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

#20
July 13, 2014, 06:50:58 PM Last Edit: July 13, 2014, 06:52:29 PM by Govmnt_Lacky
Quote from: armdnrdy on July 13, 2014, 06:42:52 PM
Do you have an oscilloscope? Do you have a frequency function on your meter? Do you have a meter?  ::)

Larry... I posted this above bro!!  ::)

I get 48.5KHz at BOTH of the 3102's outputs (2 total) AND at BOTH of the 3208's Inputs (4 total). This is with all of the control pots at full CCW.

So... it appears there is a clock coming out. What I DIDN'T try was to measure the frequency whilst turning the Delay pot. I could try that if you think it will get us somewhere.

Otherwise, some good audio probe point recommendations would be good...  ;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

#21
July 13, 2014, 06:58:47 PM
Oh...I didn't see that...I just read the voltages and disregarded the rest as you babbling again!  ;D

Let me take another look at the drawing then...damn this thing is so hard to read the way that it's drawn!
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#22
July 13, 2014, 07:03:27 PM
Quote from: armdnrdy on July 13, 2014, 06:58:47 PM
Oh...I didn't see that...I just read the voltages and disregarded the rest as you babbling again!  ;D

Ugh.... Wait.....uh..... I don't babble...... uhhhh......

Usually I can figure these things out but in this case, I am pretty stumped. Everything looks as it should when debugging EXCEPT for the wet signal at the output. Just like my avatar says...  ::)
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

#23
July 13, 2014, 07:13:22 PM
No sense of humor Greg!

Okay..
The signal input for the 571 is pin 6, the output is pins 2&3 to the BBD.
After the BBD, as Federico stated, it goes through filtering/op amps and then into pins 14&15. Pins 10&11 is the wet output that goes to the mixing and then to the effect out.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Fender3D

#24
July 13, 2014, 07:29:50 PM
Quote from: Govmnt_Lacky on July 13, 2014, 03:34:10 PM
OK... just took some quick readings with DMM...
FIRST 3208

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


I would investigate about that bias voltage...
bias is fed by 3R42 (3R46 for second BBD).
I'd try a more typical bias circuit...

Otherwise:
signal generator (almost mandatory in this debugging case) > check in order:
1) 571's pin 6
2) 571's pins 2-3
3) 1st BBD's pin 3
4) 1st BBD's pins 7-8

If no "meat", lift 3R42, check voltage at BBD's pin 3, eventually try with separate bias (usual 100k trimmer + 100k resistor from wiper to pin 3)
"NOT FLAMMABLE" is not a challenge

Fender3D

#25
July 13, 2014, 07:33:14 PM
Quote from: armdnrdy on July 13, 2014, 07:13:22 PM
...
After the BBD, as Federico stated, it goes through filtering/op amps and then into pins 14&15. Pins 10&11 is the wet output that goes to the mixing and then to the effect out.

Don't forget 3Q4, when it shorts pin 16 to GND, it will shut off 571's output...
"NOT FLAMMABLE" is not a challenge

armdnrdy

#26
July 13, 2014, 07:39:32 PM Last Edit: July 13, 2014, 07:42:20 PM by armdnrdy
Hey Federico,

Check out the voltage on pin 5.

Greg, Why are you feeding this effect that has a low voltage BBD (max voltage 10V) with 11 volts?

http://www.takkyparts.com/datasheet/bl3208-e.pdf
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#27
July 13, 2014, 07:44:18 PM
Took some quick audio probe readings.

571:

Pin 6: Good signal
Pin 7: Good signal (a bit louder than pin 6)
Pins 10, 11, 14, and 15: NOTHING!

3208 (U6)

Pin 3: Good. Same as 571 Pin 7.
Pins 7 and 8: High pitched whine that changes pitch with the Delay pot  :-\

3208 (U5)

Pin 3: NOTHING
Pins 7 and 8: NOTHING

Everything points to the BBDs but they have been replaced with known good ones  :-\
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.'

mth5044

#28
July 13, 2014, 07:46:55 PM Last Edit: July 13, 2014, 07:59:20 PM by mth5044
Why are you getting 11V from 9V? I don't think the BBD can handle that.

EDIT: oops, seems Larry had mentioned it just before. Seems I don't read well either  :icon_lol: All that babbling  :icon_lol:

armdnrdy

#29
July 13, 2014, 07:50:11 PM Last Edit: July 13, 2014, 07:57:49 PM by armdnrdy
Check the voltage at the source. Wall wart, power supply, etc whatever you are powering this thing with.

