Dead End FX Larry

[29palms]

Hi all,

I've recently built this project but I'm having problems. It was working but with a very low volume with the effect engaged. I adjusted the BBD balance and this improved but somewhere during trying to calibrate the clock settings the sweep has stopped working.

The frequency trimmers don't seem to do anything anymore and I can only get 100kHz to 26kHz at tp1 depending on how the start stop pots are set.

I tried swapping out the 4046 but no joy. One weird thing is, the rate LED was pulsing previously when I powered up the board previously but is not anymore. I replaced the manual pedal function with a 1MA pot and this mode does create a flanging effect when turned.  I'm planning to check solder joints later but any thoughts on where to start looking for issues would be much appreciated!

thanks,
G

[Govmnt_Lacky]

Provide voltage measurements for IC1, IC2, and Q1. Sounds like your LFO is not functioning properly.

[29palms]

OK voltages below. I noticed IC2 was a little loose in the socket, gave it a nudge and LED is pulsing again. I get some flanging but TP1 still gives me around 30kHz at both ends of start/stop range.

IC 1
12.28
12.28
12.28
0
7.46
7.46
13.16
14.9


IC2
13.49
13.47
7.43
0
14.24
1.42
7.46
1.55 - changes if rate pot set to lowest- goes up to around 12v then falls again


Q1
e 1.35
c 1.48
b 2.03

thanks again for your help!
G

[Govmnt_Lacky]

I get some flanging but TP1 still gives me around 30kHz at both ends of start/stop range.

Are you following the calibration process in the build doc? (To include the part about the timing cap issues?)

P.S. I think you posted your IC pins incorrectly. Try to post them numbered in the proper order. Dot closest to Pin 1 or indent between 1 and 8.

1      8
2      7
3      6
4      5

[29palms]

yes I think I did them in the right order, will double check but if I did them correctly are any of those voltages funky?

I'll check the cap thing, if I remember rightly before it stopped working, I was able to get 70kHz at one end and between 700-800 at the other.
ta
g

[Govmnt_Lacky]

yes I think I did them in the right order, will double check but if I did them correctly are any of those voltages funky?

Please re-post with pin numbers next to voltages when you get time.

[ElectricDruid]

if I did them correctly are any of those voltages funky?

If you did them correctly (and the apparent power pins suggest you did) then a lot of those voltages are weird.

Repost them like Lacky suggested just as a double-check and we'll take another look.

Oh, and have you got a link to the schematic? That'd help too. Thanks.

[29palms]

Govt Lacky was right, I did get IC2 wrong 

schematic at the end of this doc - https://drive.google.com/file/d/1LDdOgaEvKD7LMD93oQv7EVDiAeX3N072/view

thanks for your input.

new voltages as follows clockwise from top left of IC- I don't know if you need measurements with effect on or bypassed?

IC1
1 12.28
2 12.28
3 12.28
4 0
5 7.46
6 7.46
7 13.16 *changing if engaged
8 14.9


IC2
1 13.49 *changing if engaged
2 7.48
3 7.43
4 0
5 1.56  *changing if engaged
6 7.46
7 1.46 *changing if engaged
8 14.24

Q1
e 1.35 0.6 - 1.3 engaged
c 1.48 1.5-4.2 engaged
b 2.03 1.3-2 engaged                                                     

[Govmnt_Lacky]

HELPFUL HINT: When recording voltages on IC Pins where the voltage 'swings' it is helpful to record the HI and LO voltages (don't just post "voltage changes." 

One thing that bothers me is that IC1 Pin 6 and IC2 Pin 1 are connected via R16 yet, in your voltage readings IC2 Pin 1 is a varying voltage and IC1 Pin 6 is stationary  This could be my lack of knowledge but, are you sure that IC1 Pin 6 does not vary?

As for the clocking issue, recommend you double check component values around IC4. Particularly R21-R27, R32-R37, and D16-D17. Verify proper values.

If you multimeter has a frequency counter option, possibly post the clock frequencies at Pins 2 & 6 of IC9 (MN3007)

[duck_arse]

new voltages as follows clockwise from top left of IC- I don't know if you need measurements with effect on or bypassed?
                                               

anticlockwise. it's about this stage we ask to see photos of your build.

it's generally well before this point that we say welcome to the forum, too.

[29palms]

HELPFUL HINT: When recording voltages on IC Pins where the voltage 'swings' it is helpful to record the HI and LO voltages (don't just post "voltage changes." 

YES- sorry

anticlockwise.

- yeah, I meant anti-clockwise, I may have used up all my concentration taking measurements  thanks for the welcome!

I have had a breakthrough this afternoon while taking some more measurements of changing voltages  - I was checking round IC4 as suggested by GL and I noticed some interaction between the probe and a pin on IC4, so I decided to pull out ICs 1,2 and 4 and reflow the sockets and the components around them as well. The result is we have some sweeping flange.

I was thinking of doing this to begin with but without the help from you guys I wouldn't have known where to begin and probably would have ended up doing the whole board so thanks for saving me some time...

It's evening here now so I'm going to try and calibrate tomorrow so I might still have some Qs for you, but in the meantime I'm going to relax and raise a glass to you guys!

thanks again,
G

[29palms]

Ok update for anyone who's interested. I've got it sounding good now, though there were some anomalies when I was calibrating.

The docs say to calibrate the clock with the effect bypassed- doing this I was only able to get down to 70ish kHz and 600 or so at the other end. When engaed to check to sweep I get 34kHz to over 700kHz so wider than expected? Sounds good so I guess going lower than 50k isn't a problem.

My software scope did not like a test tone apllied to TP3 for bias and balance adjustment so I used a synth to send a 440Hz sine wave to the effect input and seemed to be able to make adjustments like that.

These things could be down to me doing something daft or just not having top quality equipment but feel free to school me if I've got anything wrong here. At the end of the day it sounds great to me and I've been playing around and getting a huge variety of flange tones, which is why I wanted to build it in the first place.

I wouldn't have got it to this point without some help from the guys above, particularyly GL who pointed me in the right direction to look for problems- thanks again!
G

[Govmnt_Lacky]

Glad you got it working well! All of the DEFX projects are Awesome!