LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #2   Report Post  
Old February 1st 10, 07:40 PM posted to rec.radio.amateur.equipment
external usenet poster
 
First recorded activity by RadioBanter: Dec 2006
Posts: 3
Default icom r71a distortion fix on AM

triode wrote:
Having suffered for years with tiring audio on my R71, decided to fix
it. These are one of the best radios ever made, worth hanging on to.

Hello Triode:

With your permission, I would like to post your solution and schematic
from Mods.DK on the R71 yahoo group. OK?

Thanks,

Dave

The problem is the switching diode D75. The Emitter follower Q26 is
enabled for AM reception, the 3 volts or so being used to forward bias
D75, thereby passing the audio to IC6a. The current through the diode
being only a few hundred microamps is insufficient to turn it on fully,
causing the forward dynamic `resistance to be modulated with the audio,
causing distortion. The fix is simple. Replace R202, (100k) to 15k,
and replace R128 (1K) with a jumper. This increases the current to a
more satisfactory.3 mA or so. The results are great.




 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
FS - Icom R71A [email protected] Equipment 0 April 15th 09 09:15 PM
Icom R71A FS [email protected] Shortwave 1 October 12th 06 11:51 PM
FS ICOM R71A & IC-SP3 Rigali5 Shortwave 0 February 7th 04 03:51 PM
Icom R71A Brian Shortwave 16 February 4th 04 08:13 AM
FT: Icom R71A MB Swap 0 January 1st 04 07:45 PM


All times are GMT +1. The time now is 11:05 AM.

Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017