Author Topic: TC Electronic Echobrain Signal Loss in Bypass  (Read 317 times)

Big Monk

TC Electronic Echobrain Signal Loss in Bypass
« on: February 18, 2020, 08:17:46 AM »
Just a shot in the dark here while I wait to see if TC will send me a service schematic and before I build a True Bypass loop box.

I recently acquired an Echobrain. I used to own an Ibanez AD9 and I have a real soft spot for these types of analog delay pedal. The good news is that the pedal sounds really great. Nice and lush with a good range of very slight accent type of echo that works well with distortion, as well as really nice slapback.

I do notice, however, a significant drop in signal level when the pedal is bypassed. At first I didn't notice because I was just using the pedal on all the time (very short time, low repeats to thicken up the sound) but when running through the chain the other day, I noticed it. I did some basic tests and verified equivalent levels plugged straight into amp and with pedal enagaged, but in bypass mode (it claims to be True Bypass) there is a significant drop in volume and high frequency content.

Just thought i'd poll the regulars to see if anyone had any insights. I asked TC for the schematic to see the signal path in bypass and worst case i'll just build a loop box.
We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.

duck_arse

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #1 on: February 18, 2020, 08:33:03 AM »
put a blank plug into both in jack and out jack, switch to bypass, measure resistance from tip in to tip out, and from each tip to ground. might reveal something.
I started a joke, which started the whole world laughing - Bee Gees
"You're going to look like a bunch of jerks."
You look just like an Elvis from hell - J. L. Pierce
Oww-owh, but I couldn't see, that the joke was on me oww-oh - Bee Gees

Big Monk

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #2 on: February 18, 2020, 08:39:42 AM »
put a blank plug into both in jack and out jack, switch to bypass, measure resistance from tip in to tip out, and from each tip to ground. might reveal something.

Great idea Duck! Should have thought of that.

Frankly, I think even if I diagnose it and/or TC gives me the schematic, a loop box might be best anyway. There are surface mount components all over this thing and i'd prefer to just use a bypass box so i don't smoke a good pedal goofing around.
We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.

Big Monk

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #3 on: February 18, 2020, 10:28:13 PM »
put a blank plug into both in jack and out jack, switch to bypass, measure resistance from tip in to tip out, and from each tip to ground. might reveal something.

Measured about 500k ohms when I check it out this evening. Something aint right!
We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.

antonis

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #4 on: February 19, 2020, 06:47:27 AM »
500k between tips (IN-OUT) smells an "open" switching FET..
(either defective or not properly biased..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Big Monk

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #5 on: February 19, 2020, 07:33:10 AM »
500k between tips (IN-OUT) smells an "open" switching FET..
(either defective or not properly biased..)

Unfortunately, I have not gotten a response back from TC to my request for the service schematic. For the time being I have the spare parts for a true bypass loop box. That should do the trick.

We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.

duck_arse

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #6 on: February 19, 2020, 10:01:53 AM »
500k between tips (IN-OUT) smells an "open" switching FET..
(either defective or not properly biased..)

an open fet in a true bypass pedal, when bypassed, measures how many ohms?


[there's coffee here if needed.]
I started a joke, which started the whole world laughing - Bee Gees
"You're going to look like a bunch of jerks."
You look just like an Elvis from hell - J. L. Pierce
Oww-owh, but I couldn't see, that the joke was on me oww-oh - Bee Gees

antonis

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #7 on: February 19, 2020, 10:52:33 AM »
I might lead you down the garden path, Stephen...
(and I can ensure you I don't wish for it..) :icon_redface:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

duck_arse

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #8 on: February 20, 2020, 02:22:18 AM »
are we off to smell the roses, then?
I started a joke, which started the whole world laughing - Bee Gees
"You're going to look like a bunch of jerks."
You look just like an Elvis from hell - J. L. Pierce
Oww-owh, but I couldn't see, that the joke was on me oww-oh - Bee Gees

antonis

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #9 on: February 20, 2020, 06:42:17 AM »
I presume local moderator should feel a sudden impulse for violent ban so let's stay on topic.. :icon_redface:

In case of true bypass pedal only means a DPDT mechanical switch (neither IN/OUT buffering nor JFET switching arrangement) 500k resistance between IN-OUT tips calls for a defective DPDT switch, period..

In case of IN/OUT buffering & JFET switching, it calls for defective JFET (500k RDSON) or some bias issue, period again..
(as far as effect ON works fine, both buffers & series JFET switch should be OK..)

P.S.
In any of the above periods case, due to local time, cider is much appreciated..
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

Big Monk

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #10 on: February 20, 2020, 07:23:02 AM »
I presume local moderator should feel a sudden impulse for violent ban so let's stay on topic.. :icon_redface:

In case of true bypass pedal only means a DPDT mechanical switch (neither IN/OUT buffering nor JFET switching arrangement) 500k resistance between IN-OUT tips calls for a defective DPDT switch, period..

In case of IN/OUT buffering & JFET switching, it calls for defective JFET (500k RDSON) or some bias issue, period again..
(as far as effect ON works fine, both buffers & series JFET switch should be OK..)

P.S.
In any of the above periods case, due to local time, cider is much appreciated..

The TC switches are notoriously bad. I'm not complaining too bad because they are a budget pedal but they have these sturdy cases and are otherwise well built. Why would you throw a plastic switch on these things?
We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.

Big Monk

Re: TC Electronic Echobrain Signal Loss in Bypass
« Reply #11 on: February 21, 2020, 01:50:49 PM »
Ok.

TC Electronic got back to me with the schem:



I know at this point it is stating the obvious but looks like a switch issue for sure. It's a 4PDT but it looks like replacement wirth a 3PDT will be suitable because SW1-A and SW1-B are essentially a single switch.
« Last Edit: February 21, 2020, 02:03:18 PM by Big Monk »
We are what we repeatedly do. Excellence, therefore, is not an act, but a habit. Aristotle

WARNING: I try to make Excel calculators for EVERYTHING. Its mostly a useful quirk.