| Author |
Message |
    
Salty_bones
Junior Member
Username: Salty_bones
Post Number: 28
Registered: 5-2005
| | Posted on Sunday, March 19, 2006 - 4:42 pm: | 
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I have a Cobra 142 GTL base that has no audio from speaker and no rx or tx. I replaced the audio ic with a TA 7222AP and replaced 2SC-2166 also 2SC-1969 and the radio is still doing the same thing. Anyone else have any ideas what the problem is with this radio? Also when I key the mic down the tx light don't even light up.
Thanks for any help. |
Goat373
Intermediate Member
Username: Goat373
Post Number: 188
Registered: 3-2005
| | Posted on Sunday, March 19, 2006 - 8:42 pm: |
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youe mic may not be wired right, i think that radio has a rx pin on the mic that grounds out on non-keyed conditions, so sheck that first, also the rx wire may have come off the mic plug on the INSIDE of the radio, all these things checking ok, im not sure what else without having a radio infront of me. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1328
Registered: 9-2004
| | Posted on Sunday, March 19, 2006 - 10:22 pm: |
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get a copy of "the screwdriver experts guide to CB repair" by lou franklin.
this book will guide you through all the steps to find out whats going on with your radio; its easy to understand, and you will learn alot!
great book.
matt |
Tech808
Moderator
Username: Tech808
Post Number: 9495
Registered: 8-2002
| | Posted on Monday, March 20, 2006 - 12:41 am: |
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Copper Electronics has The Screwdriver Expert's Guide in stock and ready to be shipped.
Just CLICK on the LINK below to place your order.
The Screwdriver Expert's Guide
Hope this helps,
Lon
Tech808
CEF808
N9CEF
CVC#2 |
Salty_bones
Junior Member
Username: Salty_bones
Post Number: 30
Registered: 5-2005
| | Posted on Monday, March 20, 2006 - 2:45 pm: |
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Its not the mic. It don't recieve anything and the meter does not move. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1329
Registered: 9-2004
| | Posted on Tuesday, March 21, 2006 - 12:11 am: |
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if you're sure its not the mic, (i would try using another mic to be sure. it will save you headaches later) then your VCO may be out of lock.
if the radio has been converted for extra channels, this might have occured.
using your voltmeter set to read DC volts in a range that will allow you to read between 2 to 10 volts; put the black test lead to PC board ground, and the red lead to the top leg of R72 (TP9).
make sure you are using the correct plastic tuning tool. if you break the core, you will have to unsolder the whole coil and turn the core over and try again. if you are planning to use jewelers screwdrivers to do the adjustment, you might as well stop reading now, because everything i tell you wont work.
with the radio on CH.1 (26.965) check for 2.0 volts at TP9 (top leg of R72).
if no voltage is present, then you have a problem that requires test equipment that you probably dont have.
if there is voltage present but its not 2.0 volts, adjust L13 for 2.0 volts.
try to key the mic.
anything?
if it worked, then check your highest and lowest channels, and try to key the mic on them. if you get transmit power, you are done.
if it wont key on either the highest or lowest channel, then you need to adjust L13 SLIGHTLY (and i mean SLIGHTLY!) one way or the other.
what you are adjusting is the VCO range. if no ammount of adjustment will get it to cover the whole channel range, then you will have to broadband it, which is another thread all together.
as a last resort, if all of this doesnt do anything; go to the center of your freq. spread (ch.19 on a stock radio), key the mic, and adjust L13 slowly until the TX light comes on and the meter moves to the right.
if that works, just leave it there.
good luck,
matt
good luck,
matt |
Salty_bones
Junior Member
Username: Salty_bones
Post Number: 32
Registered: 5-2005
| | Posted on Tuesday, March 21, 2006 - 5:04 pm: |
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The Tx light is on just can't hear anything and the meter doesnt move. When you key down the mic the tx light does not come on. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1335
Registered: 9-2004
| | Posted on Tuesday, March 21, 2006 - 11:06 pm: |
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have you tried any of my suggestions yet?
matt |
Salty_bones
Junior Member
Username: Salty_bones
Post Number: 33
Registered: 5-2005
| | Posted on Wednesday, March 22, 2006 - 3:45 pm: |
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I did what you said on *the center of your freq. spread (ch.19 on a stock radio), key the mic, and adjust L13 slowly until the TX light comes on and the meter moves to the right*.
The TX light was already on but I adjusted L13 and it did nothing. This radio was working when I first got it then it just stoped. |
Goat373
Intermediate Member
Username: Goat373
Post Number: 190
Registered: 3-2005
| | Posted on Wednesday, March 22, 2006 - 6:05 pm: |
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if the tx light is on with out your mic keys...its in the keying section of the radio...i think that radio uses relay keying does it not? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1337
Registered: 9-2004
| | Posted on Wednesday, March 22, 2006 - 7:17 pm: |
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salty bones, im confused here.
in your original post, you stated that the TX light would not even come on.
now you're saying that it is on.
is it on all the time?
when you say on, do you mean that its green all the time?
or do you mean that its green and turns red when you key the mic.
you say that it worked and then just stopped.
can you try to detail for us what the conditions were of you discovering your radio didnt work?
how did you notice?
did it happen with the radio on or just turned in on one day and it didnt work?
give as much detail as you can.
i noticed that you went right past my suggestion of properly aligning the VCO and went right for my "last resort" method.
you really should try to get it set right, because if it wasnt the problem before, its messed up now and you wont know if your radio is fixed because no matter what you do, its not going to lock onto any freq.
if you do not have a voltmeter or my instructions seemed over your head, then i have to change my suggestion to, "find a good tech and take it to them."
seriously, im not commenting on your level of intelligence or anything else, but if this stuff is difficult, then you need to be realistic about where you are in your repair abilities.
matt |
Salty_bones
Junior Member
Username: Salty_bones
Post Number: 34
Registered: 5-2005
| | Posted on Thursday, March 23, 2006 - 2:59 pm: |
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Sorry about that, I ment to say the RX light is on all the time there is no sound coming from the speaker the meters will not move and it will not key down no Tx light working. I just turned it on one day and it didn't work. Worked fine before. I have been trying to find someone to fix it but can't. I guess I can try to check the volts. Around here I know its sad but I trust my work better then anyone in the area but would like a tech to fix it. |
Viking
Intermediate Member
Username: Viking
Post Number: 243
Registered: 2-2002
| | Posted on Thursday, March 23, 2006 - 5:51 pm: |
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While you're checking voltages:
Check Pin 9 of IC2 for 8 volts. If it doesn't have 8v, check Pin 1 of IC5 for 8 volts. If this also doesn't have 8v, then IC5 is bad. Or if you're lucky C66 is shorted (it's easier to replace). |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1340
Registered: 9-2004
| | Posted on Thursday, March 23, 2006 - 10:00 pm: |
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good info viking! |
