Copper Talk » Modifications » Radios » Another channel mod for cobra 148 MB8719 « Previous Next »

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Fusebreaker
Intermediate Member
Username: Fusebreaker

Post Number: 176
Registered: 3-2004
Posted on Wednesday, September 14, 2005 - 2:31 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I seen that you can ground pin 8 and pin 9 threw a switch you get the same freqs and a few more a channels with this version.
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Yankee
Advanced Member
Username: Yankee

Post Number: 900
Registered: 7-2003
Posted on Wednesday, September 14, 2005 - 7:13 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Allen: Excuse me, Before someone corrects me Pin 9 is the B+, and pin 8 is the oscillator output. Therefore neither of these 2 pins of the MB-8719 PLL IC can be grounded. BTW: Pin 9 is where you would pick up your B+ voltage for the B+ side of the 10 KHz. plus or minus mod.
Pins 10 thru 16 are the only programming pins that you can work with.
Hope this is of some help. Had to get out the factory shop service manual for the MB-8719 pin out.
Carl CEF-357
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Kid_vicious
Advanced Member
Username: Kid_vicious

Post Number: 615
Registered: 9-2004
Posted on Thursday, September 15, 2005 - 9:40 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

fusebreaker, i found the mods you are referring to, and yes, the info is just wrong.
dont do that mod.
the first one is ok but #2 is wrong.

here is a link to a mod that i know works if done correctly. this is the one i did to my 2000gtl.
if you dont have a freq. counter, find one before you attempt this mod. if you dont, you will be very frustrated trying to retune the VCO. yes, you will have to tune it a bit, and doing it without a freq. counter, well, good luck, im sure it's possible but i wouldnt do it.
hope the link is good.
matt

Moderators Note!

Your Link had to be deleted as it contains links to Competitors of Copper Electronics Web Sites.
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Yankee
Advanced Member
Username: Yankee

Post Number: 905
Registered: 7-2003
Posted on Friday, September 16, 2005 - 3:01 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Allen, I only believe about half of what I read for mods. on the Internet. I will first check here on the Copper Talk Forum, to see if anyone has done a mod. on the Internet and if it worked for them. Many of the members here on the forum know more about mods. than any posted on other forums and even CB Tricks website.
Need to remember that most of the posts on CB Tricks are much the same as any other forum, and a great share of the mods. on CB Tricks are not all tried and tested mods. some of the people posting them will even say,"I'VE HEARD ABOUT THIS. BUT HAVEN'T TRIED THIS MOD. ON MY OWN EQUIPMENT". So in most cases, ask the Copper Forum Members First. All you need to ask is, (has anyone done this?)
I for one am in agreement with Matt about the second poorman's MB-8719 PLL mod. Posted on the CB Tricks site being incorrect, although the first one works great, along with the pin 13 mod. for chnls 41-44, and the pin 16 mod. for the plus or minus 10 KHz. jump. And have been done and proven to work.
Hopes this is of some help.
Carl CEF-357
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Yankee
Advanced Member
Username: Yankee

Post Number: 906
Registered: 7-2003
Posted on Friday, September 16, 2005 - 10:57 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Some time ago there were many sites on the Internet pretaining to modifing CB radios that are no longer on the Internet, I have many of them that have something to do with the older uPD-858 sideband chassis and the newer MB-8719 sideband chassis.
One of the best was "Welcome to my Cobra 148 GTL page", of which I have a print out.
In the Sams Photofacts shop manuals for each radio there is a 40 channel truth chart and once you have figured out how to read a truth chart you can figure from there what any PLL circuit can or can't be made to do. A few of the newer PLL chips are made so they can't be modified such as the one in the Cobra 2000 GTL from the factory, that has to be changed to the MB-8719 before you can do any PLL modifications.
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Kid_vicious
Advanced Member
Username: Kid_vicious

Post Number: 622
Registered: 9-2004
Posted on Friday, September 16, 2005 - 10:07 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

can you believe that yankee, they make a radio like the 2000, that all the hardcore modders are going to drool over, and then they put the MB8734 in it!!!

sorry about the link, i wasnt sure what the rules were. i know now!
matt
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Fusebreaker
Intermediate Member
Username: Fusebreaker

Post Number: 178
Registered: 3-2004
Posted on Saturday, September 17, 2005 - 11:30 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

kid good point on the mb8734 in the 2000`s kinda ignorant to me
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Yankee
Advanced Member
Username: Yankee

Post Number: 909
Registered: 7-2003
Posted on Saturday, September 17, 2005 - 12:43 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

At this day and age I can believe almost anything. As yet I haven't been able to figure why Uniden engineered the MB-8734 into the Cobra 2000-GTL and it's the only radio they did this on. Another thing Uniden did was to use a crystal in the Cobra 142 GTL series of radios that had to be changed before the PLL mods. would work.
Carl CEF-357
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Fusebreaker
Intermediate Member
Username: Fusebreaker

Post Number: 182
Registered: 3-2004
Posted on Saturday, September 17, 2005 - 3:44 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

LOL that is kinda ignorant
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Yankee
Advanced Member
Username: Yankee

Post Number: 910
Registered: 7-2003
Posted on Saturday, September 17, 2005 - 5:11 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Allen, Have you been getting my E-mails in the past few days, just wondering? Haven't had any answers.
Carl CEF-357
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Fusebreaker
Intermediate Member
Username: Fusebreaker

Post Number: 184
Registered: 3-2004
Posted on Saturday, September 17, 2005 - 5:57 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

i have 3 email accounts i have not checked inbox i will though. sorry
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Patzerozero
Senior Member
Username: Patzerozero

Post Number: 1495
Registered: 7-2004


Posted on Saturday, September 17, 2005 - 8:32 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

that was cobra's attempt at satisfying fcc threats of retribution for designing so easily modified of a radio. others were just as easy, if not easier to mod, why'd they pick on cobra? grab a quick settlement from a company with lots of cash, that 'settled without admitting guilt'. that the 8719 was a direct drop in for the 8734 was merely coincidental.
uniden went through the same thing with the 2510/2600.
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Yankee
Advanced Member
Username: Yankee

Post Number: 912
Registered: 7-2003
Posted on Saturday, September 17, 2005 - 9:42 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks Pat, I was thinking it might have been done to please the FCC. Because if memory serves me correctly I remember hearing about the FCC crack down on easily modified PLL circuits about the time the Cobra 2000GTL first came on the market.
Carl CEF-357
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Kid_vicious
Advanced Member
Username: Kid_vicious

Post Number: 641
Registered: 9-2004
Posted on Sunday, September 18, 2005 - 12:11 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

did you guys know that uniden got smart and made sure the contract they had to build those radios with that design had no expiration date.
previous radios had the problem of their contract expiring and they would have to "reappease" the FCC with a new design.
my point is, uniden could be producing those same radios today if they so chose.
what's wrong with these people.
matt
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Fusebreaker
Intermediate Member
Username: Fusebreaker

Post Number: 189
Registered: 3-2004
Posted on Sunday, September 18, 2005 - 2:55 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

the email with six position switch did not come threw right

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