Ampex 351 - Page 55

6-7
time for the tape to stop completely
when switching from either of the
fast modes to play.
NOTE
In the LARGE reel position, both the
rewind and take-up reels must be NAB
type and in the SMALL reel position
both reels must be EIA.
ROUTINE MAINTENANCE
Carefully follow the routine maintenance
program outlined below if proper performance
is to be expected of the equipment at all times.
It is recommended that an Operation and Main 
tenance Log be kept.
Cleanliness of all parts of the tape drive
mechanism is required for consistent optimum
performance. Clean all parts except the head
assembly using a lintless cloth moistened with
Iso-Propyl alcohol (easily obtained). This clean 
ing is of particular importance because most
tape manufacturers lubricate their tapes, and
the lubricant will gradually form a coating on
the components in the tape threading path
which will result in a loss of positive drive at
the capstan, flutter and wow, drop-outs or poor
high frequency response.
NOTE
It is imperative that Iso-Propyl alcohol
be used on the cleaning of the cap
stan idler wheel (rubber) and not
the recommended Xylene cleaner for
heads.
CAUTION
Do not use any other solvents as there
are some which may damage the lam 
inations of the head assembly. Do not
use metal swab-sticks.
89-0131
89-0144
Issue A
NOTE
The Catalog Number 5700 tape trans 
ports used on earlier models changed
PLAY tension only when in the
SMALL reel position.
Cleaning
Clean the capstan, the head faces and tape
guides daily. Clean the capstan idler wheel
weekly. Great care must be taken to see that
oil does not reach the rubber tire. Avoid, as
much as possible, touching the tire with the
fingers.
The agent for cleaning A mpex head assem 
blies is a mixture of Xylene and 0.1% Aerosol,
and is available in 4 oz. bottles (A mpex A udio
Part No. 823). Other solvents can have detri 
mental effects on these precision parts.
To clean any head assembly, wind a clean,
lintless cloth on a wooden swab-stick and
moisten with this mixture. Swab the heads
periodically to remove all dirt and accumulated
oxide deposited from some tapes.
Reel Size Switch
Selection of proper holdback tension, de 
pending on reel hub size, is made at the two
position toggle switch labeled LARGE-SMALL.
Idoldback tension is not a constant in any mode
of operation, varying directly as a function of
the trailing turntable motor torque, and in 
versely as a function of the effective trailing
reel hub diameter (hub meter includes the
tape wound on the hub). For a given torque
on the trailing motor, the holdback tension will
increase as the effective hub diameter of the
trailing reel decreases. Reducing the torque on
the trailing turntable motor will decrease the
holdback tension.
The holdback tension resistors for adjust 
ment of take-up and rewind motor torques
are factory-set for NAB 10 ‘ /2 inch reels. If
the smaller (7 or 5 inch) EIA (formerly
RETMA) reels are used, compensation for the
overall increase in holdback tension must be
made by placing the switch in the SMALL
position. This places resistor R502 in series
with the take-up and rewind motors, thus re 
ducing the torque of both motors in any mode
of operation when the EIA reels are used. If it
is desired to accelerate faster in the rewind or
fast forward modes, the switch may be placed
in the LARGE position during these modes.
The REEL SIZE switch is a SPST switch placed
across the resistor R502. It is closed when the
LARGE position for 10 ‘ /2 inch diameter NAB
is selected; and open (resistor R502 in the
torque motor circuits) when the SMALL posi 
tion is selected.