Broken Roland tr 606 question

[jim 2tall]

Hi

I am repairing a 606 at the moment, and wondered if there any real 606 nerds who can give me some advice -

basically I am not getting any power through the system..

today am doing a continuity test so see if theres any components, am getting voltage across the circuit generally but no life - i.e. nothing lighting up no sound..

My main question is, if in fact the central CPU is faulty would it produce this kind of result?

thanks

Jim

[forumuser695516]

I like those drum boxes.. Shame it's broken

Generally speaking.. A device that is completely dead is often the easiest to fix, in my experience, as the fault tends to be something relatively obvious.
I think you are starting the right way, with the continuity thing. But you'll need to check voltages too. If you are any good at reading circuit diagrams it will help too. Im sure they are on the net somewhere (303 ones for example, are all over the place)
Im not sure it would be the CPU.. Even if that was dead, I'd still expect some signs of life from the box. Also, are you using the original PSU, or a replacement? You want to double check it is the right one.
Things like diodes and capacitors in the power supply/regulation area would also be likely suspects.

Paul

[jim 2tall]

Thanks for the encouragement.

I have located a missing resistor which goes to earth.

(R243 @ 180k on this schematic (near q45 / 46) - http://www.synthdiy.com/files/2001/TR-606_Schematics.pdf

would this explain it?

[jim 2tall]

and also in reply to your question about power - i am using a variable AC-DC @ 9V (800ma max) - i also tried 4 1.5v batteries internally but to no avail (despite checking battery connections)

[forumuser695516]

Some gear can be picky about those variable power supplies. But if you say the 606 isn't working with batteries either, then it probably isn't that.. I notice it requires an AC supply though.. And I can't see on the schematic where the DC battery power would come in..
If the wrong psu has been used in the past, it could potentially break something that prevents it from working with batteries too.

Missing R243.. After squinting for a while at the diagrams, I can see where it goes. The schematic is well labelled for the most part, although this particular area isn't as clear as i'd like. Still, it certainly looks like the power supply area, and that particular resistor is in the +15v and +5v section. So those are the first 2 voltages I would be checking for. Im not an electronics genius, plus this kind of power supply isn't one im very familiar with, so i'll take an educated guess and say the voltages you are looking for would be DC rather than AC (Check for both anyway)
Does the area of the missing resistor look like the component was ever soldered in? There should be traces of it.. The drum machine must have worked once, and resistors tend not to just drop out! So there is a chance that it was left out intentionally due to design/spec changes.
Also, check resistance/continuity of R237, as this appears to be used as some kind of soldered in fuse.

Good luck Paul

[jim 2tall]

ok resistor replaced.

still no dice

will contine to check stuff, anyone gets any ideas, let me know.

thanks

Jim

[jim 2tall]

Some gear can be picky about those variable power supplies. But if you say the 606 isn't working with batteries either, then it probably isn't that.. I notice it requires an AC supply though.. And I can't see on the schematic where the DC battery power would come in..
If the wrong psu has been used in the past, it could potentially break something that prevents it from working with batteries too.

Missing R243.. After squinting for a while at the diagrams, I can see where it goes. The schematic is well labelled for the most part, although this particular area isn't as clear as i'd like. Still, it certainly looks like the power supply area, and that particular resistor is in the +15v and +5v section. So those are the first 2 voltages I would be checking for. Im not an electronics genius, plus this kind of power supply isn't one im very familiar with, so i'll take an educated guess and say the voltages you are looking for would be DC rather than AC (Check for both anyway)
Does the area of the missing resistor look like the component was ever soldered in? There should be traces of it.. The drum machine must have worked once, and resistors tend not to just drop out! So there is a chance that it was left out intentionally due to design/spec changes.
Also, check resistance/continuity of R237, as this appears to be used as some kind of soldered in fuse.

Good luck Paul

Paul your a Don

on the outside of the unit it says 9V DC labelled for the power input.

(the service manual says it draws 70-150ma) but also says 9V AC

with regards to the resistor, there was one in there but someone appears to have chopped it out, when i got this there was signs of tampering.

I will check R237 next time I go in..

getting closer at least!

[jim 2tall]

Post deleted by jim 2tall

[jim 2tall]

no reading on R233 - you think that would explain this? maybe the battery not working i guess?

[forumuser695516]

R233 is also grounded on one side, and has a cap on the other side, so I wouldn't expect to see much on there, if anything.

Im still a bit confused about the AC/DC thing as I see conflicting info on the net.
All I did notice was that the power supply is a 'switching' type, which explains why it didn't make much sense to me on the schematic, as it is largely alien territory for me!
Did you manage to check for those voltages yet though? That should yield some clues.
I can't easily explain how to do that, as i've not had my hands on a 606 before, but going on the schematic, and using a good test meter.. If you can probe the positive side of the capacitors C105, C100 and C9, you should see +6v, +15v and +5v respectively. Each one powers different sections of the 606, and it only takes 1 to pack up and the thing won't work.

