142 gtl issue

[nomadradio]

I gotta get some pics pulled together. There is one electrolytic cap that kills the receiver audio, but not the transmit audio.

Another one will shut down ALL transmit, but your radio still transmits sideband, so that one isn't bad.

A 2SC1419 transistor that controls the AM carrier and modulation will frequently fail and shut down AM transmit.

You didn't say if the S-meter reveals any activity in the receiver upstream from the volume control.

Would make a difference.

73

 

[Spec2079]

I gotta get some pics pulled together. There is one electrolytic cap that kills the receiver audio, but not the transmit audio.

Another one will shut down ALL transmit, but your radio still transmits sideband, so that one isn't bad.

A 2SC1419 transistor that controls the AM carrier and modulation will frequently fail and shut down AM transmit.

You didn't say if the S-meter reveals any activity in the receiver upstream from the volume control.

Would make a difference.

73

Receiver is alive on ssb meter does move bit but I get nothing on am

 

[Spec2079]

Update: replaced a bad can has fully transmit power on all modes now but still have very low recieve even with my signal gen

 

[Spec2079]

Update: replaced a bad can has fully transmit power on all modes now but still have very low recieve even with my signal gen, also I recapped the radio as there where bad caps

 

[SuperLid]

look at the 7.8 MHz cans

 

[kaos513]

look at the 7.8 MHz cans

i tried my genertor at 7.800 mhz eems to have a louder tone thats about it

 

[nomadradio]

Have a close look at the 10mm RF/IF coils with the small tuning slug. Any of them that appear to peak with the slug DEAD EVEN with the rim of the hole are part of the problem.

That physical position of the tuning slug is the max inductance end of its adjustment range. As the slug unwinds further, and protrudes above the rim, the inductance will begin to reduce, same as it would turning it clockwise as it moves lower inside the can.

This "flush with the rim" issue reveals that the internal capacitor in that can has died, and become an open circuit. This naturally drop-kicks the can's resonant frequency way higher than it should be. Maxing out the coil's inductance helps, but never reaches an actual resonant peak. Since the signal will fall off turning the slug either way from this position it appears to be a peak. But it isn't.

That radio is old enough to be susceptible to this failure. And if every coil appears to "peak" when you turn the slug, make sure that none of them are positioned flush with the rim.

73


73

 

[Spec2079]

Thanks will work on it

 

[Spec2079]

Thanks will work on it

They don’t do anything also hear the tone on all channels

 

[SuperLid]

Now you are describing PLL unlock.