President Washington 858 help

[orbieswar]

Hi All... I have a Washington that has full power and modulation on AM.
PA has full audio.
SSB is a no go no output at all. I assume its an Audio problem. But cant seem to narrow it down.
Also rx sensitivity is down.
Any thought as to what I am not seeing.
Thank you all in advance.

 

[nomadradio]

Hi All... I have a Washington that has full power and modulation on AM.
PA has full audio.
SSB is a no go no output at all. I assume its an Audio problem. But cant seem to narrow it down.

That's odd. Usual failure is the other way around. SSB works but no AM.

The mike audio is shared for AM and SSB. It splits off and goes to each separate modulator circuit at the junction of L10 and C71.

If you have a sideband receiver that covers 7.8 MHz you could put a coax jumper on it, thread the shell back off the plug and use the end of it to "sniff" for the radio's sideband transmit signal that way. You'll want to sniff very near to IC2, the MC1496 chip. If you can hear your USB and LSB signals, each centered on 7.8 MHz, this tells you the trouble is downstream from there.

And if you can't hear it, you have narrowed down where to look next.

73

 

[orbieswar]

Turns out it was TR 6 the first IF amp was faulty So did 5-6 and 7.
All good now.

 

[nomadradio]

Rock on! Good to hear you tracked it down.

73