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Midland 13-898B Low SSB Power Out

Justin B. said:
I continue going through this neglected radio and I think I have got most of the gremlins exorcised except SSB power. Receive seems fine so I left the synthesizer alignments alone and I went through the transmitter alignments and have about 2.5W dead-key and 5-5.5 W modulated. I have set the SSB bias and carrier null but can only get a little less than 2W out on both USB and LSB.

The only adjustments that did not go perfectly is the USB and LSB carrier freq adjust. They are both off and adjusting the associated trimmers doesn't seem to have any effect on the frequency.

Just for grins I replaced ALL of the electrolytics on the audio and main boards, cleaned all trim-pots before adjusting, etc. Any ideas of what else to look at would be appreciated.

73,
Click to expand...
Justin B. said:
I continue going through this neglected radio and I think I have got most of the gremlins exorcised except SSB power. Receive seems fine so I left the synthesizer alignments alone and I went through the transmitter alignments and have about 2.5W dead-key and 5-5.5 W modulated. I have set the SSB bias and carrier null but can only get a little less than 2W out on both USB and LSB.

The only adjustments that did not go perfectly is the USB and LSB carrier freq adjust. They are both off and adjusting the associated trimmers doesn't seem to have any effect on the frequency.

Just for grins I replaced ALL of the electrolytics on the audio and main boards, cleaned all trim-pots before adjusting, etc. Any ideas of what else to look at would be appreciated.

73,
Click to expand...
You should NOT have ANY “2.5 watt dead key” on ssb!
 
I think that resistor is ok if you have 13v there.

I just don't understand what could be pulling the audio down to 320mV pk-pk with almost 3vpk-pk on the other side of that cap (C309). Something must be pulling it down. With the radio off, what resistance do you have between the cathode of C309 and ground? It may take a few seconds for the reading to settle as the meter charges the caps.

Schematic suggests 8.3k
 
I'll try to check that out tomorrow, I've shut down things for the night. I finally found R357, it's that big goober on the audio board!

73,
 

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