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amplifier and the Heathkit W A-P2. Should other units

with different power plug wiring be used the takeoff

socket may be rewired

suit requirements. The wire

jumper between lugs #2 and #3 of the 5 lug terminal

may have to be cut depending on the type of preamp

be used. This jumper should be cut for use when

powering a Dynakit PAM-l preamplifier or Heath-

kit WA-P2 or any other preamplifier which requires

power from a "floating" or ungrounded heater sup-

ply. The jumper should not be cut when using any

preamplifier which has its own, or a separate, power

supply.

PROTECTIVE COVER

The protective cover supplied with the MARK IV

has been designed to be both functional and attrac-

tive. In normal home usage the cover should always

be used; although the voltage at the top of the printed

circuit is not lethal, an unpleasant shock can be ex-

perienced, plus the fact that the tubes in normal

operation run hot enough to produce a minor burn if

touched.

The amplifier should be located where there is am-

ple ventilation-at least one foot of space above it

and several inches all around. The amplifier can be

located away from other elements of your system so

there is no need to place it in a confined area. Never

place anything directly on the cover which might

limit the ventilation. It is always advisable to operate

the amplifier in its normal vertical position.

The cover and bottom plate are attached at the

same time. Place the amplifier on the bottom plate,

then lower the cover over the unit, the tabs on the

cover will fit between the ends of the bottom plate

and the chassis. The three pieces are fastened simul-

taneously with sheet metal screws through the sides.

IN CASE OF TROUBLE

Your Dynakit MARK IV has been conservatively

designed

be as trouble free as possible. Error in

assembly or possibly a defective component may

affect performance or render it inoperative. Here are

some suggestions which may help. First of all the wir-

ing and assembly should be doubly checked, by some-

one other than the constructor if possible.

The tubes should light a few seconds after the unit

is turned on. If not, miswiring or a blown fuse will

probably be the answer. Replace a blown fuse only

with the type (2 ampere) originally supplied.

If the fuse blows when all tubes are removed from

sockets a defective power transformer or miswiring is

indicated.

If one or the pair of EL-34 output tubes glow a cherry

red after warm-up, it is possible that a tube is defec-

tive, or there may be a fault in the bias supply

which controls the current flow of the output tubes.

When the biaset reading is 1.56 volts the bias voltage

at the grids (pins 5) of the output tubes should be

within 20% of 34 volts NEGATIVE. A VTVM or

high impedance meter must be used here.

the volt-

age at each of the grids is not exactly the same, one

of the .1 mfd coupling capacitors on the printed cir-

cuit board may be at fault. If one tube has no negative

voltage at pin #5, an open circuit exists between the

tube and bias supply.

If no meter is available and one tube glows, inter-

changing the two tubes will help indicate the fault. If

the same tube glows in the other socket, the tube is at

fault. If the other tube glows in the original socket

position then wiring or components are at fault.

The output tubes supplied with your MARK IV

are carefully matched at the factory. When replacing

output tubes a matched pair should be used, or a new

one should be rna tched

the remaining good one.

In emergencies, substitution of tubes can be made.

Type 5881 or KT66 may be used in place of EL-34's

provided the bias is readjusted for these tubes. Type

5U4 or 5U4GB can be substituted for the GZ-34/

5AR4 rectifier. Either of these substitutions will re-

sult in somewhat lowered power output, however.

There is at present no substitute for the 7199 tube.

No Signal

If the momentary insertion of a small screw driver

in the input socket causes a loud hum, the trouble is

probably in the associated equipment. If the ampli-

fier is at fault, testing or substitution of tubes may

help. Voltages may be checked in accordance with

the voltage chart provided in the instructions.

Hum and Noise

If excessive hum or noise is apparent, it is essential

determine whether the disturbance is from the

power amplifier or associated equipment. Power am-

plifiers are often blamed for noise coming from the

preamp. The quick and simple way to determine this

is to remove all but the speaker from the amplifier.

the hum or noise disappears, the noise comes from

other than the amplifier; if it persists, it can safely be

assumed it is in the unit.

Sizzling sounds may be caused by poor solder con-

nections and occasionally by a defective resistor.

Loud cracking or popping sounds are generally caused

by loose tube elements and in rare cases a defective

quad section filter capacitor.

In the event that the trouble cannot be found, fac-

tory consultation is available at no charge and service

at moderate fees.

FACTORY SERVICE AND GUARANTEE

The MARK IV is designed to provide good service

for a long time.

is intended for operation at the

conventional 117 volt line voltage supply to most

homes and may be operated at up to 125 volts with-

out problems. Operation with line voltage above 125

volts will shorten tube and component life, and is not

covered by the guarantee.

All parts in the MARK IV are guaranteed for a

period of one fuB year from purchase date with the

exception of the tubes which are covered by the stand-

ard EIA guarantee of 90 days. Defective parts will be

replaced at no charge if they are returned prepaid di-

rectly to the factory or through the dealer from whom

the kit was purchased. Many DYNACO dealers stock

parts for convenience of replacement. After the guar-