What's wrong with my Boss DR55?

[Stakker]

I just sold my 100% working Boss DR55, and the guy who bought it sent it back claiming it wasn't working.

I hooked it up and it's completely fine, however since I had it last week, it has developed a problem.

When i write the first BD sound in the 16 steps, it writes one when I button down, and another when I release, meaning I can only write a double BD at the begining of a sequence. The only way I can get a single hit at the beginning of a sequence is to press the write button as normal, but then press the clear button before I release the write button.

However this still makes timing difficult as it's hard to place the first snare or rimshot or even the next BD as i'm not sure to count 3 or two.

Anyway, its damaged somehow and I'd like to fix it, but then I thought, why not get it modded. So i came here.

Firstly, how easy would it be to just fix the problem? As a novice, could I do it?

...and secondly, how expensive would it be to mod it with pots to control snare and kick decay and things like that? Or is this forum devoted purely to DIY efforts?

I look forward to some advice!

Thanks!

[Gordonjcp]

Google around for the circuit diagram.  There's not a lot in a DR-55, so finding places to add pots for pitch and decay is easy enough.

For example, Q2 and its surrounding components form a resonant filter.  If you reduce the values of the middle two resistors in the filter section (R7 and R8) you'll raise the pitch, although it will shorten the decay.  You could reduce R12 to increase the gain and get a longer bass drum.

As for the double-triggering, is it really only on the first note?  It sounds like contact bounce, possibly caused by a bad connection in the "Start" switch.

[Circuitbenders]

As for the double-triggering, is it really only on the first note?  It sounds like contact bounce, possibly caused by a bad connection in the "Start" switch.

Possibly the most valuable lesson i've learnt in fault finding: think mechanical before electronic. I just spent ages trying to track down a fault in the VCA of an MB33 beofre discovering the switching was intermittant on the jack that cuts the VCO when you plug in an external input. I could have had that sorted in minutes if i hadn't assumed it was something electronic. 

[Stakker]

So, to a layman, like me...I need to check the contacts...the physical link from the button to the board?

Thing is, why doesn't the double trigger happen elswhere in the 16 beat pattern? Why doesn't it happen when set to another sound? Why just on the BD?

I'm lost to be honest! Just had a word back from my first synth repair place who told me they can't help as they can't get the parts.

bugger.

[Circuitbenders]

I'm lost to be honest! Just had a word back from my first synth repair place who told me they can't help as they can't get the parts.

Thats most likely complete crap. Its probably just not worth their while. I'd be willing to bet that you could probably replace every single part of a DR55 one by one for about a quarter of what a repair company would charge you to even look at it and tell you its broken.

[Gordonjcp]

Yeah, they don't want to do it.  The only bit that might be a challenge is the memory IC.  If that goes you'd probably struggle to find one, and end up having to buy about a thousand ;-)

If it really is just the bass drum, really just on the first step of the bar then something else odd is going on - but I don't know what.  I'll need to have a think about how the circuit works before I can come up with a theory...

[Stakker]

This weekend I bought another DR55 and an SR88. I'd love to get them running with Decay pots for each sound.

Does anyone fancy having a go at it, or can anyone recommend someone who might be able?