• Recommended Reading
  One of the best books I've ever encountered is 'Solid State Design' published by the ARRL. Yes, it says 'solid state' and the Drake stuff uses toobs. What gives?

  This book will provide you with an excellent background in receiver AGC, performance measurement, power supplies (R4C reference), noise figure, product detectors - an almost endless, PRACTICAL application of electronics to amateur radio. My copy is so ragged and worn, I need to replace it, just for that reason.

  The 'aether' knows not if you are using transistors, glassFETS or even a coherer. Physics is physics. Far better to learn for $15 why .1 uV on 80 meters is a useless achievement rather than spend hours 'improving' your R4B for nothing.

  Considerable detail is presented about receivers and multiple conversion designs. This can be applied to the R4B and R4C in that there need not be any difference in sensitivity and noise figure of a double conversion compared to triple or even quad. It all depnds on design goals, cost, engineering preference and other factors.

  A highly recommended publication, even if you don't build. Do not let the title intimidate you.

• R4any and T4any Tuning Rack
  Leave the slugs alone! There should never be a valid reason to pull a tuning rack apart except under the most unusual of circumstances. These slugs are color coded for permeability - mix them up during reassembly and you'll have a fun time getting the receiver to track - if ever. There should be ample adjustment available in the trim capacitors to set up the front end on the individual bands.

  Sometimes you may find a particular receiver will not peak properly when the preselector is set to the indicated value. Generally, don't worry about it. There is no law that says you cannot move the pre- selector a bit to accommodate the compression trimmers. Ideally, you want the compression trimmers set about 1 to 1 1/2 turns from 'snug'. If the trimmers are backed off too far to accomodate the (arbitrary) preselector setting, they won't hold long term alignment. In this case, rotate the preselector a bit to raise the slugs and try again.

• Rotary Switches
  Sometimes you may encounter either a dead radio or an intermittent one and just can't find the sore spot. Check the rotary switches for a sawed off selector tab. Sometimes just enough of a stub is left to select some positions - just barely. This is just wear and tear and is simply the rubbing action of the selector tab going past the fingers.

• T4any Microphone Connector
  The microphone connector plug is a Switchcraft S230 and has a diameter of .210". This was used so you couldn't plug the microphone into the earphone connector and have the output fry the element. These plugs are a little rare. The reason why the PTT line is the tip and not the ring is simple. If it were the other way around, you'd put the keyed line across the mic element as you pushed the connector in. In desperation, I've seen a standard 1/4" stereo socket used and it could be an expensive expedient. Microphones don't make good speakers or speakers for very long.

• S230 Part II (from I/Net)
  "I just sent off for two of these last week. Have not got them back but he said they are NOS Switchcraft S-230 right angle plugs. Danny in VA has them for sale. He said he got about 200 a few years back. Had 20 or 30 left. He sells them for $8 each or 2 for $15. No connect with him, just heard him on the Drake Net. His phone number is 804-448-3008."
  73s Mike WD5xxx The DRAKE Collector

  Another potential source is:
  Mouser has them (502-S-260, $7.08 ea.), so does Digi-Key You can usually find them at swap meets ....
  Mark AA7TA

  (I have referred a few folks to Danny for the S/230 and there have been no reports of any problems whatsoever <wm>)

• Radio Miscellaneous
  For trim paint, Collins trim rings and related items that may prove to be hard to find, you can try:
  R and R Designs
  1-800-372-4287
  1-608-255-0400

• Cinch Jones Plugs
  Modern radios tend to use the Molex style plugs. The other style plugs commonly used up to the late 70's were the Cinch Jones connectors. These are becoming a little more difficult but not impossible to find. Try the following:
  • Try Allied Electonics 1-800-433-7500. I got a couple of plugs for my TR7 from them, Vinnie N2TAI
  • The S-300 and P-300 series are available from Digi-Key, and in the past I have gotten the S-400 series of Cinch Jones connectors from Newark Electronics. I would suggest looking in Digi-Key for the S-400 series as well as Newark tends to be rather costly.
    Harvey, N6MM.

• AM Operation
  The transmitters and transceivers will operate AM. But why is it so 'different'?

  During reception, Drake wants you to treat an AM signal as 'Single sideband *Reduced* Carrier'. The sideband filter chops a sideband off and reduces the carrier. You detect it by zero beating the carrier thats left.

