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Message |
    
Pickj
New member
Username: Pickj
Post Number: 1
Registered: 12-2008
| | Posted on Friday, December 12, 2008 - 10:35 am: | 
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I have a President Lincoln unit that I purchased new. Used several years then packaged for storage. Removed unit a few weeks ago to check over, and sell but I now have a unit that mysteriously does not transmit. The only modification that was made by me when purchased was frequency expansion, 26 to 29.9. When I press the PTT on the mic, I get a "TX" on the display but the unit does not come out of receive mode. When I press the CW key while in the CW mode, I get a faint side tone and again the unit does not come out of receive mode. I measure 7.7 volts out of the 8.0 volt regulator. I have also checked several of the "transistor" switches ie TX, RX, TX cont, AM Mod, and CW switches, all test okay out of ckt. When I press the PTT or depress the CW key, I see absolutely no change in voltages on any of the switches. IS THERE A SIGNAL FROM THE COMPUTER THAT EITHER PROHIBITS OR ENABLES THE TRANSMIT ??? I am not able to transmit in any mode. What I need here is more patience.............. help ! |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4433
Registered: 7-2004
| | Posted on Friday, December 12, 2008 - 9:06 pm: |
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used to see that with old relay switched radios, even microphone slide switch problems, but you say nothing from a cw key, either, hmmmmm...... |
Pickj
New member
Username: Pickj
Post Number: 2
Registered: 12-2008
| | Posted on Saturday, December 13, 2008 - 9:24 am: |
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I am thinking that IC104 may be the problem. I know that the PTT on the mic and the wiring from there to the radio is in tack because of the "TX" being displayed when pressing the mic button or the CW key. I am going to order a new chip for IC104 (NJM4558S) and go from there. According to the block diagram that I have, 1/2 of that chip is mic amp and the other 1/2 is PTT SW. The CW portion of the ckt in this transceiver looks like it goes "indirectly" to IC104. If changing IC104 doesn't fix the problem, I don't know ......... I'll have to re-group. |
Pickj
New member
Username: Pickj
Post Number: 4
Registered: 12-2008
| | Posted on Friday, December 26, 2008 - 5:11 pm: |
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Purchased a NJM4558S 9 pin dual op amp chip, installed and still have the same problem. All of the data sheets that I find on the internet for this chip show a 8 pin chip??? I don't believe that the computer in this radio either prohibits or enables the transmit. Does anybody have any suggestions. |
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