AMZ FX ANALOG ALCHEMY GEOFX MEF ROG DIY WIKI

Help repair AXL Echo Analog Delay

Started by Govmnt_Lacky, June 23, 2014, 09:36:54 AM

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Govmnt_Lacky

June 23, 2014, 09:36:54 AM Last Edit: June 23, 2014, 11:10:11 AM by Govmnt_Lacky
Got this multipedal for a steal. Only problem is that the Analog delay...... doesn't Delay!

I get clean signal when the effect is on. When I turn the "Mix" pot fully CW, I get nothing. The clean signal will slowly fade in as I slowly turn the Mix pot CCW.

I probed the PCB and I get clean signal into the BBDs (3208s) but I get nothing but HISS out of them. So.... here is the hard part....

I SWAPPED BOTH BBDs and CLOCK CHIP! Still getting the same results. I am wondering if it could be something else. Possibly between the BBD output and the Compander chip? OR the Compander chip itself??

IDEAS??

https://dl.dropboxusercontent.com/u/19888009/Echo_Analog_Delay_AXL.pdf
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

#1
June 23, 2014, 10:26:12 AM Last Edit: June 23, 2014, 10:28:27 AM by armdnrdy
First the Dropbox issue:

Open Dropbox, click on "public", drag your drawing or image into the public folder, wait until the blue circle with a white check mark turns green, right click on the image you just inserted, left click on "copy public link".

In DIYstompboxes right click on "insert image" (third icon from left) something like this will appear [img][img] right click between the two inner brackets, and hit paste.

Done!

Now for the delay issue.

The way that the schematic is drawn makes it a bit difficult to easily follow the signal path so....you should redraw it and repost!
Just kidding!  ;D

Check for the proper clock signal at pin 4 of the 3102. If you have that....I would check into the 4007. The 4007 seems to be controlling the signal bypass JFET. Check to see if the JFET is turning on and off when you hit the "Echo Analog Delay" switch.

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

Govmnt_Lacky

#2
June 23, 2014, 10:37:46 AM Last Edit: June 23, 2014, 10:41:20 AM by Govmnt_Lacky
Thanks Larry... Ill check those when I get some time (hopefully tonight)

I did the cut-n-paste like you said. I only see a Red "X" on my computer. Can someone else confirm that the schematic is visable?

P.S. I didn't know if the IMG would work seeing as the schematic is a PDF document  ???
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

#3
June 23, 2014, 10:41:27 AM Last Edit: June 23, 2014, 10:43:24 AM by armdnrdy
You have to make sure that when you paste the image that it lands between the brackets.

Edit: You are trying to post a PDF. You have to convert it to some other format. JPEG
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Dave W

#4
June 23, 2014, 10:43:25 AM
it posted. it really is a mess to follow. similar to some of those dod schems.
That's where it's at.

Govmnt_Lacky

#5
June 23, 2014, 10:50:51 AM
So can we see it? Dave says YES. Larry says I need to convert it  ???

I would rather replace every passive in the circuit then redraw the schematic!  :icon_eek:

I suppose I can try replacing 3Q2 and/or 3D1 and see what happens (if the clocks are good). Could I use a J113 for the FET? Does it HAVE TO be a 2SK30?

Then, I can move on to the 4007. If I remember right,m I took voltages on all of the pins of the 4007 with the stomp on and off. It looked like all of the voltages "swung" from HI to LO accordingly.
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

#6
June 23, 2014, 10:53:13 AM
After some thought....

Couldn't I confirm that the FET is switching because when the effect is ON, and I turn the Mix pot... it just mutes the signal? IF the FET wasn't switching, wouldn't the Mix pot have no effect?
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

#7
June 23, 2014, 11:05:05 AM
Quote from: Govmnt_Lacky on June 23, 2014, 10:53:13 AM
After some thought....

Couldn't I confirm that the FET is switching because when the effect is ON, and I turn the Mix pot... it just mutes the signal? IF the FET wasn't switching, wouldn't the Mix pot have no effect?

Looking at it again...I'm not sure. This schematic is hard to follow!

Try audio probing the input of the BBD and turn on and off the switch. That will tell you if the switching is operational.

Your image is not posted. You posted a PDF link.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

armdnrdy

#8
June 23, 2014, 11:06:29 AM
Here you go:

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

Govmnt_Lacky

#9
June 23, 2014, 11:13:12 AM
Thanks Larry. I will look at the clock when I get time and post findings
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

#10
July 13, 2014, 02:34:20 PM
OK... had a quick chance to record some reading on this today and hopefully get some feedback!

First thing... The schematic says to adjust the trimmer so that the resistance between Pin 1 and Pins 2/3 read 217K. This is all fine and dandy BUT... it does NOT say what position the Delay pot has to be in  :icon_evil: I just set the Delay pot to full CW and adjusted to 217K.

So, this time I focused on the switching. I took voltage readings of the 4007 and 3Q2 with the effect off and on. Here is what I got. Reading in RED are when effect was ON:

4007:

1) 11V 0V
2) 11V 11V
3) 0V (11V)
4) 0V 0V
5) 11V 0V
6) 11V 0V
7) 0V 0V
8] 0V 11V
9) 6.5V 0V
10) 10V 0V
11) 0V (11V)
12) 10V 0V
13) 0V 11V
14) 11V 11V

NOTE: Pins voltages in parenthesis were pins that, when touched with the DMM, caused the "Effect LED" to turn off. These numbers were taken while holding the DMM lead on the Pin and activating the On/Off stomp again.

