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Cobra 29ltd classic : no rx / tx

Radio was plugged in backwards , with 3 amp fuse inline . I replaced d23 , and fuse ,brought it back to life .I tried several ( known good ) mics .Still no rx / tx .
Altho the rx / tx light does switch back and forth showing rx / tx

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  • ejramsey Feb 05, 2008

    Thanks for advice , I will let you know how it turns out .

    Thank You

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Hi,

D23 is the reverse protection diode and it shorting is the primary reason your fuse blew. As you posted, power was applied in reverse, hence other components would also fail. Pls check:
1. D22 - 9.1V Zener Diode
2. TR23 (2SC1096) 9 Volts regulator
3. D19 - 5.1 Zener Diode
4. IC4 (TA7222) - Audio Amp
5. TR14 (2SC2029B/10) - Finals
6. TR15 (2SC2028B/20) - Driver
7. Most capacitors over 220uF (like C123, C114 & C112)

Hope that this be of help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Posted on Feb 04, 2008

  • Radio-tech155 Nov 12, 2015

    not all had a ta7222ap for an audio chip. they switched to a TDA2003 ..

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