Up to Arcom index
Up to ACC index
Back to Home
Installing an Arcom Digital Audio Delay board into any ACC Controller
By Darrin Stanley KB6WAS
This web page was developed by Mike WA6ILQ from an email
Thanks go to Darrin for permission to present his work.
Print this Page


Notes from the Editor (WA6ILQ):
The repeater controllers made by Advanced Computer Controls are fine controllers, but are old enough that many parts are no longer available.   One is the SAD4096 audio delay line chip (the so-called "bucket-brigade" chip)... which has been out of production for years and nobody has any in stock...   The simple solution is to replace it with a coupling capacitor (but you will end up without any delay).   The better way is to replace the old dead or dying ACC audio delay with a new Arcom digital delay board (at about US$50) - which is more flexible ( the delay is anywhere from 8ms to 2 seconds), has better signal-to-noise performance, a bunch less audio distortion, and best of all, it drops right in...

From: Darrin Stanley KB6WAS
Date: Mon, 27 Aug 2005
Subject: Re: ACC audio delay replacement

Hooking up the "RAD" audio delay board to an RC-850 is rather simple:

Hook pin 1 of RAD to a source of clean +12 volts DC.
Hook pin 2 of RAD to pin 6 of U35 (where the audio delay chip used to be) this is 
audio in.
Hook pin 3 of RAD to pin 16 of U35 (this is delayed audio out).
Hook ground pin on RAD to pin 9 of U35 (ground) or to the closest circuit board ground.
You do not have to hook up the COS signal to the RAD if you are sending it audio that 
is already squelch muted.

RAD board pin out:
pin 1 = filtered +12 volts DC
pin 2 = audio in
pin 3 = delayed audio out
pin 4 = Ground
pin 5 = COS (optional - if not used connect this pin to ground)

RC-850 U35 pinout (only two pins plus ground are used):
pin 6 = to the RAD audio input pin
pin 16 = from the RAD delayed audio out pin

See the photo of how I installed it using the same standoff
that was used for the original ACC Audio Delay Board.

The RAD board is dip switch programmable, and the manual is on 
the Arcom web site.  The configuration that I found was the 
closest to my ACC delay board are switches 1-5 = on, and 6-9 = off.

Two notes from the Editor (WA6ILQ):
1) Note that while an 850 is mentioned above the same idea can be used in any ACC controller that uses the audio delay board.

2) The hookup of the COS lead is not necessary if the board is being fed squelch gated (i.e. muted) audio.   Lastly, the RAD COS pin passes audio when low, and floats itself low... bringing it high with a logic level or pulling it up to +V will mute the audio.

3) Pin 5 of the RAD board is nearest the edge.


Back to the top of the page
Up to Arcom index
Up to ACC index
Back to Home


Original text (the white background) © Copyright 2005 Darrin Stanley KB6WAS
Comments, artistic layout and hand-coded HTML © Copyright 2005 and date of last update by Mike Morris WA6ILQ
This page last updated 20-Dec-2005

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.