This is a speed-up mod for the slow 2021 that does work. It will increase 
the scan speed to about 11 channels per second. It has no effects on the 
delay time.

Unplug the radio, remove the 9volt batt.

Remove the upper case, by removing the four screws on both sides of the 
outer case, as well as the one screw on the rear apron of the radio which 
fastens the upper case to this surface.

Lift the top case section and unplug the white plastic two conductor 
speaker plug, allowing removal of the upper case entirely.

With the scanner sitting upright and facing you, locate resistor R-147 (a 
39k-ohm resistor to the left-front of the main board-almost behind the 
vicinity of the LCD display). Snip the leads at the resistor body with a 
pair of wirecutters to leave as much of the existing leads as possible. 

Solder a 15K-ohm resistor to those remaining leads.  

I found this mod in Monitoring times and have done it to several Pro 2021 
scanners and have seen no negative drawbacks to it.



From randy_ware%nwmail@sparc.ncpa.olemiss.edu Sun Aug 29 08:48:38 PDT 1993
Article: 8504 of alt.radio.scanner
Path: elroy.jpl.nasa.gov!swrinde!emory!nntp.msstate.edu!sparc.ncpa.olemiss.edu!randy_ware%nwmail
From: randy_ware%nwmail@sparc.ncpa.olemiss.edu (Randy Ware)
Newsgroups: alt.radio.scanner
Subject: Re: A Pro 2021 Mod
Date: 28 Aug 1993 19:24:55 GMT
Organization: NCPA/University of Mississippi
Lines: 31
Message-ID: <randy_ware%nwmail.15.0@sparc.ncpa.olemiss.edu>
References: <randy_ware%nwmail.14.0@sparc.ncpa.olemiss.edu>
NNTP-Posting-Host: rc.ncpa.olemiss.edu

In article <randy_ware%nwmail.14.0@sparc.ncpa.olemiss.edu> randy_ware%nwmail@sparc.ncpa.olemiss.edu (Randy Ware) writes:
>From: randy_ware%nwmail@sparc.ncpa.olemiss.edu (Randy Ware)
>Subject: A Pro 2021 Mod
>Date: 28 Aug 1993 19:08:07 GMT
>This is a speed-up mod for the slow 2021 that does work. It will increase 
>the scan speed to about 11 channels per second. It has no effects on the 
>delay time.
>
>Unplug the radio, remove the 9volt batt.
>
>Remove the upper case, by removing the four screws on both sides of the 
>outer case, as well as the one screw on the rear apron of the radio which 
>fastens the upper case to this surface.
>
>Lift the top case section and unplug the white plastic two conductor 
>speaker plug, allowing removal of the upper case entirely.
>
>With the scanner sitting upright and facing you, locate resistor R-147 (a 
>39k-ohm resistor to the left-front of the main board-almost behind the 
>vicinity of the LCD display). Snip the leads at the resistor body with a 
>pair of wirecutters to leave as much of the existing leads as possible. 
>
>Solder a 15K-ohm resistor to those remaining leads.  
>
>I found this mod in Monitoring times and have done it to several Pro 2021 
>scanners and have seen no negative drawbacks to it.
>
I want to add one more note to this mod, Overall what you are doing is 
adding 15k-ohm resistance to R-147. For a total resistance of 54k-ohms.
YOU ARE NOT REPLACING THE 39k WITH 15K.  
total of