Ampex 300 OP Maintenance

Page 2

SEC TION 1
SECTION II

SECTION III

I

INSTRUCTION MANUAL
. FOR» .
AMPEX MODEL 300 RECORDER \

TA BLE OF CONTENTS

SPECIFICATIONS

INSTALLA TION~

OPERATION

Al. Electrical
B. Mechanical

SECTION IV - OPERATING PRECAUTIONS AND MAINTENANCE
A. Mechanical Assemblies
B. Head Assembly
5 C. Electronics Assembly
SECTION V - ALIGNMENT \
A. Overall Performance Checks
B. Head Alignment
C. Electronic Alignment
SECTION VI - PARTS LIST
FIGURE I - Top Plate - Bottom View
FIGURE 2 - Capstan Assembly
FIGURE 3 - Reel Idler Assembly
FIGURE 4 - Take-Up Tension Arm
FIGURE 6 - Record Amplifier and Power Supply Schematic
FIGURE 7 {Top Plate Control Circuits
FIGURE 8 a Playback Amplifier Schematic
, FIGURE 9 - Electronics Chassis - Top View /
FIGURE 10 - Recommended Layouts:
FIGURE II - Inter-Unit Connection Diagram
FIGUREIZ - Meter Control Panel (Bridging) Schematic
FIGURE 13 - Meter Control Panel (Matching) Schematic
FIGURE I4 - Remote Control Circuit
FIGURE 15 - Oscillator Coil Aszsembly Schematic
FIGURE lb - Record Equalization Curves
FIGURE 17 - Playback Equalization Curves /

MODEL 300 - INDEX
V 9-1-52

Page 14

HEAD MAGNETIZATION.

Occasionally the heads may become magnetized through anelectrical
fault in the amplifiers, improper use of the machine, or by the heads coming
in contact with a magnetized object. This will result in an increase of noise
level from 5 to 10 db. It is especially important that the heads be free of mag-
netization if you are to realize the dynamic range of type Ill tape. 'it should
be remembered that any phenomena that tends to put an unbalanced pulse
through the record head will magnetize it. Such pulses can appear in the form
of signal or power line pulses. If the following precautions are observed, no
difficulty should be experiencedy
.

1. Do not remove any tube from the record amplifier while the

machine is recording. .

2. Do not connect or disconnect input leads or head leads while

recording.

3. Do not depress the Record button until after depressing the Start

button. In other words, allow the transient caused by switching the

motors and solenoids to die out before the record head is connected.
~A one-half second pause is sufficient. 1

4. Do not saturate the record amplifier with an abnormally high

input signal. Such a signal would be 10 db. greater than. tape satura-

tion and 30 db. greater than normal operating level.

5. Do not test continuity in the heads with an ohm meter.

HEAD DEMAGNETIZA TION.
-_.____________

Should the heads become magnetized, they can be demagnetized with an
AMPEX head demagnetizer (stock number B-704). In the event that time does
not permit the owner of the machine to wait for delivery of a demagnetizer. he
may make one as follows: Cut a piece of transformerlamination to a 1/4" x 2"
size. Wrap the strip of metal with suitable insulating material and wind ap-
proximately 400 turns of No. 36 wire and attach a 4 length of Z connector cord.
Bend the iron strip into a "U" shape and bring the ends of the "U" to a spacing
of 1/4". Connect to a 6 volt source of A.C., open the gate on the head housing
and bring the ends of the "U" in contact with the Z poles on the magnetized head.
Remove the demagnetizer very slowly. allowing the A.C. field to die off grad-
ually. Repeat this operation on record and playback heads only, as the erase
head will demagnetize itself. In the event demagnetization is not effected, re-
peat the process several times. I

' SERiES 300 SECTION Iv' - Page 6
9-15-52

c/

Page 21

A 1.»,

a '
, ,. , . inmu.,...m _ a.» ,

HEAD MAGNETIZA TION.
__...__.__.___,_____

Occasionally the heads may become magnetized through an electrical
fault in the amplifiers, improper use of the machine, or by the heads coming
in contact with a magnetized object. This will result in anincrease of noise
level from 5 to 10 db. It is especially important that the heads be free of mag-
netization if you are to realize the dynamic range of type 111 tape. It should
be remembered that any phenomena that tends to put an unbalanced pulse
through the record head will magnetize it. Such pulses can appear in the form
of signal or power line pulses. If the following precautions are observed, no
difficulty should be experienced:

L

1. Do not remove any tube from the record amplifier while the

"machine is recording.

2. Do not connect or disconnect input leads or head leads while

recording.

