty D50 for parts for my old one, but now I am trying to get this one working. It has a problem on the Main Board, the 5 volt rail is being dragged down to about 3.5 volts and about 1 amp is being drawn. I know this is far too much as the Regulator in the PSU is only rated at 0.5 amp. Does anyone know of any common causes for this or do I have to try and isolate the faulty part the hard way. I have replaced the back up battery which was extremely flat and had been in there for about 6 years. I have the service manual for this and the circuit diagram, the fault on the unit when I bought it was No Sound Output and the display just lighting a few blocks. The reset voltage is low (due to the +5v being low) so I assume the board is unable to initialise. Any help would be appreciated.

Thanks, Paul

[Enzo]

Look for something getting hot. That power is going somewhere.

[pp10050]

I've checked and found that that 2 or 3 of the RAM chips are getting hot (IC 1 thro 6). I removed L2 which feeds the 5v to them and the rail has come back up and the front panel etc works ok. I don't understand why more than one should be getting hot/faulty. Is it likely that more than one chip is faulty or will something else be causing them to overheat. At least I now know what is pulling down the 5 volt rail. I will isolate each chip one by one tomorrow to see which one(s) are causing the problem.

Thanks for the quick reply, Paul

[Enzo]

Or just replace them both.

The failure of one could be enough to lock up the processor, leaving the "good" one unaddressed, so it sits on one address cooking. I wouldn;t trust it anymore even if it was innocent.

[mgmcgill]

Hi pp

Don't suppose you'd could spare 2 of the grey buttons from the Patch Bank

I've got 2 broken ones and I'm having trouble sourcing replacements in the UK

Will happily pay for them

[pp10050]

Yes, you can have some buttons. I've given up on repairing this board as the chips (D41416C) seem to be impossible to obtain. I will need your address, can you PM me or put it up on here?

Paul

[mgmcgill]

Thanks PP

Sent you a pm

[mgmcgill]

Thanks Paul

Buttons arrived today

If I can help you with anything in return let me know

I've got left over tact switches from when I replaced mine on my switch board and got tonnes of sys ex files for the D50 & DX7 if you want

Thanks again

[pp10050]

As regards sysex files for the D50, at the last count I have about 32500! so I don't need any more. I have just installed the M.EX mod board from Musitronics so now I can have 192 patches on board at a time However, some of the tact switches on my D50 are troublesome. How many do you have left over, I bought some off E-bay the other day which looked identical to the originals, but when I put them in I found that they would not operate when the board was put back in place. I take it that yours did not have the same problem?

Paul

[mgmcgill]

Hi Paul,

I've plenty. I bought 60 off (3 packs of 20), to replace all the tact switches on the board (there's 54 of them) but I only replaced the bottom row (Tune, MIDI, Internal, Card, Bank & Patches). I also replaced the row below the LCD and after a test, the Enter button, so still got about half left.
I ended up not replacing the others because after I did the button test diagnostic, all others where working perfectly fine.
To be honest, some of the others were soldered a bit to close to an adjacent resistor for comfort.

They're of top quality purchased from RS Components & made by Alps and are identical in size etc
They solved my problems of problematic buttons and now all my buttons are great (thanks to your replacement plastic)

Tell me how many you need and I'll send them to you.
If you want more, let me know & I'll order them for you (my work has an account)

Michael

[pp10050]

Hi Paul,

I've plenty. I bought 60 off (3 packs of 20), to replace all the tact switches on the board (there's 54 of them) but I only replaced the bottom row (Tune, MIDI, Internal, Card, Bank & Patches). I also replaced the row below the LCD and after a test, the Enter button, so still got about half left.
I ended up not replacing the others because after I did the button test diagnostic, all others where working perfectly fine.
To be honest, some of the others were soldered a bit to close to an adjacent resistor for comfort.

They're of top quality purchased from RS Components & made by Alps and are identical in size etc
They solved my problems of problematic buttons and now all my buttons are great (thanks to your replacement plastic)

Tell me how many you need and I'll send them to you.
If you want more, let me know & I'll order them for you (my work has an account)

Michael

I sent you a PM

[mgmcgill]

Hi Paul,

You want to check that PM you sent to me?

I don't see anything in my mailbox

M

[Enzo]

If they are the common little tactile switches, I'll wager the problem with the ones you bought that don't work is they have the wrong length actuator. If they are too short, the panel button can;t reach them, and if they are too long, the panel button winds up pushing them down even at rest. A simple test is to power the system up with that board out of the panel and see if the new microbuttons will operate by finger. The difference between a 4.5mm and a 5mm can be all it takes.

[doctor]

If they are the common little tactile switches, I'll wager the problem with the ones you bought that don't work is they have the wrong length actuator. If they are too short, the panel button can;t reach them, and if they are too long, the panel button winds up pushing them down even at rest. A simple test is to power the system up with that board out of the panel and see if the new microbuttons will operate by finger. The difference between a 4.5mm and a 5mm can be all it takes.

The SKHHAMA010 switches having 5mm stem height are used in the D-50.
They can be replaced with the SKHHAKA010 switches having the same stem height, but less operating force (1N instead of 1.6N).

[mgmcgill]

The SKHHAMA010 switches having 5mm stem height are used in the D-50.
They can be replaced with the SKHHAKA010 switches having the same stem height, but less operating force (1N instead of 1.6N).

I used the MA010 switches