Garey Barrell <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- Eric -
There isn't a "good" way to correct the wafer "play" once it occurs, short of wafer replacement. I have seen some with very thin Teflon? tape wrapped around the shaft that seemed to work. I saw one where someone had cut small pieces of brass shim stock, carved out the hole, and epoxied them to the wafer. Inexpensive, but highly labor intensive! :-)
The Load control should be in the 2.5 - 4.5 range for a non-reactive 50 ohm load. The Plate control should be in the 3 - 8 range. As long as a "dip" can be achieved, it doesn't really matter.
Your power output is very low. If you load for maximum output, you should get 130 plus watts out on 80 - 20 in Tune position, 150 -160 watts in CW. Power that low is most likely from weak finals. With "new finals", you probably have an alignment problem. If you have done the alignment, check the 680 ohm resistor at R44, (located under T7, just at the end of the final feedthrough panel under the chassis,) especially if you did the alignment with a metal screwdriver. Shorting the alignment caps to the chassis, hard not to do with a metal screwdriver in those little holes, will damage this resistor. With regard to the plate current, this is most often a result of a meter shunt resistor that has gone up in value. This is a 3.3 ohm resistor on a small board under the chassis near the relay. The 'best" way to correct this is to replace it with a 1W (the original is 1/2W) carbon film resistor. At the same time, check the 15 ohm 1W cathode resistors for the final tubes. They should be close to 15 ohms, (+/- 5%) and closer to each other, (2%). Best replacements are Ohmite OY ceramic composition, although the carbon film types seem to work fine. If you haven't already, check the screen resistors for the finals as well.
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 <http://hr99.home.mindspring.com/R-4C_Servicez/>
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
<http://us.rd.yahoo.com/evt=30648/*http://movies.yahoo.com/movies/feature/jibjabinaugural.html>
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