| Author |
Message |
    
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 17
Registered: 12-2002
| | Posted on Tuesday, November 21, 2006 - 6:02 pm: | 
|
This seems to be happening more often now. When I unkey the microphone, the receive audio wont come back on. sometimes it works fine. It does this with all microphones wired for it. If I turn it on with out the microphone It will continue to fine until its keyed up then the rx cuts right back out? |
N8xfj
Intermediate Member
Username: N8xfj
Post Number: 217
Registered: 8-2006
| | Posted on Tuesday, November 21, 2006 - 9:49 pm: |
|
The problem sounds like it is in the relay and needs a good electronic cleaner to clean it and give it a try..
It is a clear plastic box with a spring clip holding the clear cover in place.
Good Luck |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2296
Registered: 9-2004
| | Posted on Tuesday, November 21, 2006 - 10:16 pm: |
|
i second the relay idea.
it should be in a socket so you can just unlatch it and pull it out.
use actual contact cleaner. dont substitute some other solvent.
clean all the pins on the bottom, then take the plastic cover off and spray the contact cleaner all over it making sure to get inside the little contacts.
veryu carefully manipulate the relay back and forth a few times before reassembly.
if it still wont spring bach and forth freely after cleaning, you may need a new relay.
good luck,
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 18
Registered: 12-2002
| | Posted on Wednesday, November 22, 2006 - 10:21 am: |
|
sure enough, that was the problem! that seems to be taken care of. thanks so much. of course another problem has reared its ugly head. I have no indicated output on am and its motorboating on sideband. the lights are dimming when this happens. the 1419's have been replaced except for the one in the power supply section. thanks again. steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2299
Registered: 9-2004
| | Posted on Wednesday, November 22, 2006 - 9:41 pm: |
|
this is also a very common problem.
look near the final and driver transistors. you will see a small blue capacitor labeled C179.
remove it and replace it with a 2.2uF 16 volt electrolytic capacitor. make sure the polarity is correct.
yes, the new part is different, and will work better.
do not continue to operate the radio until this part is replaced.
as for the 2SC1419's, what did you replace them with?
best is a 2N6487, if you cant find those, you can use an NTE152. both are big improvements over the 1419, it is weak and underrated.
also, if you use the power supply that is built in, replace the big cap on the PS board with a 5600-6800uF 50 volt cap. again, watch polarity.
good luck,
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 19
Registered: 12-2002
| | Posted on Thursday, November 23, 2006 - 12:51 pm: |
|
hey matt, found the evil blue bean c179. I'll replace that with the electrolytic model. I have the NTE152 version regulators in it. The power supply cap will be replaced along with the 1419 in there, just to be on the safe side. one of the resistors r301 looks a little toasty too.The radio itself has all the limiters intact and no removed transistors.somebody did convert the cb/pa to get the upper channels. I'm even thinking of recapping this bad boy! it will probably turn into a winter project. I disconnected it imediately after the motor boating. the royce 1-641 got hooked back up for now. Thanks again for all the help with the radio. happy thanksgiving!!! steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2305
Registered: 9-2004
| | Posted on Thursday, November 23, 2006 - 10:10 pm: |
|
hey steve,
i love these radios.
with a good tune up, and a good mic, they dont need any parts clipped. they actually have a speech compressor built into the circuitry.
if you want the radio to sound its best, definitely re-cap it. it makes a big difference and lends some peace of mind because you arent always waiting for the next one to go.
lots of mods for this radio, and if you're interested, i will post some.
the biggest deals to watch out for with this radio are the PC board cracking from being stressed, and one of the 2SC1419's is mounted in a bad spot and will cause a certain resistor to burn out. also, it causes the radio to drift off freq. because it is too close to the clarifier circuitry.
i cant remember the part number off hand, but it is on the right hand side of the component side of the board, mounted to the short metal sheild around the clarifier crystals.
