Cobra 29 no TX/Weak RX

[Vegas_Nick]

Radio Make and Model: Cobra 29 LTD
PCB Number:
PLL Number:

Test gear available: Watt Meter/Modulation Meter/Freq Counter/Signal Gen/VU Meter/Fluke Meter

Symptoms: Did the ERF 2030 mod as described here:
http://www.cbtricks.com/miscellaneous/f ... 29_mod.jpg
Was doing the final alignment when the TX went dead. Found D11 blown completely in half. No power output, no modulation.

What is working:
TX/RX switching on key up. RX is there but very, very weak even when directly injecting a signal.

What has been tried:
Replaced D11 1N4148, no help. Checked for 5V at D19 and R94. No voltage. (millivolts at best). Pulled R70 out of the board to isolate sections of the radio. 5V returned to R94.



Did it suddenly happen ?: Yes!

Anything else that may be of help?: After doing some reading I am guessing that I did not insulate the 2030 properly? Perhaps blown IC4? Will do some further voltage measurements when I return to the shop today. Plan is to pull the 2030 off of the board and try to get the RX back first.


Any thoughts/ideas are much appreciated!

[Vegas_Nick]

Nobody home?

[Vegas_Nick]

Ok, so I now have 5V at R94 and have R70 back in place. The 8V that is supposed to be at R41 is only about 2 Volts, so I am really leaning towards something gone awry in the audio section. Especially with D11 blown up.

[johny3329]

I have received a Synchro Landmaster, 6 channel 29MHz AM, for repair and I am looking for info on this unit. I cannot trace any on the internet. It is marked Sychro Landmaster, I have also seen Synchro Seamaster, on the front panel and Sea Hawk 2170 on the rear. It also has Australian type approval and the importer is given as President Electronics, Sydney. A number of Synchro models were imported to South Africa but I cannot trace who by.

The main PCB is marked Sea Hawk EPT271010z and the switch PCB EPT271040z. The third board restricts the number of channels and was clearly locally produced. The EPT prefix suggests Ranger or Galaxy but I have been unable to find the 271010 in any info I have access to.

Anyone in Australia/NZ have a schematic or any other info on these units?