Bring Roland SH2000 back to life? [SOLVED]

[zorgitron]

OK, now that you have ruled out the switch, you should check the transformer.
Based on the previous attachment , take VAC readings on the 2 secondaries, you should read near 20V on both windings.
CAUTION: playing around with transformers could be lethal !

Okay! Following your previous schematic post, I tested : Red & Gray, then Yellow & Black
These terminals, tested by oscilloscope, produced a ~3v AC.


I guess that's a problem!

Edit: But checking the schematicbit looks like the test below is correct: red&black, yellow&gray, but the schematic just shows 0.5A AC, it doesn't show voltage.

By myself, I had tested this way (Red & Black, then Gray & Yellow) which produced a 30v AC somewhat flattened sine wave on the scope.

That made me think the transformer was okay, but if those are not the right terminals to test, then it's a problem.

I'll have to remove the diodes for testing after work tonight.

[Yekuku]

Thanks for the photos , sorry I was not clear enough.
Power on the unit , and use a multimeter set on AC, to read voltages on :
- (21) & (24) it should be 20 VAC or higher
- (22) & (23) it should be 20 VAC or higher ( this is important because it feeds the negative power line)
If you dont have the appropriate voltage on (22) & (23), and you are sure that you have tested the switch right, then you have an open secondary transformer winding.
Please confirm so that we continue the troubleshooting.


Message to madtheory: Please forgive my asking but since you mentioned it, I have a Sh2000 that is missing 4 sliders caps, do you have any available that you would like to sell/trade? Many thanks!

[zorgitron]

Hi Yekuku,

Yes, I tested (21) & (24) and also (22) & (23), they both give out ~30 volts. Since you said 20 volts or higher, I guess that's okay.

The new capacitors are coming very slowly, due to the dang Corona virus....

Yekuku, you said you're missing slider caps, but is the panel surface on your sh2000 nice and smooth? I'm thinking of giving mine some kind of polish in the mean time. It's got really stubborn caked on stuff.

[Yekuku]

I got my beat up sh2000 in pieces with missing parts , overall condition 2 out of 10.
Unfortunately the original transformer was missing , so I dont know what the correct voltages should be.
2x 30Volt is on the high side, it will put more stress on the regulators but it should work, usually vintage synths have transformers that output 2x20 the higher I have seen is 2x25V .
Anyways, concerning your aesthetics question , my panel was rusty with lots of chips. I removed the rust and used a black marker to cover the missing paint, then sprayed a few coats with crystal clear lacquer.
It looks good now, the whole wooden case is painted black, sorry i cant share a pic right now, as I dont have it in my house .
Since the transformer is ok and according to your tests , the problem lies in the power supply.
Test D603 & D604 as advised previously.
Read the voltage on C602 and report back. Compare it to the voltage on C601 that is working right.
Test D606 for short.
I believe that IC602 is to blame, but lets exclude all others before focusing on it.

[zorgitron]

Quite embarrassing, I've dragged everyone through a few posts without checking the fuses... sorry about that!

Anyway, by lack of attention, the fuse had to take matters into its own hands in order for me to notice it. In other words, the fuse holder just seemed to disintegrate while I was starting some desoldering work on the power supply. I heard something drop, and it was was the fuse itself. I put it somewhat back together and took a picture. I guess old age can make fuse holders turn brittle.



I had to look at it for quite a while to determine if it was blown or not. Visually, I kept thinking I was seeing a very thin wire spanning across the inside, but I think that was just a wrinkle in my hand showing through the glass. It failed a multimeter continuity test of course.


So perhaps this is why the powersupply only half works! Wish I had another fuse to pop in there right away and see if the whole thing comes back alive!

Can't say for sure this is the issue, but if it is, it'll be another example of a foolish guy who wouldn't check the easy stuff people told him to check early on!

[Yekuku]

Hey these are some good news man
Dont forget to clean the switch, if it is not doing proper contact it can blow the fuse.
Let us know how it goes when you replace the fuse !