Beyond that, I don't think I can help much im afraid, as my experience becomes too limited

Paul

[jim 2tall]

Paul i know nothing honestly i'm a beginner (kinda - i did some electronics so i know the basics)

my power supply reads..

ac - dc adaptor

3- 4.5 - 6 - 7.5 - 9 - 12 V

___
---

800mA9.6VA(max)

[jim 2tall]

ok weirdly i checked the voltage coming out of my power supply - at 9v it's actually delivering 12!!

at 12v its reading at nearly 17..

this unit was broken beforehand however but that really doesnt help!

[jim 2tall]

i set the voltage rating to around 9 (actually 7.5 on the supply) and checked the above points.

I got full voltage of around 9 on all 3 positive points of all 3 capacitors

c'est tros bizzare

i am going to go and get a decent bloody supply tomorrow me thinks

[Folderol]

Hmmm The Internet seems to have eaten my comment yesterday

NEway
I tried to look at the schematic - never know, I might recognise something - but the link comes back 404 - not found

[jim 2tall]

hey, thanks for getting involved

here's a link to the schematics http://machines.hyperreal.org/manufacturers/Roland/TR-606/schematics/

[Adam Inglis]

The 606 (I have) definitely requires DC 9 volts with negative tip at the connector, about 100-200ma tops. Same as the Boss pedals from that era.

[forumuser695516]

the link comes back 404 - not found

There was a bracket tacked onto the end of the URL. With that deleted it worked fine. Although googling found a clearer, and generally better quality schematic anyway. (But it was otherwise the same one)

-------

Im pretty sure I identified 3 good caps to take a reading from 9v on all 3 doesn't seem right from where im sitting. And i'd imagine that is an unhealthy voltage for many components to be on the receiving end of too.

Re: the power brick. Yes, DC seems right, despite the schematic saying otherwise. Also, many of them will show more voltage when unloaded. So it's worth checking again with it plugged in to the drum box.

Im not Mr Experienced either though! But I learned quite a bit when I built my x0xb0x (An excellent TB-303 clone) not to mention some other electronic shenanigans i've poked at with soldering irons in the past. Yet I still need a "Dummies guide to Resistor colour bands"
That said, my money is still on it being a buggered power supply section in the 606 itself. But being a switching supply, it's not as easy to suss out..

Good luck with it! It would be nice to see it saved I occasionally check the readers adds for these, although prices are a tad ambitious for a goodun now.

Paul

[jim 2tall]

thanks again Paul.

I am waiting on an order for a proper boss 9v power supply which i know work in these units - to rule out any dodgyness.

re: schematic - did you mean this one?

http://machines.hyperreal.org/manufacturers/Roland/TR-606/schematics/roland.TR-606.schem-4.gif

if not do you have a link?

[forumuser695516]

Theres 2 from this page I was looking at:
http://www.kolumbus.fi/janne.husu/specs.html
As I say, it's the same schematic, but appears to be a better quality scan. Plus it is white text/graphics on a black background. So I found it a bit easier on the eyes.

Paul

[jim 2tall]

nice one Paul

here's a photo for sheer nerdy posterity

[Folderol]

Righty Ho {rolls up sleeves}

First off, don't switch it on again!
You might be lucky, and it might have survived so far

This is one of the crapiest internal PSUs I have seen in over 40 years!!!

Q41 is some form of current limiter. Q2 is a voltage regulator for the incoming DC - yes definitely - but it sort of hangs the supply off the positive rather than the negative, so depending on where you put your probes that could account for the 9V everywhere.

The true supply is 6V or less (depending on battery state) measured directly across C105.

Q44 is the switching oscillator, and if it is running, as well as seeing the +15V DC supply you should see probably about 10V AC if you go directly across pins 1 & 2 of T2. If it's not oscillating you'll read a fraction less than 6V directly across C100. You'll probably still get 5V across C9.

D42 and Q43 back off the oscillator when the output reaches 15V and D44,D45 are a sort of 'start-up' for the 5V supply so it doesn't load the oscillator too much at switch on.

The 6V and 15V supplies are probably pretty tolerant of variation. The 5V one must be exactly that - too low and it won't work, too high and it's bye bye processor.

R243 being missing is slightly concerning. between them, R239-243 define the actual 5V supply (along with the actual voltage of the 15V supply - crap!). That being missing would tend to make it slightly high.

Likely faults:
Q41/R237 O/C - nuttin at all (might still get your funny readings if you use the external supply negative as your ground - DONT!

Q44 O/C - no +15V
Q44 S/C - no +15 (might also take out Q41/R237)

Q42 O/C - work on battery, not on external supply.
Q42 S/C - work on battery - all voltages too high on external supply

There you go for starters

Hope this helps.

[jim 2tall]

this is awesome info.

I will wait for proper ac/dc adapter and keep it switched off for now then.

its quite likely the CPU is blown i was told but you never know.. we'll see, it would just be great to get the heart beating at least to see if the brain works if you get my meaning.

will report back in a few days.

thanks all! you've been great, this is actually a lot of fun to do in spare moments and i'm learning a lot too.

[Richie Royale]

I hope you get it working again. I love my little 606, but I'm afraid I love her sister even more, Miss 808!

[Adam Inglis]

Fol that was very educational.
I've never seen a PS resembling that.
I'm pretty sure it's not covered in Horowitz and Hill!!

oh btw what's O/C and S/C?

[MarkOne]

oh btw what's O/C and S/C?

Open Circuit...

and Short Circuit