Page 1 of 1
rci 2950 low power old version
Posted: Wednesday 26th Nov 2008, 0:53
by too-seven
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!
rci 2950 low power old version
Posted: Wednesday 26th Nov 2008, 4:05
by Rick
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.
rci 2950 low power old version
Posted: Wednesday 26th Nov 2008, 22:37
by too-seven
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!
rci 2950 low power old version
Posted: Saturday 29th Nov 2008, 14:26
by too-seven
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!
rci 2950 low power old version
Posted: Saturday 29th Nov 2008, 22:37
by Rick
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.
rci 2950 low power old version
Posted: Saturday 13th Dec 2008, 10:16
by too-seven
Repalced driver and new outputs, all is working well. Thanks for the kind help, great forum!