Erica BBD delay quiet

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patched
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Erica BBD delay quiet

Post by patched » Sat Feb 08, 2020 6:25 am

A while back, I built the Erica BBD delay module. While I like it a lot, it is way too quiet. Even when setting the dry/wet to totally dry, it is very noticeably quieter than if I didn't put the signal through the delay at all.

I'm thinking of putting a 10k resistor in R19 to raise the input gain, but does anybody know why the signal is attenuated? I can't see where in the schematic this voltage drop would appear, and am wondering if I have soldered anything poorly.

Schematics available here: https://www.ericasynths.lv/shop/diy/diy ... ayflanger/

Thanks!

ixtern
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Re: Erica BBD delay quiet

Post by ixtern » Sat Feb 08, 2020 7:17 am

If you set max Dry and max Audio In, signal is going from input to output through two voltage followers (non-inverting op amps with voltage amplification =1). So there is no reason for signal to be quiet if everything was assembled right and R19 and R56 not soldered, as in build doc.
Check if protection diodes are soldered correctly (not in opposite direction), check input and output capacitors and values of resistors there also. Op amps also should be checked.

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patched
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Re: Erica BBD delay quiet

Post by patched » Sat Feb 08, 2020 8:47 am

ixtern wrote:
Sat Feb 08, 2020 7:17 am
If you set max Dry and max Audio In, signal is going from input to output through two voltage followers (non-inverting op amps with voltage amplification =1). So there is no reason for signal to be quiet if everything was assembled right and R19 and R56 not soldered, as in build doc.
Check if protection diodes are soldered correctly (not in opposite direction), check input and output capacitors and values of resistors there also. Op amps also should be checked.
Thanks, I noticed that I can hear a sound difference when jiggling the input pot, I already tried reflowing it once but maybe I should try again.
Looks like the middle leg has a bad joint when I try to measure the resistance with a multimeter.
The joint doesn't look bad from just a visual inspection but it seems as if the fault should be there somewhere

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patched
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Re: Erica BBD delay quiet

Post by patched » Wed Feb 12, 2020 3:57 pm

I've tried reflowing the joints multiple times now. Still only works properly when I apply pressure to the side of the pot. What are the chances that the potentiometer is faulty? I bought it at thonk. Could it be a problem with the solder pads?

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Re: Erica BBD delay quiet

Post by jorg » Wed Feb 12, 2020 5:26 pm

It's pretty easy to damage a pot by over-soldering it. I've done that.

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Re: Erica BBD delay quiet

Post by patched » Wed Feb 12, 2020 5:45 pm

jorg wrote:
Wed Feb 12, 2020 5:26 pm
It's pretty easy to damage a pot by over-soldering it. I've done that.
Really hoped this wasn't the case, going to be a *** to desolder... Got any tips to ease the process? Or for making sure it actually is damaged?

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joem
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Re: Erica BBD delay quiet

Post by joem » Wed Feb 12, 2020 6:05 pm

patched wrote:
Wed Feb 12, 2020 5:45 pm
jorg wrote:
Wed Feb 12, 2020 5:26 pm
It's pretty easy to damage a pot by over-soldering it. I've done that.
Really hoped this wasn't the case, going to be a *** to desolder... Got any tips to ease the process? Or for making sure it actually is damaged?
Easiest way to desolder a pot (or anything with a lot of pins that's a pain to desolder) is to just clip the leads off with your cutters, and then desolder the remaining bits one by one. Sure you waste a pot (or whatever it is you're replacing) but the dollar or two cost is usually worth it. Plus in this case it sounds like your pot might be bad so no point in keeping it anyway.

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emmaker
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Re: Erica BBD delay quiet

Post by emmaker » Wed Feb 12, 2020 7:06 pm

The pot typically would be the first guess.

Things like pots, switches, jacks that connect to the front panel or have mechanical stress can break PCB traces. You might look really close at the area around the pot with a magnifier and light to check that out. Another trick is to take something that is insulated like a dowel or something plastic and start putting pressure on the PCB around the area in question. Some times that will make or break a marginal connection and that will give you a clue to what area to look at.

Good luck.
Jay S

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Re: Erica BBD delay quiet

Post by ixtern » Thu Feb 13, 2020 1:17 pm

Previous month I've succesfully desoldered six 9mm Alpha pots from Eurorack module (to replace them with another ones, without knobs).

My procedure was as follows:
- first with desoldering braid I've sucked off all solder from two side legs,
- then with about 10mm-long thick silvered coper wire (1mm diameter or more) I've desoldered simultaneously all three pot legs.

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Re: Erica BBD delay quiet

Post by patched » Thu Feb 13, 2020 3:36 pm

Thanks for the replies, I'll have to live with the quiet input then until the next time I make an order from Thonk and can get myself a new pot.
Then I'll hopefully manage to get this to work
emmaker wrote:
Wed Feb 12, 2020 7:06 pm
Things like pots, switches, jacks that connect to the front panel or have mechanical stress can break PCB traces. You might look really close at the area around the pot with a magnifier and light to check that out.
I'm not sure I understand exactly where you mean, should I look around the pot legs?

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Re: Erica BBD delay quiet

Post by emmaker » Thu Feb 13, 2020 5:09 pm

patched wrote:
Thu Feb 13, 2020 3:36 pm
Thanks for the replies, I'll have to live with the quiet input then until the next time I make an order from Thonk and can get myself a new pot.
Then I'll hopefully manage to get this to work
emmaker wrote:
Wed Feb 12, 2020 7:06 pm
Things like pots, switches, jacks that connect to the front panel or have mechanical stress can break PCB traces. You might look really close at the area around the pot with a magnifier and light to check that out.
I'm not sure I understand exactly where you mean, should I look around the pot legs?
Yes look for cracks or breaks in the PCB traces that go to the pot legs. This is more of a problem with single sided or poorly manufactured circuit boards. But it can happen on good boards if things have been stressed mechanically.

Another thing is if you have an ohm meter and can read the schematics you can measure the resistance between the pot legs and where the traces go.

Good luck.
Jay S.

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Re: Erica BBD delay quiet

Post by patched » Sun Feb 23, 2020 8:58 am

Ok, so I've finally, after a lot of troube, managed to desolder the pot. However, looks like two of the solder pads also went away with the legs:
desoldered1.png
desoldered2.png
Ignoring all the nasty gunk, one pad on each side is gone. Will it be possible to just solder on the other side?
You do not have the required permissions to view the files attached to this post.

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kamielsd
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Re: Erica BBD delay quiet

Post by kamielsd » Mon Feb 24, 2020 4:23 am

It might be better to check the schematic and see where these pads should connect to, and ensure these connections with a bit of insulated wire..

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Re: Erica BBD delay quiet

Post by patched » Mon Feb 24, 2020 5:33 am

kamielsd wrote:
Mon Feb 24, 2020 4:23 am
It might be better to check the schematic and see where these pads should connect to, and ensure these connections with a bit of insulated wire..
True, I'll try that

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