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MXR Flanger trim questions

Started by Govmnt_Lacky, January 26, 2012, 01:23:55 PM

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Govmnt_Lacky

January 26, 2012, 01:23:55 PM
Since most of the MXR flanger posts are pretty old, I figured I would start a new one for this round of questions  ;D

Backstory:

I built an M117 clone from madbean's compact layout (The One-One-Seven) and kinda tinkered with it to get it sorta working then I shelved it.

New Story:

I recently decided to bring this bad boy to the pedal board and play! It sounds like utter rubbish! I am using the madbean Road Rage charge pump circuit to power it (which does a fine job by the way!)

The Data:

I built the circuit according to the layout (which is just a compact version of the same old MXR schemo) and used a 33pF cap for the timing circuit. With this value, I am able to get a nominal 32KHz to 970KHz sweep for the time which is ideal. I have a signal generator, DMM, and o-scope at my disposal. Here is where the questions come to light.

1) What is the best recommended way (in detail is preferred) to adjust the Distortion and Level trimmers using the test equipment I have available?

I have followed the recommended steps that have been posted many, many times but I really do not know what "to look for" on the scope. For instance, when adjusting the Distortion trimmer. What should I be looking for in the signal to see if it is set correctly?

Also, when adjusting the Level trimmer. What should I see on the scope to know that I have a good 50/50 output of modulated and un-modulated signal? I tried to use the DMM at the SAD pins 5/6 and 11/12 to get the voltages even but, they ALWAYS seem to be split by at least 0.5V.

If someone could possibly give me some detail on what the waveforms should look like it would help HUGE!  :icon_cool:

A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#1
January 26, 2012, 02:48:08 PM
"someone" eh...  :icon_mrgreen:

Bias:
raise input signal (100Hz, sine is better) 'till clipping, trim to obtain a symmetrical clipping. (this will give you the max out level from BBD too). Increase AND decrease input signal to check...

Level:
same input signal as for bias,
test points at 150K and 82K out mixer op-amp's input resistors (r5 and r9 on madbean's layout): check for 5.5dB level difference... (wet lower)
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#2
January 26, 2012, 02:55:12 PM
Quote from: Fender3D on January 26, 2012, 02:48:08 PM
"someone" eh...  :icon_mrgreen:

Bias:
raise input signal (100Hz, sine is better) 'till clipping, trim to obtain a symmetrical clipping. (this will give you the max out level from BBD too). Increase AND decrease input signal to check...

Level:
same input signal as for bias,
test points at 150K and 82K out mixer op-amp's input resistors (r5 and r9 on madbean's layout): check for 5.5dB level difference... (wet lower)

Thanks Fender  ;)

Could you possibly elaborate on the setup for these tests? Specifically, the pot positions. Manual, Width, Speed, Regen... where should they be for these "readings?"

I may need to take some pics of what I see on the oscope and post. It may clarify things a bit. If so, that will need to be done sometime next week.

To be continued.... (if I can't fix it by ear this weekend of course  :icon_eek:)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#3
January 26, 2012, 03:08:12 PM
I usually set Regen and Width fully CCW while trimming, check for no feedback with Regen fully CW.
Check Bias and level within the full Manual coarse, of coarse... ehm course  :icon_mrgreen:
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#4
January 27, 2012, 10:06:11 AM
Ok... I managed to get this pedal trimmed perfectly BUT...

I now (or I suppose I always had it) have a wicked bad HUMMMMMMMMM that faintly pulses with the LFO  >:(

I used the road rage pump circuit for the 9v to 15v conversion which is regulated fairly well. I am also using a regulated 9v supply for the input that is quiet on my other builds.

Any ideas on where to start?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#5
January 27, 2012, 10:34:33 AM Last Edit: January 27, 2012, 10:39:06 AM by Fender3D
Did you try with a 18Vcc regulated supply?

edit:
sorry mate just realized that madbeans layout has no 7815 regulator.
please read "Did you try with a 18Vcc regulated supply?" as
Did you try with a 15Vcc regulated supply?
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#6
January 27, 2012, 12:10:15 PM
Quote from: Fender3D on January 27, 2012, 10:34:33 AM
Did you try with a 18Vcc regulated supply?

edit:
sorry mate just realized that madbeans layout has no 7815 regulator.
please read "Did you try with a 18Vcc regulated supply?" as
Did you try with a 15Vcc regulated supply?

I have the road rage circuit installed. It is operating on 14.8V from that circuit.

Is the power from the road rage unregulated? I am powering the road rage from a 9V regulated PS.

