Crumar Musical Instruments User Group.

Hi

I am new to this group and to the Bit 01.  I bought one yesterday from a person on Craigslist 
and it has a weird problem, not a "bad jack" as he stated.

It doesn't sound like it has a dead voice.  Instead it sounds like a capacitor somewhere is bad 
-- if I hold down many keys, it sounds fine, but if i just press one, it sounds weak.  Here's a 
recording of it:

http://code404.com/CrumarProblems.mp3

I just saw the other bit one problem thread, but this seems different.  Can anyone suggest a 
fix for this issue?

Many thanks in advance,
Justin

Almost certainly a decoupling cap -- I forget exactly where they are but I replaced all six on my Bit 01. Recommend you do the same --mpa

I seem to recall that they were online and I try to point to all that
stuff on my global synth resource page at www.imt.net/~sounddoctorin.
 IF there are free service docs that I'm not aware of please let me
know. -Bob 406-582-5849
--- In crumar@yahoogroups.com, Justin Maxwell <soc@...> wrote:

>
> (re-sent.  sorry for the digital signature on the last one...)
> 
> Thanks, Michael!  Can anyone share the schematics that were floating  
> around here last month?
> 
> On Mar 16, 2007, at 8:52 AM, Michael Ashton wrote:
> 
> > Almost certainly a decoupling cap -- I forget exactly where they  
> > are but I replaced all six on my Bit 01. Recommend you do the same  
> > --mpa
>

--- In crumar@yahoogroups.com, Justin Maxwell <soc@...> wrote:
>
> Thanks, Michael!  Can anyone share the schematics that were floating  
> around here last month?
> 
> On Mar 16, 2007, at 8:52 AM, Michael Ashton wrote:
> 
> > Almost certainly a decoupling cap -- I forget exactly where they  
> > are but I replaced all six on my Bit 01. Recommend you do the same  
> > --mpa
>


Hi. I would be interested to hear that sound example ( http://code404.com/CrumarProblems.mp3 ) but it's not there anymore..

I have Crumar Bit-01 with one dead or more like very silent voice. It's also third one so if that Justins Bit-01 ever got repaired i would be gratefull of any advice what to do with it.

What i have done so far is that i tried to swap filter chips to different slots to see if it has any effect -it did not. Nothing changed.

I made many tests like one as example when i removed all filter chips except first. Then of course it had only one working sound.
After that i replaced that 1st. chip with the one from slot 3. It worked perfectly again as one voice synth like it should of course. I found out that way that all chips were working a OK.

I still did not trust my self and bought one from EBAY. It also worked but did not fix 3rd. voice problem.

Then i bought few LM13700N chips (they were cheap at least) and replaced all three -again with no anykind of effect on problem.

I have TL082 chips too but somehow i suspect that replacing those is useless as well.

Could you or anyone give a clue what capacitors could have this effect or if it is wise to replace them all?

Someone on another forum suggested that idea. Said that it removed doubts that some other cap would fry also soon after replacing faulty one -and that replacing them all would also made soundquality better.. .  .

Before i start to randomly replace those caps i thought that i ask from this forum if somebody would know exactly what this all about.

.a33e

Hi,

sorry to bother with this again. But if anyone of you would know anything that might help in this topic i would be extremely grateful.

Like where to get schematics for Bit-01 or any idea about what capacitors to replace from which circuit board?

.ja



--- In crumar@yahoogroups.com, "a33e" <dr.3.tri@...> wrote:

>
> 
> 
> --- In crumar@yahoogroups.com, Justin Maxwell <soc@> wrote:
> >
> > Thanks, Michael!  Can anyone share the schematics that were floating  
> > around here last month?
> > 
> > On Mar 16, 2007, at 8:52 AM, Michael Ashton wrote:
> > 
> > > Almost certainly a decoupling cap -- I forget exactly where they  
> > > are but I replaced all six on my Bit 01. Recommend you do the same  
> > > --mpa
> >
> 
> 
> Hi. I would be interested to hear that sound example ( http://code404.com/CrumarProblems.mp3 ) but it's not there anymore..
> 
> I have Crumar Bit-01 with one dead or more like very silent voice. It's also third one so if that Justins Bit-01 ever got repaired i would be gratefull of any advice what to do with it.
> 
> What i have done so far is that i tried to swap filter chips to different slots to see if it has any effect -it did not. Nothing changed.
> 
> I made many tests like one as example when i removed all filter chips except first. Then of course it had only one working sound.
> After that i replaced that 1st. chip with the one from slot 3. It worked perfectly again as one voice synth like it should of course. I found out that way that all chips were working a OK.
> 
> I still did not trust my self and bought one from EBAY. It also worked but did not fix 3rd. voice problem.
> 
> Then i bought few LM13700N chips (they were cheap at least) and replaced all three -again with no anykind of effect on problem.
> 
> I have TL082 chips too but somehow i suspect that replacing those is useless as well.
> 
> Could you or anyone give a clue what capacitors could have this effect or if it is wise to replace them all?
> 
> Someone on another forum suggested that idea. Said that it removed doubts that some other cap would fry also soon after replacing faulty one -and that replacing them all would also made soundquality better.. .  .
> 
> Before i start to randomly replace those caps i thought that i ask from this forum if somebody would know exactly what this all about.
> 
> .a33e
>

Nice, thanks! I guess this helps and definitely kicks process forward..
I also downloaded schematics.

I'll inform about results some day. :)

.ja



--- In crumar@yahoogroups.com, Michael Ashton <data@...> wrote:

>
> I had the same problem, and my guess is electrolytic capacitors. They pretty
> much have a shelf life, and the originals are definitely all past it. That
> goes for almost any electronic equipment over about 25 years old --
> electrolytic caps are not long-lasting components.
> 
> Dead voices may indicate AC coupling caps, which I think are the ones
> following the VCA stage -- I'm pretty sure those are the ones I had to
> replace in mine. I don't have the schematic handy, but they were definitely
> coupling caps.
> 
> In any case, you should replace as many of the electrolytics as you can;
> you'll have to anyway. Definitely do the ones in the power supply, so it
> doesn't ripple and fry your Curtis chips! Fortunately, those are the only
> really rare ICs in the unit, AFAIR.
> 
> --mpa
>