[sdiy] Who apart from me things the whole MIDI board needs replacing ?

Roman Sowa modular at go2.pl
Thu Jan 27 10:40:51 CET 2022


For that purpose I've got permanently connected 20k resistor between my 
test bench power supply black terminal (GND or negative whatever you 
call it) to Earth terminal. This way PSU lines are not floating on 
hundreds of volts whenever they want but are close to 0 while not 
causing short with PC chasis when I use for example a programmer. It was 
enough to keep my IDC3 in good condition for years, but when I took it 
home, where I use floating PSU (laptop brick feeding DC/DC) I have fried 
my ICD after 3 days :(

Roman

W dniu 2022-01-26 o 14:16, Mike Bryant pisze:
> Good idea.  Might stop people lifting the grounds on equipment they really shouldn't do so on !!
> 
> 
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Gordonjcp
> Sent: 26 January 2022 12:12
> To: synth-diy at synth-diy.org
> Subject: Re: [sdiy] Who apart from me things the whole MIDI board needs replacing ?
> 
> On Tue, Jan 25, 2022 at 10:41:49PM -0500, Mike Beauchamp wrote:
>> On 1/25/22 10:31 PM, Brian Willoughby wrote:
>>> I brought this up with designers before, and someone claimed that it's easy to select panel-mount 1/8" jacks that are electrically isolated from the panel. Of course, that works until there are supply issues and someone in your sourcing department decides that another panel-mount 1/8" jack is "equivalent" ... except that it's no longer isolated.
>>>
>>> I prefer the DIN where the shield and ground are separate from each other *and* separate from the MIDI signaling. That makes it *much* easier to ensure against ground loops.
>>
>> I've never used 3.5mm midi. .but could this problem be "solved" with a
>> custom cable where the shield doesn't connect at one of the ends?
>>
> 
> I have solved a similar problem in the past with a custom jack cable with the braid connected with a 470 ohm resistor at each end.
> 
> Makes bugger all difference to shielding (because 470 ohms or 235 ohms if both ends are grounded is peanuts compared to the infinite impedance of the braid in free space), drastically reduces ground loop currents to the point where they don't have an effect.
> 
> --
> Gordonjcp
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