Cobra 2000 GTL

[lucas]

I know this has been posted 100000000 times, but its a bit diffent this time, I want to add the extra channels to my Cobra 2000 GTL which uses the Unmod'able PLL chip. HOW ever my buddy that i gave my grant XL to, it has the mb8719 PLL chip, the one i need. My question is, if i take the chip out of my Cobra put it into the grant and took the one from the grant and put it in to my cobra will this work. I know the 8719 chip should work in the cobra. Also what else would i need from the grant to finsh this idea up..


Thanks Guys

[Night Crawler]

Also what else would i need from the grant to finsh this idea up.

The mixer crystal.

[lucas]

which one is that, mixer crystal..

[Night Crawler]

Crystal X3 I think the frequency is 11.3258mhz.

[TheCBDoctor]

Hi lucas,

Unless the PLL MB 8719 is the Fujitsu made in Japan it will not work. The PLLs are different. There is no Divide by"N" function on the MB 8719 not made by Fujitsu. This would be PIn 10. The Loop crystal is the same in both radios it is the 11.3258 MHz and will not have to be changed. The Cobra 2000 GTL uses an 11.325 and is close enough.

You can get the Fujitsu PLL made in Japan out of a Philippine Cobra radio 148 GTL or the Cobra 142 GTL. Click on my Website for a complete explanation.

Good luck,

Respectfully

[lucas]

Hi lucas,

Unless the PLL MB 8719 is the Fujitsu made in Japan it will not work. The PLLs are different. There is no Divide by"N" function on the MB 8719 not made by Fujitsu. This would be PIn 10. The Loop crystal is the same in both radios it is the 11.3258 MHz and will not have to be changed. The Cobra 2000 GTL uses an 11.325 and is close enough.

You can get the Fujitsu PLL made in Japan out of a Philippine Cobra radio 148 GTL or the Cobra 142 GTL. Click on my Website for a complete explanation.

Good luck,

Respectfully

Under stood loud and clear. I did some more homework last night on this little project. And that was one of the problems i had in mind, If it isnt a fujitsu chip i may as well forget that plan, if it is im good to go. Would it be marked on the chip if it is?

[lucas]

they say a picture say's a 1000 words, well here one

[lucas]

this is whats in the grant xl

[lucas]

this is whats in the grant xl

execpt the bottom numbers read 9405 r43 instead of 8323 c71

[TheCBDoctor]

Hi lucas,

The original MB 8719 is clearly marked "Fujitsu made in Japan" If it doesn't say that then the PIn 10 function will not give you uppers. Pin 11 will still give you lowers and that seems to be the case with your mod. I found a supplier that specializes in hard to find obsolete parts. He found some in Japan; the cost was $61.95 per PLL with a minimum order of 10.

I suggest finding scrap Taiwan or Philippine MB 8719 chassis radios. The Cobra 148 GTL, Washington base, Cobra 142 GTL all have the PLL you need. The cost would be cheaper and it is rare that a PLL will fail for no reason. I am sure you can find these chassis on eBay or a yard sale. I have a few that I keep for my repairs. Any chassis that is made in Malaysia or China will not work. If it says RCI or Ranger, then it will not work.

If you want uppers you can order a crystal 11.4758 MHz and put it on a switch to switch between the 11.325 and the 11.4748. This will give you 40 channels above CB. If you keep the lowers you can get a number of "A" channels as well. The 11.4758 is a common cut crystal and does not have to be specially ordered and cut. I suggest getting an 11.3258 MHz crystal as well because these are also common cut crystals. This way you won't have to play with the Voice-lock going from the CB band to the uppers. For lowers order 11.1758 MHz for 40 below.

Good luck, and keep me informed on how you make out. If I can answer any more of your questions just ask. One thing more if you unlock the voice-lock you must use the 11.3258 MHz loop crystal or the USB will have to be turned to the 3 o'clock position because L59 will not adjust far enough with the 11.325. The tuning slug will bottom out.

Respectfully

[fat boy]

Hey cb doctor can you draw me a schematic to use to install the switched crystal mod and does the radio need realignment after doing the switched crystal mod?

[TheCBDoctor]

Hey cb doctor can you draw me a schematic to use to install the switched crystal mod and does the radio need realignment after doing the switched crystal mod?

Good morning fat boy,

When switching crystals one has to keep in mind stray capacitance and inductance created by any length of wire running to the 11.3258 mixing crystal. I have seen mods where one side of the crystals that I have previously posted would all be tied together at one point, and a switch would be used to switch in one of the three legs of the switching crystals. (11.1758 MHz-low /11.4758 MHz Upper/ 11.3258 MHz CB band) There is always a problem with added reactance when switching from one band to another; the frequency will not align and you may have to clarify that band. Some mods add adjustable capacitors to compensate.

I found it is best to use a relay that can handle 27 MHz and place the crystals on the relay at the point where the 11.3258 MHz mixing crystal goes. This way the length of wire won't matter. You will only be able to switch between 2 bands unless you get creative and use 2 relays.

The best thing to use is an "N" kit, which comes with the 11.1758 and 11.4758 MHz crystals. You just take the mixer crystal from the board (11.3258) and place it on the kit in the empty crystal socket. If the radio uses an 11.3250 MHz crystal you will need to compensate on the CB band by using the voice-lock. It is best to use an 11.3258 MHz crystal found on most MB-8719 chassis to avoid this.

Keep the wire from the "N" kit as short as possible and adjust the upper and lower channels using the variable caps on the "N" Kit. It is an easy conversion if you can still find an Expo "N" Kit.

Good luck with your project,