3. Do not depress the Record button until after depressing the Start

button. In other words, allow the transient caused by switching the

motors and solenoids to die out before the record head is connected.

A one-half second pause is sufficient.

4. Do not saturate the record amplifier with an abnormally high

'input signal. Such a signal would he 10 db. greater than tape satura-

tion and 30 db. greater than normal operating level.

5. Do not test continuity in the heads with an ohm meter.

HEAD DE MAGNETIZA TION.
M

Should the heads become magnetized, they can be demagnetized with an.
AMPEX head demagnetizer (stock number 13-704). In the event that time does
not permit the owner of the machine to wait for delivery of a demagnetizer, he
may make one as follows: Cut a piece of transformeriamination to a 1/4" x 2"
size. Wrap'the strip of metal with suitable insulating material and wind ap~

proximately 400 turns of No. 36 wire and attach a 4' length of Z connector cord.

Bend the iron strip into a "U" shape and bring the ends of the "U to a spacing
of 1/4". Connect to a 6 volt source of A.C., open the gate on the head housing
and bring the ends of the "U" in contact with the 2 poles on the magnetized head.
Remove the demagnetizer very slowly, allowing the'A.C. field to die off grad-u
ually. Repeat this operation on record and playback heads only, as the erase
head will demagnetize itself. In the event demagnetization is not effected,5re-
peat the process several times.

' SERlES"300 . SECTION H - Page 6
9~15-52

Page 24

Ampex

Schematic 7| ' V ' I Stock
Ref. No. Description ' :l . Number»
F101 1/4 Amp Fast Biowing Fuse ' 1 ; FU~4
JIOIS Chassis Connector 3 131,585
.1102? Chassis Connector PL-61P
J103P Chassis Connector » PL-éZP
J104P , Chassis Connector '2 PL-13P
Jioss .Chassis Connector _ , ; PL-54s
JZOIP '1 "Chassis Connector PL-59P
JZOZPr Chassis Connector ) . PL-4P
.1203P Chassis Connector (Meter Panel Only) '3 PL-26P
,KlOl 3 Pole Double Throw DC Relay ' RL-26
K102 3 Pole Double Throw DC Relay j RL-Z -
K201 3 Pole Double Throw DC Relay (Model 301 Only) , RLuZ
L101 ' 7 20 Mi11ihenry Choke 4 CH-S
L102 12 Henry Choke 3479
L103 , 20 Henry Choke . 3480
L104 " 100 Millihenry Choke 1 .* (SH-15
R101 I 100, 000 Ohm Carbon Potentiometer RE-227
R102 2200 Ohm 1 Watt Composition Resistor 0 RE-7
R103 47, 000 Ohm 1 Watt Composition Resistor RE~22
R104 10, 000 Ohm 1 Watt Composition Resistor RE-15
R105 ' 1 Megohm 1 Watt Composition Resistor RED-32
R106 39,000 Ohm *1 Watt Composition Resistor 5% RIB-44
R107 100.000 Ohm 1 Watt Composition Resistor REE-26
R108 22.00 Ohm 1 Watt Composition Resistor , RE-7
R109 47. 000 Ohm 1 Watt Composition Resistor RE-22
R110 10. 000 Ohm 1 Watt Composition Resistor RE-15
R111 470,000 Ohm 1 Watt Composition Resistor RE-31
R112 1200 Ohm 2 Watt Composition Resistor RIB-158
R113 220 Ohm 1 Watt Composition Resistor RE-i
R114 2200 Ohm 1 Watt Composition Resistor RE-7
R115 10.000 Ohm 10 Watt W. W. Resistor REE-90
R116 470, 000 Ohm 1 Watt Composition Resistor RE-31
R117 50, 000 Ohm Carbon Potentiometer REi-226
R118 1 Megohm 1 Watt Composition Resistor » RE-32
R119 1 47:000 Ohm 1 Watt Composition Resistor RE-22
R120 6000 Ohm 40 Watt W. W. Resistor RE-Z44
R121 , 220,000 Ohm 1 Watt Composition Resistor REE-28
R122. - 10,000 Ohm 25 Watt W. W. Resistor RE-IZZ
R123 600 Ohm 10 Watt W. W. Resistor ' RE-73
R124 I 10, 000 Ohm 10 Watt W. W. Resistor . RE-90
R125 100 Ohm 1 Watt Composition Resistor IRE-260
R126 _ > 10,000 Ohm W. W. Potentiometer RE-255
3201 "~\ ' 470, 000 Ohm 1 Watt Composition Resistor IRE-47
R202 1 Megohm 1 Watt Composition Resistor ran-32