the resistor is big and usually covered with a teflon sleeve. (nice solution eh cobra?!)
the real solution to this problem is to move the transistor to another location.
see that aluminum tab sticking up at the back of the radio? it should already have one 2SC1419 (NTE152)mounted upside down on it.
drill a small hole about an inch to the right of the transistor and remount the other one next to it. just run wires from the PC board traces of the old mounting location to the legs of the transistor, just like the other one. be sure to get the lead orientation right, and be sure to properly insulate the transistor from the chassis. (look at the other one for guideance)
make sure you use a thin layer of heat sink compound.
i would go ahead and replace the resistor in case it has already been stressed by heat.
im pretty sure its 47ohms @2 watts. i would replace it with a 5 watt resistor.
good luck to ya, and happy turkey day,
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 20
Registered: 12-2002
| | Posted on Saturday, November 25, 2006 - 11:36 pm: |
|
hey matt, looks like both nte152's are all ready mounted there. I have no plans of hacking this radios audio circuitry. like you said you dont need to. I would like to try some receiver improvements. the receive is excellent already.but maybe some schottky diodes in the proper spots? I'll be running my turner ssk into it hopefully with good results. the siver eagle was just to harsh to listen to on ssb. once again thanks matt!! you've been super helpful . steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2312
Registered: 9-2004
| | Posted on Sunday, November 26, 2006 - 1:03 am: |
|
good deal,
remember to be very very careful when working on the radio as the PC board is known to crack under pressure.
i have a couple of ANL mods that really bring down the noise level on receive.
it may take me a few days to find them so check back.
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 21
Registered: 12-2002
| | Posted on Sunday, November 26, 2006 - 8:05 am: |
|
matt that would be great! I'll keep an I on the forum here for some new info from you. If you like I can keep you abreast of the 139xlr's progress. thanks again matt!! steve |
1861
Advanced Member
Username: 1861
Post Number: 607
Registered: 2-2004
| | Posted on Sunday, November 26, 2006 - 2:02 pm: |
|
KID , I also would like the rx noise mod . I use a Turner + 3 mic on mine and it is one of my favorite radios . The rx is superb but noisy . |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 22
Registered: 12-2002
| | Posted on Wednesday, November 29, 2006 - 9:22 am: |
|
I just finished recapping all the electrolytics in the 139xlr. It took about 6 hrs total. i had a fairly new but messed up tomahawk to cannibalize. First thing i noticed was the relay operation. no more lazyness, a very nice snick, snick to it. receive audio quality is improved as general improvement of radio. I also replaced the 3300 uF cap in the ps. radioslack didn't have the proper replacement. I bought a 4400uf and a 2200uF axial leed and ran them in parallel to get in the 6000uF range. I found a president wahington schematic on line to refer to. I was under the impression that a 1419 was residing in the ps. turns out it's a 2sc1096. I put a little heat sink on it. Right now its running cool as a cucumber. It would probably be close to or over 200 dollars to have shop do the work. that doesn't include a receive alignment. not very cost effective!! I'll wait for the kid to post the receive improvements before i align the rx. I really love this radio. the turner ssk sounds superb on sideband, it lacks some on am. but im comparing to the silver eagle. hats off to matt the kid and the rest of the forum techs. the info i've gotten from this forum is "priceless" thanks steve. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2323
Registered: 9-2004
| | Posted on Wednesday, November 29, 2006 - 7:15 pm: |
|
im not a tech, just a hobbiest with alot of net time on my hands. (im at work right now)
but thanks for the compliment.
i like the "radioslack" pun; that was funny.
best to leave that 1096 in place, as i think the leads are different than the NTE152's.
remember you can also use the 2N6487 in place of a 2SC1419, which is a more robust part.
the ANL mod is to remove R43 and replace it with a 1.5Mohm (meg-ohm) resistor.
thats it.
now when you turn your ANL on, it will make a REAL difference.
sometimes the receive sounds a little TOO quiet, but its not reduced sensitivity, just low noise floor.
good luck,
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 24
Registered: 12-2002
| | Posted on Wednesday, November 29, 2006 - 8:06 pm: |
|
Well you must be giving good info. I don't see any of the techs on the forum saying other wise!!
