In article , writes: Path: maple.enet.net!asuvax!cs.utexas.edu!swrinde!ihnp4.ucsd.edu!network.ucsd.edu!vig ra.com!news.vigra.com!steve From: steve@vigra.com (Steve Haehnichen) Newsgroups: rec.radio.amateur.equipment Subject: Re: TM-733A.DOC Date: Thu, 8 Sep 1994 04:11:43 GMT Organization: Vigra, San Diego, CA Lines: 126 Message-ID: References: <26AUG199417405897@elroy.uh.edu> Reply-To: steve@vigra.com NNTP-Posting-Host: dbrown.extern.ucsd.edu In-Reply-To: steveflu@microsoft.com's message of Wed, 7 Sep 1994 02:16:12 GMT -=> On Wed, 7 Sep 1994 02:16:12 GMT, steveflu@microsoft.com (Steve Fluegel) said: > In article <26AUG199417405897@elroy.uh.edu> st3qi@elroy.uh.edu wrote: >> >> If enough people call about the PL problem, >> maybe they will come out with a real fix and offer it under warranty >> to all the radios out there (since they're all pretty new). My guess >> is that it will involve a free TSU-8 tone decode module, but don't >> hold your breath. :-) > This implies (as do other things I've read) that the problem is > fixed by installing the TSU-8 tone decode module which presumably > takes over the tone encoding function as well. Can anyone confirm > this? I can now say that this is *not* the fix. Kenwood has finally released an official Service Bulletin on the PL distortion problem, and the solution is to replace several discrete resistors with more carefully chosen values. The TSU-8, and even the resistor network DAC is not involved. They claim the distortion goes from 9% to 4%, and the folks that have had the fix performed says that it is no longer noticible. I haven't sent mine in yet. I posted a summary of the Service Bulletin some time ago, but it may not have had the right distribution. I'm attaching a copy of it below this article. Happy Hacking! ----------8<----------8<----- CUT HERE -----8<----------8<---------- #Newsgroups: rec.radio.amateur.equipment #From: steve@vigra.com (Steve Haehnichen) #Subject: Kenwood TM-733A PL Tone distortion service bulletin. (At last!) #Date: Thu, 1 Sep 1994 01:17:27 GMT #Lines: 88 Kenwood just released a Service Bulletin to address the transmitted PL tone noise on the TM-733A. (Yeah!!) Call the Kenwood Service Dept. (1-310-639-7140) if you want a hardcopy. Here's a summary of the text. Use it at your own risk. If you are going to get into your radio with a hot iron, you should first get the real paper from Kenwood with the drawing. (Note that Kenwood allows licensed amateur operators to perform these modifications *without* voiding the factory warranty. I was surprised to learn this. This applies to any published Kenwood bulletin or modification. Cool, eh?) -Steve Steve Haehnichen Vigra, Inc. San Diego, CA steve@vigra.com (619) 597-7080 x116 Fax: (619) 597-7094 ----------8<----------8<----- CUT HERE -----8<----------8<---------- Kenwood Service Bulletin #ASB-1060 2 Pages Subject: TM-733A PL Tone Distortion August 30, 1994 Symptom: -------- Transmitted PL tones at the receiving station have a relatively high level of distortion. This is easily seen when the incoming signal is viewed on an oscilliscope. Countermeasure: --------------- Cange the value of the "Pull-up" resistors in the PL tone encoder circuit as shown in the accompanying chart and illustration. This reduces the distortion from around 9% to approximately 4%. Part OLD value NEW value ---- --------- --------- R542 1.8k 2.7k R543 1.8k 3.3k R544 1.8k 4.7k R545 1.8k 6.8k R546 1.8k 10k R547 1.8k 10k R548 1.8k 10k Procedure: ---------- 1. Disconnect the power cable, microphone and antenna's, etc. 2. Detach the front panel and set it aside. 3. Remove the top and bottom covers. 4. Remove the speaker and speaker mounting bracket. 5. Disengage the plastic front panel from the main chassis. 6. Carefully disconnect the two ribbon cables from the Tx/Rx unit C/4. 7. Remove the two Phillips head screws that secure the Tx/Rx unit to the chassis. 8. Turn the circuit board over and replace the resistors using the parts list and illustration as a guide. 9. Reverse steps 1-7 for reassembly. TX-RX Unit (X57-4360-00) Foil Side View --------------------------------------------------------------- R R R R542 5 5 5 4 4 4 R543 7 6 4 R545 (IC403 on component side) R 5 4 8 _______ -| |- -| |- -| |- -| IC402 |- -| |- -| |- -|_______|- --------------------------------------------------------------- Caution: This modification requires advanced surface mount soldering equipment that is rated for CMOS circuits. It also requires familiarity with advanced surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance from your closest Kenwood Service Center (Long Beach, CA, or Virginia Beach, VA).