Subtle Chorus BBD

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

I'm slightly puzzled here. Finished this today but can't get my MN3007's to work in it. These are known good BBD's (they work fine in a Tonepad chorus). I have clock from the MN3101 (71.7 kHz) and the correct smaller voltage on pin 4. Still I only get clock bleed through on pin 7and nothing on pin 8. (and yes, input does get up to pin 3).

I've had BBD's not shifting signals before, but I can't remember what it was then....

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Chorus BBD Board

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etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

Okay, never mind, the same ICs work perfectly fine in the right channel, so I probably just made a mistake somewhere in the left...

[edit] incredible noob-error by the way; I reversed C16... It works fine now.

whomper · Posted: Mon Feb 09, 2009 3:24 pm Post subject:

Hi,

I am testing my BBD boards and have some difficulties:

1. The LFO rate is fast. Even when lowering the rate via the pot, it does not go slow enough. Only when coupling the pot with CV can I get a low enough rate.
2. The DEPTH POT only works between step 2-3, the rest it does nothing. Can I have a faulty 13600?

What does 100K trimpot? I though it could change the LFO rate initial setting, but turning it does nothing.

jhaible · Posted: Mon Feb 09, 2009 3:53 pm Post subject:

whomper · Posted: Tue Feb 10, 2009 2:39 am Post subject:

I went through the resistors values (of the Option A and B in schematics 2, the LFO and summing) and they seem ok. I have also noted that my interpolating scanner has a similar problem of depth and rate (I noted a similar circuit).

I have used 100k lin pots.

I must have done in those three cases (I have 2 BBD and 1 scanner) something wrong to get a similar result out of the CV LFO.

Any inputs as to trace the LFO signal across the components? What should be the ballpark voltages at important sections with a mid point setting of rate and depth?

jhaible · Posted: Tue Feb 10, 2009 6:13 pm Post subject:

whomper · Posted: Wed Feb 11, 2009 4:22 pm Post subject:

jhaible · Posted: Wed Feb 11, 2009 4:29 pm Post subject:

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

Hello,

I am a total beginner at this and i am troubleshooting my boards-- Dimension D version.

The bypass signal is fine but the wet signal has a pretty loud hum, a bit like a loud ground loop. I decided to check the power supply to the BBD. I am using the 15vac wall wart PSU. at the pins of the connection to the BBD i get 9.6v and -9v, not +-15v. is it not supposed to be +-15v to the BBD board? could i have blown the regulators? how can i check them? any help appreciated.

thanks in advance,

jay

jhaible · Posted: Tue Mar 10, 2009 2:32 pm Post subject: Re: beginner help

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

Hi JH thanks for replying,

mine is 1000ma. do you have any other suggestions?

jay

jhaible · Posted: Tue Mar 10, 2009 2:43 pm Post subject:

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

ok i will start to take it apart.

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

oh my god i found out that i had a LM317m instead of a LM317. the label was covered by the heatsinks so i didnt check it. i cut 3 traces already trying to isolate the problem. Rolling Eyes

i will replace it and let you know. thanks again for your help

jhaible · Posted: Wed Mar 11, 2009 3:04 pm Post subject: Re: stupid me

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

hello i am back! Wink

well i cut enough traces and lifted some resistors so that the power section is completely isolated. no power is going to the rest of the board, anywhere. still i have only +-10v. so what are my possibilites?

1. the PSU is fucked. it doesn't put out the current that is written on it. here it is, in case i am doing something stupid:

http://www.velleman.be/be/en/product/view/?id=365838

but what are the chances of a wall wart not working as it is written on it?

2. the diode rectifier is somehow not working right. i checked continuity and it seems to be OK at each point.

3. something else? i have replaced both regulators, so thats not it. i have moved the 470u caps around with a known good one, i dont think thats it. i checked resistor values both with a multimeter and by color code, so i guess the are probably right.

4. its supposed to be that way. Shocked

aaah its driving me crazy.

please help!

thanks

jay

jhaible · Posted: Thu Mar 12, 2009 8:21 am Post subject:

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

ok i will have a shot at it. will a soundcard oscilloscope work? i don't have a real one.

EDIT: i googled it and i guess not.

jhaible · Posted: Thu Mar 12, 2009 9:42 am Post subject:

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

no i dont know anyone w/ a scope. Crying or Very sad

jhaible · Posted: Thu Mar 12, 2009 12:10 pm Post subject:

jayjayevans · Joined: Mar 10, 2009 Posts: 11 Location: munich

i did some more research and figured out what the problem was. it was really ignorant on my part: i wired the AC leads wrong. i thought ac leads should have been on the far right and left (i told you i was a total beginner). Embarassed

well at least i know now how a power supply works. anyway i might have more questions...please be patient with me.

thanks again for your help.

jay