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Roland TR-606 Constant Triggering.
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author Roland TR-606 Constant Triggering.
oldsoulsound
I got my 606 working after a long time. Replaced the power supply transistors and caps desoldered the battery leads and it was working for several months. Then it started to loose saved patterns when the internal batts got low. I tried using the AC adapter mostly but it still would start to loose its patterns. I replaced the memory IC's still not good. It slowly started to get to the point where now if I have nothing programmed into it's steps it still fires continuous hits mostly all cymbals but I think drums also. Any ideas on where to look any further. I would be willing to send to someone for a repair job.
guest
what are the power supply voltages like? in particular, the ones labeled BU. its possible the diodes are bad. Q13 might be another culprit. when you check the PS voltages, check on the ICs, that will help figure out if traces are cracked. you might want to check all the chips in the digital section.
hw408
This Old Synth in CA fixed mine beautiful again. There was stuff going wrong in there I never would have figured out. He is great, hopefully he never retires.
BugBrand
oldsoulsound wrote:
I got my 606 working after a long time. Replaced the power supply transistors and caps desoldered the battery leads and it was working for several months. Then it started to loose saved patterns when the internal batts got low. I tried using the AC adapter mostly but it still would start to loose its patterns. I replaced the memory IC's still not good. It slowly started to get to the point where now if I have nothing programmed into it's steps it still fires continuous hits mostly all cymbals but I think drums also. Any ideas on where to look any further. I would be willing to send to someone for a repair job.


Certainly one I have would go into random fire-all-steps memory corruption when switched off for a while without batteries (the other I have a little 4xAA battery pack fixed to the side - the main battery bits being dead). It is unclear from your post whether you can clear these random firings and then program your steps?
oldsoulsound
Thanks all. I will. Check voltages as suggested. As far as clearing out the random triggers the answer is no. No matter more or what I select or deselect it just constantly triggers and the pattern length defaults to 4 or 8 steps.
BugBrand
Do the switches appear to be functioning?
I honestly can't remember details of what I might have done to my old machines - 2 non-functioners, at least one of which took a good few attempts to finally figure what was up.
I seem to remember thinking a logic chip (4001 or 4011) might have helped - sure I changed memory chips too sometime.
But also pretty sure I changed switches on both.

Sending to a pro might well sound the best way!
oldsoulsound
Power supply voltages look spot on (6V 15V 5V). Replaced Q13. Button and tempo work fine. Even if the machine is not running I hear constant triggering of all drums. The volumes for each work. I can clear the pattern but the sounds are still there. I reached out to Old Synth but is was un willing to take the project on. Any suggestions welcome.
guest
by "not running", do you mean that you have the sequencer stopped, but the all the voices are still sounding? in stopped mode, do the sequencer lights still light up?

[EDIT] if the sequencer lights arent going, and its sounding, id check the trigger circuitry around Q9,10,11 and D6,7,12. its probably stuck on.
oldsoulsound
Yes I meant the sequencer “stopped” and the sounds are still triggering. The lights do work as they should.
guest
ok, sounds like the trigger circuitry. do you have a scope? you can debug it without it, but it would make it easier.
oldsoulsound
I do have a scope, but quite a novice.
guest
take a look at the emitter of Q11 with your scope, and the sequencer stopped. it should be constantly low. when you start the sequencer, it should go high on each step. im betting its stuck high.
oldsoulsound
OK, q few questions. On the schematic it says that all NPN transistors on the Main board & Sub Board are 2SC945(P) but on the component layout page the symbol for Q11 says it's a 2SC536F.
Also Q11 looks to be part of the Accent circuit. Is that correct?
guest
the old roland stuff would interchange 536 and 945, so either is fine for this portion of the circuit. and the accent circuit is the trigger circuit. basically, when trigger turns on, the voltage level determines the accent. so its doing two things.
oldsoulsound
Ok, not sure if I’ve tested this properly or not. Link has some screen shots of my scope.
https://drive.google.com/drive/folders/1--G17T98NKdWjehcIo7Go_B8nqq_zu Hz

Basically with the machine not running or running this is what I get when I measure the emitter of pretty much any transistor. Q11. Q10 etc. even with lower off it still shows the same.
guest
that looks like 60Hz hum on the scope, is your ground connected on the probe?
oldsoulsound
Oh duh! Of course. I forgot that. I did at one point and didn't get anything on the scope. I think it disconnected itself.
oldsoulsound
I will Check again and make sure I’m grounded.[/quote]
oldsoulsound
OK here is a link with some measurements.
https://drive.google.com/drive/folders/11Jlzz1fsARVs1ffF2Cag3ckK-CvwwJ YR?usp=sharing

Not sure if I did this correctly.
guest
that still looks not right. whats the vertical scale set to? its very noisey.

lets try this instead: set the tempo to as fast as it will go, and then use your multimeter to measure the voltage at the emitter of Q11. do this for both the sequencer running and stopped. is there a difference?
oldsoulsound
OK, so I measured Q11 emitter and got 2.3VDC in standby and running.
guest
ok, so that doesnt sound right. repeat this test, but now measure the voltages at:

Q9 collector
Q10 collector

and if your meter has diode check on it, check D6,7,12.

also, does changing the accent level change the drum sounds in either mode?
oldsoulsound
Here are my findings.

Q9 collector (RUN) 14.6VDC (STANDBY) 14.6VDC

Q10 collector (RUN) .505-.519VDC (STANDBY) .519VDC

Diodes D6,7,12 all check good.

Here is a video demonstrating the triggering behavior. If I program in steps for each drum they do work, its just hard to hear over all the other triggering.

https://drive.google.com/open?id=1H0pUR2bA47rJmKjSsE_kkJFmpAOXNmed
guest
ok, still looking like a stuck gate. what are the voltages:

1. base of Q10
2. where D7 and D6 come togethere
3. the side of D12 that goes to the microcontroller
oldsoulsound
OK, this is what I'm getting.

Q10 Base (RUN) 14.5V (STANDBY) 14.4V

D6 & D7 (RUN) 220mV (STANDBY) 16.6mV

D12 side @ micro controller (RUN) 5.9V (STANDBY) 5.89V
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