Cobra 29LTD chrome T1 question

[Crambone]

I believe my T1 (EI 28) is bad but would like to test it. I removed it but not sure how to check it. I looked at the data sheet but I’m not sure? I found D8 cracked.
The issue is 0 output when I key it goes out of RX but no TX light or output even if I connect scope directly to coax.

 

[buickid]

I believe my T1 (EI 28) is bad but would like to test it. I removed it but not sure how to check it. I looked at the data sheet but I’m not sure? I found D8 cracked.
The issue is 0 output when I key it goes out of RX but no TX light or output even if I connect scope directly to coax.

I hardly call myself a tech, but I do know you're definitely not supposed to be connecting radios to scope inputs...

 

[Crambone]

I hardly call myself a tech, but I do know you're definitely not supposed to be connecting radios to scope inputs...

Your correct but with zero watts out on my watt meter into a load I connect to see if any very weak signal is present.

 

[Handy Andy]

D8 - If I have my boards correct, is a 1N4003 - (try to replace it with a 100PIV rating) that is the diode that is from the output of the Audio Transformer (Modulator) and just keeps everything Positive towards the Driver and Final - so that would explain no power.

But a "cracked" D8 also means a LOT of power might have surged thru it into the Driver and Final - damaging the output of D8 and possibly both other parts in this process.

Continuity check is needed and the Driver and Final can be tested - see if they can still work - otherwise you'll have more work to do.

Google a search for CB Tricks website and call up the Cobra >> 29LTD - index and see if any information on it can help you with this radio.

 

[nomadradio]

D8 cracks when either the driver or final transistor (or both) fail as a short circuit.

**AND** the fuse size is dangerously excessive.

Should be 2 Amp. Frequent first response when the 2 Amp fuse trips is to replace it with one that has a higher current rating.

The higher the rating the more damage.

D8 is the casualty here, not the cause of the trouble. If you have loud speaker audio, then T1 is not bad.

Yet.

73

 

[Crambone]

D8 cracks when either the driver or final transistor (or both) fail as a short circuit.

**AND** the fuse size is dangerously excessive.

Should be 2 Amp. Frequent first response when the 2 Amp fuse trips is to replace it with one that has a higher current rating.

The higher the rating the more damage.

D8 is the casualty here, not the cause of the trouble. If you have loud speaker audio, then T1 is not bad.

Yet.

73

Ok thank you I pull the final and driver and check. Appreciate the help everyone!