| Author |
Message |
    
Jake
| | Posted on Saturday, February 08, 2003 - 10:51 am: | 
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I have a tiawan made 148gtl that everything works except the "am receive". vol,squel,mic gain,pa,everything. when you connect the coax with the volume up you get no increase in noise or anything, It's like you didnt connect the coax up at all. can you please help, thanks jake. |
2600
| | Posted on Sunday, February 09, 2003 - 9:06 pm: |
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Uh, did you try SSB receive? If my hunch is right, SSB receive is dead, too. I'm betting that transmit works okay, and that the S-meter (if it isn't stuck) still kicks around on channel chatter.
If ALL this sounds right, find C186, a 220 uF TEN VOLT capacitor, next to the TA7222 audio power chip. Unsolder one leg of C186 or just pull it out completely. Power up the radio. If the receiver audio returns, replace C186. A higher voltage rating is a good idea. The capacitance value can be anything from 100 uF to 470 uF. 220 uF is fine, but not a PRECISION spec. It DOES have to be small enough to fit. If you just leave it out, receiver audio will be wimpy, but not dead.
73 |
Jake
| | Posted on Monday, February 10, 2003 - 12:08 am: |
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2600 thanks for the help everything works except the receive. It trans fine in ssb and am, it receives fine in ssb both usb and lsb,the s-meter works fine only in the ssb mode however when you switch to AM you get just a loud rushing noise just like pink noise and the s-meter is inop, it just doesn't want to receive in the AM mode |
2600
| | Posted on Monday, February 10, 2003 - 10:42 am: |
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Hi Jake,
Now that I have more of the picture, the stuff I said about capacitors doesn't sound relevant.
Loud rushing noise and no S-meter on AM receive? That's not a common one, at all. If it was dead silent on AM receive, I'd know what to check first. My only educated "guess" concerns L3, L13 and L14, the three IF transformers (slug-tuned 'cans') with the large hole and large screw slot on top. Trouble is, they're tough to test.
Sounds more and more like a job for someone with a 'scope, diagram and spares for those three IF 'cans'. IT could be one of a dozen small ceramic disc capacitors in that section. They ALMOST never fail on their own. When they do, it turns into a real "Sherlock Holmes" adventure. Sorry I can't narrow it down much more than that.
73 |
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