2SA733 TRANSISTOR HELP

[dss56]

What is a good replacement for this 2SA733 TRANSISTOR What have you used.

thanks HAPPY NEW YEAR TO ALL

 

[BayouRadioAmplifier]

a good old 2N3906A should do.

what are you working on?

I usually use 2N3904/3906/2222 types to repair
or build most small circuits.

 

[dss56]

Its a cobra 29ltd the transmit is on all the time without the mic and suspecting tr21
to be shorted

 

[NZ8N]

Most likely culprit is C117 next to L3 is shorted. But, can be any of the other red circled items, too, these are either tied directly to, or low resistance to the PTT line of the Mic socket. last time I helped someone with a Cobra 29 a few months ago, that had TX all the time, it turned out to be a cracked (shorted) C121 up by the mic plug area.

 

[BayouRadioAmplifier]

yep, could be any of a few things.

here is what I would check..

with the mic out of the radio, measure the voltage at
TR21-base. it should be "high" about 8 V
if not, then find out why. maybe C117 is bad as mentioned.
And it sounds like you have about 8 V a TR21-collector if it is
in TX all the time.

if TR21 is bad, cut it off board, to be able to receive again.

..

 

[dss56]

Well
thanks guys I will try in next few days to look at it.
Dont have much time as scheduled for January 7th triple bypass surgery here in Boston Ma. Hope all will go well and then back to my daily routine.

HAPPY NEW YEAR TO ALL IN THE GROUP

 

[dss56]

Thanks all who suggested c117 that was shorted installed a new one and now radio works fine.

Happy New Year to all in the group