Unusual question

[Mike Ross]

My one small gripe with the pidp-11 is that the LEDs are... unprototypically bright. They really are quite dazzling; to the extent that my wife has complained about having a pidp-11 on the living room wall! And yes I do have real pdp-11/70s to compare them to!

Does anyone know an easy method of reducing their brightness???

Thanks

Mike 

[John Johnson]

You should be able to increase the value of the current limiting resistors for the LEDs. That would be the twelve 390ohm resistors. 

You could even  put a pot in series with one of the existing resistors and adjust it for spousal approval, then use the closest standard value and replace all 12. 

John

On Aug 14, 2025, at 4:33 PM, Mike Ross <tmfd...@gmail.com> wrote:



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[John Bruner]

A software alternative is to change the duty cycle of the LEDs. Look at the table "brightness_phase_lookup" in

src/11_pidp_server/pidp11/gpiopattern.c

--John

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From: pid...@googlegroups.com <pid...@googlegroups.com> on behalf of John Johnson <jjte...@gmail.com>
Sent: Thursday, August 14, 2025 19:38
To: Mike Ross <tmfd...@gmail.com>
Cc: pid...@googlegroups.com <pid...@googlegroups.com>
Subject: Re: [PiDP-11] Unusual question

 

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