| Author |
Message |
    
Hootyal
| | Posted on Tuesday, January 28, 2003 - 6:38 am: | 
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Any Techs know of a good swing mod for a uniden washington? Maybe a diode &resistor combination?
Thanks, HootyAl |
Bigbob
| | Posted on Tuesday, January 28, 2003 - 10:54 pm: |
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I don't.But that rig will punch almost 7 watts dk and 21 watts swing as is thats pretty much it unless you can find a loose meter,it'll do 21 on ssb too,one of the best dam radios I ever had,till a guy with a 600-12 next door wiped out the reciever strip. |
Lvlooney
| | Posted on Saturday, January 10, 2004 - 6:28 pm: |
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how do you get the washington to swing like that?
what do you have to do exactly? i have a washington and cant find power mods for it. any help is appriciated.you can email me at donpg2@aol.com |
Bigbob
| | Posted on Tuesday, January 13, 2004 - 9:45 pm: |
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Jack up the voltage from the mb3749 regulator about 1.5 volts,to the final on am,get a tech to do this,he should replace associated caps from 10 volt units to 16 volt ones,to avoid failure,no more than 1.5 volts or you'll take out the reg.,then peak the tx strip,and increase your avg. modulation to 100%,oh and a complete realignment wouldn't hurt either,you might try volting the final and bypass the mb3749 alltogether. |
Kc0gxz
| | Posted on Friday, January 16, 2004 - 3:19 pm: |
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Hootyal and others. Try this.
This modification will work on the following radios.
President Washington-McKinley
Cobra 140-142
Realistic TRC450-490
Tram D80-D300
Midland 79-900
This modification is for the single final, single conversion SSB radios. Also known as NPC and Final to Linear
Before attempting this modification, study the PC board very thoroughly and go over these instructions a few times so there is no doubt in your mind as to what you are doing and what has to be done. This mod WORKS and works well. If it doesn't work in your radio when completed, you screwed up somewhere.
Note: To save yourself a lot of time when asking for mods, you should check the Archives first. Almost every CB mod you can think of has been posted at one time or another on Coppers Forum and new ones keep croping up all the time. I believe this is now the third time I have posted this particular modification.
Ok, here we go. Good luck with it my friends.
1. Remove TR-32
2. Solder jumper over R-123.
3. Add a 10 uF 25 or higher volt electrolytic cap to these points: Attach the positive leg of the cap to pin 9 of IC4, and attach the negative leg to the junction of R-121/D-62/R-204.
4. Set the driver bias to 50 mA.
5. Set the final bias to 100 mA.
6. Solder the end of the final bias wire that is furthest from the final transistor to the cathode (banded) end of D-60. If you don't know where it is located, just look for the audio transformer and you will see two wires plugged into a couple of upright pins sticking out of the PC board. Just unplug the one that is furthest from the final.
(Note: Sometimes they are soldered to the pins. If so, just snip it off the pin and solder it to the (banded end) of D-60).
7. Set the dead-key power to 1.5 watts using VR-6.
8. Tune the RF amp chain coils (L36 and L26 through L29) for maximum peak (modulated) output power using a Audio Generator set at about a 1K Hz tone. If you don't have one, key your mic and say awwwwwwww into the mic while tuning the coils for maximum power. NEVER WHISTLE INTO THE MIC FOR TUNING PURPOSES.
9. Now check the dead-key power again. If it's higher than 1.5 watts, use VR-6 to reset set it to 1.5 watts. Don't over do it. Keep in mind that the carrier power (aka dead-key)increases up to 10+ watts with modulation, so there's absolutely no point in having the dead-key power any higher than is required to reliably key an amplifier.
Most amps will key with as little as 1/2 watt of dead-key power put to them. If you over-do the dead-key, the transmitted audio will (sound) weak because the negative modulation peaks will not reach 100%. In other words, YOU WILL BE DEFEATING THE PURPOSE OF THIS MODIFICATION!!
The dead-key wattage should be 1.5 while the maximum average power will be around 10 to 12 watts. And the maximum peak power should be around 25 watts, give or take a watt or two either way. These results are very impressive for a single final radio and will work beautifully into a RF amplifier. Also, the amplifier will run much cooler and live longer.
When performing this modification, please, please, please do it all into a dummyload. That is the ONLY way you are going to see true RF power readings from your meter. Doing your tests on the air is very unprofessional. Regular, run-of-the-mill CBers do this all the time. The good CB radio operators do not.
Good luck with this mod.
PS: By the way, I'm back from a "extended vacation".
Jeff, kc0gxz. |
Bigbob
| | Posted on Saturday, January 17, 2004 - 6:43 pm: |
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I definitely need a diff job been two years since I had one. |
Aircop12
Junior Member
Username: Aircop12
Post Number: 19
Registered: 5-2004
| | Posted on Wednesday, October 13, 2004 - 2:14 pm: |
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Where do I find the R-104 to cut to get the modulation up an this radio. I have been unable to find a schematic for the Washington,and have no idea where the R-104 is located.
Thanks: |
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