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281 clone project- taking orders now for last run of these..
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interested in a PCB or 4?
yep
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nope
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Total Votes : 148

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LektroiD



Joined: Aug 23, 2008
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PostPosted: Tue Nov 30, 2010 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

The Bad Producer wrote:
no skype but u can pm?

what board is your peak circuit on?

edit: your diagram looks wrong for one reason, I should have noticed this earlier... the PEAK circuitry is only built on one board - think of it as a separate sub-circuit - so the PEAK IN socket should go to the same PI pad as A PKO and B PKO, the output of this sub-circuit is PO.

edit edit: just working on a diagram


I think a diagram would definitely be of use here, as you can clearly see from my efforts!

Quote:
edit edit edit - you know you need to supply +15v, GND and -15V to each board? (sorry!)


This could well be the problem then! I never noticed this in the build docs!

Many thanks for taking the time to help, hugely appreciated Wink

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The Bad Producer



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PostPosted: Tue Nov 30, 2010 1:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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The Bad Producer



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PostPosted: Tue Nov 30, 2010 1:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

For more details check the blog, link below...

EDIT - also on blog is power wiring... I'll not bother to upload here too...

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LektroiD



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PostPosted: Tue Nov 30, 2010 2:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have them both working now (sort of)..

The B Level pot I have wired (similar to my diagram - or the bottom most pot of your diagram) does nothing?

On your diagram there are now 3 pots. This has made it even more confusing - none of them are labelled as to their function.. I'm not sure which of the 3 pots is the "B Level" pot? (I have no space on my panel to place the additional two pots anyway)...

I noticed you are using revision 2 boards, mine are revision 3...

I'll try to get a pic of the front panel, but the whole thing is a mess until I can get it all bolted back together, once it's working.

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LektroiD



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PostPosted: Tue Nov 30, 2010 3:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, there's something odd going on, they both seem to generate waveforms correctly, but in quad mode they don't seem to do anything except occasionally I can get it to switch A on and off from B, it stays at +10V constantly then pulses A on and off leaving the DC offset at +10V.. It is literally an ON-OFF pulse, even though it should have an attack/decay slope, not a square modulating it

For example, it is absolutely impossible to create a waveform like this:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Also if I switch modes away from cycle, it will not start again in cycle mode unless I kick start it with an external trigger

This is the best I can get it to do:


scope.jpg
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scope.jpg



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The Bad Producer



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PostPosted: Tue Nov 30, 2010 4:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

The three pots (from top to bottom) are amount of external signal in to the PEAKcircuit (not on your panel, so ignore the pot and just go PEAK IN thru a 1N4148, amount of A to PEAK circuit, Amount of B. If you don't have pots ignore them, as it says on the blog.

V2 vs V3 - they look the same to me in this area apart from R47 being on the V3 board, if you compare them you would see that.

So do both boards cycle if left in cycle mode? or do you mean they just stop after a while? Mine stops unless triggered once, which I thought was a feature?

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LektroiD



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PostPosted: Tue Nov 30, 2010 5:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

The Bad Producer wrote:
The three pots (from top to bottom) are amount of external signal in to the PEAKcircuit (not on your panel, so ignore the pot and just go PEAK IN thru a 1N4148, amount of A to PEAK circuit, Amount of B. If you don't have pots ignore them, as it says on the blog.

V2 vs V3 - they look the same to me in this area apart from R47 being on the V3 board, if you compare them you would see that.

So do both boards cycle if left in cycle mode? or do you mean they just stop after a while? Mine stops unless triggered once, which I thought was a feature?


all seems to be sorted now, have it syncing some oscillators in a crazy fashion.

