Pork Barrel Chorus

[marmaliser]

Hope you guys can help me out here with my first madbean build

(1) Project Name - Pork Barell Chorus - Latest version

(2) General description of the problem - With the 10k Trimmer all the way to the left I get a nice clean signal but after about a third of the way around the chorus kicks in but I am getting a fair bit of noise and if I strike a chord I get a bit of distortion as well.  The sound stays the same with the trimmer all the way clockwise

(3) Steps that you have taken to try to resolve the issue - I have tried all new Transaistors and IC's with no change.  Both pots alter the sound as you would expect

(4) List any substitutions you used for parts/values
R40 - 39r instead of 33r

Thanks in advance

[marmaliser]

Some pictures - Its not boxed up and there is no switching.  The pots are there until I can get some proper board mounted ones

[jkokura]

As usual, I recommend that you:

Check you've used the correct value for all your parts.
Check you've used the correct orientation for all your parts.
Check your wiring.

Your soldering looks pretty good. One glaring problem is that you have no ground wire connected at the top, however I think there's a ground wire at the bottom. I'm not really seeing a big problem, so you'll have to go through and check and recheck, and use an audio probe if everything seems to check out.

Jacob

[Scruffie]

What guitar are you using...??

Any chance it has Active Pickups? Or Humbuckers?

If so, try slowly biasing with a single coil guitar.

Did you build the 3007 or 3207 version?

[marmaliser]

Thanks 

I have tripple checked all parts but we all know once you have made an error sometimes you just can't see it.  I did some voltages yesterday and those on the 4558 looked high compared to some posted by Lacesensor in another thread.  I have an  audio probe built into my test rig so will give that a go but I am not great at following a circuit.

There is a ground at the bottom but I will wire in the one at the top as well.

I built the 3007 version and yes I have been using Humbuckers.  I will get my Strat out and give that a try

[marmaliser]

Wired the ground in and tried with single coils. Still exactly the same. 

[Scruffie]

Wired the ground in and tried with single coils. Still exactly the same. 

It was just something to rule out, some people try and use Active/High Output pickups with BBDs which will clip them (especially without companding).

What are the voltages you took that were suspect?

It is possible you have a bad MN3007, i've had it happen with an 3208 and a builder I know has to throw away some of the 3007s he buys as they're no good, so if you have a spare, try it in there, otherwise, lets rule everything else out before you go buying a new BBD... i'm interested as to how off your 4558 voltages are.

[bigmufffuzzwizz]

I must say your soldering looks very clean. I built the older version, when I finished I wasn't getting any chorus signal. Luckily I ordered 10 pairs of the MN3101/MN3007 IC's so I tried a second pair which did work. I still have yet to go through and see how many of the 10 pair work, but that could be it.

[marmaliser]

Thanks,

I will post up voltages for all IC's tonight and check all parts again.

I have tried two sets of IC's both from Dr Tweek who seems a very reputable top bloke.

EDIT - VOLTAGES

tlo72      
1   1.8 varying to 5
2   3.9   
3   2.7 varying to 4.8
4   0   
5   3.8   
6   2.8   
7   2 varying to 4.6
8   7.8   

4558d   
1   6.15
2   6.15
3   6.05
4   0
5   5.88
6   5.88
7   5.88
8   7.8

mn3101   
1   7.8
2   4
3   0
4   4
5   0.5
6   6.8
7   6.8
8   0.25
mn3007   
1   7.8
2   4
3   5.15
4   0.5
5   5.2
6   5.18
7   3.95
8   0

[jkokura]

Your dual op amp voltages look fishy to me, but I don't have a pork barrel to compare them to. The fact that you're getting some strange readings is interesting and worrisome. Indicates you do have a problem on the board, and the usual suspects are a wrong/backwards part, a cold solder joint, or a solder bridge.

Jacob

[Scruffie]

Yeah those voltages look wrong, your 4558 should have approximatley 1/2 Supply on there pins and both  halfs are different and quite high.

I assume you're using a battery? Otherwise you should have more than 7.8V on your supply pins...

Somethings going on, I know you've triple checked but quadruple check for wrongly orientated electrolytics and wrong valued components.

I also notice there's an issue between your clock and bbd, pins 2 & 6 on the 3007 should both be getting 4V such as the 3101 is putting out but one pin is off...

As Jacob said, have a look over the board.

[marmaliser]

Yep Battery,  Just done it with PSU and get 8.98 on supply pins
The others pins are varied by turning the Trimmer 1 is this right?
Going to go over all connections and values again today

EDIT: I re soldered a few connections yesterday and have just set up a small amp / test rig on my desk and it sounds fine now with no distortion.  I think perhaps sitting in fornt of my HT5 Stack was perhaps making the perceived noise worse.  So I am going to get the right pots and get it boxed up .

[marmaliser]

Boxed it up and got my burkey 6 out and ran it at 15v.  No HUM and no Distortion on chords etc
Thanks for the help guys.  I will post a picture up when I have finished a little something

[marmaliser]

Can't think of a name for this thing....Any ideas ? ! Gfx are attached and it has a light plate on the bottom that flashes with the depth.  The pink is the colour of the enclosure

[jkokura]

I would just leave it like that. Does it really need a name!

You could do a good ol "whoo hoo" in a cartoon voice bubble from Homer.

Jacob