High Voltage Power Supply - Heathkit DX-100 Manual

The 12 volt tubes are operated across both halves of the winding. The low voltage supply with a
5V4G rectifier and condenser input filter, delivers 360 voits at 150 mils to the low power audio
and RF stages. The taps on the secondary deliver 75 volts to the GALS bias rectifier, also with
a condenser input filter. A resistance networkon the bias supply applies the correct bias to the
final amplifier, modulator and driver stages.
HIGH VOLTAGE POWER SUPPLY
'The highvoltage supply consists of the platetransformer, parallel 5R4GY rectifiers, choke input
filter and two 125 yfd electrolytic capacitors in series.' A center tapped bleeder balances the
series capacitors and aiso furnishes the modulator screen voltage.
Ordinarily well designed power supplies, using conventional values of paper or oi capacitors ,
have been found to make violent voltage excursions as loads are suddenly applied or removed.
This is known as the dynamic regulation characteristic. To eliminate these voltage excursions,
larger capacitors than are practical in the paper or oil type are necessary. This makes the use
of electrolytic types mandatory. The DX-100 uses two 125 fd 450 volt electrolytic capacitors
in series, resulting in a filter capacity of 62.5 ufd at 900 volts. This is sufficient capacity to
assure good dynamic regulation under keying conditions and a fair safety factor on voltage break-
down. Both sides of the AC Line are fused in a special line plug andall circuits entering or leav-
ing the transmitter chassis have LC harmonfc filters,
NOTES ON ASSEMBLY AND WIRING
In the design of the Heathkit DX-100, no effort was spared to obtain the highest quality compon-
ents andassemble them in the best possible arrangement. As this transmitter represents a sub-
stantial investment, the kit builder should exercise a great deal of care during assembly and wir-
ing. Only by putting the best possible workmanship into the kit, can the best results be obtained
from it, There is also a great deal of personal satisfaction in a neat, professional looking trans-
mitter, resulting from careful assembly and wiring. A common factor of radio frequency in-
struments is the critical placement of leads and components. The use of extensive shielding in
the DX-100 has eliminated a great dealof this. However, the lead dress shown in the pictorials
should be followed carefully.
Due to the complexity of the DX-100, the construction has been sub-divided into several stages.
'This unit method of construction reduces one large difficult project to several small easy ones.
It algo postpones the bulkiness and weight to be encountered in a large transmitter until it is
nearly completed. This manual is supplied to assist you in every way to complete the DX-100
with the least possible chance for error. We suggest that you take a few minutes now and read
the entire manual through before any work ia started. 'This will enable you to proceed with the
work much faster when construction is begun. The large fold-in pictorials are handy to attach
to the wall above your work space. Their use greatly simplify the construction of the kit.
'These diagramé are repeated in smaller form within the manual. We suggest that you retain the
manual in your files for future reference, both inthe use of the DX-100 and for its maintenance.
During the initial testing of the transmitter, i t will not be in its cabinet. REMEMBER VOLT-
AGES DANGEROUS TO LIFE ARE PRESENT AT PRACTICALLY ALL POINTS ON THE CHAS-
sis.
UNPACK THE KIT CAREFULLY AND CHECK EACH PART AGAINST THE PARTS LIST. In
so doing, yon will become acquainted with each part. Refer to the charts and other information
shown on the inside covers of the manual and on Page 63 to help you identify any parts about
which there may be a question. If some shortage is found in checking the parts, please notify
us promptly and return the inspection slip with your letter to us. Hardware items are counted
by weight and if a few are missing, please obtain them locally if at all possible.
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