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[nochtanseenspecht]

btw, in my dr55 mod, it is at least possible to vary the hihats in a fixed way,
i even found a "crash", only with some shortcuts.
but i didn't dig to deep, as there wasn't enough space anyway (i wanted to keep all mods in the original box)
but who knows what's possible if you invest that area..
http://www.esnips.com/doc/ef5c3d3a-1689-40d2-903f-cabd99760101/dr-55-fills--breaks-control

hey, but it will rock sweet along with the jx3p i guess.. nice basic acid combination
sometimes i miss my jx3p to 
 

[Gordonjcp]

http://fa.utfs.org/diy/boss_dr55/dr55_schematic.jpg

The line is drawn in pencil.  On the web page this comes from it says that it was a mod that the author had made.

[DenDer]

Thanks for the link Gordon. Although i don't quite understand how to connect it. The hot tab (tip)  goes to the off point and the ring to ground or what?

[Gordonjcp]

For an external trigger?  Yes, that sounds about right.  It looks like it  wants a positive-going edge to trigger the hihats.

[DenDer]

Yeah should be something like 5V.....the other triggers react on my 606 triggers so that could be right.

[DenDer]

Okay guys i'm busy putting in the external triggers for the sounds.....one question though....

The triggers come from pins 12, 14, 16 for RS, SD and BD. But if i hook this up to a jack connection should it be a switching jack?

And for individual outs i checked the schematic........is BD after C26 and SD after C18 and RS after C25???

[Gordonjcp]

You could use a jack with a break contact, or you could duplicate the trigger circuitry for that particular voice.  For instance, for the snare drum you could add an extra 470K resistor joined to the junction of R30 and R28, and an extra diode joined to the junction of D3 and R32.

Separate outs may be tricky - you might have noticed that there are two "busses" that form the output, one passing through the accent circuit and one passing directly to the volume control.  The BD output is easy - take another capacitor off the collector of Q1, and perhaps build a little buffer circuit for the socket.  The RS output would come off the collector of Q6 and would be best with some sort of buffer too.  Neither of these will have the accent applied to them - they'll be full volume all the time.

The snare and hihat outputs present a problem, because they feed an output through the accent bit and straight to the volume control, and in the case of the snare you've got both the "skin" oscillator and the noise burst.  You'd need to work out the right proportions to mix them in, with a bit of experimentation.

I think I'll get some veroboard and start building a DR55 clone ;-)

[DenDer]

Okee will try the switching jack variant i will add a diode though...

But if and only if you decide to build a Dr55 clone maybe its a good idea to make an accent part per voice ....do you think this is possible? Then you would have individual outs with accent and maybe with a volume control per voice. That would really be cool although i don't know if Q3 = 2SK30A (y) is easy to find for that matter.......

[Gordonjcp]

Not many of the parts are critical ;-)  I reckon you could use just about any small-signal n-channel FET in there.  I'd probably use a 2N3819 which is actually an RF part, because I've got loads of them.

[DenDer]

But Gordon are you serious about building a Dr55 clone? If yes let's do it together.....i'm making a BOM list as we speak only have to identify some of the Q's....but this ain't aproblem. I'm getting a Dr55 this afternoon that i'm going to modify for a guy so i won't have to open mine again.
And are you a good pcb designer? Maybe we can make a batch or so.

[DenDer]

Okay a terrible thing just happened...no more sound out of the Dr55. I tried to put in the midi kit and after soldering it kept on firing the first step. I took the whole kit out and the clock is working fine but no sounds whatsoever..


HELP!!!!!

I think it killed I killed the memory chip. When i put it in write mode i can hear voices being fired but nothing is memorized. Damn i'm pretty down now. Does anyone have such a chip?

[Gordonjcp]

Well it's possible the memory chip is borked.

Things to check:

The address lines are "counting up" with the clock running
CE2 is pulsing
RD/-WR is high, pulsing low when recording a step
the DI and DO lines are connected together, as per the circuit diagram.

If not, it's possible you can find an equivalent memory chip.  You could bodge just about anything CMOS in there, as long as you've got the physical space to do so.

[DenDer]

I just ordered one from Vintage Planet. They got them on stock. Will report again when the chip arrives and put in.

The strange thing is when i programm like the accent and play it back i only get noise for that pattern.

[DenDer]

For instance: i program a BD. When I push start i can hear the BD but nothing in playback. Also the hats aren't working no more so its got to be the 5501.

The adress lines are not counting.
CE2 is not pulsing.

[Gordonjcp]

Hrm, shouldn't the hats tick all the time that the clock is running?  Unless there's something drastically wrong with the memory chip, it won't stop the counters counting.

It wouldn't hurt to have a spare memory chip, but I don't think that's the problem.

Measure pin 9 of IC and check that it toggles when you press start and stop.
Check for pulses at pin 11 when the pattern is started - in PLAY this is sent to the hihat "16" setting.

If you're not getting that, the oscillator isn't running for some reason.