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WIGGLING 'LITE' IN GUEST MODE

Broken TR-606 - Repair advice/help needed.
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Author Broken TR-606 - Repair advice/help needed.
my606isbroken
Hey wigglers; first post here, long time reader. I'm looking for some professional advice on repairing a newly acquired TR-606.

I purchased a TR-606 locally through a Craigslist ad and was told it had "some issues", but the price was right so I purchased it as-is. I've managed to bring back a few choice pieces from the dead in the past and figured I could to the same with this particular unit. I've narrowed down the problems and would like a few second opinions.

The 606 powers on using batteries and/or the original power supply, but only the "Pattern Group I" and "RUN/STOP" LEDs light up. The only form of feedback I receive from any of the buttons/knobs is the "RUN/STOP" button, which I can turn on and off. Nothing works beyond this. No sound, except for a (very) faint hissing which sounds like an open hat. The SYNC function is set to output, so no worries there.

I opened the 606 and there's no obvious damage. I re-soldered all wires and cables, checked for leaky caps/broken traces and cold solder joints. I noticed two resistors were missing completely from locations R10 & R243 (weird) and it looked like these were missing since the unit was originally assembled. No new solder, flux, etc; so I added the correct value resistors but still no luck. All switches & knobs checked out with the multimeter.

I then measured the voltage on the IC's after reading around online that it might be faulty RAM and here's what I measured:

hd14584bp #1 - 5.55v - pin 14 (5.06 after adding missing resistor)
hd14584bp #2 - 5.55v - pin 14 (5.06 after adding missing resistor)
d444c - 5.85v - pin 18
d444c - 5.85v - pin 18
mn4013b - 5.93v - pin 14
mc14001b - 5.93v - pin14
tc4011bp - 5.82v - pin14
an6912 - 15.18v - pin3
d650c cpu - 5.94v - pin21

I feel like I've gone as far as I can before I start buying replacement parts. My questions are these:

Would faulty RAM prevent the 606 from doing anything at all?
Is it possible the missing resistors killed the ram over time, accounting for the difference in measurements?
If the CPU needs to be replaced, is there a known replacement without throwing down for the (albeit, very nice) Quicksilver CPU drop-in?
Does anything stand out as being obviously faulty?

The 606 doesn't look abused, but shows a little wear around a few knobs so I know it worked at some point. I'm stumped. hmmm.....
sneak-thief
Faulty ram could possibly be a culprit. If the working ram is faulty, then nothing can initialize.

I bought one of these recently and successfully repaired a 303 with it:

http://www.ebay.com/itm/D444C-Manu-NEC-Encapsulation-DIP-18-Video-Came ra-Applications-/110887949052?pt=LH_DefaultDomain_0&hash=item19d16fd2f c

If it came out of the factory without certain components, then I wouldn't go shoving new ones in. Many hardware revisions happen with any device and occasionally leave empty component spaces.
meatcliff
I'll 2nd sneak-thief's comments. #1 culprit from my experience with 606/303s is the ram. Bad ram causes all sorts of bizarre issues.

I use this SRAM from Jameco:
https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId =-1&storeId=10001&catalogId=10001&productId=43238

If it still isn't responding after that, go through each section systematically. that IC 6 is good (selects which ram IC is active), make sure the CPU is scanning the switch matrix (cpu pins 22-29, 37-40), that there's activity coming back in on 33-36, that CPU and tempo clock work, etc... but those could be tricky without a scope.
cscairney
good luck. a working 606 is a beautiful thing!
antto
the RUN/STOP button (and its LED) are not connected to the CPU, they are analog.. that's why they work
so it's probably bad digital section (cpu maybe)

there is no direct "replacement" for the cpu, unless you can take out the working cpu from another 606
you already know about qs606, that's your only option afaik
my606isbroken
So here's an update -

I ordered the RAM (w/ sockets) from the Jameco link Meatcliff provided and replaced the faulty RAM.

...

Turns out the RAM was not the culprit. sad banana

I'm considering going through and checking the suggested ICs, but I do not own a scope. Moving on to IC6 next.
my606isbroken
Oh, and thank you all for your suggestions and advice. I really appreciate it.
PrimateSynthesis
If you get it working, does that mean you'll have to change your user name? hihi

Anyway, I have the service notes if you have any specific questions.
my606isbroken
PrimateSynthesis wrote:
If you get it working, does that mean you'll have to change your user name? hihi


I didn't get that far. 8_)

So I built a poor man's oscilloscope using the headphone jack on my laptop and a copy of Audacity to test the CPU and I found a few things.

CPU Pins 22-25: No feedback (cannot activate steps, so no LEDs)
CPU Pins 26-29: No feedback (cannot activate anything)


CPU Pin 33: Feedback via Pattern Clear/Function buttons
CPU Pin 34: Feedback via Instrument knob/Scale/Function and Run/Stop
CPU Pin 35: Feedback via Pattern Group/Instrument

CPU Pin 36: No feedback - I believe this connects to MC14001B quad 2-input NOR gate

CPU Pin 37: Feedback via step 1/5/9/13
CPU Pin 38: Feedback via step 2/6/10/14
CPU Pin 39: Feedback via step 3/7/11/15 (11 gives much smaller value compared to others)
CPU Pin 40: Feedback via step 4/8/12/16

I feel like I'm getting closer in finding the faulty component. I'm leaning toward the MC14001B and/or something on the switch board which is causing the small value when pressing step 11. I'm not entirely sure what I'm doing or looking for when using the oscilloscope though. thumbs up

Thoughts?
BugBrand
In my broke 606, I did change the 4001 and 4011 - was never sure if it was one of these chips or the new buttons or QuickSilver CPU that sorted things out..

