Working on a grant xl for a friend of mine. This one has the 8719 chip in it and has had the 10khz channel mod done to it. It came to me with the complaint of no/weak rx. Checked the caps and double checked the channel mods. All seems ok. Here is the issue, it will rx like normal if you have a speaker hooked into the pa jack. No tx when in pa mode but it is working. No resistor across the jacks either. Any ideas? The hi/lol switch and bright/dim switch was used for the channel mod.
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Uniden Grant xl odd rx
- Thread starter 200eazy
- Start date
clean the external speaker jack or check to make sure it does not have a bad solder joint,,,,has he been using a external speaker? it could have made the jack go south some way,,,,,
you should read the owners manual.
the receive audio is routed through the PA speaker when you plug one in.
this is normal operation.
as midnight special already said, check the external speaker jack.
looking at the schematic, you should be able to jumper around the connections in the jack and find your problem. you can also see how plugging in a PA speaker takes the external jack out of the equation.
my guess is that the external speaker jack is worn out and not making good contact any more.
one easy way to check this would be to switch the PA and EXT SP jacks around and see if the problem follows the jack.
LC
the receive audio is routed through the PA speaker when you plug one in.
this is normal operation.
as midnight special already said, check the external speaker jack.
looking at the schematic, you should be able to jumper around the connections in the jack and find your problem. you can also see how plugging in a PA speaker takes the external jack out of the equation.
my guess is that the external speaker jack is worn out and not making good contact any more.
one easy way to check this would be to switch the PA and EXT SP jacks around and see if the problem follows the jack.
LC
Pulled the jack and could see no visible issues. Installed a new jack just for good measure. Still the only way to get rx audio on the cb side is with the jumping resistor across the pa and ext jack. Stumped on this one. Fixed a few poor looking solder joints but still no audio from the ext speaker when in cb mode.
Yea the mic is in and it’s a good mic. So it has been covered the rx coming through the pa while in pa mode is normal. Switch it to cb mode and the rx audio stops. It is still receiving as it can be seen on the meter. The channel mod was done prior to it coming to me and the hi/lo switch now serves as one of the switches to pull the channels down. There is a black wire and a purple wire sharing a leg on one side of the switch. Purple wire runs to the board and the black runs to the squelch control. Makes me wonder if the actual rx audio has been bypassed when they rewired to use the switch.
If it has talkback, he should get some receiver audio with the mike unplugged.
Never have had a diagram that shows wire colors. The only missing link has to be the PA switch, or the wire from the PA switch to the external speaker jack. The internal speaker gets fed from the switch inside that jack.
Bad PA switch? Would be nice if I had a XL here to look inside.
The wire from the PA switch to the external speaker jack is where I would look next.
73
Never have had a diagram that shows wire colors. The only missing link has to be the PA switch, or the wire from the PA switch to the external speaker jack. The internal speaker gets fed from the switch inside that jack.
Bad PA switch? Would be nice if I had a XL here to look inside.
The wire from the PA switch to the external speaker jack is where I would look next.
73
i agree with nomad, if the jack itself is ok, and there are no cut traces back there; then the next culprit is the CB/PA switch wiring.
use this schematic as it should be pretty close if not the same:
http://www.cbtricks.com/radios/uniden/grant_lt/graphics/Grant_ltsch.gif
trace the wires on the switch and compare to your radio to see if you have a missing wire or one that looks to be connected but is actually broken off.
it's not uncommon to see a problem crop up on a switch right next to another that was being messed with (channel mod).
LC
use this schematic as it should be pretty close if not the same:
http://www.cbtricks.com/radios/uniden/grant_lt/graphics/Grant_ltsch.gif
trace the wires on the switch and compare to your radio to see if you have a missing wire or one that looks to be connected but is actually broken off.
it's not uncommon to see a problem crop up on a switch right next to another that was being messed with (channel mod).
LC
It did not have factory talk back. I installed the resistor across the jacks. This brought full audio to the ext speaker. It’s switching from cb to pa mode but I’ll look at it again. Question if c77 is shorted, would the audio on the pa side still work as it should? It is a tantilium cap.
C77 being shorted would only affect the receive if the tone control was soldered together in the LO tone position after the switch was converted for use as a channel mod.
it would affect the receive in both CB and PA modes, as that audio is picked off after the audio chip, which is downstream of where this cap does its thing.
a neat mod i have done for a few customers who expressed interest is to add a 5K linear taper trimmer resistor between C77 and ground with the trimmer wired as a rheostat (one end tied to wiper).
this gives an internal tone control that can be set to the listener's preference and then forgotten about inside the radio.
obviously you want to get the radio working before trying this, but it is a cool option to have.
LC
it would affect the receive in both CB and PA modes, as that audio is picked off after the audio chip, which is downstream of where this cap does its thing.
a neat mod i have done for a few customers who expressed interest is to add a 5K linear taper trimmer resistor between C77 and ground with the trimmer wired as a rheostat (one end tied to wiper).
this gives an internal tone control that can be set to the listener's preference and then forgotten about inside the radio.
obviously you want to get the radio working before trying this, but it is a cool option to have.
LC