From: Eric Webner 
Subject: Re: [drakelist] R4C xtal bank bad


After you replace the 3.3 ohm resistor, it is best to measure it's 
actual resistance and the voltage drop across it with an accurate DMM to 
determine the "actual" plate current, then use this information to 
verify that the Plate meter is measuring accurately at 100 mA. The 
meter is not great, and not highly linear. The 100 mA point is most 
important since that is what you use to set the bias for the final. If 
it is NOT accurately reading at 100 mA, you will have to reselect the 
resistor marked (select at test) which is mounted on the slide switch 
linked to the meter switch between the Plate and Load controls. It's 
usually around 200 ohms, but can be anything from 47 to 360 ohms.

The 50-123 knob will work, but you'll be amazed at how it's "difference" 
sticks out. Of course it will bother YOU much more than anyone else! 
Same phenomenon as that little paint slip on the wall in the living 
room. No one else ever sees it, but its the first thing you see every 
time you walk into the room!! :-)

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual




Eric Webner wrote:

> Garey et al,
> 
> I appreciate your comments. Perhaps I did a little too much work on my 
> T-4XC.
> 
> I just finished restoring my transmitter, and during my work I found a 
> few problems with wafer misalignment and too much "play" on certain 
> wafers. Can you comment on the best ways to correct these problems?
> 
> I would also like to know what typical settings for plate and load 
> controls should be when loading into a dummy load. I have never owned 
> a working C-line before, so I am not sure what "normal" is.
Suffice it 
> to say, I believe my plate control is turned relatively high. I just 
> about "run out of room" on 10 meters.
> 
> Also, what kind of output power should I be getting. When I follow the 
> tuning procedure given in an errata sheet indicating that I should 
> limit my plate current to 340 mA in order to meet FCC regs, I only get 
> about 85 watts out on 80 and 40 meters. When loading to full power, 
> what is the maximum plate current I can load to without melting my new 
> finals?
> 
> For those of us that were discussing how to obtain knobs for the 
> Drake: I called Caltronix today and they confirmed that the 50-133 
> knob is only available from the manufacturer if they buy 500 pieces. 
> They are looking for another vendor who will sell in more reasonable 
> quantities. In the meantime, they have available the 50-123 knob, 
> which is 1.04" in diameter vs. the 50-133, which is 0.93" diameter. 
> Has anybody had any luck with other vendors? I still need to replace 
> one knob.
> 
> I hope to chat with you guys this Sunday during the CE Contest.
> 
> 73,
> 
> Eric KA8FAN
>
>
> 


		
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Garey,
 
Several weeks ago when I discovered the play in one of the
bandswitch wafers, I set the wafer where it should be and used
adhesive  on the inner wafer and shaft. It appears to work very
well, and with no binding. I wouldn't recommend that for all the wafers,
but just one seemed ok.
 
Regarding my low output, I may be ok. First of all, I was not
loading it to full power, since one of the errata sheets that Drake put out
said to load it for only 340 mA in order to avoid any spurious output.
After reading your latest message, I loaded 80 and 40 meters to full power,
obtaining 135-140 watts measured on my Bird wattmeter. Loading it to full
power ran the plate current to 500 mA!
 
I also took your suggestion and checked a few components. R44,
the 680 ohm resistor, is good. The cathode resistors are good and very well
balanced. The screen resistors checked out as well. However, the resistor
across the meter measured 5.6 ohms. I disconnected one end from the circuit
board and the 
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