[zorgitron]

Ok so replacing the fuse just returned the synth to having a working LFO, VCF, Noise, and VCA.
You can see in the video, https://www.youtube.com/watch?v=132fqBF-Ssk.
When the fuse rolls out of its broken holder, it returns to the previous state of not making any sound at all. Gotta replace the fuse holders, they really need a good contact to work.

Testing the voltage from the transformer again, and it became just 22 volts, closer to what you were saying.


Just a quick test of output Pin 1 from the VCO board, and it's still just a flat voltage, even when the filter is working.

[Yekuku]

Close but no cigar
I guess that you have proper clean contacts both on the VCO board and the mainboard, then you should check :
- On VCO board test 555 pin 8 for 15V
- On VCO board test 555 pin 3 for Pulse wave. No pulse ->Replace IC .
Also IC 101 might be in fault, buy a few 1458 or replace with 4558.

[zorgitron]

Close but no cigar
I guess that you have proper clean contacts both on the VCO board and the mainboard, then you should check :
- On VCO board test 555 pin 8 for 15V
- On VCO board test 555 pin 3 for Pulse wave. No pulse ->Replace IC .
Also IC 101 might be in fault, buy a few 1458 or replace with 4558.

I've researched about the 555 IC and I can't find any definite information that it's a special kind of 555, although common 555s, like NE555, are usually described as "bistable", but the RC555 says its monolithic (the RC is also much harder to find). Do you have any insight on this? I think i've heard of a few other synths using 555s in their oscillators.

EDIT: So I retested, same results.

- On VCO board test 555 pin 8 for 15V
Test produced ~10 volts
- On VCO board test 555 pin 3 for Pulse wave.
Test produced no pulse.

I'm think I'll put an IC socket in place of the RC555 and try putting in a generic 555 to see what happens! I really haven't been able to find any hard info on that chip, so maybe it could be a useful experiment. If it doesn't work out, I'll just search for a genuine replacement I guess.

[Yekuku]

The only synths that i have seen using the 555 timer ic is the sh2000 and some DIY PAIA kits.
I bet that any 555 will do, there is no risk of doing any damage. Always use IC sockets!
10V on pin 8 is no good, let me check the schematics and i ll get back to you.

Edit : 10V on pin 8 makes no sense, VCO card connector pin 2 , is it 15V or 10 V ? This pin is directly connected to 555s pin 8 and it should be 15V , is there proper continuity ? Inspect the connector for oxidisation or bent contacts

[madtheory]

The 555 is not the actual oscillator (i.e. you don't hear it directly). That blog I linked has a good clear explanation of its role. Any 555 will do.

[zorgitron]

Thank you so much for all the help! I wish I could send some high quality beers through the internet.

Replacing the 555 is what did it. And yes, any 555 works fine. Every function of the synth is back now, even portamento, which was behaving strangely even before it broke down.

I can't button it up and call it finished yet though. I still need to replace the fuse clips. Also, I'm weary of recapping it. That would be a shame if I broke it again while recapping, I've barely had time to get acquainted.

I hope another guy with a broken SH 2k can find this post and get it fixed up.

[Yekuku]

Good job! I am glad you got it working.
I was a HUGE SH2000 hater, until I got one.
Personally I find the aftertouch to be so expressive, maybe the best aftertouch i have ever used.
There is a modification that you can do, so that all sounds can play simultaneously, although it has some drawbacks.
Enjoy your SH2000!

[madtheory]

If it works fine, don't recap it. Only the PSU should be recapped as a matter of course.

[LUKAS]

friends I have a problem, I recently acquired a sh 2000 but it does not come with its transformer from what I read in the service manual it is 12 v/o/-12 v, that is correct, now from what I see the psu seems to have two negatives because there are four connection pins, my question is the wiring which is +12 and which is -12? Another question is, from what I see the current transformers are single negative, would I have to make a bridge between the negative dops? or it will not work??? Greetings from Mexico, this is a great forum!!! I also don't understand why there are three wires apparently connected from the AC outlet to the transformer, thank you very much in advance for your help!I don't know how to insert some photos to be able to explain better