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Ranger built cobra 148F GTL

S

skybolt58

Active Member
Nov 9, 2008
189
9
28
Tug Hill NY
I went to test the bias on my 148f and set the driver to 30MA and went to set the driver and I get 0.00 reading on my meter,? even tried turning VR9 and it did nothing, this could be my reason only swinging to 7 watts max? what could the problem be? Final bad? am regulator bad, but tested on USB, or could it be the other regulator? HELP :(
 

skybolt58 said:
I went to test the bias on my 148f and set the driver to 30MA and went to set the driver and I get 0.00 reading on my meter,? even tried turning VR9 and it did nothing, this could be my reason only swinging to 7 watts max? what could the problem be? Final bad? am regulator bad, but tested on USB, or could it be the other regulator? HELP :(
Click to expand...

check the resister feeding the vr for the final bias adjust. the vr could also be bad. I have ran into the vr being bad on a few radios over the past few years. did any one do any mods to this ection of the radio. are the tp wires where they should be. what voltage are you getting at the center leg of the final also.
just a place to start.
 
I just reread your post and vr8 is the final bias. vr9 is the driver bias. and make sure you are hooked up to the right tp positions. also make sure the little fuse inside the meter is not blown. this will cause you meter not to register either.
 
sonoma said:
I just reread your post and vr8 is the final bias. vr9 is the driver bias. and make sure you are hooked up to the right tp positions. also make sure the little fuse inside the meter is not blown. this will cause you meter not to register either.
Click to expand...

Sorry I meant VR8 for Final.. I get 12 volts on the collector of both finals, I get 12 volts on TP8 keyed and unkeyed.

Set radio to CH 19, USB TX mode. MOD off.
Connect current meter to TP8 (+) and green
lead wire (-).
Connect current meter to TP7 (+) and violet
lead wire (-).
VR9
VR8
30 mA
50 mA
 
sonoma said:
check the resister feeding the vr for the final bias adjust. the vr could also be bad. I have ran into the vr being bad on a few radios over the past few years. did any one do any mods to this ection of the radio. are the tp wires where they should be. what voltage are you getting at the center leg of the final also.
just a place to start.
Click to expand...

Only mod done was extra channels and unlock clarifier. I am getting 12 volts on both? do you know what th resistor Number is? I couldn't find a service manual for the 148f ranger built with the EPT014811z board so I am using the man for the TR 296 Texas ranger, same board as the 148f
 
have you verified the fuse is not blown inside the meter. . the miliamps will not work if the fuse is blown. make sure the meter is set to dc miliamps also. it will not read on regular dc volt scale.
 
sonoma said:
have you verified the fuse is not blown inside the meter. . the miliamps will not work if the fuse is blown. make sure the meter is set to dc miliamps also. it will not read on regular dc volt scale.
Click to expand...

Yes the meter works, set the driver to 30ma and get 0.00 on the final
 
check for voltage at vr8 and the resisiter feeding it is R179 a 100 ohm see if you have voltage there. also check D49 at the final.

at cbtricks.com there is a service manual and schematics so you can look this stuff up and not have to wait for some one to reply
 
sonoma said:
check for voltage at vr8 and the resisiter feeding it is R179 a 100 ohm see if you have voltage there. also check D49 at the final.

at cbtricks.com there is a service manual and schematics so you can look this stuff up and not have to wait for some one to reply
Click to expand...

Thanks for the info, but cb tricks does not have the 148f info except for the freq counter? this is the ranger built 148f with the ept0148z board. big difference than the pc412 I think it is,

Now when I check for voltage on vr 8 is on tx?

Thanks
 
Here's a thought:
If you are getting 7w out; then there isn't anything wrong with either the final or the driver. In my limited experience, I have never seen any output with either part being fried.

Try peaking the output coils and see if the wattage doesn't come up a bunch.

Are you sure that the final hasn't been volted first?
There would be no current there if it had been bypassed by that mod.

FWIW . . .
 
Robb said:
Here's a thought:
If you are getting 7w out; then there isn't anything wrong with either the final or the driver. In my limited experience, I have never seen any output with either part being fried.

Try peaking the output coils and see if the wattage doesn't come up a bunch.

Are you sure that the final hasn't been volted first?
There would be no current there if it had been bypassed by that mod.

FWIW . . .
Click to expand...

No! it does not have the volted mod! when I got the radio it was only swinging to 4 watts, I did tune it up and that is the best I can get out of it is 6-7 watt swing, now with the AM power pot VR10, that does very little also, it only DK around 1 watt max. well bed time I will check this page out in the AM..
 
OK at R179 I get 7.40 volts on tx on the final on tx I get 7.6volts on the driver I get 6.4 volts on D49 I get .464mv on the vr8 diode of R179 I get the7.40 volts on the other side of r179 I get 8.2 volts
 

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