Roland D-50 D50 keyboard repair forum..

[niteowl]

I looked at the dynascan board with my scope. With no keys pressed, I see a normal scan on the 8 row drives. Each
line is normally high (5V) and each line goes low in sequence for about 22us each, a total of about 176us per scan. The
16 column lines are all high when no keys are pressed. If I press a key, I see the row scan pattern change, and its too
irregular for my scope to capture properly (its almost as old as the D-50...). With a key down, the expected column line
shows activity. I don't see anything wrong or suspicious with the row/column scanning.

This sounds very similar to the situation reported over at electro-music.com :: View topic - New problem with trusty old D-50,
which also has a pointer to the dynascan schematic: http://home.arcor.de/richardon/richy2001/d50/sch4.gif

You're right that a _short_ on the address/data cable would be catastrophic, but an open would only affect the
data going to/from the dynascan board. I verified activity on all the wires going to the CPU but I can't tell
much about what's happening. So I guess it could be a short/open on the wires between the 6116 and the 63H149.
The 63H149 is a surface mount device so it would be easy for one of those 80 pins to come loose with a bump. I don't
think I tried retouching those solder points. The resistor packs are also surface mount but the signals look okay.

Pinball eh? I used to have a Gigi pinball machine. Learned a lot about electro-mechanical devices from it.

[niteowl]

Success!! I retouched all of the pins going between the 6116 and 63H149 and the keyboard works again! Everything looks and
sounds normal.

[Enzo]

Great!



I used to be pretty darn good with electromechanical pins, I really honed my troubleshooting, reading their relay logic. Then around 1976 it all turned digital and a whole new learning curve started.

[doctor]

Great!



I used to be pretty darn good with electromechanical pins, I really honed my troubleshooting, reading their relay logic. Then around 1976 it all turned digital and a whole new learning curve started.

Well done, niteowl.

Some tips on digital circuitry troubleshooting.

If you assume that the digital core (Controller + RAM + ROM)
of the device under repair does not work properly, the RAM
activity is the first suspected item.

All RAM control signals (CE, OE and WE for SRAM and additionally
CAS/RAS for DRAM) should be examined firstly.

Address and data buses should be checked after that.

Data bus is both asynchronous and bidirectional, for this reason it
is impossible to capture a stable picture by regular digital scope.
If you see stable pulses, it means that something is wrong.

The third item, which should be checked, is data bus continuity among
Controller-RAM-ROM. You can see the “live” data bus by means of scope,
but this is insufficient due to bus bidirectionality, (for example, controller
sends data to the RAM, but defected RAM does not send data back).

If the data bus continuity is intact as well, replace the RAM chip.
It is a standard chip and as a rule is relatively cheap.

Good luck.

[Enzo]

There have been times in the past - haven't been in this sort of digital stuff in a while - when I wanted to see if some tri state thingie was getting the information onto the data buss or not. Lacking a scope that would latch onto it, a data analyzer, I often could watch the data lines and toggle whatever I was interested in, and watch. It couldn;t be resolved into anything, but I could still see in the data stream SOMETHING was changing back and forth, so for better or worse it meant a good likelihood that gate was working.



Oh, and by the way, you DID convince me otherwise.

[niteowl]

Failure!! A day or so after I 'fixed' the keyboard, it started failing again in exactly the same way as before. I swear it was working after touching up
the solder points. I had buttoned it up and was playing it for a few hours. I turned it off and let it sit for a few days. Then I came back, turned it
on and the keyboard was back to only making sounds when releasing the keys.

I am suspicious of the 6116 SRAM so I have ordered a replacement chip. In the mean time, I removed the original SRAM. The crazy thing now is
that with the SRAM removed, the keyboard is failing in the exact same way.

[niteowl]

Success!! The replacement SRAM arrived today and I soldered it in and the D-50 is working again. Hopefully, it will stay working now.
I purchased the chip from Avnet for about $2. The part# was IDT 6116SA15TPG which is the narrow plastic package.

