29 Ltd Classic Weak To No Receive

[roy]

Ok first post so here goes.
I have a 29 with weak to no receive lots of static,rf gain works shows 4 to 5 watts output on meter and scope shows modulation good carrier and its on frequency.
Check voltages in tr7 and other trans in receive path and they all read what they should if i was transmitting only im not transmitting.
Its like the receive side thinks i have the mike keyed up only i don't.
Everything works just like it should when i key the mike.
Im not a total beginner but i dont have alot of experience trouble shooting

 

[Robb]

Are you sure that it isn't a mic problem; because that is what you have described.

 

[roy]

I have used 2 different know good mics.

 

[mechanic]

I have used 2 different know good mics.

Ok first post so here goes.
I have a 29 with weak to no receive lots of static,rf gain works shows 4 to 5 watts output on meter and scope shows modulation good carrier and its on frequency.
Check voltages in tr7 and other trans in receive path and they all read what they should if i was transmitting only im not transmitting.
Its like the receive side thinks i have the mike keyed up only i don't.
Everything works just like it should when i key the mike.
Im not a total beginner but i dont have alot of experience trouble shooting

Ok first post so here goes.
I have a 29 with weak to no receive lots of static,rf gain works shows 4 to 5 watts output on meter and scope shows modulation good carrier and its on frequency.
Check voltages in tr7 and other trans in receive path and they all read what they should if i was transmitting only im not transmitting.
Its like the receive side thinks i have the mike keyed up only i don't.
Everything works just like it should when i key the mike.
Im not a total beginner but i dont have alot of experience trouble shooting

The receive IF chain may have a bad component or the IFs have been changed. I would suspect the last one if the radio was bought used and depending on age, there may be a failing component. Most likely an electrolytic capacitor.
There is an electronic switch between receive and transmit, usually a diode with buffer capacitors, these could be shunting the receive signals to ground. Since you are hearing static, this fault may be unlikely.

73 mechanic

 

[roy]

I fed a test signal at 27.185 30% modulation radio on 19 could just barely hear it.
It does get quiet with mic unplugged and comes back when it is plugged back in like it should.
Radio is a buddies it is pre-soundtracker so guessing fairly old.
Checked some of the diodes in the receive circuit and they conduct both ways but i havent lifted one leg to check off board i need to get some more de-soldering braid.
From looking at the radios a recap wouldnt hurt anyways.
I dont see any leakage and no bulges anywhere though.

 

[Robb]

As I really don't like to recap radios; I will only do it if they are 20+ years old or older. It could be a bad cap; but doubt it. If there are any 10v caps in that circuit; then by all means replace them with a higher voltage cap.

You could put the signal back in and test transistor voltages through the stages. But as a hunch, I would check back from the mic circuit too . . .eg the receive wire path.

BTW - did you test the audio chip by trying the PA function yet?
Or tr23? Does the receive meter respond to the signal input?

 

[roy]

The.meter is bad stuck in one spot with radio on or off i have one in the junk box to replace it.
Haven't tested the pa function need to get my speaker from work.
Ill try to trace the signal through and check tr23 and the audio chip this weekend.
And thanx to all for the help so far.