Star Tech Journal

3
UPDATING OLDER 11 SHP 11
SEEBURG AMPS
by Fred Rice
The See burg SH P series amps have been
around almost 10 years. Due to interchange-
ability, many earlier amps end up in late
model machines. Here are some modifications
I strongly recommend.
First, if your amp is designated SHP 1
CODE A, these were from early OLYMPIAN
models. This amp does not have a fused
power lead for the PRVC or TPI K MICRO-
PHONE. A shorted PRVC or mike line (from
rolling the machine over these cables) can
cause blown outputs or power diodes. The
TSA amplifiers had a different setup and will
play but not trip off as the record ends (the
shorted line kills 30 volts to the trip relay).
Looking at the amp with the tone switches
pointing up, the brown wires coming from the
volume control and MIC plugs should be cut
from the junction of CR 5113 and CR 5115,
and moved to the blank lug on the terminal
strip to the right. A 2 amp quickblow pig-tail
fuse can be used between the junction of the
two diodes and the brown wires. I prefer
mounting a fuse holder on the side of the
chassis with wire jumpers to the points
mentioned. This saves having to take time to
solder a replacement fuse in a bad location in
the future.
Another modification I suggest is for the
emitter resistors for the four drivers. These are
marked R5175, R5176, R5198, and R5199. In
early amps these were 560 ohms,½ watt.
These should be changed to 100 ohms,½
watt. Don't use carbon resistors here, I have
seen shorted drivers cause these resistors to
burn one inch holes in the board. RCA and
SYLVANIA make½ watt flame proof resistors
with a 2% tolerance which are available at
most electronic supply houses. It is a good
idea to change the 4 resistors to flameproofs
in later SH P amplifiers, also.