Cobra 25 issues

[338_MtRushmore]

I have two cobra 25's that have been boxed up due to problems.

The first is a Chinese unit that actually sounds amazing on tx, but it has no rx audio. The needle will swing with rx, but nothing on internal or external speaker. Any idea where to start?

The second is a Philippine unit. This one has audio issues. Sometimes the internal speaker can't be heard, and sometimes it is loud. I'm wondering if it is in the external speaker jack. Just as I think it is fixed, it will cut out again. I also used the speaker out of the other 25 with the same results. An external speaker seems to always work.

Any help would be appreciated, thanks.

 

[Robb]

Check the vol knob for excessive play - first off.

 

[338_MtRushmore]

Check the vol knob for excessive play - first off.

The knob is tight with nice resistance, and was cleaned with deoxit.

 

[Robb]

My next guess would be a bad cap in the audio circuit of the Philippine, since that radio is around 20 years old. It could be the jack itself, as I've seen these fail before.

The Chinese radio may just have a bad audio chip.

 

[redbeast]

My next guess would be a bad cap in the audio circuit of the Philippine, since that radio is around 20 years old. It could be the jack itself, as I've seen these fail before.

The Chinese radio may just have a bad audio chip.

Hey 338, does it change if you grab the antenna jack and move it up and down?? My 25 had a bad solder joint at the resistor directly under the antenna plug.

 

[Robb]

Hey 338, does it change if you grab the antenna jack and move it up and down?? My 25 had a bad solder joint at the resistor directly under the antenna plug.

If you re-read his first post, the receive meter moves with a signal present.
So the radio is receiving; just no audio output.

 

[sp5it]

What is a voltage on 455kHz ceramic filter in and out pins?

 

[redbeast]

What is a voltage on 455kHz ceramic filter in and out pins?

Ok, Rob....i defer and did reread. Sounded like a problem with mine, but -hey, I'm not a tech and do not try to talk over my head. Justa thought was all.

 

[338_MtRushmore]

The Chinese is working now, so I'm guessing it is a bad solder joint.

I'm thinking the external speaker is working 100% on the philly, but the internal is still hit and miss. I assume the audio output is the same, it is just switched at the ext speaker jack. I worked the jack with a pick, trying to make contact but still couldn't get it to work.