Ikegami HTM-1990R M, Service Manual

Page: 38 / 109

1-B-27
RGB OUT BOARD
(1) Circuit Structure
(a) Voltage amplifying Circuit
(b) Current amplifying BFS(Beam Feedback System) switch Circuit
(c) BFS (Beam Feedback System) sampling-hold Circuit
(d) Ripple Filter
(2) Adjustment Method
* When not otherwise indicated, HDTV is the standard for the input signal in the analog component of YPbPr.
* The figures are images are differ from the actual signals.
(a) VR101 [G FREQ.COMP]
VR201 [B FREQ.COMP]
VR301 [R FREQ.COMP]
Input the sweep signal to Y and flatten the difference in the levels of the encircled sections from low level
to medium level in the test points TP1 (B), TP3 (R), TP5 (G) of the CRT SOCKET BOARD.
Finally, adjust the Frequency Characteristic 1dB/-3dB up to 30 MHz.
Note: Use the 100:1 high resist voltage/low capacity probe.
60Hz
+1dB -1dB Standard
25MHz 30MHz
-3dB
60Hz
+1dB -1dB Standard
25MHz 30MHz
-3dB
60Hz
+1dB -1dB Standard
25MHz 30MHz
-3dB
(b) VR102 [G CLIP]
VR202 [B CLIP]
VR302 [R CLIP]
Input the lamp signal to Y at the test points TP1 (B), TP3 (R), TP5 (G) of the CRT SOCKET BOARD and,
with the Terminal Resistoropen, gradually raise the contrast VR to increase the video level so that Adjust
the signal clips in the vicinity of about 55V.
Clamp (applox. 120V)
55V
0V
Normal video level
Clip video level
Section where video level clips