Many thanks for all your help, I'm off to build the other pair now Smile

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The Bad Producer



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PostPosted: Wed Dec 01, 2010 2:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Good news! To be honest I wasn't sure mine were working at first!
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toppobrillo



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PostPosted: Wed Dec 01, 2010 3:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey thats great u got it working Smile
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russma



Joined: Oct 22, 2007
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PostPosted: Thu Dec 02, 2010 12:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Based on the information in this thread, I made a builder's FAQ document so people wouldn't have to parse through all the PCB-ordering posts. Maybe someone will find it useful. Here's a link:

http://dl.dropbox.com/u/168766/281_notes.docx
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russma



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PostPosted: Thu Dec 02, 2010 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is one 10v voltage regulator and one cap C4 enough for four boards? I'm using an LM7810C for the regulator.
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rosch



Joined: Oct 03, 2009
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PostPosted: Fri Dec 03, 2010 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

thank you, russma!
this helps a lot!
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ultrashock



Joined: Dec 10, 2009
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PostPosted: Thu Aug 25, 2011 8:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Dear ALL!
Just a simple question nothing really in depth just:
in sustained mode /------------\
if you release the key (the gate) in the middle of the attack phase - will the envelope:
1) decrease to zero at once without reaching the maximum (decay phase) or:
2) it will anyway reach maximum (10 volts or so) and then will fall down to zero?

The first case seems more convenient for me reminding an ordinary "ad\ar\asr" generators, but I have a suspicion that it's second stated above case (i'm just experimented with my own designs using discrete integrator and ota on the 281 cmos).

Thank you for your answers in advance!
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Terrafractyl



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PostPosted: Thu Sep 22, 2011 5:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok I am at the end of my nerve people, Its been an awful week of DIY and I just finished building my 2nd 281. Unfortunately it has exactly the same problem that my first one did (and still does) so now I have two dual 281's that don't work. Sad
Basically I have the same problem that 2 other people in this thread had (very short envelopes, attack and decay knobs do nothing, in cycle mode it produces a high 1khz approx tone)

But both of these other problems were fixed by either replacing the 5240 diode or switching the pins on the mpf102.

I have replaced these parts several times now, and still have the same problem. I have checked all the Cmos chips are getting 10v and the other IC's are getting the appropriate power.
I also have tried a bunch of different IC's and have swapped the cd4016 with a cd4066. Same deal, the outputs of the cd4066 DO seem to be passing the voltage changes from the attack and decay knobs, maybe the lm13700 is not functioning properly? I have tried swapping them out also.

Please, any advice on getting these 281's to work would make my day!
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arnoid



Joined: Aug 23, 2009
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PostPosted: Mon Dec 12, 2011 5:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi

I build a quad 281 15V version. R7 & R8 1K

But the module doesn't cycle on 15V in cycling mode if I give it a trigger signal
The weird thing is if I put 12,80V to the module its cycling and working correct.

What shoud I do raising R7 & R8 ?
Sombody had the same issues Question

thx in advance
Smile

PS: it's not my power supply is strong enough (3,3A) and I tested it with just the 281 connected.

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beautyofdecay_



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PostPosted: Mon Dec 12, 2011 8:19 am    Post subject: Reply with quote  Mark this post and the followings unread

The trigger pulse should be 10V.
I had trouble triggering cycle mode at first but found out my trigger pulse peak voltage was too low.

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arnoid



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PostPosted: Mon Dec 12, 2011 8:53 am    Post subject: Reply with quote  Mark this post and the followings unread

beautyofdecay_ wrote:
The trigger pulse should be 10V.
I had trouble triggering cycle mode at first but found out my trigger pulse peak voltage was too low.


the trigger pulse isn't the problem

If I run 15V to the module from the power supply the module doesn't work correct if I lower this and run 12,80V to the quad 281 everything works as it should...
But I builded a 15V version so I want it to work on 15V Smile Because my main power suplly is 15V

the trigger pulse is strong enough to get the module cycling

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arnoid



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PostPosted: Thu Dec 22, 2011 1:21 am    Post subject: Reply with quote  Mark this post and the followings unread

arnoid wrote:
beautyofdecay_ wrote:
The trigger pulse should be 10V.
I had trouble triggering cycle mode at first but found out my trigger pulse peak voltage was too low.


the trigger pulse isn't the problem

If I run 15V to the module from the power supply the module doesn't work correct if I lower this and run 12,80V to the quad 281 everything works as it should...
But I builded a 15V version so I want it to work on 15V Smile Because my main power suplly is 15V

the trigger pulse is strong enough to get the module cycling


Nobody with a suggestions for my problem ? Smile
Or maybe somebody has the same problem ?

