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Roland D-50 Major Problem
Old 25th February 2020
  #61
Gear Head
Quote:
Originally Posted by Lector View Post
Crbt means card battery. Even if rhere was a ram card installed, at best thered be a voltage drop across the other end of the resistor, not an increase. If there are no stray solder bridges around then pin 3 must be the source, which means that ic is busted.
Upc4062 opamp. I believe tl062 can replace it.
Thanks!
Also completely unrelated - probing IC7 RAM pins 11, 12, 13, 15, 16, 17, 18, 19 are all not responsive. They all map back to IC8 Chorus RD lines 0 - 7. Those pins are also not responsive. Guessing that is also not normal?
Old 25th February 2020
  #62
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Quote:
Originally Posted by mIIwaukee View Post
Thanks!
Also completely unrelated - probing IC7 RAM pins 11, 12, 13, 15, 16, 17, 18, 19 are all not responsive. They all map back to IC8 Chorus RD lines 0 - 7. Those pins are also not responsive. Guessing that is also not normal?
No idea atm sorry. Someone else ought to chime in.
Old 25th February 2020
  #63
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Please be aware that I don't have any schematics or other design/troubleshooting information specific to the D50, so this is just general musing.

It sounds as though this is some sort of memory dedicated to the chorus delay lines from the names of things you've given. Particularly if the chorus is not engaged, I would not be the least bit surprised if there is no activity on those signals. Even if it is engaged but there is no sound going through it, one may very well not see any changing values. Regardless, I would not particularly expect a problem there to cause the problems you're seeing; it might cause the chorus to sound wrong (maybe very wrong) or be missing, but I wouldn't think it would affect the speed of things happening in the main control processor.
Old 26th February 2020
  #64
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A complete scan of the service notes is available at synfo.com.

The pins in question appear to be tri-state, they can be Hi, Lo, or stand-by mode, so you are probably correct.

Now, the CPU seems to use pin37 'A Vref' Analog Voltage Reference to compare with the voltages present at pin34 AN1 and pin35 AN2 analog inputs. When the voltages at the inputs are lower than the vref, the CPU assumes the RAM and Card batteries are low.
The Vref comes from the bender board. It's only there because it uses a certain +4.5V rail. This rail also feeds the bender, the aftertouch and the joystick. And the external controller as well. But I can't find where these 4.5V are coming from!

Edit - I found it. It's IC4a. I'd check if that voltage is present at pin1 and also the electrolytic capacitor.
Attached Thumbnails
Roland D-50 Major Problem-sem-titulo.jpg  
Old 26th February 2020
  #65
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The above doesn't make much sense, come to think of it: even a fully charged coin cell would always be at a lower voltage than Vref if the latter is near +5V.
There must be a way the CPU monitors the batteries, but this one isn't...
Whatever, checking IC4 and IC2 is still valid because the bender, joystick, AT etc aren´t responding.
Old 26th February 2020
  #66
Gear Head
Hi, IC4 and IC2 checked out ok. I can see voltages moving when i move the joystick and bender as well.
Saw a bad solder point on the volume slider so touched that up.
Old 26th February 2020
  #67
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Ok. What about ic3, vref should be close to +5v at cpu pin 37...
Old 26th February 2020
  #68
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The mysterious 16MHz does exist. It is generated by the Synthe chip and it's half the frequency of its master clock. As already found by the OP. Following the lines, this slower clock signal should go to the Dyna Scan board and to the gate array that is responsable for the LCD etc. Check that out. Pin78 of IC28 and pin 46 of IC1 in the Dyna board. I'd even use both channels of the scope to compare the source at pin 3 of IC16 and destination signals in real time. Pin88 of the Chorus chip as well BTW.
Old 27th February 2020
  #69
Gear Head
IC3 -
Pin1 is at 5.4V,
Pin2 is at 4.62V

CN6 (vRef) Pin 1 is at 4.62V.
Old 27th February 2020
  #70
Gear Head
Scope Captures - 16mhz

All a match!

DS1Z_QuickPrint6.png
IC28 - Pin 78 (yellow)
Dynascan - Pin 46 (blue)

DS1Z_QuickPrint7.png
IC28 - Pin 78 (yellow)
Chorus - 88 (blue)

DS1Z_QuickPrint8.png
IC28 - Pin 78 (yellow)
IC16 - Pin3 (blue)
Attached Thumbnails
Roland D-50 Major Problem-ds1z_quickprint6.png   Roland D-50 Major Problem-ds1z_quickprint7.png   Roland D-50 Major Problem-ds1z_quickprint8.png  

Last edited by mIIwaukee; 27th February 2020 at 03:14 AM.. Reason: Forgot IC16
Old 27th February 2020
  #71
Gear Head
Ran through the Panel tests again for the heck of it. All panel buttons are responding with the exception of 3.

