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RCI-2990 RF Variable Power

KD2GOE

KD2GOE

W9WDX Amateur Radio Club Member
May 30, 2013
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Buffalo
ok so some thing is not right with my RF Variable Power I can only get it to 60% and then it will jump to 200 watts!


here is a video that will help

RCI-2990 - YouTube


I think it may have some thing to do with the final amplifier what is the burnt out adjustment that some one maxed out for? it had 102 stamped on it and seems to be 1K ohm if I bypass the burnt spot


 
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Are you sure it's not a squeal or RF feedback in the mic line that you can see as modulation? Did you change the radio final to a MOSFET or did it have one originally? Did you mess with the VC variable capacitor in the final stage? Did you change the bias settings? Any one of the above could cause this symptom.

Now that I see your picture, that is the bias adjustment for the amplifier stage.
 
Shockwave said:
Are you sure it's not a squeal or RF feedback in the mic line that you can see as modulation? Did you change the radio final to a MOSFET or did it have one originally? Did you mess with the VC variable capacitor in the final stage? Did you change the bias settings? Any one of the above could cause this symptom.

Now that I see your picture, that is the bias adjustment for the amplifier stage.
Click to expand...

I got the radio messed up I am slowly putting it back together again, The radio has came a long way and get a lot of good reports. This is all most the last thing I need to fix.



Are you sure it's not a squeal or RF feedback in the mic line? no but I have tried 3 diff mic's on it. I had my other radio on in a diff room and my wife didn't here a squeal if that helps. I was thinking the same thing.


Did you change the radio final or to a MOSFET? no. but some one put a 2sc1969 in there from the 2SC2312

Did you mess with the VC variable capacitor in the final stage? no but it may have been what variable capacitor are you referring to?

Did you change the bias settings? the last guy had it MAXED out! I set it back to 50~52ma
 
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Sounds like your low and high power adjustments for AM/FM are out of wack.

With your variable power knob in the front of the radio turned all the way counter clockwise, you'll want to adjust VR15 (AM/FM low power) for 15W deadkey on AM. Once that is set, turn the variable power knob on the radio fully clockwise, and adjust VR13 (AM/FM high power) for about 50-60W deadkey on AM. Do that first and see if your output comes around. Let us know how you get on.


~Cheers~
 
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ExitThirteen said:
Sounds like your low and high power adjustments for AM/FM are out of wack.

With your variable power knob in the front of the radio turned all the way counter clockwise, you'll want to adjust VR15 (AM/FM low power) for 15W deadkey on AM. Once that is set, turn the variable power knob on the radio fully clockwise, and adjust VR13 (AM/FM high power) for about 50-60W deadkey on AM. Do that first and see if your output comes around. Let us know how you get on.


~Cheers~
Click to expand...
i agree with this. but shouldnt he adjust high power first? as this will change the low power
anyway. then tune the low power??? way i do it
 
You can adjust high power first, but I'm guessing at 200W, the high power adjustment is/was probably fully cranked open. At worst, if the low power adjustment didn't come up to 15W, he can just go to the high power adjustment and bring up the high power adjustment until he achieves 15W deadkey on low.

Either way, it'll probably require adjusting both of the high/low power pots inside the radio a couple times to get the right numbers. As they say, there's no wrong way to eat a Reese's. :)


~Cheers~
 
I adjusted every thing on my dummy load it is still acting funky ill get a new video up...


I would just take it in but the DAY I was going to drop it off my wife called and she was let go from her job... I think the smart thing to do now is just put it away till she finds work...
 
I agree on the carrier settings out of wack, but did this just start acting up? Dont give up, you can do it. I would set it for 40w all the way up though.
 
This might be too simple, but I have seen dirty control pots exhibit the same type of behavior in other radios.
Cleaning/replacing solved it.


(Regarding the power jumping around)


73
Jeff
 
Save yourself some time and check to see if it's 100% stable on SSB. Try to modulate the SSB transmitter at low power. Less than 50% of full power to see if it can produce this output level consistently. This will bypass any carrier control and determine if this is an oscillation.
 
People have told me is sounds Varey clean on SSB but with my D104 I need to have the Mic gain no more then 50%

I all so cleaned all the pots it is defiantly only AM and FM. the AMC for AM is all so Varey touchy, I get no modulation till 3/4 a turn on the trimmer pot then max. I metered all the pots there with in spec
 
If the radio and internal amp are producing a clean SSB signal and the watt meter returns to zero between words, this greatly reduces the chances of it being any type of self oscillation and makes ExitThirteen's diagnosis much more likely.

The only difference is I think the 2990 radio places the low power carrier adjustment on the switch board mounted to the front left panel. The number for the pot was VR-601. I'm only 90% sure of this. If you can't find the low power adjustment on the main board, then it's 100%.
 

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