[Rhodesplyr]

In college, I got roped into playing keyboards for a musical, and the director wanted me to use his Roland D-50 for some of the songs. In the middle of one of the performances, it suddenly seized up. No amount of rebooting would get it going again. Fortunately, I was able to finish the rest of the shows on my Rhodes Suitcase 88, atop which the D-50 was sitting. Thus, the D-50 has the honor of being the only keyboard I've ever played that failed completely during a performance, and I think that that experience has something to do with my large collection of vintage analog organs and keyboards :-)

[PANCHO]

Hi there
how can i recognize the 6116, where is it ? I can see the 63h149 on the dyna scan board. But i been searching for hours trying to identify the idt6116sa15tpg.
Please help

[Jazz P Bass]

IC SRAM 16KBIT 15NS 24DIP - IDT6116SA15TPG

[PANCHO]

Hi there
thanks a lot.
Sadly my english is not so good.........what i want to know is wher i can see the idt6116sa15tpg on the d50.
I can not find wher it is located.
Is it in the dyna scan board ? In the main board ? Somewhere else in the synth?
Can it have another number or name in my d50? Is that the reason i can't find it ? How can i recognize it in one of the boards?
Anyway , i know where to buy it now !!!!! Thanks a lot.
Help
thanks
pancho

[niteowl]

It's the only other IC on the dynascan board. It's a 24-pin DIP. The
schematic shows it as 'IC2 LC3517 AS 12 (RAM)' but its just a standard 6116 SRAM.

[kennyz]

Hi niteowl, Enzo, et al,

Last night, I decided to take out my Roland D-50, which has been in its case for about 20 years. The unit still shines like it's brand new. I powered it on, and received the "Replace battery" message, so I replaced the battery with a new CR2032.

After replacing the battery, the unit powered up fine. However, I am finding one annoying problem: There is a set of about 8 black keys on the keyboard that are malfunctioning in a strange way. When I press one of these keys, I get a sound the FIRST time I press that particular key. The sound continues forever, as if the key is being held down. I can stop the sound by changing patches. However, that key then ceases functioning. This happens for each of these "bad" keys - first keypress is registered, then subsequent keypresses are ignored.

I went into diagnostic mode (power on + 0 + Decrement), and took a look at the keyboard output. For these particular black keys, when I press one, the velocity always registers as "07", no matter how quickly I press the key. Other keys (ie. all white keys and the other black keys) will register velocity values up to 100+. But for this set of 8 black keys, the velocity registers "07", and then the key is effectively disabled.

Any ideas on what could be going wrong, and what I can do to fix this?

Just to be clear, I am not an electronics expert, and cannot read schematic diagrams. I came across this thread in a Google search, and saw some activity only a week ago. So I thought it would be a good place to start.

Thanks for any help/advice you can provide.

[kennyz]

Well, in a most amazing fashion, my D-50 has healed itself. Each day that I used it since posting my problem report a little over a week ago, more keys started working. On 4/12, I had 8 black keys that were not working properly (first keypress produced a faint sound, subsequent keypresses produced nothing).

On 4/14, 3 of those keys started working again. On 4/15, 2 more started working. On 4/17, 2 more. Finally, on 4/19, the last key (G#6) started working.

This is truly the strangest thing I've ever seen. I did not open the keyboard to do any sort of cleaning work. I simply used it each day, and the unit amazingly self-healed a little each day.

Problem solved!

[Enzo]

If you have a dirty volume control, turning it a lot usually cleans it. If you have an unused input jack on an amp that is iffy, the more you plug in and out of it the better it will be.

Your key contacts were at the least dirty and possibly had some small debris in the works. By playing the keys you are pushing the contacts up and down, and they slowly rubbed themselves clean.

What I would have done here is pull thye keybed, removed the contacts and cleaned them, then reassembled. But if your unit is now working on its own, leave well enough alone.