Hi Everyone,, I am Building an Electric Mistress Clone and I am having trouble trying to Figure out if I have fried the MN3207 BBD chip or if it's something else in the circuit..
I have checked all the inputs to the chip and as far as I know they are working (as far as I know?) whether they are working properly is another thing I do not know...
The guitar or instrument signal is entering Pin 3 of the 3207 and is a good clean sine wave signal but there is no Flanging effect at all... Just a noisy signal output. I have looked at all the wave forms on my Oscilloscope and the signal output is a really fuzzy looking sine wave.. Is that an indication that I have fried the MN3207 chip,,?
I was wondering also if anyone has built a EM Clone and has pictures of the Working flanger output?
All and any Help would truly be appreciated. Thank you Terence.
p.s. For some strange reason I cannot post my schematic!,, I'm not sure why or what's happening with that? If some one can tell me how to post my schematic I was gladly post it!
Some voltages would be a good place to start to help with debugging :)
Fried BBD usually has no output at all rather than noisy output.
Try vary your BBD bias level also (i.e. DC voltage at pin 3).
If you are on 9V supply then BBD bias will be between 5V and 6V (if you have an MN3207 or BL3207).
I have not used a Coolaudio 3207 but have seen a post recently where bias level on those chips was closer to 4V than 5V.
Note that even a correctly biased BBD will show you fuzz on the audio wave at the BBD output.
Zoom into the fuzz with a DSO and you see it consists of lots of little zig-zags (that's the BBD clock noise) and that is just the way BBDs construct their output signal. The fuzz should be mostly gone by the time you reach circuit output due to the filtering after the BBD.
Quote from: TK2 on September 04, 2020, 11:22:21 AM
For some strange reason I cannot post my schematic
What did you try? There's a Mona Lisa button (https://www.diystompboxes.com/smfforum/Themes/DIYTheme2/images/bbc/img.gif) which will insert [I
MG] tags, between which you put the URL to your picture. There's also an "Add image to post" link beneath if your picture doesn't yet have a home on the Internet.
Thank you for replying you guys,,, So,,, If there is any output from the Chip, that could be a possibility that I haven't fried the MN3207 chip,,, Yay,,,
The voltages that I have on the pins are as follows:
Pin 1 = 0 volts Pin 8 = 7.41 volts
Pin 2 = 4.18 volts Pin 7 = 7.32 volts
Pin 3 = 4.76 volts Pin 6 = 4.24 volts
Pin 4 = 8.14 volts Pin 5 = 8.87 volts
https://i.postimg.cc/W1Z0CDFZ/screenshot-1.png
Posting a Schematic the only way I could,, It's not the greatest but hopefully it worked,, Please click on the URL,, and let me know if it works,, I have no way of checking it... Thank you..
BBD output voltages at pins 7 and 8 should be not too far from the bias voltage at pin 3. Should be less than 1V difference.
Hi DrAlx,,
Even with the Bias set to minimum on the MN3207 the voltage On pins 7, 8 stays over 5 volts,,
Believe it or not I actually had some flanging before, but there was no input signal being mixed through the BBD,, It sounded like Chipmunks flanging,, way too high,, I found a solder bridge at one point and straightened that out and after I did, it stopped flanging completely..
So this is why I thought I fried the BBD,,, At this point I'm wondering what would stop the Input signal going through the BBD and being Flanged? :icon_cry:
If you have 500Hz sine wave at BBD input then you should get output wave of roughly same size at BBD output. If not then the BBD is either...
Not being clocked (use a scope to check you actually have clock signals).
Or
Has bad bias level
Or
Is no good
Or
Has some problem on the output load (so check soldering of all parts from BBD output up to the transistor base)
Just a thought, but have you tried running it at 12V? I have an EM3007 clone that really doesn't like being on 9V. Noise, squealing, which forced a rather short sweep, in my case. Feeding it 12V solved everything for me.
Hi,, The 3007 can handle up to 15 volts if I'm not mistaken,, I'm using a 3207. It's only good for 10 volts... My 3207 is regulated to 9 volts...