  The transceivers and transmitters were designed to be operated with a linear. A true AM signal through a linear amplifier is not only very inefficient, its really rough on the linear, especially when operated improperly. Instead of simply unbalancing the balanced modulator to get sorta AM, Drake made a terrific compromise and went 'controlled carrier AM'. This mode has a small carrier at idle and the amplitude of *both* the carrier and sidebands goes up as you modulate. Its easy on the PA tubes and it works well. It is superior to unbalancing the SSB balanced modulator to generate AM and reason- able in terms of trade off to 'real' plate modulated AM.

  This is similar in principle to the AM mode in the Heath DX60, Knight T60 and Knight T150.

• T4 and TR4 Relay Cycling
  With the age of these units some of the electrolytics are starting to dry out. Sometimes they'll go leaky from cell to cell if there are multiples in the can. If you have problems with the T/R relay chattering or cycling, quite likely it could be one of these filter cans. The only way to roughly suspect an element has gone is to clip in a 100 Uf 300 volts across an element. If the cycling stops or slows down this is the likely problem. Beware of some funny problems you may get with cell to cell leakage, however. These can be tricky to nail.

  These canned capacitors are dated and largely unavailable as re- placements. Due to their age, even if replacements were available, I would advise some caution. Whether in use or not, they've been sitting on the shelves for too long. Modern capacitors are much better. My recommendation is to replace the whole can with discrete electrolytics. You can either leave the old cap in there for appearances or pull it and put in a hole plug.

  In the receivers, weak power supply electolytics are characterized by hum, low B+ and 'funny' audio on SSB. The funny audio is caused by harmonic mixing of the 60/120 cycle hum and the detected audio. In this case, sometimes there is not enough hum out the speaker to be too objectionable, but the speaker audio sounds 'funny' for some reason or another. You can verify this with the calibrator on SSB. As you sweep across the calibrator slowly, you'll hear some spots where the audio goes muddy. Once you detect it, and have your ears trained, its very obvious.

• Schematic Date Codes
  On the 4 line B series and above you'll notice a series of numbers in small print on the schematic. I have an T4C schematic with the numbers 10077626470. This is in mmddyy/serial no format. It means that this schematic was revised on October 7, 1976 and applies to serial numbers above 26470. I do not see this notation after the TR4Cw-RIT.

• Drake Equipment Wiring
  Drake did not color code their wiring to any appreciable degree. In most cases, their hook up wiring seems to be white colored and some wires may have a color trace. More than one wire may have the same color trace, so be careful and verify with an ohm meter from end to end.

  Additional care should be used when soldering to Drake hook up wire. The insulation melts very, very easily and will crawl up the wire and peel off while doing so. When replacing items like those canned filter caps, sometimes it causes less damage and is more expedient to simply cut the wires. One can easily and quickly loose 3/4" of insulation just in desoldering.

• Line Cords
  Some line cords will be 2 wire - no ground pin. This may appear on the receivers or on the AC4 transmitter power supply. Users are urged to change the line cord to a 3 wire configuration with a grounded centre pin. Without this centre pin, the chassis leakage will float to about 50 volts AC. In the event of the primary windings shorting to the chassis, this can prove to be lethal.

• Loose Knobs
  On some controls it may be difficult to keep the knobs tight to the shaft. Overtightening will split the knob. Quite often the problem is simply caused by the knob not being exactly square to the shaft flat when the set screw is being tightened. Rock the knob slightly while tightening the setscrew. The knob setscrews are not all that easy to deal with in the long term. A better setscrew is an Allen (hex) head screw. This type of setscrew will provide better torque control.

  Some knobs have no set screw and instead are held in place by a piece of bent flat spring steel. Sometimes it is these knobs that always fall off, because the spring steel gets flattened just before the shaft rotates. In this case, try that particular knob in a location with less torque such as a volume control. Just swap the knobs.

• Source for Knobs (K4OAH)
  1. Drake still has them, but they are $4.03, plus shipping and handling.
  2. The knob is made by "DAKAWARE", but is not shown in the latest Allied or Mouser catalogs.
  3. A local distributor has them on a peg board display under the name of "Caltronics" for about $3 each. I think this is a popular brand among independent distributors.

The "B" knobs are of two types. One is a set-screw type (as in number 2 and 3 above,) and the other is a slip-on type with the little metal spring like Collins uses. The set-screw type will work to replace either of the originals.