[sdiy] Digital encoders missing codes in many devices - why?

Mike Bryant mbryant at futurehorizons.com
Sun Aug 22 13:38:01 CEST 2021


Ah sorry yes.  I used to run those sort of contacts from +15v back in the 70s to keep them reliable

-----Original Message-----
From: Roman Sowa [mailto:modular at go2.pl] 
Sent: 22 August 2021 11:26
To: Mike Bryant; synth-diy at synth-diy.org
Subject: Re: [sdiy] Digital encoders missing codes in many devices - why?

I was rather refering to wire and spring contacts commonly used in old organs.
It's not that simple to just replace hundreds of contacts in there.
Unless replace them with non-contact solution like halls or optos.

Roman

W dniu 2021-08-21 o 21:55, Mike Bryant pisze:
> Not convinced it matters what voltage it is, provided you get the current.  I've found 5V and 300 Ohms works well.  As you say it seems to clean up the contacts.  But how long they last is unknown.  Better to just put a quality brand in.
>
>
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of 
> Roman Sowa
> Sent: 21 August 2021 19:23
> To: MTG; synth-diy at synth-diy.org
> Subject: Re: [sdiy] Digital encoders missing codes in many devices - why?
>
> To self-clean contact you need at least 11V on them. That is enough to make a tiny invisible spark when they are getting really close and burn the oxidation, or better yet - siler sulfide, making the contact good as new. That's the reason why old organs have worked for 30 years if played regularly but when someone installed MIDI encoders on the same contacts (and they work at 5V) then after some time contacts went bad even if the organ was played daily.
> That's my job to know that and I've learn it the hard way. And why 
> it's
> 11 and not 12 or 10.5 - I've read that in some wise document I can't remember where, but the number 11 is carved in my head with a nail.
> It's the voltage (think spark) that works here more than current, but anyway some people have gone one step further and changed pullups in their organs' contacts to 200 ohms. From 15V rail. That's a lot of heat.
> Well, higher current may also burn something out, opening path to better conducting layer below.
>
> I've also "restored" old unreliable switches in Elka Synthex this way, connecting them to 30V via resistor and pushing few dozen times. The on-resistance went down to sub-ohm and didn't change regardless how and where you pushed it. In contrary to their condition before that.
>
> Roman
>
> W dniu 2021-08-21 o 19:47, MTG pisze:
>> What was the Dave Smith encoder debacle all about (and solution)? 
>> This was quite a while ago, I don't even remember what synth it was.
>>
>> Someone in this thread also mentioned current and pull-up resistors. 
>> I think Moog had an issue around the time of the MemoryMoog or maybe 
>> the Source where the panel switches were oxidizing and getting 
>> intermittent. The ECO was to reduce the pullup resistor value 
>> substantially.
>>
>> GB
>>
>> On 8/21/2021 9:04 AM, David Riley via Synth-diy wrote:
>>> On Aug 21, 2021, at 09:24, cheater cheater via Synth-diy 
>>> <synth-diy at synth-diy.org> wrote:
>>>>
>>>> Why does this happen? Why is it so spread out? Is this a 
>>>> programming issue, or a mechanical issue related to the lifetime of the encoder?
>>> Having made these before at various different scales, I’d guess that 
>>> it’s probably mechanical quadrature encoders using brushes to 
>>> contact. If so, intermittent brush contact would do exactly that; a 
>>> lot of decoders also don’t handle things like simultaneous 
>>> transitions well.
>>>
>>> There’s a reason ball mice used optical encoders. They last 
>>> practically forever. Most brushless DC motors and other servos also 
>>> use optical encoders. For some military hardware I worked with (the 
>>> carrier-side instrument landing system antenna motors), we used a 
>>> magnetic encoder, which I’ve not seen elsewhere.
>>>
>>> Anyway, degrading contacts would be my guess. Either bent or dirty 
>>> brushes. Does a hit of De-Ox-It help?
>>>
>>>
>>> - Dave
>>>
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at synth-diy.org
>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace at synth-diy.org
>>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org





More information about the Synth-diy mailing list