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toppobrillo



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PostPosted: Thu Dec 22, 2011 3:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
What shoud I do raising R7 & R8 ?


they have nothing to do with it, OK so are you saying, when powerng the unit from +/-15V, you cannot trigger the envelopes at all? or- that ASR and AR mode work fine, but no cycling?
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arnoid



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PostPosted: Thu Dec 22, 2011 3:55 am    Post subject: Reply with quote  Mark this post and the followings unread

toppobrillo wrote:
Quote:
What shoud I do raising R7 & R8 ?


they have nothing to do with it, OK so are you saying, when powerng the unit from +/-15V, you cannot trigger the envelopes at all? or- that ASR and AR mode work fine, but no cycling?


Gonna test the ASR and AR on 15V tonight but indeed there is no cycling when a trig is given in lfo mode.

If i power it with 12,80V the lfo mode work as it should...And cycles when a trig is given.

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henrikgo



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PostPosted: Sat Feb 04, 2012 1:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have built four V3 PCBs and have some problems.

I can't get none of them to cycle, when in cycle mode, they will cycle twice then stop.

Also this one is really strange. After about 5 minutes one of the A-boards will hang in quadrature mode and just give a continuous gate, it happens every time. It release the gate when I flip the quadrature switch, but will hang again if I turn on the quadrature.
The other tho 281s that are linked will both hang in quadrature mode.
If I power off and then on again directly the modules will do the same thing. If I leave the power off for a while it's all good again for another 5 minutes.

Also the end pulses just work sometimes on some of the modules.

I really can't figure these problems out!?
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henrikgo



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PostPosted: Wed Feb 08, 2012 9:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Anybody?
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djg



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PostPosted: Wed Mar 21, 2012 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

To those with having cycle problems, my dual has been working great until I switched to a different power supply recently.

'A' would cycle fine, but 'B' would not. I always noticed that my 'B' was sort of "softer" and needed a stronger gate to get going in in the first place, but nothing would get it to cycle with the new PSU.

I checked it out on my bench supply and my 'B' would indeed cycle. I had noticed my new PSU was running going a little hot, measuring 15.65V +/ when I installed it, but figured it would be fine. So I cracked it open just now and trimmed it down to the appropriate levels, and lo and behold, 'B' is back to cycling.

Perhaps with too hot a power supply it is expecting a proportionally larger gate than 10V and with the circuit even the smallest deviation in the supply makes a difference? Just a heads up for those having troubles that it might be worth checking your supply voltages thoroughly.
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henrikgo



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PostPosted: Mon Oct 08, 2012 2:37 am    Post subject: Reply with quote  Mark this post and the followings unread

My PSU is exactly +/-15V, but still these strange problems on all four of my 281 V3. End pulse will just work sometimes on some of the 281s, but then only when ASR is selected, AR doesn't give any end pulse. Quadrature works sometimes but usually just gives a continuous gate to both 281s. Cycle mode doesn't work properly either, most of the time it cycles twice then stop.
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arnoid



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PostPosted: Sun Mar 24, 2013 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Bump
I still having cycling issues when driving the module on 15V

I took the module apart and checked with just one 281pcb because I tought It had something to do with using one voltage regulator for 4 pcb's but I have the same problem with just one pcb ?? It stops cycling when I go above 14V on the positve rail ? I have the same problem with the 4 pcb's ?

Sombody can help me out plz ?
I tryed to read the schematics I guess it has something to do with the CA3080 IC ?

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