| Author |
Message |
    
Troyota
Junior Member
Username: Troyota
Post Number: 32
Registered: 4-2004
| | Posted on Saturday, June 21, 2008 - 1:39 am: | 
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ok this is strange. i have just bought a superstar 3900 turbo zx, with built in frequency readout. dual finals with the ept360014b board. when i key the mike it has a chirping sound on tx with a 1w carrier. not feedback etc as i cant hear it. i can go outside in my mobile and have someone key it and hear it then transmitting. it has no modulation just this sound. it bumps the meter from 1w to 2w when it chirps. when i turn up the variable key it goes to a solid squeal on tx. also when i go to ssb it is transmitting a carrier squeal. on fm it does nothing, no carrier.
this is not a mic issue as i have tried many different ones with no change. i can turn the mic gain all the way down or up with no change. it was hacked up a bit on the inside. but i have repaired most of it. the mod resistor i havent replaced yet. but i did put back tr32. and remove some kind of super mod or something, but with no change. sorry so long just trying to give as much info as possible.
thanks |
Starface
Senior Member
Username: Starface
Post Number: 1968
Registered: 1-2005
| | Posted on Saturday, June 21, 2008 - 2:17 am: |
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It still sounds like it might be a Mic issue, maybe not the mic it's self but maybe a bad solder joint on the radio plug on the inside of the radio and if so no matter how many mic's you chance it's not going to matter if there is a bad radio plug ( Pin,Missing or lose wire)
Just a thought.
George
CEF#Ø476
KI4NBE Amateur Extra
HAM#Ø181
CVC#ØØ14
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Troyota
Junior Member
Username: Troyota
Post Number: 33
Registered: 4-2004
| | Posted on Saturday, June 21, 2008 - 11:20 am: |
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thanks for the reply. i had already thought of that. i have pulled the plug and checked it thorughly. checked for cracked traces and cold solder joints. checked pins for looseness and continuity with my tester. also checked where it goes into the board. im thinking some component insideis failing. maybe im out in left field tho. any more suggestions?
thanks again |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2525
Registered: 1-2005
| | Posted on Saturday, June 21, 2008 - 1:10 pm: |
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I would say that it needs to have a complete alignment of the receiver and transmitter. Done by a pro with the necessary gear.
Even though you have repaired the "hack" jobs inside much more could be wrong or just out of wack. Problems you cannot detect by ear you can discover by looking at the waveform on a scope.
Bet it's in need of just a basic tune up.
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Troyota
Junior Member
Username: Troyota
Post Number: 34
Registered: 4-2004
| | Posted on Saturday, June 21, 2008 - 4:51 pm: |
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id say you are right on it. because the frequency counter is off nearly a whole channel. i can clarify it to be on frequency but it is way off center. then it receives on frequency.
they took out c43 and put some kind of kit in it with a little board and components on it. 4 wires ground, hot, and each side where c43 was. they aso put the diode super mod in it at location r240. they used 2 diodes and 2 resistors in parallel. the thing is one diode stripe pointed one way, and the other one the other way.
anyway im still trying.
thanks for the replys |
Carolinagold
Member
Username: Carolinagold
Post Number: 91
Registered: 12-2002
| | Posted on Wednesday, July 02, 2008 - 1:38 pm: |
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Troyota i worked on a SS3900 that had the same problem. what i found is there was a resistor solider'd to the back of the mic gain pot. all i done was clipped it and the chirping and junk went away may not be a resistor on the back of yours but worth a look.
JAMES
CAROLINAGOLD
865
CEF#416
CCRC#2
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Troyota
Junior Member
Username: Troyota
Post Number: 35
Registered: 4-2004
| | Posted on Friday, July 04, 2008 - 5:21 pm: |
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thanks for the info, i will check into it. i sent it to a tech friend of mine, but havent heard anything from him yet.
thanks for the response |
Foxhunter
Junior Member
Username: Foxhunter
Post Number: 34
Registered: 4-2008
| | Posted on Thursday, July 10, 2008 - 7:58 pm: |
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I have asked about that at an Amateur shop then subsequently read about in several places that a "chirp" upon keying is an indication of voltage drop. That may suggest possibly a need for more supply or bigger supply lines. Anyone else think this may be the case? |
