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Hi there! My first topic here, I hope you enjoy it and you'll excuse my poor english! Unfortunately there's nothing mysterious in this stompbox: it's a Swartz's AD-3208 delay (great) with 3205 BBD (longer delay) and some other minor changes.
A friend of mine gave it to me because it has a problem: it's impossible to set the clock frequency trim for proper delay time (400ms with delay ctrl at max) without having a ridicolous whine. This whine is still there when I disconnect BBDs and SA571, and it only disappears when I ground the input (or if I set clock trimpot for really short delay time...just a little more than a slapback). Any idea? Thanks in advance,

Fabio

There should be a trimpot for clock cancellation. It should be possible to adjust this to make the whine go away. It would be located directly after the output of the BBD chip.
If this does not help, then it may be a problem with the board layout.

Thanks for sharing!


*edit*
I see now you said that it still whines with the BBD chips removed. This must be a problem with the clock interfering with the rest of the circuit.
I see that the grounds for the pots are connected to the backs of the controls and grounded through the chassis. Maybe try connecting wires to the ground lugs and connect them directly to the input jack ground?

There are 2 BBDs each one with its "clock cancellation" trimpot. Unfortunately they have no influence on the whine and, as I said in the description, the whine goes on even with no BBD (and expander/compander) on board (all ICs are on sockets in this circuit).

I can't believe in a layout problem because the pedal used to work perfect till some days ago...no one knows (or wanna say) what happened. I contacted HBE support via mail, but they wasn't able to help me...I assume they would tell me about a bad layout on old units or something like this...isn't it? Thank you!

I'm thinking about a bad component that is working like an antenna...could it be possible? What should I look for? I think cables and wirings are ok because whine intensity doesn't change while I move the board...

soulsonic wrote: *edit*
I see now you said that it still whines with the BBD chips removed. This must be a problem with the clock interfering with the rest of the circuit.
I see that the grounds for the pots are connected to the backs of the controls and grounded through the chassis. Maybe try connecting wires to the ground lugs and connect them directly to the input jack ground?

Well, I tried to "star ground" things a bit, but nothing changed whinewise. BTW it can't be such a bad thing, since the original grounding scheme didn't seem so perfect to me...

also, the filters are implemented with bjt transistors, which catch easily noise on the power line

i would try to break the ground paths from (and the power if necessary) the oscillator area and wire it directly to the power jack.
or maybe there is not enough filtering for that clock frequency...

at least there is no goop in there, like other hbe's