NOTE: ORDER PARTS BY AMPEX CATALOG NUMBER ONLY!
. ' " . , MODEL 300 8: 301 SECTION VI - Page 3

x ', . ' 915-52

Page 26

4

TOP PLATE ASSEMBLY MODEL 300 CATALOG #511

TOP PLATE ASSEMBLY MODEL 301 CATALOG #l122. Ampcx
Schematic , . V , Stock
Ref. No. Description k Number
A801 (n-8 V. Panel Lamp - Bayonet Base LA-S
A802. 120 V. 6 Watt Lamp - Candelabra Screw LA-6
C501 5 MFD 330 V. A. C. Capacitor 60-80
6601 ' 3.75 MFD 330 V. AC Capacitor CO-86
C701 3.75 MFD 330 V. AC, Capacitor (30-86
6801 . 1 MFD 600 V. Tubular Condenser CO-33 L
C802 . _ . 1 MFD 600 V. Tubular Condenser CO-33
C803 ' ', .1 MFD 600 V. Tubular Condenser CO- 33
C804 .1 MFD 600 V. Tubular Condenser 'CO- 33
6805 $0 MFD 150 V. Electrolytic Condenser CO- 105
C806 80 MFD 150 V. Electrolytic Condenser 60-105
(3807 .1 MFD 600 v. Tubular Condenser (10-33
C808 . l MFD 600 V. Tubular Condenser CO-33
C809 .1 MFD 600 V. Tubular Condenser CO-33
F801 ,' 5 Amp 250 Y. Fuse A.- FLT-5
F802. 5 Amp 250 V. Fuse , FU«5
F803 2 Amp 250 V. Fuse FUnZ
.7801}D . Chassis Connector PL-27P
JBOZS . ChassisConnector Flo-685
38045 ' Chassis Connector . PL-54s
JBOGS Chassis Connector -- Utility Outlet PL-il-lS
K801 3 Pole Double Throw DC Relay RL-ZE)
K802 3 Pole Double Throw DCRelay Rig-26
R801 150 Ohm 50 Watt Adjustable Resistor REuZS)
R802 500 Ohm 50 Watt Adjustable Resistor -» RED-221
R803, 150 Ohm 50 Watt Adjustable Resistor HIS-259
11804 " 10 Ohm 5 Watt W. W. Resistor BIS-264
8501 Micro Switch SW-Z
5502 Dual DPDT Toggle Switch SW-Sl
5503. Dual DPDT Toggle Switch SW-Sl , /
5801 DPST Toggle Switch SW~4 ' "

[$5802 6 Pole 3 Position Snorting Switch SW-lB'

. 5803 Single Pole Pushbotton N.C. (Stop) SW-«35 V
8804 Single Pole Pushbutton N. 0. (Record) swan. -
5805 Double Pole Pushbutton N. 0. (Start) SW~lZ
SR801 , ' Selenium Rectifier Slit-4
T5501 , Terminal Strip - 9 Terminals TS~l-9 .

. T5601 Terminal Strip - 6 Terminals S~1e6
T5701 " ' Terminal Strip a. 6 Terminals , TS-l-é
T5801 p _ Terminal Strip - 4 Terminals , TS-Z-4

NOTE: ORDER PARTS BY AMPEX CATALOG NUMBER ONLY}.

MODEL 300 & $301 SECTION VI - Page 5

9-45-52

Page 94

1h September 19h?

Gentlemen:

Enclosed is AMPEX Service Bulletin No. 1A.

It will be our policy to send out Service
Bulletins covering any information concerned with the
performance or maintenance of the model 300 recorder.
All bulletins which will be of interest to all machine
owners will have consecutive numbers. Those bulletins
which are of interest only to service personnel and
distributors will have a letter following the number,
as the one enclosed. Thus if the next bulletin were
for service personnel only, it would be numbered 1B.
If it were for general distribution, it would become
number 2.

Sincerely yours

AMPEX ELECTRIC CORPORATION

(/4677. Eon/144459 /

President

ANGbniatoff:fj

Page 124

£2 lugust 19149

Gentlemen:

Enclosed is SERVICE BULLETIN No. 1
for the AHPEX Model 300 Magnetic Tape Recorder.
This is the first in a series of bulletins which
we will publish to keep you infomed of the lat-
est advances in the art of magnetic recording,
and to provide all information possible to keep
your Model 300 operating in first class condition.

These will not alone give detailed infor-
mation of any mechanical or electronic modifica-
tions which we have found advisable in models
already released,but will also, in so far as
possible, review uses and applications for the
equipment which are outside of its normal employ-
ment.

If at any time you should encounter
any oporatingproblem or difficulties with your
AMPEX equipmnt, we would greatly appreciate your
calling it to our attention; If the problem is of
such a nature as to be of general interest to other
Model 300 users, it will be discussed in future
service bulletins.

