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208p build thread (papz's PCBs)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author 208p build thread (papz's PCBs)
papz
Hi

Several sets were delivered, so let's start a build thread.
The sets are available on http://www.portabellabz.be/208pcb.html

Although many informations shared in the 208r build threads are relevant,
https://www.muffwiggler.com/forum/viewtopic.php?t=174863&highlight=
https://www.muffwiggler.com/forum/viewtopic.php?t=127084&highlight=
it will be more comfortable to have a dedicated one to reply questions related to this specific build.

Before asking a question, please read the FAQ, maybe it was already replied http://www.portabellabz.be/208pcbfaq.html

The build notes and BOM are on http://www.portabellabz.be/images/208/208%20build%20notes.pdf

The components layout and values are on http://www.portabellabz.be/images/208/cards.zip

The schematics are on http://www.portabellabz.be/images/208/schemas_208.zip

Thank you and happy building nanners
the bad producer
thumbs up
papz
I updated the cards pics with components layout and values and the build notes.
The C5 47µF tantalum cap mentioned in the BOM works fine in the CO instead of the 56µF.
R45 100k instead of 20k eases tracking calibration.
Karl71
this is gonna be good. hyper looking forward to a thread of well documented success stories.
papz
Me too for sure ! lol
beautyofdecay_
I started my build today and populated the motherboard.
I have to wait for the cards components before I can continue...

papz
thumbs up
papz
Some extra infos added in the build notes.

It's better to match the vactrols on boards 10 and 11, or use dual VTL5C3/2.

Vactrols VT4 and VT2 on board 5 need to be selected on test for proper AM performance.

On board 7, R3 should be selected on test, a value between 3k8 and 12k, depending on the vactrol, to set the desired timbre amplitude. I find 4-5 folding is good, as shown on http://modularsynthesis.com/buchla/208/buchla_208.htm but others prefer more foldings. It's up to the builder to select what best suits his needs.

On board 8 the 2N4399 needs selection on test for proper sine waveshape.

I think this depends not only on the part itself but on the other parts in the circuit as well, therefore I use to select parts on test directly in each circuit.
pathein
thanks for the updates

I have just received the pcbs and panel. Got to say that the panel is really looking good. Next up will be waiting for the various parts to arrive, cant wait to start working on it
papz
Thanks for the feedback Chugging Beers
pathein
hi papz, some questions regarding the pA726 board. For the electrolytic, is it necessary to get at least 35v rating type or 25v type depending if its +-12v/+-15v?

for tab 1/1tab, it will be populated with male pin header?

for the resistors, will 1/10w rating be ok or stick to 1/4w type?
papz
25V is ok for the electrolytics, these are between each +15V/-15V/+10V rails and ground. But higher voltage is ok, I generally use 50V since I mostly stock these, are the same size and price as 25V and can do more. Also, the higher the voltage rating, the longer the life expectancy.

I'd rather use 1/4W resistors.

The DIP10 emplacements are to connect the pA726 to the boards, vertical one to 6 and horizontal one to 7.
I'm not sure the holes are large enough for headers.
I simply use thick components legs, there are much more than needed when building a 208. lol
"1" shows the µA726's pin 1, "tab" the µA726's tab/pin 10.
The trimpot should be on the same side as the other trimpots, this way you can't be wrong.
More details and pics on http://www.portabellabz.be/pa726.html
pathein
Cool, thanks for the info, much appreciated!
heapish
Has anyone done a mouser cart for this?
beautyofdecay_
papz wrote:
Some extra infos added in the build notes.

It's better to match the vactrols on boards 10 and 11, or use dual VTL5C3/2.

That's a good idea.
I think a VTL5C3/2 should work like this? The vertical blue line is a wire link.



The wires of the original VTL5C3/2 are long enough to connect the vactrol this way. I don't know about the current clones however...
papz
Or this way.
Legs can be extended with wire if needed.

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