All of the Drake 4 line will transceive amongst themselves. Between the
T4X and the T4C there was little difference. Most of the changes in the
T4C from even the T4X were cosmetic or for better operator convenience.
The B series used neon bulbs to indicate the active PTO when set up for
transceive; the C line turned the dial lights on and off.
A properly working T4any will give about 150 watts output on 80 meters,
dropping to 80 or 90 watts on 10. The audio should be really clean and
with properly operating ALC you should not be able overdrive the finals.
There should be LOTS of drive on all bands.
6.1.1 T4 Evolution
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The T4X and the T4B differ very little, except mostly in the PTO dial
plates. The T4C functionally was not much different from the T4B, except
in areas of operator convenience. The T4C is noted for the following ma-
jor differences:
o Separate BFO Line
o FETs in the BFO oscillator
o Different method of ALC detection
o VOX on/off from front panel
o Controls moved to back of set
o Dual concentric PTO dial plates
o Plain chassis
o Meter switch activated by pushing LOAD control shaft
o Active PTO indication by dial light
o Blank RCA jack holes for VHF transverter drive kit
o Separate VOX delay controls for SSB and CW
6.1.2 T4any Mods and Tech
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o Can't Tune 10 Meter Driver Plate
This is characteristic of 'generic' 6JB6 tubes. Replace with
Sylvania 6JB6. Problem caused by high input capacitance of tube(s).
o VOX Gain - T4X and T4B
In cases where more VOX gain is required pick up the VOX input from
the mic gain control instead of from the plate of V9b pin 6. When
re-routing the audio pickup point, bypass pin 6 with a .05 uF cap.
o T4C TX Lock up
Lock up on a T4C is usually caused by a gassy mixer or 12BY7 driver
tube. Other causes include leakage either to ground or B+ of the TX
keyed line. This is a high impedance line. In extreme cases the
cause can be T6. Inside T6 is a rubber washer that can contact the
coil pins internally. The fix is to remove T6 and the shield and in-
stall a fish paper washer between the bottom of the rubber washer
and the bottom of the transformer base.
o T4C Side Tone - Elimination
Standby CW sidetone may be eliminated by placing a 22 Meg ohm resis-
tor between the pin in the centre of the circuit board in front of
V7 (the one with the wire going to pin 1 of V7) and the lug at the
top left of the board (the one with the 150K resistor).
o Substitute VOX relay tube
A 6AQ8 will replace the 6EV7 if a 47 ohm 2 watt resistor is added
across pins 4 and 5 of V10. The tube change is applicable across the
entire 4 line (and TR3). The resistor IS NOT needed in any of the
transceivers. Just swap the tube, in this case.
o Fan
The PA cage area gets quite hot when in use and some forced air
cooling is desirable. The easiest way of accomplishing this is to
use a small 1 1/2" 12 volt DC fan. Mount the fan on the outside of
the PA cage through the perf holes on the back of the PA cage. Power
the fan from a half wave rectifier filtered with about 100 uF de-
rived from the 12 volt filament supply. Route the fan wires through
a chassis hole along back top of the chassis. The rectifier can be
connected between the filament fuse and an insulated standoff. This
mod can be done without drilling any holes or destroying the units
originality. Orient the fan to blow in.
These types of fans are CPU coolers and can be bought for less than
$10. They do not move a lot of air and move even less through the
perf holes. What is necessary is not cooling, but circulation, and
this simple expedient helps a lot.
This mod will greatly extend the service life of the 6JB6 tubes at
the expense of faster accumulating radio dust bunnies.
6.1.3 T4 Reciter
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This is a T4X with the PTO and crystal deck removed. It was intended to
provide a transmit function in conjunction with the R4A and R4B receiv-
ers. The only other similar device that I know of is the Atlas 210 se-
ries. A similar series of devices was the Atlas RX-110 receiver and
TX-110 transmitter. The TX-110 used the VFO signal of the receiver in a
way similar to the Drake R4B/T4 Reciter combination.
Obviously, the Reciter is duplicated whenever you slave a separate T4any
completely to the receiver.
I've never seen one. This is an item for the curious or the collector
and may sell for either next to nothing or might demand a high price
from its 'rare' nature. For the practical, and with the used Drake 4
line so readily available, it does not serve much of a purpose other
than its novelty value. Any modifications or service notes that gener-
ally apply to the Drake T4 series transmitters would apply to this unit.
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