| Author |
Message |
    
Bmwed
New member
Username: Bmwed
Post Number: 1
Registered: 5-2014
| | Posted on Friday, May 23, 2014 - 8:17 am: | 
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Hello All
I have just acquired a Midland Road Max 77-160XLT. I have been told that when I transmit I sound muffled and distorted. The radio dead keys at 4 watts, and doesn’t go higher when I speak. My understanding is that the radio should dead key at say, 1 watt and swing to 4 as I speak. Therefore, Is this a case of over modulation? I have eliminated the coax, and the antenna (Shakespeare Bick Stick Base), as I have another radio which works fine. I found a list of the adjustment points for the radio, and modulation is pot VR204. Problem is, I can’t find any pot with that number, if indeed over modulation is the problem, or could it be something else?
Thanks
Ed |
Press_man
Advanced Member
Username: Press_man
Post Number: 770
Registered: 5-2008
| | Posted on Friday, May 23, 2014 - 5:04 pm: |
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L304/305/306 are power out, all the Midlands I've had like 3w carrier on AM. At 4w you could be getting a backward swing depending on the output stage. VR204 is a variable resistor and should be laying down and may be close to the audio transformer depending on the board layout. Turn it down till you get 95% modulation while saying auhhhh into the mic. Hope your meter has peak and modulation function! Do not use metal screw drivers!!!! Don't let any smoke out of the radio.
For experimental purpose only.
73 Pressman
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Dale
Senior Member
Username: Dale
Post Number: 2088
Registered: 12-2002
| | Posted on Friday, May 23, 2014 - 7:39 pm: |
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no not over modulated at all. actually
if deadkey is 4 watts with no swing then
you only have little audio which is probaly
why its distorted.if it was overmodulated
you would have the complete OPPISITE. it would
swing way past 4 watts.imho i try to find a cb shop
and have them properly tune it.also make sure
mic gain is all way up.if you can find the power
vr pot turn it down so radio keys 2 watts.only go
1 watt if ya gonna run a low drive amp with it.
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Bmwed
New member
Username: Bmwed
Post Number: 2
Registered: 5-2014
| | Posted on Tuesday, August 05, 2014 - 7:49 am: |
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Thanks for the replies. I think I found the problem. I am not getting audio from the PA, just a click when I key up. Which would lead me to think that it’s the microphone or the audio chip. I will swap out the mic and check, does anyone off hand know the part number for the audio chip? I’m thinking is probably a TA7222AP. Can’t see the number as its facing the chassis.
Thanks
Ed |
