Buchla 208r problem

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OscillatorScream
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Buchla 208r problem

Post by OscillatorScream » Sun Mar 15, 2020 4:13 am

I love my easel. Truly.
But I'm having a bit of an issue. IDK if this is common, but when I need precise control of a slider, I rest my middle or ring finger on the panel, and then maneuver the slider with my index and thumb.
I'm not pressing hard on it. But when I do that over by the modulating oscillator, the pitch changes. A lot. Is that how it's made or is that some bullshit?
The guy I bought it from was super cool and let me make payments over the course of three months to pay it off so I don't wanna be a dick.

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papz
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Re: Buchla 208r problem

Post by papz » Sun Mar 15, 2020 1:02 pm

That is some bullshit.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

jimfowler
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Re: Buchla 208r problem

Post by jimfowler » Sun Mar 15, 2020 3:34 pm

Just to clarify: you can alter the pitch by pushing down on the front panel? As in: not touching anything else but just pushing down with a finger and the pitch varies?

OscillatorScream
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Re: Buchla 208r problem

Post by OscillatorScream » Sun Mar 15, 2020 8:11 pm

Yep. That's exactly what happens. Not sure what to do about it or why it happens or that's just a finicky thing that happens with the 208r.

PacificState
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Re: Buchla 208r problem

Post by PacificState » Sun Mar 15, 2020 11:40 pm

That's not normal! It might be that there's a bad solder joint on one of the sliders.

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Siren
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Re: Buchla 208r problem

Post by Siren » Mon Mar 16, 2020 6:58 am

I don’t understand how touching the panel in a certain area can make a difference - it’s not like it’s flexible?!
Surely the pitch changes regardless where on the panel you put your finger?

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papz
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Re: Buchla 208r problem

Post by papz » Mon Mar 16, 2020 7:30 am

Sound slike your 208 would enjoy a good check up.
If you're in the EU, feel free to pm me ;)
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

KSS
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Re: Buchla 208r problem

Post by KSS » Mon Mar 16, 2020 11:07 am

Siren wrote:
Mon Mar 16, 2020 6:58 am
I don’t understand how touching the panel in a certain area can make a difference - it’s not like it’s flexible?!
Aluminum panel is more flexible than you realize. There is also the possibility of capacitive coupling from your body to the panel.
Surely the pitch changes regardless where on the panel you put your finger?
Not necessarily. But pressing in various places -noting whether more pressure is required to effect the change in one area vs another- *is* a good first step in troubleshooting the possible sources of the problem. Pressing with the eraser of a pencil is a second step to eliminate capacitive coupling from your skin. Do both.

This creates a pressure-effect result 'map' of the panel which can then be related to the panel component locations and functions, along with the possible physical coupling of this tiny movement to other PCBs, components and the connectors between them. (as was mentioned before as bad solder joint)

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Siren
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Re: Buchla 208r problem

Post by Siren » Mon Mar 16, 2020 12:36 pm

KSS wrote:
Mon Mar 16, 2020 11:07 am

Not necessarily. But pressing in various places -noting whether more pressure is required to effect the change in one area vs another- *is* a good first step in troubleshooting the possible sources of the problem. Pressing with the eraser of a pencil is a second step to eliminate capacitive coupling from your skin. Do both.
Just to clarify, I wasn't the one with the troubled 208. It just sounded unlikely to me that there would be that much give in the OP´s panel, and that the problem therefore had to be related to capacitive coupling. My own 208 is far from flexible, but maybe my panel is thicker. Or I read the OP wrong. :despair:

KSS
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Re: Buchla 208r problem

Post by KSS » Mon Mar 16, 2020 3:20 pm

Yes, I understood it was not your 208.
Siren wrote:
Mon Mar 16, 2020 12:36 pm
My own 208 is far from flexible, but maybe my panel is thicker.
I say again, even your panel is more flexible than you realize.

As a loose comparison -since it is larger than a 208, the ARP2600 panel is 1.5mm .060" aluminum. It flexed so much that the design had to change to remove all the jacks using normals becausethe pressure of actuating the controls made the jack normals of the PCB mounted jacks fail. ARP switched to non-PCB mounted jacks and the panel could now flex without interrupting the normalled signal and CV paths.

Even the smaller 208 panel will be flexible enough to present problems if there is a bad connector or solder joint.

If you know a machinist, have them set up a dial indicator on your panel, and then you go ahead and press lightly on the panel. When -not if- you see that dial indicator jump you'll have a fresh understanding about how flexible a synth panel can be. edit typos

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Re: Buchla 208r problem

Post by papz » Mon Mar 16, 2020 3:45 pm

KSS wrote:
Mon Mar 16, 2020 3:20 pm
Even the smaller 208 panel will be flexible enough to present problems if there is a bad connector or solder joint.
This is very likely the cause.
Finest EMS gear service and Music Easel/208 goodies

I'm not a synths dealer and I'm not aware of an inexpensive Synthi secret market, please don't ask me if I know one for sale.
I don't offer support of any kind to people attempting to build clones of EMS equipment.

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Siren
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Re: Buchla 208r problem

Post by Siren » Mon Mar 16, 2020 4:08 pm

KSS wrote:
Mon Mar 16, 2020 3:20 pm
Yes, I understood it was not your 208.
Siren wrote:
Mon Mar 16, 2020 12:36 pm
My own 208 is far from flexible, but maybe my panel is thicker.
I say again, even your panel is more flexible than you realize.

As a loose comparison -since it is larger than a 208, the ARP2600 panel is 1.5mm .060" aluminum. It flexed so much that the design had to change to remove all the jacks using normals becausethe pressure of actuating the controls made the jack normals of the PCB mounted jacks fail. ARP switched to non-PCB mounted jacks and the panel could now flex without interrupting the normalled signal and CV paths.

Even the smaller 208 panel will be flexible enough to present problems if there is a bad connector or solder joint.

If you know a machinist, have them set up a dial indicator on your panel, and then you go ahead and press lightly on the panel. When -not if- you see that dial indicator jump you'll have a fresh understanding about how flexible a synth panel can be. edit typos
Fair enough, you learn something new every day. :party:

Good luck to the OP with getting the problem fixed.

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