Pioneer PL-990 User manual

Add A PreAmp On/Off Swith
to Pioneer PL-990
(ca. 2014 Model)
D. MCDONALD
14-FEBRUARY-2016

BACKGROUND
•Pioneer PL-990 Turntable has a built-in PreAmplifier
•This is useful for many because the Turntable Output is already amplified, and it
can be connected to AUX or CD (Line Level) Inputs
•If a PreAmplifier is NOT present in a turntable, then the output from the
turntable must be amplified before it becomes “Line Level” and useful.
•Old-School Amplifiers have a “Phono” Input for this express purpose
•Vintage Turntables do not have built-in PreAmplifiers, and Vintage
Amplifiers always had a “Phono” input that would appropriately
amplify the raw output signal from a turntable.

BACKGROUND
•Why would one need or want a switch?
•If you want to connect this turntable to the “Phono” input of your vintage amplifier and have it
work correctly, then a switch will help…
•If you don’t like the PreAmplifier included with this Turntable and want to use one of your own
choosing, then a switch will help…
•If you just want to have a turntable, and just want to listen to sounds from vinyl LPs, and don’t have
an amplifier with a “Phono” input that you want to use, then this switch doesn’t really matter.
•If you are more than a little picky about the quality of sounds you listen to, or if you
care about the quality of the hardware you use to produce these sounds then you
probably won’t have a turntable like this, and then this switch doesn’t really matter.

BACKGROUND
•It appears that this Turntable model was designed with the capability of
having a PreAmp On/Off switch.
•This option seems to have only been enabled rarely, if ever.
•There is a hole molded in the plastic below the platter which allows access to the PreAmp PCB
where a switch would have been/could have been installed
•The PCB includes a location for a switch and nearly all of the electrical traces necessary for such a
switch
•Note that the PreAmplifier PCB in my turntable unit is significantly different
from the one described in a service manual available online.
•But the provision for a switch is available on both versions.
•My Turntable’s PreAmp is based on a TI-DRV602 chip.

A LOOK AT WHERE THE SWITCH SHOULD BE
•2. Remove Pad,
Rotate Platter
•1. Remove Top Cover •3. Look Here
(No Switch!)

A LOOK AT WHERE THE SWITCH SHOULD BE
•Look Here (No Switch!)
No Switch (As Received)
•Look Here (No Switch!)

WHAT TO DO (SUMMARY)
•Dismantle Turntable, to gain access to PreAmp PCB
•Remove some jumpers from the PCB
•Some jumpers are present which make the PCB Default to PreAmp
Always-On
•Install some additional jumpers to the PCB
•Some jumpers will be needed to complete the electrical pathways for the
unamplified signal
•Install an appropriate switch into the position provided
•Reassemble Turntable

MY MODEL IDENTIFICATION
•Pioneer PL-990
•Mfr Date: Jan-2014
•Made in China

DISMANTLE THE TURNTABLE

REMOVE THE PLATTER
•Unhook the Belt
•Then Pull the Platter straight up