9V regulated -> Road rage circuit (14.8V) -> madbean 117 circuit
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#7
January 29, 2012, 09:36:14 AM
Any ideas?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#8
January 29, 2012, 12:48:55 PM
I asked about regulated 15Vcc, to be sure road rage wasn't the issue.
I've always hated charge pumps (but from girls  :icon_mrgreen:  ) 'cause issues are always behind the corner (with girls either...   :icon_twisted: )
"NOT FLAMMABLE" is not a challenge

oldschoolanalog

#9
January 29, 2012, 09:12:04 PM
Do you think the 1044 charge pump can supply enough current for this project?
Quote from: Fender3D on January 29, 2012, 12:48:55 PMI've always hated charge pumps (but from girls  :icon_mrgreen:  )...
+1   :icon_cool: !!!
Quote...'cause issues are always behind the corner (with girls either...   :icon_twisted: )
;D ;D ;D
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#10
January 30, 2012, 07:05:10 AM
Quote from: oldschoolanalog on January 29, 2012, 09:12:04 PM
Do you think the 1044 charge pump can supply enough current for this project?

I am using the LT1054 in the charge pump circuit. That chip can handle up to 100mA so it should not be an issue I would think  :-\

Didn't get to mess with it this weekend. I will try a wall wart tonight BUT, my unregulated 9V wall wart puts out 16V without a load and I do not know how the charge pump circuit will react with that.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#11
January 31, 2012, 07:20:08 AM
Well, I tried the pedal with my unregulated 9V wall wart (16V at output)

The low level hum went away  ;D  I am guessing because my regulated PS does not have the gusto to handle the draw from the flanger. If I remember correctly, the PS can handle about 50mA. I guess the flanger is drawing above that.

On the down side.... there was a lot of distortion with the new voltage input. (would need to trim it out) Also, the sweep just didn't sound right  ??? I don't know if that could be fixed with a bit of trimming or not.

I am guessing it is time to invest in a good high mA regulated 9VDC power supply.

Does the 1-spot put out REGULATED 9V? My regulated PS puts out 9.2V dead silent. Just wondering if the 1-spot puts out more than it's rated for, like other wall warts do.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#12
January 31, 2012, 07:31:08 AM
Quote from: Govmnt_Lacky on January 31, 2012, 07:20:08 AM
...
I am guessing it is time to invest in a good high mA regulated 9VDC power supply.
...

Why not investing in a regulated 15Vdc power supply then?
Transformer, bridge, 3-4 caps, diode and regulator, you may even avoid the vero board...
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#13
January 31, 2012, 08:24:06 AM
Quote from: Fender3D on January 31, 2012, 07:31:08 AM
Why not investing in a regulated 15Vdc power supply then?
Transformer, bridge, 3-4 caps, diode and regulator, you may even avoid the vero board...

Because this is my only pedal that runs on something other than 9V  ;D

The flanger will run fine on a 9V PS, it just needs to be able to handle the current draw from the charge pump & circuit. Hence... the 1 Spot question. 1 power source for ALL of my pedal board.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

oldschoolanalog

#14
January 31, 2012, 08:49:42 AM
According to the info on the Visual Sound site the One Spot is regulated.
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#15
February 20, 2012, 04:21:27 PM
Quote from: oldschoolanalog on January 31, 2012, 08:49:42 AM
According to the info on the Visual Sound site the One Spot is regulated.

Thanks Dave!  ;)

Can anyone tell me the output voltage of a 1Spot without ANY load?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

armdnrdy

#16
June 23, 2014, 03:03:48 PM Last Edit: June 23, 2014, 03:53:20 PM by armdnrdy
Last year I purchased a SAD512 which is basically half of a SAD1024. As it turned out...I couldn't find any stomp boxes that used it! All of the stomp boxes used either the SAD1024 or SAD512D.

This weekend I was looking through some old project files on my PC when I came across the MXR 117 3007 retrofit that I built. I took a look at the original factory schematic and saw that only half of the 1024 was used. The other half is connected to +V.
I instantly thought of the 512.

Stuffed in that project folder was a PDF that Brian (Madbean) worked out for a 1024 version M117 build. Brian named it the One One Seven.

While working out what I would have to change to throw in the 512, I made a little discovery.....The SAD1024 is not grounded in Brian's layout. I looked up some gut shots online and confirmed it. Pin 1 (GND) and pin 16 (NC) go to ground on the original MXR layout.

If anyone has built this and couldn't get it working correctly, (Greg) you might want to add a jumper wire from ground to those two pins.



I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#17
June 23, 2014, 03:18:42 PM
Thanks Larry.

Funny thing is..... I DID get it to work great with the layout AS IS  :icon_eek: I must have had a magic chip or something.

I noticed that as well when I was building the last one (this post was when I built it the first time)

What about Pins 4 &13. They look to be floating too  :-\

BTW... the pots are also wired INCORRECTLY if I recall  ;)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

armdnrdy

#18
June 23, 2014, 03:31:18 PM
I don't know how it could work with the ground pin not connected!

Pins 4 (NC) & 13 (NC) are grounded as well.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#19
June 23, 2014, 03:42:14 PM
Well... it would have to be wire jumpers. Don't think theres an easy way to connect ground to those pins with that layout as is  :-\
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'
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