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Uniden Grant has carier but no audio output

R

rainmanhsv

Member
Jun 25, 2011
4
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Hello, I recently picked up a Uniden Grant at an antique store, it has the PC-409 board in it. The radio receives fine and puts out a 4 watt carrier on AM but has no audio output, the mic is good ( I have checked it on another radio) I went ahead and replaced the audio IC (TA7222AP) and nothing changed, it has 0 output on SSB and nothing through the PA, I checked C95 and it is good, I'm hoping someone here can point me in the right direction on what to check next.

Thank you!
 

Dmans said:
Is the mike amp healthy? Getting enough to eat? (voltage, audio, etc)

73
David
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Hello David, thanks for the quick reply... I'm honestly not 100% sure how to check the mike amp, I have some degree of expertise with electronics but not enough to know where to begin to check that, but if I knew what to look at I could test it.

Thank you!
-Matt
 
do you have a scope?

if so, we can check the audio coming in to the mic jack and try to trace it through the mic amp sections.
This is a bit above "basic repair" levels, but if you are willing to try, we can try to help.

If not, or if you don't think you want to mess with it on a component level, PM me here on the forum and i can provide some other options.
LC
 
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loosecannon said:
do you have a scope?

if so, we can check the audio coming in to the mic jack and try to trace it through the mic amp sections.
This is a bit above "basic repair" levels, but if you are willing to try, we can try to help.

If not, or if you don't think you want to mess with it on a component level, PM me here on the forum and i can provide some other options.
LC
Click to expand...
Hello LC, I unfortunately do not have a scope... it is possible that I could get access to one but I'm not 100% sure that I will be able to, I was hoping to save this radio because it's in such great shape cosmetically and appears to have never been modded.

-Matt
 
Definitely check C18 as Nomad suggested.

If you do decide to replace C18, you can use a larger value for better filtering on the mic amp. It can help to eliminate mic squeal.
100-470uf will work fine.
LC
 
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Good point. We found that the factory value for that cap would permit some radios to 'squeal' when the AM carrier is turned down. A 470uf part puts and end to that.

How much smaller the value can be, I never tried to find out. Once we saw that boosting this part's capacitance to 470uf worked, we moved on to other questions.

73
 

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