According to the schematic we have been working from, there is no voltage regulator. If your wall wart is over voltage (as they often are) you are frying the BBDs.

The original unit most likely came with a regulated power supply and warned against using anything but that!

Edit:

I missed it when you originally posted the BBD voltages and the frequencies and didn't see the 11 volts until Federico posted the voltages as a quote.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

armdnrdy

#30
July 13, 2014, 08:44:38 PM
If by chance the BBDs aren't fried.....dropping the voltage down to 9V might put the bias (that's non adjustable) into the right range to pass signal. Cross your fingers!
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Fender3D

#31
July 13, 2014, 08:46:01 PM
Quote from: armdnrdy on July 13, 2014, 07:50:11 PM
Check the voltage at the source. Wall wart, power supply, etc whatever you are powering this thing with.

According to the schematic we have been working from, there is no voltage regulator. If your wall wart is over voltage (as they often are) you are frying the BBDs.
...

Quote from: armdnrdy on July 13, 2014, 07:50:11 PM
...
I missed it when you originally posted the BBD voltages and the frequencies and didn't see the 11 volts until Federico posted the voltages as a quote.

lol  :icon_mrgreen:
I was busy about why those BBDs stopped working I didn't see the obvious...
"NOT FLAMMABLE" is not a challenge

armdnrdy

#32
July 13, 2014, 09:00:36 PM
Neither did I!

Voltages...who needs stinking voltages!  ;D
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#33
July 13, 2014, 09:22:30 PM Last Edit: July 13, 2014, 09:24:59 PM by Govmnt_Lacky
MOTHER$%@&... C0@KA$$... BULLS&*!.... SUM-B!T$&^!!!!!!!!!!!!!!!!!!!  :icon_evil:

Larry got it! Switched from the PS that it came with to a 1Spot with the inverting adapter (to make the tip positive)

Not only did it fix the voltages..... I can now hear SWEET delay coming from BOTH BBDs!!!!  ;D  ::)

LET THIS BE A LESSON TO SOME OF THE NEW GUYS...... EVEN US "SEASONED" FOLKS GET BIT BY THE EASY CRAP!!!

Many thanks Larry and Federico!  ;)

Funny story..... the Chorus in this pedal runs on a 3207. I guess they have a higher tolerance than the 3208s  :icon_rolleyes:

Funny story #2..... I bet the original BBDs DID work! And I just pulled them and tossed them like the Samsonite monkey!!!  :icon_redface:  :icon_evil:
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

#34
July 13, 2014, 09:47:33 PM
Quote from: Govmnt_Lacky on July 13, 2014, 09:22:30 PM
the Chorus in this pedal runs on a 3207. I guess they have a higher tolerance than the 3208s

Was the chorus working and the delay wasn't? The chorus circuit could have had a regulator in it's power supply circuit.
I looked at a DOD FX96 delay earlier today....this AX looks like a pretty good rip off so...AX may have just collected up circuits and thrown them in one enclosure.

Quote from: Govmnt_Lacky on July 13, 2014, 09:22:30 PM
I bet the original BBDs DID work! And I just pulled them and tossed them like the Samsonite monkey!!!  :icon_redface:  :icon_evil:

Can you please throw away some SAD1024s and some MN3005s and then tell me where you keep your trashcan?  :icon_wink:
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#35
July 13, 2014, 10:18:16 PM
Quote from: armdnrdy on July 13, 2014, 09:47:33 PM
Was the chorus working and the delay wasn't? The chorus circuit could have had a regulator in it's power supply circuit.
I looked at a DOD FX96 delay earlier today....this AX looks like a pretty good rip off so...AX may have just collected up circuits and thrown them in one enclosure.

I just looked at the schematic. It looks like they have the V+ from the pedal going through a transistor circuit a-la BOSS pedals to regulate the voltage into the BBD and Clock. Wonder why they didn't do that with the Delay  ???

Quote
Can you please throw away some SAD1024s and some MN3005s and then tell me where you keep your trashcan?  :icon_wink:

Ha..... I would be doing some dumpster diving myself for those!  :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.'

armdnrdy

#36
July 13, 2014, 10:51:33 PM
I took another look at the FX-96. It has a MN3005 running at 9 volts. The circuit looks identical. It looks like they took this circuit, threw in two BL3208s, changed a few things around for the positive voltage BBD, left the power supply for the clock and BBD 9volts, and called it good.
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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