Card
Tone Detune
Key Mode

Seems suspicious because they're all in close proximity. I had already gone through to test the diodes. Perhaps I missed something or these guys are somehow bad? The LCD and Panel are the only connections I haven't disconnected to try and find the issue.
Old 27th February 2020
  #72
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Quote:
Originally Posted by mIIwaukee View Post
IC3 -
Pin1 is at 5.4V,
Pin2 is at 4.62V

CN6 (vRef) Pin 1 is at 4.62V.
What about pin37 of the CPU? Measure right on the pin, to rule out a possible broken trace between the connector and the chip. Measure it against pins 36 and/or 38 (digital ground). Failing to read Vref, the bender board etc wouldn't pass the bootup sequence and the CPU could reach a stall...
Old 27th February 2020
  #73
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Quote:
Originally Posted by mIIwaukee View Post
All a match!

DS1Z_QuickPrint6.png
IC28 - Pin 78 (yellow)
Dynascan - Pin 46 (blue)

DS1Z_QuickPrint7.png
IC28 - Pin 78 (yellow)
Chorus - 88 (blue)

DS1Z_QuickPrint8.png
IC28 - Pin 78 (yellow)
IC16 - Pin3 (blue)
There goes another hunch.
Old 27th February 2020
  #74
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Quote:
Originally Posted by mIIwaukee View Post
Ran through the Panel tests again for the heck of it. All panel buttons are responding with the exception of 3.

Card
Tone Detune
Key Mode

Seems suspicious because they're all in close proximity. I had already gone through to test the diodes. Perhaps I missed something or these guys are somehow bad? The LCD and Panel are the only connections I haven't disconnected to try and find the issue.
Doesn´t seem there's a connection. Only Tone Detune and Key Mode share a line, but a failure would also affect Patch, Tone Balance, etc.
Probably beer or coffee residue?


Another thought: My D550 still has the original ROM chip soldered to the mainboard. I assume all D50 and D550 are like this, so updating of the firmware requires desoldering. And these double-sided boards can be tough. So I'd desolder the socket to check if there is no lifted solder pad, or plainly missing, left by a previous user...

Edit - better yet, just lift the ROM chip off its socket and test for continuity between the socket´s pins and everything they connect with.
Old 28th February 2020
  #75
Gear Head
IC25 CPU - pin37 is at 4.51V
Old 28th February 2020
  #76
Gear Head
The Roland D50 main board version I have has an Eprom that can be pulled to update without desoldering. Everything with that looks good. I even tried a few eproms with various version of the os to rule that out.
Old 28th February 2020
  #77
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To pull, that's the verb I just couldn't remember. My vocabulary is getting worse. Those days are coming, and the sad thing is that I don't really like meeting new people every day...

Well, I'm running out of ideas.
Old 28th February 2020
  #78
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Guys, what about monitoring the control lines? CS, CE, WE, OE and all that.
When we know the active state of those lines, it's not difficult to determine the states of the inputs and outputs of the logic chips.
I checked the datasheets before, it's just a bunch of NANDs. Some are presented as negative input ORs for conveniance, but they're all the same. The rest is a couple of decoders.
The initial difficulty is to know when should a chip be enabled. Like the Working RAM. Should it be active right during startup? Or idle?
Old 3rd March 2020
  #79
Gear Head
This is where things get confusing

Looking at the data sheet for the PD78312 (IC25)

Trying envision the boot sequence. This is where things get confusing. I would think on startup the chip immediately starts reading instructions from the eprom and then writing data to set the LED display. All the while scanning the keypad for startup instructions (hard reset, test mode, etc)

Perhaps HALT or STOP is being triggered
Attached Files
File Type: pdf upd78312.pdf (1.77 MB, 13 views)
Old 18th March 2020
  #80
Gear Head
Lots of time on my hands coming up. Managed to get the keypad working. Now back to the drawing board.
Old 18th March 2020
  #81
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Good to hear. What was causing the problem?
Old 19th March 2020
  #82
Gear Head
Sticky flux all over the board. Took a lot of deoxit and button pushing.

The cpu/system is still extremely unresponsive. Still wondering if it is a faulty chip but which one. The ALE lines/pins are very active and “low”. Still investigating.
Old 19th March 2020
  #83
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I'd make sure ic26a is ok, by rechecking the voltages. If the channel is leaking into an2, the cpu reads it like if a ram card is present and will wait for data.

Everything else seems fine, so replacing the cpu looks the best possible bet. No easy task though. Cut all the 64 pins and extract the remains with the iron and tweezers. This kind of myriapod ic is more difficult to install than to remove.
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