[BUILD] TBDD

Great!  It's always some silly thing, right?

If the Off button works, the remote should work.  They sit in parallel and work exactly the same.  It's more of a guitar rig feature, though..

And yes, pics please!  I love seeing these done.

I have no idea why the remote bypass doesn't work, cos the switch on the front does, & the cable to the jack socket shows continuity .....

& the guts.  I didn't use shielded wire anywhere, & there isn't any noise.

This is a great project Brian, thanks for your time & effort realizing it.  To anyone thinking of making this, it sounds great & the boards are quite easy to solder, as most solder pads are quite spaced out, apart from things like ic pins & molex connectors.  If you follow Brian's tips it should be easy.  Although I wouldn't make this your first project, it requires a bit more experience than being able to successfully make a guitar lead....

rob_gould said:

rob_gould said:

Please may I take up your offer of a replacement MN3101?

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No problem at all.  I'll get one tested and out today.

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Hi Brian,

Thank you.  I received the replacement chip a few weeks ago now.  Various issues with studio PC and life in general have meant I've only just had a chance to look at this.

Everything seems to be working now as per the test procedure, but when actually listening to the effect it seems very subtle.  I know this is not an 'in your face effect' per se, but still it seems really rather subdued (I've never had the pleasure of working with a real Dim D by the way).  Certain sources highlight the effect quite nicely, but on some sources it's inaudible.

I'm going to go through the same test advice you gave to Rob Flinn I think just to double check everything, and then I'm wondering perhaps if I sent a short sample of audio you'd mind processing it through a TBDD to see how close your unit sounds to mine. Would you mind doing that?

Thanks,

Rob

Rob,

You are certainly correct that some material interacts with the chorus differently than others.  I'll be happy to run a test for you if you like.  Send me both before and after and let me know exactly which settings you have it on and we can do a comparison.

  Brian

I tried running audio through mine yesterday after not using it for many months. First, I heard no signal. Turning up the preamp gave some weak, distorted audio but appeared to drag down the power supply as lights and meters on both lunchboxes all went wonky. Cycling the power supply resolved that until I tried putting audio through the TBDD again.

Any ideas on where to start looking first? Bad opamp in the input section? BTW, no signal in bypass either.

Man, that's a bummer!  Is it both channels?  I'm curious if you had it in mono or stereo mode.  If you put it in stereo mode and inject a signal on both channels and then you still get nothing at all on the output, that's more of a base problem with the thing.

IC5 is really the only op amp that you could lose that would impact both sides.

The TBDD checks out. I pulled it from the rack and I'm still having issues so it was probably a coincidence (lunchbox A went down, the TBDD was in lunchbox B).

I'm curious to see how the Rob Gould files compared?
I was thinking it would have been awesome to chorus a little gospel choir and the effect was completely inaudible. I had a few sources where it seemed like the real thing (even compared with a Dim D) but there is a lot of sources where TBH I feel I can't hear it.

jplebre said:

I'm curious to see how the Rob Gould files compared?
I was thinking it would have been awesome to chorus a little gospel choir and the effect was completely inaudible. I had a few sources where it seemed like the real thing (even compared with a Dim D) but there is a lot of sources where TBH I feel I can't hear it.

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Although it does seem to be more or less apparent depending upon the source material, I've never experienced the effect being completely inaudible.  I'm curious, did you do the clock cancel calibration with a scope?  I'm not asking because that would necessarily have a huge impact on the sound, but it can be revealing about other issues in the circuit.  For instance, I've seen a bad compander that was only identified after looking at that clock output since it was affecting things down the line.

Hey sorry for the delay but I wanted to actually check again everything.
OK, so BIAS is fine, now for the clock, this is what I get at both TPs:


And no matter what direction I turn the trimers it doesn't change, so something is wrong is my guess?
Should the clock look more like Rob Gould's pics?

Well that certainly doesn't look right.  If you flip back to post #176, you'll see where I posted a properly calibrated clock signal.

Since it's on both channels, let's assume for now that it's not the clock chip although of course you could have two bad chips.  I'd think though that if they were both bad, you'd get something different on each channel.

This just leaves us to diagnose the LFO.  Unfortunately, since this is all on the left board, it's a little tough to reach.  The place to start is pin 1 on IC3.  If you grab your DMM and look at DC volts on that pin, you should see it oscillate from about -14 to +14V.  In mode 1 and 2, it will flip approx. every 2 seconds and on 3 or 4, approximately every second.  See what that shows you and let's go from there.

Sorry for the delay.
Yeap IC3 (pin 1) is jumping 14/-14v every few seconds, depending on the preset used

jplebre said:

Sorry for the delay.
Yeap IC3 (pin 1) is jumping 14/-14v every few seconds, depending on the preset used

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OK, good start.  So there's a bunch of circuitry in between, but let's hop up to the LFO input to the clock chip.  Have a look with you DMM on DC volts at pin 7 one of the 3101.  With mode 1 to 4 selected, you should see this oscillate between about -14.3V and -14.6V.  Whether or not that is happening will help us narrow down the problem a bit further.

Also, could you please take some good hi-res pictures of the front and back of both PCBs?  Never hurts to get another set of eyes on it.

Brian

ok!
left board only goes to -14.3ish after I go mono/stereo. Guessing it's a contact on the switch.
Will do some listening tests at some point and see if this was the only issue

right board same behaviour.

pics:
https://dl.dropboxusercontent.com/u/3370162/GroupDIY/TBDD_sep2014_01.JPG
https://dl.dropboxusercontent.com/u/3370162/GroupDIY/TBDD_sep2014_02.JPG
https://dl.dropboxusercontent.com/u/3370162/GroupDIY/TBDD_sep2014_03.JPG
https://dl.dropboxusercontent.com/u/3370162/GroupDIY/TBDD_sep2014_04.JPG

Thank you again Brian!

J

jplebre said:

ok!
left board only goes to -14.3ish after I go mono/stereo. Guessing it's a contact on the switch.
Will do some listening tests at some point and see if this was the only issue

Click to expand...

OK, this is a little stranger.  The position of that switch should have nothing at all to do with the function of the LFO.  They are completely different sections of the circuit.

Let's do a quick check on the input select switch.  First, inject a test tone on the right input only.  Set it to mono input and have a look at the outputs of IC5.  In this case, you should see your signal on both pin 1 and pin 7.

Next, with the signal still only on the right channel, switch it to stereo input.  Now, you should see that signal on pin 1 but NOT pin 7.

If that's all good, inject a test tone into both right and left inputs.  Set the input switch to stereo and you should see your signal again on both pins 1 and 7 of IC5.

Let me know what all that does.

i know this is a zombie thread, but if anyone here has a line on this module or even parts/pcb's, i need it in my life! talk to me!

Hi there,

I know this topic is off since long time but i need your help to fix my second hand TBDD.
Can anyone provide the schematic of the unit?

Help much appreciate

Best regards,
Vincent

xarolium said:

Hi there,

I know this topic is off since long time but i need your help to fix my second hand TBDD.
Can anyone provide the schematic of the unit?

Help much appreciate

Best regards,
Vincent

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I think it's the same as the original from memory.  I have the docs for the rack version of this project. If you need them pm me your email address.

Rob Flinn said:

I think it's the same as the original from memory. I have the docs for the rack version of this project. If you need them pm me your email address.

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Chiming in to say I found this thread looking for a place to get the PCB/schematic and all that but the site's down! Any chance you can send that to me too?