I've noticed you are knowledgable on this style chassis. I really enjoy the info you are sharing.I'm also learning in the process. The proof is in seeing the good results from the upgrades. I'll post back with the results on the anl mod. thank you for your time and effort matt. steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2329
Registered: 9-2004
| | Posted on Thursday, November 30, 2006 - 11:26 pm: |
|
one thing to remember when modding your radios.
try to resist the urge to do more than one mod at a time.
if you do two or more things to your radio without checking it in between, you can get lost real quick as to why its not working right now.
i know its tough to reassemble the radio and turn it on in between mods, but it really will save you headaches and dollars in the end.
i really like this chassis, also the MB8719 uniden chassis.
have fun,
matt |
1861
Advanced Member
Username: 1861
Post Number: 611
Registered: 2-2004
| | Posted on Friday, December 01, 2006 - 12:45 pm: |
|
Matt , could you help me find R 43 , also what mohm is the stock resistor ? |
Yankee
Senior Member
Username: Yankee
Post Number: 1376
Registered: 7-2003
| | Posted on Friday, December 01, 2006 - 7:39 pm: |
|
Looking at the board so the 858 PLL will be in the upper right corner. Now come close to the center of the board, look for the silver (chrome metal) colored crystal filter, just below the filter find a trimer control, to the left of this trimer you will see R-42 and R-43 is just to left of R-42. R-43 will be a 1.5 meg ohm resistor. This information is taken from Sams Photofacts.
Carl CEF-357 |
1861
Advanced Member
Username: 1861
Post Number: 612
Registered: 2-2004
| | Posted on Friday, December 01, 2006 - 9:04 pm: |
|
Thanks CARL |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2332
Registered: 9-2004
| | Posted on Saturday, December 02, 2006 - 10:38 pm: |
|
it SHOULD have been a 1.5Mohm resistor, but if you look in the radio itself, you will most likely find a 680K or something like that.
most likely, the manufacturing plant didnt have the 1.5Mohm resistors in stock, and just cheaped out.
of the four radios i have done this mod to, they have all had 680K resistors in the R43 spot.
you can run the radio with no R43. just cut one side or unsolder it from the board.
i have one like this.
very very quiet receive, but i suspect that the gain has been reduced a bit.
try both ways, see how you like it.
maybe put it on a switch for a "quiet receive mode" or something like that.
thanks for the help carl.
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 25
Registered: 12-2002
| | Posted on Tuesday, December 05, 2006 - 8:14 am: |
|
hey matt, I couldn't find a readily available 1.5 m ohm. I did find a 1 meg and put it in place. I have the 680k model by the way. I noticed a slight improvement on the noise floor as you stated. I tried taking the resistor out of the circuit, but it got scary quiet.thanks for the mod! now hows about some diode mods for the nb circuit? somewhere on the forum somebody had posted a president washington schematic. If I could find it again maybe I can figure out some mods myself. steve |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2345
Registered: 9-2004
| | Posted on Friday, December 22, 2006 - 11:08 pm: |
|
hi all,
looked through an old book of mine and saw mention of using 2.2M ohms in the R43 spot.
i have not tried this, but i have tried 1.5M and also the resistor out of the circuit, and i think 2.2M will be a happy medium.
i will find some more RX mods for this radio and post them soon. check back afteer christmas.
matt |
Rumblefish
Junior Member
Username: Rumblefish
Post Number: 26
Registered: 12-2002
| | Posted on Wednesday, December 27, 2006 - 9:54 pm: |
|
I've been super busy this holiday season. greetings to all. I should be getting more time to fuss with the 139xlr. so far I have getting excellent audio reports. steve |
