rci 2950 low power old version

too-seven · Post by **too-seven** » Wednesday 26th Nov 2008, 0:53

I have a problem with my old version 2950. Low power output on TX, about 4 watts AM/12 watts SSB. Just happend a couple days ago. Power is down about half of what it was. Voltages around outputs/driver normal, pass transistor voltages seem normal as well according to charts I have here. Before I go further I am seeking some advice here. Thanks in advance!

Rick · Post by **Rick** » Wednesday 26th Nov 2008, 4:05

Check to see how much current the PA stage is drawing, if low I would change the finals.

You could try unhooking the collectors of the finals and checking the current to see which final is low.

I have had the driver go low, but in most cases it is the finals.

too-seven · Post by **too-seven** » Wednesday 26th Nov 2008, 22:37

Thanks Rick for the reply. I will check the current on the finals and go from there. I am new here and have found some great info, much appreciated!

too-seven · Post by **too-seven** » Saturday 29th Nov 2008, 14:26

Well, got around to replacing the finals, not the problem. It appears my driver bias is very high according to the TX alignment manual, and wont adjust down to the 50-60 mA range. Would you suspect the driver in this case? Thanks!

Rick · Post by **Rick** » Saturday 29th Nov 2008, 22:37

That is why I told you it was best to check the current being drawn.

It maybe the driver has a base emitter leak but I would check R258 and D92, R258 should be 2R2 or for people in the USA 2.2 ohms.

If R258 has gone hi also change C264 and C292.

I have seen R258 go up to 70 plus ohms.

too-seven · Post by **too-seven** » Saturday 13th Dec 2008, 10:16

Repalced driver and new outputs, all is working well. Thanks for the kind help, great forum!