This service manual of the old video cassette recorder VT-LC50EM is very good readable even the tiniest numbers (i.e. IC-pins). The circuits are very clear. Many details of the schematic are very good described but in GERMAN language. Many schematic details - but complete at all. Common background information of several details are enclosed and physical knowledge of the TFT liquid crystal display for example. The manual lacks PCB drawings. If you understand german I would recommend this manual for you.
Text excerpt from page 22 (click to view)
HTV-C1 7.2 TEST MODE
7.2.1 TEST MODE 7.2.1.1 How to Enter the Test Mode
Even that is possible though there are the following two methods. (1) Receive "A55F" command with the remote control unit. (2) Short-circuit the TEST MODE points on the foil side (pin 19 of IC5001 and ground) of the DISPLAY Assy. Plug the power cord into the AC socket.
2. DSP Check
Press the SURR. MODE key � Enter the DSP check mode. DSP check mode Outputs TEST TONE in the DOLBY VIRTUAL state. Output repeatedly TEST TONE in order of LEFT � CENTER � RIGHT � SURROUND. Confirm whether DSP moves normally at the time of the SURROUND output. Press the SURROUND MODE key twice � Release the DSP check mode. FL and LED are normal display. * A key except for the designation normally moves.
C DISPLAY ASSY
IC5001 Pin 19
SIDE B
7.2.1.3 Release The Test Mode
Turn the STAND BY/OFF key to OFF during the power on or unplug the power cord from the AC socket.
Short-circuit
7.2.2 SINGLE OPERATION METHOD
HTV system doesn't move if it is not the combination of HTV-C1 and HTV-A1 fundamentally. AC26V is added to the sub-transformer (T2) when the HTV-C1 is separate and you must diagnose it. (All the functions can't be validated.)
A MAIN ASSY
� When the test mode is entered, FL displays with "TEST 1" for 1 second. � LED keeps going on and off in the Test Mode. � At this time, the setting of VOLUME becomes 10. � SURROUND mode becomes DOLBY VIRTUAL ON.
7.2.1.2 Test Mode Operation
FL Segment Check Press the DISPLAY key � Switch the movement of (1) to (5) cyclically. (1) All lighting the FL and LED (2) All light-out the FL and LED (3) (segment check 1) "ABCDEFGH" display (4) (segment check 2) "IJKLMNOP" display (5) Normal display
SIDE A
1. Check The AUTO STANDBY Function
(1) Press the INPUT key � Turn the POWER off and it becomes AUTO STANDBY mode. FL displays with "AUTO". (It becomes the condition that it passes for three minutes during POWER ON with no signal.) (2) Input the input signal to INPUT terminal � AUTO POWER ON. (It moves only when it is inputted to the selected INPUT terminal.) 20