| Author |
Message |
    
Thunderbolt
| | Posted on Wednesday, July 24, 2002 - 9:54 am: | 
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All lights are lit but no Tx or Rx. I jumped out all the mic connections and that isnt it. Just a slight pop in the speaker when I key the mic. Needle does not move at all.There are 2 capacitors near the MC145106 PLL(IC5) that get very hot. The heat is coming from that area. If it is the regulator,where is it and what does it look like? I do some repair work on radios but I am still learning. |
307
| | Posted on Thursday, July 25, 2002 - 9:27 am: |
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Do you have 5 or 8 volts on the PLL? If not common trouble is the Electrolytic Capacitor that filters the DC to the PLL...(right next to it / 100uF/15 Volt)
307 |
Thunderbolt
| | Posted on Thursday, July 25, 2002 - 1:45 pm: |
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Well,I am not sure where to test for 8 volts at on the PLL. I do show 8 volts across 2 oposite pins at divit side of PLL. I did replace the chip with another one same # and I replace the power regulater(green A473)and got no results. |
307
| | Posted on Thursday, July 25, 2002 - 2:11 pm: |
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You just did...Just because a rig does not TX/RX means the PLL is bad right away. As a matter of fact PLL's very rarely go bad. In MOST cases IF the TX indicator comes on even if it does not TX , The PLL is ok because the TX indicator only works when the Lock Detector circuit in the PLL is operating correctly. If the reference is lost or some other component and the PLL Lock Detector goes to a different state, the TX indicator will not work. This has been a trick for years to an experianced tech , to use the TX / RX indicator as a troubleshooting tool. I am positive that if "heat" is generated in a certain area that a componant is shorted , most likely an Electrolytic Capacitor that clamps the voltage and the current limiting resistor (presumed) is whats getting hot. That should be a snap to fix but guessing on where (posting where you should look) is impossible. If you want me to fix it email me direct at tech307@copperelectronics.com |
Thunderbolt
| | Posted on Thursday, July 25, 2002 - 4:39 pm: |
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I replaced the hot capacitor near PLL and got it working. The old one was a 220uf/10v and all I had was a 220uf/25v but it worked. Now the radio only keys 4 watts and swings to 20 on AM. It swings to around 40 watts on SSB. I have cranked mod open but still cant get it to swing on AM.The AM power only moves up the dead olong with the swing. I can get about a 25 watt key and a 30 watt swing before it starts swinging backwards. Is there any adjustment to get it to key around 4 watts and swing to 30 or so on AM? and does the capacitor I replaced it with have any effect on radio? |
Thunderbolt
| | Posted on Thursday, July 25, 2002 - 2:29 pm: |
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The Tx indicator does NOT light up when I key the mic. Are you saying that the Capacitors that are getting hot may need replaced? I was hoping to solve this problem myself with your help of coarse. I want to grow up and be just like you. hehe. This board has been a wealth of info for use wanna be radio techs. I usualy stick to the simple stuf. |
2600
| | Posted on Friday, July 26, 2002 - 12:13 am: |
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I have gotten into the habit of replacing ALL the 10-volt rated electrolytics in a radio whenever the first one of them fails. For some reason, the 10-volt rated parts just die sooner. Once the radio is old enough for one of them to go, others seem to follow soon after. Pulling the other 3 or 4 of them and putting in a 25-volt or higher part saves on callbacks. The 16-volt and higher parts don't seem to have this lifetime problem until they get up to 20 or 25 years old. Putting a voltmeter probe on the center pin of that (2S)A473 would be wise. It should be between 8 and 9 volts. Higher OR lower will probably mean trouble.
73 |
