148 gtl low sound on am only

[kaos513]

Helllo guys I recapped my 148gtl due to a leaking cap I have loud sound coming out of the speaker on usb and lsb but am sounds very low any help would be appreciated.

 

[ExitThirteen]

Sounds like the RX chain could use a realignment. Has the radio had a realignment done after the recap? Also, double check your work to make sure you don't have a cap soldered in backwards. Let us know how you get on.

~Cheers~

 

[kaos513]

Its a 148gtl don't know what year it is has white power jack says tiawan ,also I'm trying to look for alignment procedure for it thanks.

 

[ExitThirteen]

Taiwans are made from about 1981 to about 1989. There may be an alignment procedure on CBtricks.com. Try looking there.

~Cheers~

 

[sonoma]

look here on the cobra site to see if it has what you need.

http://downloads.cobra.com/CB/Models/148-SERIES/

 

[loosecannon]

you can use this to align your 148gtl: http://www.cbtricks.com/radios/cobra/2000gtl/graphics/cobra_2000gtl_sm.pdf

like exit13 said, check your caps polarity, but AM will be quieter than SSB on a properly working radio without an antenna connected.
LC

 

[kaos513]

Taiwans are made from about 1981 to about 1989. There may be an alignment procedure on CBtricks.com. Try looking there.

~Cheers~

I Started tuning L19 I get 3.2v on channel 1 but on channel 40 in get 4.6v .

 

[loosecannon]

the truth is kaos, that the VCO adjustment specs are different for different versions of this chassis.
for example, the SAMS for the Uniden Madison, which is the same on the inside as the 148 and the 2000 shows to set the VCO coil for 5.00 volts on channel 40.

so, unless the radio has extra channels in it, set L19 for 3.5 volts DC on channel 40, and just check the voltage on channel 1 to make sure it's around 2 volts DC or so.

then just make sure you can key the mic on both channels 1 and 40.

rule of thumb with a VCO is that if you can key the mic and transmit a carrier on AM, then your VCO is locked.

If your radio does have extra channels, then you tweak the VCO coil ever so slightly on your lowest and highest channels until it will lock on both. then you leave it there regardless of what the DC voltage is.
LC

 

[kaos513]

k will try later and report my numbers this might help others in the future.by the way its all stock.

 

[kaos513]

k will try later and report my numbers this might help others in the future.by the way its all stock.

Channel 1 I get 2.9v on channel 40 I get 4.2v.

 

[Robb]

Channel 1 I get 2.9v on channel 40 I get 4.2v.

So long as the PLL stays locked and on freq and the working voltage is less than 5v, it is acceptable - IIRC . . .

 

[kaos513]

So long as the PLL stays locked and on freq and the working voltage is less than 5v, it is acceptable - IIRC . . .

Yes its right on frequency on all channels.

 

[kaos513]

Yes its right on frequency on all channels.

Now waiting to put a new face on it i will show pictures this week thanks

 

[kaos513]

Taiwans are made from about 1981 to about 1989. There may be an alignment procedure on CBtricks.com. Try looking there.

~Cheers~

Did some research its from 1978

 

[sonoma]

here is a voltage chart if you want to verify any voltages are off. could help.

http://downloads.cobra.com/CB/Models/148-SERIES/148voltages.pdf