Ray Carlsen wrote:

It was made by Toshiba and is unlike any other CBM monitor and my
other schematics will not substitute. Note that it is nearly identical
in outward appearance and features to Commodore
monitor models 1902 (non-A model) and 1084. However, the internal
construction, components and board numbers are completely different. I
own a 1080, and I have collected some information about it to assist
those who might have to repair one. The chassis number of my monitor
is TAK8520. Although the construction of
this monitor makes troubleshooting difficult because of crowded
boards, all boards are silkscreened on both sides with component
identifier numbers. All internal controls are marked as well.
Note that each section of the monitor is numbered, and that can be
used to locate components in each circuit. The following is viewed
facing the rear of the monitor with the back cover removed. The bottom
main PC board contains the Horizontal Sweep, HV, Vertical and low
voltage power supply circuits. The PC board designation for the H
sweep section is 400 (example: H output transistor is Q404). The
vertical sweep section is designated 300. The power supply is 800.
The left upright mounted PC board is analog video and digital
signal processing (100) and an audio amplifier (600). That board
swings away to the left (remove two screws) for better access to it
and the bottom board. The rear upright PC board is an A/V and RGB
connector interface and has both 100 (signal) and 600 (audio)
components on it.
Lastly, the CRT board (500) mounted on the back of the picture
tube contains the driver and output transistors for the CRT.
The Low Voltage Power Supply (LVPS): main switcher transistor is Q801,
a 2SD1432. The line fuse is a 3 Amp F801, and the B+ fuse is a 1.2 Amp
F802. Both fuses are on the bottom PC board in fuse clips.

HV & Horiz Sweep: the Horizontal Output (Line Output) transistor is a
2SD1427 Q404
and the flyback (line output transformer) T461 is part number
TFB5017AD (which looks like a Panasonic number).
Vertical circuit: this monitor uses descrete components (no ICs). The
output transistors are Q304 2SC2073 and Q305 2SA940. Note that this
monitor has a service switch in the center of the bottom board towards
the left side. That
switch should be in the NORMAL position. If in SERVICE, the vertical
sweep
will collapse to a single horizontal line (used for CRT setup
adjustments).

Thanks Ray. The monitor is underneath my bench at work and I'm off
until the Monday after Thanksgiving so I won't get to delve into it
again until then. Maybe with this info and the datasheet for the NTE
equivalent of the big TA7644 IC I can troubleshoot the problem.

--

Rick Jones
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