Ampex 300 SB Service Manual

Page 1

AMI} EX SERVICE BULLETIN
MAGNETIC RECORDERS

0 R P RATI
C O" 0 N M 20 March 1953
934CHAR!ERSt-EMERSON 34:71 0 300
rwx krowooo cur CAII Immmnm 2
CABLE ADDRESS: AMPEK, REDWOOD CITY PM NO: 1

REDWOOD CITYr CALIFORNIA

1. Erase Aggustments For pmper erase current the erase trimmer is adjusted
to prom. e o m. a. instead of the 250 m. a. originally stated in the
Instruction Book. Actually, 180 m. a. will erase peak recording level within
specifications. In checking arose, always check with both record and erase
heads connected, as the bias on the record head provides part of the erase.

Page 2

AMI} EX | SERVICE BULLETIN
MAGNETIC RECORDERS

C ORPORATI O N i am 201izérch 1953
H_ noon; 300
934CHAEYER 5T.-EMERSON 8-17! squnu NO: 3

[WI REDWOOD CIIY CAI 4] N.

CASLE AODRESS:AMPELIEDWOODCITV PAGE- 0- a

REDWOOD CITY,CAL|FORN|A

1. Heels. It has been found in some isolated cases that when the tape is
allowed-to nun all the way out at the end of a fast wdnd, a section over a foot
long will be broken off the end. Upon investigation, this was found to be due
to the sharp edges on the slot opening of the reel hub through which the tape
is threaded. The sharp edges apparently provided high friction and did not
allow the end of the tape to run out freely. When these sharp edges were filed
off, the breakage no longer occurred. This information is being forwarded to
the NERTB Sub-Committee for the standardization of reelso

Difficulty has also been exPerienced with the reels not being properly cen-
tered. lhen inserting the hold-down knob, the knob should be pushed down with
one hand, and the reel held with the other hand. As the holdudown comes into
contact with the reel, agitate the reel slightly with the other hand to make sure
that the hold-down moves into the exact center of the opening, then push the knob
down firmly. For use of the new Cat.#554-D and #4402 Held Down Knobs, see Gen.
Service Bulletin #2.

In order for the brakes to work properly, the same size reel must always be
placed on both turntables. In using the small REA 7 inch reelsa abnormal hold-
back tensions will occur at the end or the reel due to the small hub diameter.

This may cause trouble due to slippage at the capstan idler (see item No. 8 below).
If the small type reels are to be used exclusively, resistors R401 and R403, in
series with the Rewind and makeup motors respectively, should be increased to the
maximum setting. See Service Bulletin £20 to add switch for both 7 and lO~1/?'
reels. It is recommended that the smaller 5' reels not be used for recording or
playback. {To play the 5' reels, external resistors w0uld have to be added to

R401 and R403 for proper tensions.)

2. Threadi . In threading the tape. be sure to remove any adhesive that may have
been used to seal the end. If this adhesive is not removed, the first layer may
stick and cause the end to break off at the end of Rewind.

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AMIPIEX

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CORPORATION

934 CHARTER SloEMEISON 8-117I
TWX REDWOOD {377 CA]. 4!
CAILE ADDRESS: AMPEI. REDWOOD CITY
REDWOOD CITY.CALIFORNIA

SERVICE BULLETIN
MAGNETIC RECORDERS

one
«own 303
IUlLEltN no: 19
'NOENO: 6

00-63 100 HFD 50 . Eleanrolytic Condenser
RL-Z 3 Pole Double Throw DC Relay
CO- 10 .0035 LEE 500 F. Jica Condenser 5;
03-21 .002 I?) 500 ?. fiica Condenser 5
C3-92 .0001 I?) Pzdier Condenser
fiL-32 l Jegonm l .e: Conposition Yosistcr
CO-S .0005 L?) 500 I. Iica Ger-dianser
32-255 10,000 Ohm . j. Potentiometer
EL-3?S Plug, Lrase Output (For jaking Adapter for Zeasuring Lrese Current)
h75-l Eead Assembly - Console
h75-2 iced Assembly - Peck and Portable

.LJUDJL-S S..I&L $536 890
30-43 33 IFJ 53 V. Electrolytic Sondenser
BL-E 3 1010 Double Threw DC Relay
00-13 .3035 F F0 500 V. flica Condenser 5%
60-21 .302 :ED 33 ". lice Condenser 55
00-92 9001 D Pad-dw Condenser
33-32 1 Je;ohm l ?att Corrosition esishor
CO-S .0005 T?) 300 ?. iica Condenser
33-25? 10,000 OF] T. . Patenticmeter
PL-378 Flue, Trase Output (For Laking Adapter for Lbasuring Erase Current)
b?§~l Head Assembly - Console
LTS-2 Head :sse1:)l" - EC: and Portable

.1234. 517111.; 5891-1601:
30-21 .002 EFD 330 W. Rica Condenser SE
L-BYS Plug, Era jse Output (For iéking Ldapter for Measuring Erase Current}
30-10 .0035 " 3 U. jiua- ondenser 52
LTS- 1 Ee :d n-99r" - Corsole
L?T-/ Leg' assenblv - 936k and Rortafile

3L 0 VS 5 .15L 1 3 2912
CO-lO .0033 WED 500 V. Hice .ondens er 3;
CO-Zl .002 JFJ 500 V. dice Condenser S,%