RCI 2980 EPT360014B 3 problems

[ira parker]

RCI 2980 EPT360014B 3 problems​

• Thread starter ira parker
• Start date Friday at 5:54 PM
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ira parker​

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• Friday at 5:54 PM
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The short story, No tx got that resolved. Once tx was restored there is a 4-6 watt dead key on sideband ? Also only about 10 watts output on ssb and vr#12 doesn't adjust it? AM works fine rx and tx, 22 watts out audio chain is good. Pll/vco took alignment just fine spot on frequency. Started Tx alignment bias is still a little low not sure about these hg transistor (2166,2312s) from ica manufacturing. When I got too setting high/low dead key vr#13 adjusted normal high side 8 watts however vr#16 low side would not respond, first checked the vr itself has range on the ohm meter but 0 volts. Modulation has been opened so vr#14 is mute. Vr #12 does adjust from 6.14 volts down to 0.21 volts on am, 1.77 volts to 0.03 volts on ssb both test with rf power fully clockwise, tr51 and tr50 have been replaced and voltage is correct and switches to 13 volts ssb. Voltage is present and switching with pcb board in place at tp7,8 and 9. I've started testing and checking the other transistors tr12 (good voltage good), tr17 gvg, tr 23 gvg, tr 30 gvg, tr 31 gvg, tr 34 gvg, tr 47 was bad replaced it gvg, tr 53 gvg. That's as far as I got yesterday and today working over the weekend hopefully back at it monday. Just looking for any advice or something obvious or if anyone has run across this before. Going to finish the transistors first then start tracing back from vr #16 2 legs to the back of radio 1 to the front. Back right is ground back left and front are in circuit so I'll see where it leads me.
Thanks Ira,

P.S. using the dx11b for board layout and schematics and the dx99v for transistor and ic voltage charts.

Update I've cleaned up the dead key on ssb driver bias was to low.

 

[BC Coyote]

there is a 4-6 watt dead key on sideband

Balanced modulator is out of adjustment.

 

[sp5it]

Or leaking crystal filter.

 

[ira parker]

Balanced modulator is out of adjustment.

dead key is equal on usb and lsb vr 7 makes minimal difference. IC 3 voltage is good.

 

[ira parker]

Or leaking crystal filter.

Question if fl3 10m4d was damaged would the tx/rx on sideband align on frequency?

 

[sp5it]

Yes it will be on freq, but leaking carrier.
Other failure causing that can be parasitic oscillation of predriver/driver/PA
Mike

 

[ira parker]

dead key is equal on usb and lsb vr 7 makes minimal difference. IC 3 voltage is good.

hey bc just to let you know the bias on the driver was really low i've got it up some and elimanated the ssb dead key. It still needs some more bias so thats next. thanks Ira

 

[ira parker]

Yes it will be on freq, but leaking carrier.
Other failure causing that can be parasitic oscillation of predriver/driver/PA
Mike

hey mike just to let you know the bias was really low on the driver i've got it up some and the ssb dead key is gone. But it still needs more bias thats next. Driver bias .50ma am should be about 75 if memory serves me right. Finals (2) will only come up to 53ma am. ssb driver is .002 finals are .062 I guess pa section is next. thanks Ira