cobra 200 no sound

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johndoe
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cobra 200 no sound

Post by johndoe »

Radio Make and Model: cobra 200
PCB Number:
PLL Number:
Test gear available: watt meter ,vom,soldering iron
Symptoms: no sound

What is working: everything else

What has been tried: tried for basic operation

Did it suddenly happen ?: came in this way
Anything else that may be of help?: 10kc switch doesnt seem to do anything .
this radio seems to be recieving but no sound from internal or external speaker.has good transmit audio.swings like near stock radio.havent opened it yet.
10 kc switch does nothing but radio can dail right thru the A channels and the freq counter gives them a decimal point.pretty cool feature.whats up with the sound??
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222
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cobra 200 no sound

Post by 222 »

the 10kc switch does not function in that radio, after it has been converted. so that part is normal.

i'm just guessing, but does it have talkback? the early models did not have factory t/b installed & had to be modified to have it. i'm thinking of the possibility that someone may have screwed something up in rx audio, during that process of installing t/b. also, if someone did indeed install t/b, they may have opted for a variable, which involve work at an additional location on pcb, where such problems could've occured. since it's all SMT, it's much easier to screw up.

serial #'s of 508 002 461 & after, should include factory t/b, as well as the rest of the updates mentioned in the service bulletins. this would also be identified by pcb #'s: PFM-009A-BE & after, as the factory updated radios. but that # may need to be checked further because i could've sworn the old vs new radios, had the difference between an "89" & a "90", in the number, so it's possible i have above # wrong.

aside from that, the service bulletins i mentioned, should be able to be found at cbtricks, so you can look at & make the comparisons.

another possibility: i'm not up on the circuitry of exactly how the talkback is acheived in this radio, however i know this: in many radios, there is no rx audio w/o a mic with an intact rx audio line plugged in. and in those radios, (like cobra 25's, 29's, 148's, etc.), if a t/b resistor is installed, that gives the radio a partial continuous rx audio function, without a mic plugged in, but not full volume until a mic (w/intact rx audio line) is plugged in. therefore, i'm thinking of the possibility that if that radio functions the same way, in that regard, and has not had any t/b installed, and you are plugging in a mic with no intact rx audio line, then that would result in no rx audio.

these are good facts to know, regardless of whether or not it applies in your case.

...my $2 worth..
Last edited by 222 on Sunday 18th Jan 2009, 18:36, edited 1 time in total.
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johndoe
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cobra 200 no sound

Post by johndoe »

thanks ........
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222
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cobra 200 no sound

Post by 222 »

you never answered the question about talkback, etc...
i'm curious as to whether or not you found/fixed the problem?....and if so, what it was..?
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johndoe
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cobra 200 no sound

Post by johndoe »

thanks for all your insite .i have sent the radio on its way .i do not have the ability to work on smd devices.i told the owner to go to dtb radio ,i hear he`s the man for the cobra 200`s.
wanna take a stab at my galaxy 88 drift problem???lol....i believe it to be the 10.240 crystal.i just need to change it and see.

thanks again mr 222
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222
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cobra 200 no sound

Post by 222 »

on the 200, i told you some things you could check for, in order to rule in/out what i suggested as possibilities...they were simple checks & didn't necessarily involve doing any smt work. the part about the mic possibility was real easy to check, but you didn't reply even as to whether or not you had the talkback, so i felt like: why did i even bother posting all that info? in any event, it doesn't sound like you left open any pathway to find out what the problem actually was, after it gets repaired by someone else, therefore neither you, nor myself or anyone else here gets to find out & potentially learn about this issue. i would ask, if you know the owner or know that radio is indeed going to dtb, or wherever, then if there's any possibility of you following up on that progress, it would be valuable info, esp. for yourself, but also to post here.

as to the the 88, you're asking me to 'take a stab at it', but i previously replied to you w/my take on that, as well, but again....you didn't reply, nor indicate whether or not you had at least tried the very simple starting advice i gave you there (which happens to fix problems such as your description, very often, so is a good starting point & good advice). additionally, i noticed where a tech told you categorically it wouldn't be the x-tal, but you have repeated several times now, that you feel it is needing a crystal repl. & that it has the 3 xtals you identified, so why didn't you just try changing them. in other words, you didn't take your own advice, nor mine.

good luck.
ramblingman
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cobra 200 no sound

Post by ramblingman »

hello,,,i had similiar problem on a 150 gtl dx
i think the p.c board is very similiar..
found the problem to be,,one of the regulators,the
one for receive only ,,had bad solder connection at p.c.b.
it will look o.k.,,you will have to look close under your
magnified light,,while flexing the board.
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johndoe
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cobra 200 no sound

Post by johndoe »

i passed this radio on ,i dont do smd work.thanks for your input.
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