Sincerely yours
AMPEX ELECTRIC OORPORATION

President

AMPoniatofi' :fj

Page 141

HEAD DEMAGNETIZATION

Occasionally the heads become magnetized through some electriral fault which may occur in the
amplifiers or by coming into physical contact with a magnetized object. in order to demagnetiu these
heads completely in such events, a demagnetizer should be used. A demagnetizer suitable for this
purpose is manufactured by AMPEX as an accessory item. In the event, however, that time does not
permit the owner of the mad1ine to wait for delivery of a demagnetizer, he may make one as follows:
Cut a piece of transformer lamination to a 1A" x 2" size. Wrap the strip of metal with suitable insulat-
ing material and wind approximately 400 turns of No. 36 wire and attach a 4 length of 2 connector
cord. Bend the iron strip into a "U" shape and bring the ends of the "U" to a spacing of 1/1". Connect
to a 6 volt source of A.C., open the gate on the head housing and bring the ends of the "U" in contact
with the 2 poles on the magnetized head. Remove the demagnetizer very slowly. allowing the [LC field
to die off gradually. Repeat this operation on record and playback heads only. as the erase head will de-
magnetize itself. In the event demagnetization is not effected, repeat the process more carefully.

The capstan may become magnetized by contact with a magnetized tool. Should this occur it may
be demagnetized with an A.C. solenoid placed over the shaft and slowly pulled away.

SECTION lV PAGE 3 6-15-49

Page 170

AMPIEX SERVICE BULLETIN

CORPORATION

l)r[7i[$$lfl]?fj{ R1fl CHAIN LN SI. - HtUWDOD CITY CALF. EMERSON HAIIBI ' 1W1 REDWOOD CIYV.T.-\L 41 ' CABLE ADDREES- AMFKX, RIDWOOO CITY

DAVE: 15 March 1957
month 300 Series
wtmm NO: 7-0?
PAGE NO: 1 Of 1
( Supersedes General Bulletin #9
dated September 12, 1956 )

prrfi'urlx drr {sum

REPLACEMENT OF CAPSTAN ASSEMBLIES

300 Series Tape Transport Mechanisms manufactured before November 1955
used the Ampex part number 366 and 1512 Series Capstan Assemblies. These
assemblies were mounted on the frame plate with a Tru-Arc retaining ring
#430-050.

On Tape Transports manufactured after November 1955 the Capstan Assembly
is mounted with a retaining collar on the frame plate by three 10-24 x 3/4" sock~
et head cap screws #470-108 and three lockwashers #502-011. '

When ordering replacement Capstan Assemblies , order 366 and 1512 Series for

machines with Serial numbers 55K or earlier, eg. 55J . For machines
with Serial numbers higher than 55K, eg. 55L, order 7518 Series Capstan Assem-
blies.

If the later model Capstan Assembly is to be mounted on the older Tape Trans-
port Mechanism , it will be necessary to drill and tap the frame plate for 10-24
screws. Three ( 3 ) holes on a 2.688 diameter.

The drawing shown below can be used as a template.

#10 Drill - 3 Holes on 2. 688 Diameter

Page 171

Catalog Number of Shaft Bushing

Capstan Assembly Diameter, Diameter,

Tape Speed inches inches

(ips) Retaining Collar

Ring Mount Mount

8-3/4 - 7-1/2 366-4 7518-4 . 237 ---
7-1/2 - 15 366-1 7513-3 .475 --~
15 - 30 366-1 7518-3 .475 ---
3-3/4 - 7-1/2 -15 2540-1 7518-6 . 237 . } e .431
7-1/2 - 15 - 30 1512-1 7518-1 .475 . 959

15-30-60 1512-1 7518-1 . 475 . 959

Page 174

. AM [EX SERVICE BULlETIN
_ MAGNETIC Racononns

' C R RAT] O N ,

-. 0 P0 _. our: 20 harsh 1953
93A CHARTERST.-EMEISON 84471 "9°= 300

wa REDWOOD cnr c414: lmmmuu 8

CAOLE ADDRESS: AMPEI, REDWOOD can no: no; 1

REDWOOD CITY,CALIFORNIA

l. C stan Oil Leakaqe. There is a tendency for oil to climb out of the
capstan bearinr housing during the first few Weeks of operation. The capstan
hearing has been thoroughly impregnated with oil so as to drive out any air
inclusions, as the presence of air would tend to force oil out of the bearing
housing when it becomes warm. The excess oil present climbs up the capstan
when the machine is operated. Ordinarily, this oil is caught by the felt
washer on tor of the bearing housing. (The neocrene washer shown in fig. 2
of the instruction book was eliminated in rroduction because it produced
flutter.) If this washer becooes saturated with oil, which usually happens,
then it will no longer behave as an effective seal. Therefore after the
first week or so of operation, when most of the excess oil has had a chance
to work out, the felt washer should be removed and washed out in carbon
tetrachloride. Simply remove the capstan dust cap (See fig. 2, instruction
book) to remove the felt washer. If this washer is kept reasonably dry, then
no trouble should be experienced with oil creeping up the capstan.

