RCI8719 Mods in Cobra 148GTL

[Aztec]

Hello everyone,

This is my first post! Thanks for letting me join your forum!

I was about to modify a Cobra 148GTL with the 6 position rotary switch mod (my favorite mod) for extra frequencies, I had stop because it turns out that the radio has an RCI8719 PLL chip instead of the original MB8719. This is an older made in Malaysia radio, the PLL has been replaced. In fact the are signs that this radio had already been modified but when the PLL was replaced everything was returned to stock.

I can't seem to find a very consistent source of information on the RCI 8719 and the modding possibilities with this new PLL. What I have found is that Pin 10 is held high internally and this is the main difference.

I still can't seem to find if it's possible to do any frequency mods on this chip at all and would like to ask you guys for some help. I figure the 6 position rotary mod will not be possible but I would settle for any mod that is possible with this replacement PLL.

Attached is the picture of the chip.

Thanks for your help in advance. 73s

 

[LeapFrog]

Hello everyone,

This is my first post! Thanks for letting me join your forum!

I was about to modify a Cobra 148GTL with the 6 position rotary switch mod (my favorite mod) for extra frequencies, I had stop because it turns out that the radio has an RCI8719 PLL chip instead of the original MB8719. This is an older made in Malaysia radio, the PLL has been replaced. In fact the are signs that this radio had already been modified but when the PLL was replaced everything was returned to stock.

I can't seem to find a very consistent source of information on the RCI 8719 and the modding possibilities with this new PLL. What I have found is that Pin 10 is held high internally and this is the main difference.

I still can't seem to find if it's possible to do any frequency mods on this chip at all and would like to ask you guys for some help. I figure the 6 position rotary mod will not be possible but I would settle for any mod that is possible with this replacement PLL.

Attached is the picture of the chip.

Thanks for your help in advance. 73s

Welcome to the forum Aztec!

In regards to your question, I wish I could give you a definitive answer.

Check this old post out.

It seems to me that anything with the RCI name associated with it has "freeband" capable written all over it! (Just my opinion)

If it is truly a 6 bit replacement for a 7 bit PLL, (with one bit held high) I would say it is very possible to do, I just do not have any experience with this PLL, the only experience I have PLL modding is because member Unit-399 helped me out with a 23 ch. radio.

Once again welcome, sorry I couldn't help you out more.
EDIT: Check this out, maybe modding it is
not such a great idea if you do not have a backup PLL..
The Following Translated by Google.

Hello mate I understand that they are similar but not 100% compatible. I tried to make the modification of the cb as with the mb8719 and the rci8719 was damaged. I hope my experience will serve you.

AARON DIAZ AGUIRRE161

Fighter, the PLL MB8719 is a synthesizer and among other functions is the one that interprets the selection of channels, if for any cause this freezes can happen that has no reception, transmission or ptt, or you might have rx / tx, But only on one channel.I recommend that with the MB8719, check if on pin No. 7 before the diode if you have more or less 8 v.After the diode or in the pin No.7 if it has 5 to 7 v, if the pin marks 0.2vo something like this, very low voltage, then take the diode on one side and check the voltages, if before the diode you have From 5 to 8v, this integrated insurance is bad.For this pin the synthesizer takes reference of voltages to carry out the operations of the working frequencies.Good luck and comment.

Looks like I could keep searching.

Best Regards
-LeapFrog.

 

[sonoma]

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

 

[melaza]

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.[/QUOTE

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

OH WOW! this info is lost to me since it has been so long ago on this chip. I do remember there was 2 versions of the rci8719 and the 1st version would mod but the RCI8719-99 would not convert. this is all I remember. so no luck with the chip you have comes to mind. I do have a texas ranger tr296F that is the same radio as a cobra 148 radio. it has the 1st version of the rci8719 chip in it and it took the channel mod. you will have to read some of the info left for you in the 1st post and look to see what chip is actually in your radio. look for the 99 at the end to help in your search.

Hi,
RCI8719-97

The RCI8719-99 & MMB8719 are modifiable.

 

[Aztec]

Hi thanks,

I had already come around those posts but they didn't seem to come to a conclusion in the end.

From what I've read around the main difference is that the RCI version has pin 10 internally controlled and is not externally controlled like in the MB version. Grounding this pin can burn the chip. I'm not sure if this is the case in all the RCI versions.

I se a lot of conflicting information, some say the RCI can be modified just like the original MB chip, others say it can be modified to a limited extent, others say it can't be modified at all.

At the same time some say that the ones that can't be modified are the ones that end in -99 but I haven't found any other information for the ones that supposedly can be modified.

Something else I have found is that supposedly the RCI8719 is really more an equivalent to the MB8734 which from the pinout definately seems to be similar.

The oene I have is not one of the ones marked -99 but it seems to risky to try and modify it using the traditional methods. If anyone has had any success pleas let me know. Otherwise I'll go with changing the crystal.

 

[sonoma]

rf parts sells the RCI8719-99 chip and they even tell you it is not a sub for the mb8719 chip. the plain rci8719 I have been able to add channels to but not the -99 chip. it blew up when we tried a -99 chip. this is all the info I had ran across.

 

[Aztec]

Hmmm alright thanks. I'm very hesitant to try regardless. I think I'll leave it alone for now. If I had a spare MB8719 I'd try it that way if it did ever blow up I could always just sub in a new one!

 

[ExitThirteen]

Check the voltage on the positive side of C84. That is the PLL control voltage. Tell me what this voltage is, and I can tell you if the PLL can be modded. Thanks!


~Cheers~

 

[oldpaint0]

How bout you thirteen.

 

[Yeti Communications Ltd]

my understanding is the rci8719-97 is the same as the mb8734 (pin 10 disabled) it will still do extra channels just 127 or so (forget how many exactly if you use the 1/2 vco mod in the "poormans" mods on it in other words with stock crystal with stock binary codes more down than up channels as its only 6 bit

the rci8719-99 is the same as the mb8719

for example galaxy parts sheet list the "rci8719A" as "ENRG871999" aka a rci8719-99 and we all know thats capable of 192 channels using the poormans mod method just like the old MB8718 used in the uniden grant etc (the old grey version and XL) and cobra 148gtl old style

@sonoma ..i cant see why other than doing it wrong never had a issue with subbing a 8719-97 for a -99 or mb8719 done well over 100 transceivers with them
however more into using mc145106 plls now on sub board to replace the somewhat limited range 8719 series and to gain 5khz stepping

the hardest thing is to get the vco sub boards...crazy idea epoxying a vactor vco diode in a encapsulated board ....doomed to fail

 

[ExitThirteen]

Yo! What's up Oldpaint?


~Cheers~

 

[sonoma]

I only tried the rci8719-99 one time and it popped on me. put a mb8719 in its place and it worked just fine. not sure what caused the chip to go bad. back them galaxy told me the 99 chip would not mod. that was maybe 10 years ago now.

 

[ExitThirteen]

One of the variants of these MB8719's have a different PLL control voltage. There is a variant in the RCI8719 line that has a 5 volt PLL control voltage, and if you try to mod it, it'll huff the PLL. I'd like to say some of the later Malaysian models and the newer China models have this variant of PLL in it. It's been a while since I have worked on one of these newer radios, however.


~Cheers~

 

[Yeti Communications Ltd]

thats new

in the same circuit running at 5v would limit the vco range down a bit too ..but never heard of a 5v version

 

[sonoma]

I was thinking the R130 resister version runs about 5 volts. has been a while since I have seen one. I know if you unlock the clarifier you need to drop the voltage to 5 volts to get it to work properly.

http://downloads.cobra.com/CB/TSB/TSB10002.pdf