rci-2950 usb rx problem

[yg27]

I have an old rci-2950 that when you switch to USB the signal meter always shows a signal of about 2 to 4 and the rx sounds like there is a signal there regardless of frequency or clarifier position. It is not a heterodyne that you can zero beat its just a signal reading thats there. You can hear stations on the band but you cant hear the background noise like static on the band and it covers up weak stations. LSB and other modes work fine. Also rx sensitivity is down just a little.

I did an alignment but this did nothing to help this problem but was able to get the sensitivity up some but not where it should be.

I think the problem is not as bad when you first turn the radio and then worsens after the radio has been on for a long time.



Hopefuly some one will be able to help me out some and any response is appreciated. I really got burned on this radio got it off e-bay and its pretty rough. but works ok cept for this.

I have a service manual and a scope and all but just don't know what could cause this problem juts in USB.



Thanks


</p>

 

[yg27]

I have an old rci-2950 that when you switch to USB the signal meter always shows a signal of about 2 to 4 and the rx sounds like there is a signal there regardless of frequency or clarifier position. It is not a heterodyne that you can zero beat its just a signal reading thats there. You can hear stations on the band but you cant hear the background noise like static on the band and it covers up weak stations. LSB and other modes work fine. Also rx sensitivity is down just a little.

I did an alignment but this did nothing to help this problem but was able to get the sensitivity up some but not where it should be.

I think the problem is not as bad when you first turn the radio and then worsens after the radio has been on for a long time.



Hopefuly some one will be able to help me out some and any response is appreciated. I really got burned on this radio got it off e-bay and its pretty rough. but works ok cept for this.

I have a service manual and a scope and all but just don't know what could cause this problem juts in USB.



Thanks


</p>

 

[d1g1man]

I think I might have a solution for you.

One of the common mods floating around is to change R78 (2.2Kohm) to a 6.8 kohm resistor.

When I did this my receiver did the exact same thing that yours is doing.

There are two ways to check for this.

One way is to decrease your RF gain, if the signals are low, but reception is otherwise normal. This MAY apply.

Secondly, find R78, it is almost touching the last tuning can (L9) on the back of the board near the finals, just below the vertical shorting board TP1,TP2,TP3.
Identify its value.

If it is a 2.2K (Red,Red,Red) then this is NOT your problem.

If it is a 6.8K (Blue,Gray,Red) then this could very well be your problem.

The value that worked best for me is a 4.7 Kohm resistor (Yellow, Violet, Red)
Or, just put a 2.2K (Red,Red,Red) back in.

If this does not work, then Locate R49 (next resistor over) and replace it with a 470K resistor.

All values quarter watt. (gold band)

Hope this helps....