hitachi vm Service Manual

Video Corner

Servicing the Hitachi VM Series
camcorder

By Timothy W. Durhan

VHS camcorders from all manufactur­ers have a lot in common. They have to
have a lot of similarities in order to record
and play back on the same VHS tape cas­sette. On the other hand, manufacturers
also have a great deal of freedom in the
details of how they design and construct
their camcorders.

This article will describe procedures
for servicing Hitachi models VM 3000
through VM 5000 camcorders. Many of
the problem symptoms and actions to cor­rect the problems will also apply to other
brands and models of camcorder.

Hitachi manufactured thousands of
camcorders in the late 80’s as models VM
3000 to VM 5000. Radio Shack, RCA and
Sears sold these units too, using their own
names and model numbers. All feature
the same tape mechanism. The capstan,

Durhan is an independent consumer electronics
ing

technician

and a freelance

technical writer.

service

mode cam and tape wind functions are
actuated by belts.

Symptoms of worn rubber parts

You probably know rubber parts dete-

riorate in time, even if they’re not used
often. Chances are, a five or six year old
camcorder will need new rubber. Some
common symptoms of worn belt prob­lems include:

l Tape starts to load, then camcorder

shuts off.

*Tape runs, then after a while, shuts off.

l Camcorder eats tapes.
l Tapes won’t play or record.

If you have serviced VCRs with simi­lar problems, you know it’s not too diffi­cult to replace worn rubber parts.

Many VCR technicians are reluctant to
service camcorders, even though they
wouldn’t think twice about opening up

and repairing a hand held remote control.
If you can repair a remote control unit
without destroying the case or losing any
of the buttons, performing a mechanical
repair on a camcorder shouldn’t be too
difficult. Lost screws, pinched wires and
broken pc boards can be avoided by using
a systematic disassembly and reassembly
procedure.

Getting started

Start by powering up the camcorder
using the customer’s ac adapter, since a
defective battery may also be the cause of
any of the symptoms mentioned earlier.
Moreover, there is nothing more frustrat­ing than running out of power in the mid­dle of a repair. If your customer didn’t in­clude the adapter along with their cam­corder, put this repair on hold until they do.

Slide the power switch to on, and press
eject. If the mode belt is in good shape,

the cassette lid should pop up. If it doesn’t

1. Upper Cylinder (Video Head)

2. Audio/Control (A/C Head)

3.

Dew Sensor

4.

Pressure Roller

5.

Capstan Motor

6.

Capstan Flywheel

7. Take-up End Sensor

8. Take-up Reel Disk

9.

End Lump

10. Take-up Guide Roller

11.

Supply Reed Disk

12.

Tension Band

13.

Tension Arm

14. Supply Guide Roller

15. Supply End Sensor

16.

Impedance Roller

17. Full Erase Head

18.

Cylinder Brush

Figure 1. Tape transport mechanism-Top View.

60 Electronic Servicing

&

Technology November 1993

open, you’ll have to trigger the carriage
latch manually.

To open this latch manually, unplug the
ac adapter and remove the two screws that
hold the cassette lid on. Carefully slide
off the lid, and set it out of your way. On
the right side at the top edge of the chas­sis is a tiny latch (Figure 1). Gently move
the latch to one side with a small screw­driver or pick. The housing should pop
up, and you can remove the video tape, if
one is stuck inside.

Performing the diagnosis

Once the cassette lid is off, power-up
the camcorder again. Cover up the sense
LED in the center of the transport with

black tape or other suitable light shield,
and press play. Again, if the mode belt is
in good shape, the guide posts should
move to their stoppers, and the drum will
start to spin.

To determine whether the tape-wind

belt is doing its job, use a torque gauge
on the take-up spindle. Hitachi recom­mends

80gm-cm

to 1 lOgm-cm. If you
lack such a handy tool, you can try to stop
the spindle with your fingers. Obviously,
if the spindle doesn’t turn, or stops very
easily, the tape-wind belt is defective. Is
the pinchroller turning?

If the take-up spindle and pinchroller
aren’t moving, the capstan belt is defec­tive, or there may be an electronic fault.
Listen closely for the sound of the cap­stan motor spinning. You will have to
press the play button continually in this

DISCONNECT

Figure 2. Jack circuit board removal

condition, because the lackofpulses from
the capstan and take-up sensors will alert

to order your parts from RCA instead of

ordering from Hitachi.
the system control microprocessor to
enter the protection mode, and the

cam-

corder will shut off.

If you have checked all of these func-
tions, and have determined that a belt may
need to be replaced; replace them all.

There are only three belts on the mech-

sense LED you put on earlier. Close the
cassette holder, (if you can). Unplug the
adapter cable to give yourself more room.

Unplug and remove the viewfinder.
anism, and since they were all manufac-
tured at the same time, if one is worn, the

other two can’t be far behind.

Belt part numbers 6356445, 6356472
and 6358012 should be available from
any Hitachi part distributor. Use numbers

cassette housing facing down, and the
lens assembly pointing to your left.
move the screws that hold the case shells
together. Next, carefully pull the shell
that’s facing you off and set it aside.

174757, 174758 and 174759 if you want

RELEASE
TWO TABS

BOARD

Getting to the belts

To begin, remove the covering from the

Lay the camcorder on its side, with the

Re-

Release the main pc board from the two