I also checked continuity from 3Q2's Gate all the way to the 4007's Pins 8 and 13. All was good. I also check the diode (3D1) and it read open when reverse biased and 0.6V for Fv. Looks good to me.

Here are the voltages on 3Q2. Same as above, numbers in RED are with effect ON.

D: 5.5V 5.5V
G: 0.5V 0V
S: 5.5V 5.5V

I am not familiar or smart on this type of switching so, if anyone can look these over and let me know if they see any issues... it would be appreciated!  ;D


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

#11
July 13, 2014, 03:07:58 PM
Is it this one:

http://www.effectsdatabase.com/model/axl/ead2

If so, there are probably connectors going to the main board from the pots. Make sure that they are all making a good contact.
I think the delay would be "killed" if the "delay" pot was not connected.

Did you verify a clock signal at pins 2 & 4 of the 3102?

It doesn't make sense that you have no output at the BBD if the clock is working.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#12
July 13, 2014, 03:15:49 PM
@Larry

It is not the one you linked BUT....

This Delay is part of a 4-in-1 pedal that AXL effects made. It has Fuzz, OD, Chorus, and Delay. In that order. I believe the circuit in this pedal and the one you linked are the same though.

The pots on THIS pedal are PCB mounted.

I guess I am going to have to do some more readings/looking at the BBDs. I just replaced the clock and both 3208s with new chips but, I will take some readings and report back a bit later  ;D
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

#13
July 13, 2014, 03:21:04 PM
Check to make sure that the clock is oscillating...if it isn't...the BBD will not pass the signal.

The 3102 may be good but something in the surrounding circuitry (cap, resistor, diode) might be bad or a bad solder joint.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#14
July 13, 2014, 03:34:10 PM
OK... just took some quick readings with DMM...

3102

1) 10.4V
2) 5.2V
3) 0V
4) 5.2V
5) 0.9V
6) 9.5V
7) 4.2V
8] 9.7V

FIRST 3208

1) 0V
2) 5.1V
3) 5.4V
4) 9.7V
5) 11V
6) 5.1V
7) 5.1V
8] 5.1V

With ALL pots set to full CCW, I checked for clock at Pins 2 and 4 of the 3102 and got 48.5KHz at both. Also getting the same readings at Pins 2 and 6 of BOTH of the 3208s

Im kinda lost here. This all looks good to me so far  :-\

Starting to think it is audio probe time but, I remember the last time I did it I was getting good audio to the BBD input (the first one) but nothing but dull hum/hissing out of it which is why I replaced all of the BBD/Clock chips!!  ::)
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

#15
July 13, 2014, 03:34:44 PM Last Edit: July 13, 2014, 03:53:43 PM by Fender3D
Poor BBDs, they're always supposed to fail...  :icon_mrgreen:
What about 571? if it's socketed, pull it off and insert 2 jumpers, one shorting pins 6 and 7, the other shorting pins 11 and 14, then report.

BTW
whether 3C46 exists, it seems too much small...

PS
you could try shorting above pins with a capacitor... (without pulling off the chip)  :icon_wink:
"NOT FLAMMABLE" is not a challenge

armdnrdy

#16
July 13, 2014, 03:38:24 PM
It seems to me that the output of the BBD goes into the 571...and if there is a signal at the input of the BBD there should be a signal at the output regardless of the 571.

Now if the 571 was bad...there would be other issues. Is this wrong?
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Fender3D

#17
July 13, 2014, 03:45:38 PM Last Edit: July 13, 2014, 03:52:15 PM by Fender3D
After BBDs, signal goes through filters AND 571 expander "side" (pins 8-16)...

edit:

oh wait:
I just read Greg hasn't wet signal at pedal output, not at BBD output...
His last post was at the same time as mine...  :icon_redface:
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#18
July 13, 2014, 06:30:55 PM Last Edit: July 13, 2014, 06:41:02 PM by Govmnt_Lacky
OK... I see the best minds are on this with me!!  ;D  :icon_mrgreen:

Can any of you recommend the best places to audio probe to produce a good idea of the problem? This thing is a pain in the ARSE to get into and I really don't want to make multiple trips!  :icon_eek:

Im 99% sure I got signal at the BBD inputs AND at Pin 6 of the 571. That's all I can remember right now...  :-\

Quote from: Fender3D on July 13, 2014, 03:45:38 PM
I just read Greg hasn't wet signal at pedal output, not at BBD output...

I don't have wet signal at pedal output AND I don't have ANY output at the BBD output.

When I have the effect on, and I turn the Mix pot fully CW (wet) it mutes the signal. When the Mix is turned towards the CCW, it acts kind of like a Dry signal Volume control and just sends the Dry signal to the output.
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

#19
July 13, 2014, 06:42:52 PM
If you do indeed have a signal at the BBD input and no signal at the BBD output....

Wait...I'll say it again....check to see if the clock is oscillating.

Do you have an oscilloscope? Do you have a frequency function on your meter? Do you have a meter?  ::)
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)
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