Page 222

COMPLETE PLUG-IN HEAD HOUSING: Double mumetal shield cans on
playback head, equivalent shielding on record head. matching self-aligned covers
on hinged gate. DrOp-in threading.

SIMULTANEOUS MONITORING: Independent record and playback systems
allow the tape to be menitored while recording.

RECORD AMPLIFIER: 10, 000 ohms bridging input, normallyr set up for {-4
VU in balanced or unbalanced.

PLAYBACK AMPLIFIER: Adjusted for+4 VU output, 600 ohms or 150 ohms
balanced or unbalanced. Will deliver 20 dbm without exceeding 1% total harmonic
distortion at any frequency from 30-l5. 000 Cycles.

DIMENSIONS: Mechanical unit on 24-1/2" panel and Electronic uniton 12-1/4"
panel. For standard rack. console or two case portable mounting.

SHIPEING WEIGHTS AND MOUNTING: Console 270 pounds. Portable Case
175 pounds. Rack 140 pounds.

POWER INPUT REQUIRED: 3 amperes, 115 volts. 60 cycles. (Available on
special order for 50 Cycles.g)

METER CONTROL PANEL available at extra cost with features outlined
below:

Mounted on 5-1/4" panel for rack, console, or portable case mounting.

Bridge Input step control will adjust record level for any input greater
than -20 VU. 10, 000 ohm bridging, any balanced or unbalanced line.

Output Step control will adjust level up to +8 VU regardless of tape
level - - 600 ohm or 150 ohm balanced or unbalanced line.

VU meter will meter playback output while recording or playing back.
Calibrated for 4-4 VU output.

Output key {line or cue).

Phone Jack with input-Output key (A -B Key}.

MODEL 300 SECTION I Page 2
9-1a52 '

Page 224

AM [EX SERVlCE BULLETIN
MAGNETIC RECORDERS

CORPORATION am,

noon: 3 0 0
IUlLEIIN no; 1 9

934 CHARTER ST. - EMERSON 8-1471
YWK REDWOOD CITY CAI. 41
CABLE ADDRESS: AMPEK, REDWOOD CITY GI "05 2
REDWOOD Cl1Y,CALIFOINIA

F. If the earlier Model 300 recorders are to be converted to take full ad-
vantage of the improved performance possible with present tapes and also to
have extended range 7 1/2" response. the following changes in the record
and playback electronics will have to be made depending upon the serial num-
ber category of the recorder:

SERIALS 100 through 175

l. The playback equalization circuitry in the grid stage of V203
must be changed to that circuitry shown on the attached playback
amplifier diagram. Discard the old R207, 470, 000 ohm resistor.
The new R20? is a 5, 000 ohm potentiometer, Ampex Catalog
#RE-ZT3. Discard the old C206. a .006 condenser and Substitute
the new CZUEI, a . 036 condenser, Ampex Catalog #CO-lll. Re-
wire these parts in accordance with the playback amplifier
schematic attached.

(Refer to record amplifier diagram for the following steps}

2. In the record amplifier, R106 must be changed to a 39. 000 ohrr
$570 1 watt resistor. ihis resistor is Catalog RE-44,

3. CondeHSer C123, 8 100 mfd 50 volt condensar, Catalog #CO-63.
must be added as shown 0n diagram.

4. Relay K102, Catalog #RL-Z, should be added as shown, On J104P
jumper terminals 1 and 9. Lead from R 12.2 to terminal 2 0n J105
should be reconnected to terminal 10 on J104P. Disconnect lead
to terminal 10 on .1104? from C109 {for this change compare new
schematic with schematic furnished with original instructiOn book.)

5, Wire lead from bottom side of L101 to one outside rotor contact
of 1102. Connect to stator contacts of this section of the relay the
new C109. Catalog #CO-IO, and 6110, Catalog #CO-Zl, conden-
sers as shown.

6. Connect rotor of other outside relay section to the point between
C102 and R105. Add the new trimmers C125 and C126, both bear-
ing Catalog #CO-QZ, to stator contacts of this section as sh0wn on
attached diagram.