The LA7840 is a field deflection output integrated circuit developed by Sanyo. It features a DC-coupled input, making it suitable for various television applications. The device is often used in conjunction with other ICs like the LA76810, which generates the field sawtooth voltage. This signal is then amplified by the LA7840 to drive the field deflection coil directly, ensuring stable and accurate scanning in CRT-based TVs. Internally, the LA7840 contains key components such as a sawtooth voltage operational amplifier, an overheat protection circuit, and a pump power supply circuit. It operates with a relatively low current of 1.8A for small-screen TVs. The chip is known for its low power consumption, minimal crossover distortion, single power supply operation, and a simple design that requires few external components, making it a reliable choice for many TV manufacturers. When testing the Hisense TC2199A model using an MF10B multimeter, the resistance was measured online using the R×1k range. This type of measurement helps in diagnosing potential issues within the circuit and verifying the functionality of the LA7840 IC. Adjustable Aluminum Laptop Stand, Nulaxy Adjustable Aluminum Laptop Stand, Amazon Aluminum Laptop Stand Shenzhen ChengRong Technology Co.,Ltd. , https://www.laptopstandsupplier.com
Pin number
Label
Features
Voltage value (V)
Resistance to ground (kΩ)
Black pen grounding
Red pen grounding
1
GND
Ground
0
0
0
2
V OUT
Field scan output
12.5
1.0
1.0
3
VCC2
Pump power supply voltage input
24.8
6.3
&
4
NON-INV IN
Field sawtooth voltage input
2.5
2.2
2.5
5
INV IN
Inverting input
2.5
4.4
4.1
6
VCC
Voltage
24.3
6.3
18.5
7
PUMP UP
Pump power output
1.9
7.5
35