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Broken TR-606 - Repair advice/help needed.
MUFF WIGGLER Forum Index -> General Gear  
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

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