1
Harbor Freight / Bunker Hill model 66556 B & W Security Monitor Repair Guide
GENERAL INFORMATION
The Harbor Freight/Bunker Hill security camera monitor model 66556 is a black and white monitor that
accepts composite NTSC video from any standard NTSC video source. It has a 5.5 inch (measured
diagonally) viewable area. There are two video input jacks and two audio input jacks on the rear panel
which the monitor can switch automatically or manually between the two channels. There are also two 12
volt DC output jacks on the rear panel that are intended to feed 12 volt dc power to a couple of security
cameras. The monitor operates on 12 volts DC @ 1.2 amps supplied by a wall adapter which has a center
positive connector to plug into the appropriate jack on the back of the monitor. This monitor also has an
audio output jack and a video output jack on the rear panel to feed to a digital video recorder or to an
additional monitor. There are four screws holding the plastic case together. Two are located in the finger
well area and two others are located near the swing up wire support. If you lose the screws or the heads are
stripped out, the originals are metric. You can replace them with two Phillips pan head #4 by 3/4 inches
long sheet metal screws for the two near the swing up metal support and two Phillips pan head #4 by 5/8
inches long sheet metal screws for in the finger well area. When all four screws are removed you can slide
the rear half of the plastic case back from the front half. You will need to unplug the connectors to the rear
panel jacks and to the speaker in order to fully remove the rear cover.
CRT INFORMATION
This monitor uses a type 14SX5Y4 black and white CRT which is 5.5 inches (or 14 centimeters) measured
diagonally. Deflection angle is 70 degrees. Neck diameter is 20 millimeters and the tube is 175 millimeters
long. Heater filament operates on 12 volts DC @ 75 milliamps. High voltage is 7,500 volts.
YOKE INFORMATION
GS Brand # QPH20-70-5C or GS-101120. The vertical section is the white and yellow wire and measures
3.5 ohms resistance. The horizontal section is the red and black wires and measures 1.2 ohms resistance.
Manufactured by Tianchang Guang Sheng Electronics Co. Ltd and their website is
www.tcgsdz.com
FLYBACK INFORMATION
GS Brand # BSH8-N5510F or GS-100618. Manufactured by Tianchang Guang Sheng Electronics co. Ltd
and their website is
www.tcgsdz.com
SEMICONDUCTOR INFORMATION
Q01: B834-Y (PNP) = NTE 153
Q5: KSD362R (NPN) = NTE 375
IC01: CD4066BE (quad switch) = NTE 4066B
IC2: LA7806 (B/W TV, sync, & hor/vert deflection) = NTE 1540
IC03: LM386N (audio amp, 1 watt) = NTE 823
IC04: NE555 (timer) = NTE 955M
CAPACITOR INFORMATION
There are a total of 32 electrolytic capacitors and 1 dipped tantalum capacitor on the main board. So far, I
have not made a list of them, but two of them go bad causing no vertical deflection symptom. See below in
the “Troubles” section for information regarding those two particular capacitors.
CONNECTOR INFORMATION