The good thing is that those are easy & cheap to source replacements - ie. may as well try it. I put in new DIL sockets for them so they're easy to swap if needed in the future.
PrimateSynthesis
my606isbroken wrote:

I feel like I'm getting closer in finding the faulty component. I'm leaning toward the MC14001B and/or something on the switch board which is causing the small value when pressing step 11. I'm not entirely sure what I'm doing or looking for when using the oscilloscope though. thumbs up

Thoughts?


While you might not want to purchase an actual oscilloscope, logic probes are not expensive.

Regardless, I agree with BugBrand, the CMOS parts are inexpensive to replace. Otoh, they rarely go bad.

Have you checked the switch for step 11? While they usually fail open, they can also fail to short intermittently.
my606isbroken
Another update -

I switched out both the 4001 and 4011 and

...

sad banana nothing!

Short of a replacement QS CPU, I'm not sure there's more I can do on my own. I'm going to try a hail mary switch 11 replacement this afternoon, but I'm not anticipating a working 606 afterward. 8_)
vincentneutron
did you get any further with your 606? I have one with the same problem.
Luka
play with the sync switch
sounds to me it is the cause of your problem
cn70
Did you fix the 606? and how?

I have a similar problem very frustrating
tupinamba
Hi!
I also had an issue with a TR-606 that had an erratic behavior while playing in write mode. Turned out it was a bad solder joint on one of the SRAM chips (that had previously been replaced).
Still, something weird with this machine: I cannot change the scale. It is stuck on mode 3 (as the leds show when I push the Function button in Write mode), but cannot be changed.
Also, I cannot define the number of steps to be played: it is always 16 steps.
I know the Function button works as it lightens the corresponding scale leds, but nothing more...
I checked the scale selector connections to the CPU : no faulty solder joints there unfortunately.
Any suggestion welcome...
Zenn
I have 2 cry broken 606s, 1 has a broken pot (will fix soon) the other has the hihats making a continuous sssssssssss. I talked with my synthdoctor about the issue and he told me he recently had an influx of more patients with similar issues. His conclusion was that the CPUs have started dying waah My issue was a typical symptom.

Good part is, he's working on a drop-in replacement. I'll keep you posted.
cn70
I had the same problems as my606isbroken describes, so i went ahead and replaced the cpu with a used one i bought on evilbay and now my 606 is alive and kicking again SlayerBadger!

I wasn't completely sure if the cpu was broken, but I didn't wanna go for the quicksilver cpu not knowing if it would fix it or not and because thats 185 punds compared to 35 punds for the used chip. I dont have the skills to do the mods for the quicksilver upgrade and sending it to a technician would propably push the bill to around 300.

It might not last forever as i understand that these cpus seems to have reached the end of their lifespan (and i missed out on all the nice additional features) but i'd still recommend it for anybody with similar problems and limited electronic skills as i have.
a.d.a.m.baby
Zenn wrote:
I have 2 cry broken 606s, 1 has a broken pot (will fix soon) the other has the hihats making a continuous sssssssssss.


Neither of those symptoms are due to the CPU failing.
When my 606 hats started hissing, it was a single transistor that had failed in the trigger circuit - long time ago now, can't remember the details, but shouldn't be too hard to trace for a tech.
tupinamba
Hi everyone!

Here is a real puzzle.

Let's take a 606 with an erratic behavior (writes random steps, refuses to erase certain steps...)
I changed the RAM chips : not better.
I then changed the 4011 : not better.
I changed the 4001 : not better.
Finally, I changed the CPU (had an extra one after a Quicksilver install) : not better!!!

I also tried to change the power transistor with a working one (other 606) : not better...

What the hell could that be?

I also checked solder joints around the CPU and RAP chips : they are good.

So what are your guesses?... :-)
tupinamba
UP?...
codemode
..the two shitty 8 position connectors between the switchboard and mainboard.
tupinamba
Thanks for your reply codemode. You may damn well be right... Maybe I should just replace those without any further questions...
I'll keep you posted, I will try this when I'm back home on Monday...
codemode
... Just about guaranteed. Anytime you have flaky sequencer operation in the-303 or tr-606 it's almost always those connectors. They fray right where they connect to the pcb's and become intermittent. It's hard to see it.
tupinamba
Well, I'm afraid that's not it... very frustrating
I've replaced the connectors with nice multicore coper wire. And the problem is still on. Erratic bahaviour, adds random steps on its own on several instruments, cannot erase all the steps, and after a few minutes, I cannot even start the sequencer, even though the pattern led is still blinking (the "start" led lights up, but no pattern leds light up, and no sound...)
I've tried to replace the power transistor already, with no success.
And the voltages seem OK on the ICs...
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