20
STAR*TECH JOURNAL/NOVEMBER 1983
Pioneer PR-7820 continued.
One of the "fixes" that was done has no engineering change notice
because while I was at "school" I mentioned that I was receiving quite a few
"requests" for information on how to get rid of the "F"s that appear on the
unused portion of the digital display board. Engineering was aware of the
symptom and there were ( and are) several different theories as to the "why"
of it. But the fix was found overnight thanks to several members of
Cinematronics' engineering group all playing with the problem.
The Intersil chip is a tri-state device. This means that it can operate in
three different modes of operation. When the enable is attached to V cc ( + V)
it's in one mode. When it's attached to Vss (GND) it's in another mode.
When the enable is between low and high, it's in a third state (tri-state,
remember?) which is the state that is used with Dragon's Lair. The spec
sheet shows it as internally biased to the center ( not high, not low) state, so
the engineers did not attach any connections to pin 9 of the IC. This is the
reason that you're getting the "F''s in the unactivated segments of the score
display. Apparently, the I C's internal components aren't quite up to the job,
so in order to "get rid" of the "F"s you can do the following:
Locate the V cc ( + logic voltage) and the V ss (ground) and attach two (2)
resistors to pin 9 of each Intersil chip and one resistor attached to V cc and
the other attached to Vss as shown in Figure 4.
r.□□□□ o □ □,; □ □□ □
00000000
l
NOW ... There is a way to minimize the eccentricity and here it is! (The
crosshatch display test may not be present in older discs, you'll just have to
look!)
1. Remove the 24-pin ribbon connector from the back of the unit and tum
the power on.
2. Push PLAY and wait 30 seconds. Then push SCAN FORWARD.
You'll have to use a mirror ( and probably someone to hold it) to watch the
screen. When you get to the dragon's lair, start watching for the end of the
animation. If you push the button marked FRAME DISP., a number will
appear in the upper left-hand quadrant. That number is the frame number.
The one you're hunting (frame number that is) is #31620.
3. When you find frame #31620, you'll see a crosshatch network with
dots in the crosshatch. If you push PLAY, you'll see a white bar travel from
left to right across the crosshatch network. When the bar gets fully to the
right, push SLOW REVERSE and watch the bar move the other way. When
the bar gets to the left side of the screen (not off the screen) you'll push
SCAN FORWARD and watch the screen. (You must hold the SCAN
FORWARD button down or the scan will stop.)
4. You will see either a circle or "X" and what you're going to do is
adjust the disc on the spindle until the circle or "X" is at its narrowest
position. See illustration below.
DODOO
FIGURE4
Cinematronics has never had a very good reputation for customer
service ... until now! Mr. Pierce and everyone else at Cinematronics has
really made the customer service department a number 1 priority! In fact, if
you have any trouble and call into customer service, you'll get Pat, Jerry, or
any one of a number of very qualified, technically-able persons.
There was a problem (is a problem?) with people not knowing the best
way to get disc players repaired after warranty. The disc player can be
serviced for 90 days after initial sale under warranty by following these
steps.
I . Call Cinematronics service department . . . Determine that the
problem is definitely in the disc player itself.
2. Let your distributor ( iflocal) have first shot at getting the unit fixed.
This is possible, as many distributors have already sent their techs to the
Cinematronics PR- 7820 repair course.
3. If your distributor is across the country, you can ( after talking to the
Cinematronics customer service department) call a toll-free number to
Pioneer customer service that they will give you at that time. Be prepared to
give the Pioneer telephone representative the player serial number, your
company's name, address and phone number, and the names of two persons
to contact at your company. You will then be issued a reference number.
Write down that number so that your order may be identified to theirs should
follow-up be required.
Either you will be given a phone number·of a local Pioneer factory-
authorized service center, or a local service center will contact you (usually
within 24 hours) to arrange service.
Cinematronics is making every effort to handle warranty repairs on an
advance replacement basis, but as we all know, there is a player shortage at
present. (They can't build 'em fast enough!)
The Cinematronics toll~free customer service number is 1-800/85 3-2666.
Ask for the customer service order desk. Be ready to give the game's serial
number, warranty item serial number, and P.O. number. Cinematronics will
then issue an RM.A. (Return Merchandise Authorization) number to you.
Keep track of that number for future reference. Also be sure to return the
faulty unit immediately in order not to be billed for the replacement part!
(Over $2000.00.) A brief symptomatic description of the problem will be
greatly appreciated. The customer service staff is on duty 7:00 a.m. to 4:00
p.m. California time.
There are only a few common failure problems and they are mainly heat-
related as most operators with a large number of units already know.
Heat in the disc player is caused mainly by amplifiers which drive the
tracking, mirror, carriage motor and focus motor. The more eccentricity
present in the shape of the disc, the harder these motors have to work, and-
the more heat produced.
BAD
VERY GOOD
BAD
VERY GOOD
(Note that the crosshatch with dots will be visible, but I'm not going to
draw them in!)
5. If the pattern you receive is a large (bad) one, you will:
a) Push the REJECT button.
b) Unlock the spindle "LOCK".
c) Tum the disc approximately 20 degrees (¼th tum) on the spindle.
d) Lock the spindle disc lock(this centers the disc), unlock, and then lock the
spindle disc lock again.
e) Repeat steps 2 through 4 again and again until you get the pattern to as
small a pattern as possible. (Disc is then centered correctly.)
6. When your pattern is small, this means that the tracking motor is not
being forced to work so hard, which means that the power amplifier is not
working very hard, which means that the power amp is not producing nearly
as much heat in the unit, which is the disc player's main enemy!
NEXT ... When your picture goes black & white and is very "jittery",
you're witnessing about the most common problem in the PR- 7820 player
unit. This is a transistor failure at position Q29 on the VTBC board. When
this transistor blows out, it turns off an FET which opens the loop-Jock on
the board which takes the S}TIC and throws it out the window! (For all you
strictly technical people who don't want to hear it in layman's terms, it
makes the unit unable to lock onto the video sync signal.)
There is a heavier duty transistor recommended for the replacement of
Q29 which is a 2SC1627, but it's been found that even with the higher
"junction temperature" rating and "collector power dissipation" rating that
many of these are blowing upon powerup. The ECG (Sylvania) cross for the
2SC1627 is an ECG 289A which I have not had any trouble with after
replacement. The transistor you will find in the circuit initially is a 2SC
1815-Y (which crosses with an ECG 85, an all-purpose transistor) which is
what Cinematronics is now recommending that you put back in ( at least until
the people at Pioneer make a more "official" recommendation for a
transistor replacement). Since this is a "heat" failure problem, I would
personally put a heat sink on the transistor! (In fact, I have been!) The case is
a T0-92 (small plastic case) and there are a number of heat sinks available,
but if you are having trouble finding one locally, you can phone All
Electronics and order IO for $1.00. The part number is Cat. #HS-92 and
the phone number for All Electronics Corp. is 1-800/826-5432 (in Alaska,
Hawaii and California you must call 213/380-8000).
Figure 5 shows the location of the VTBC (Video & Time Base
Connector Assembly) PC board. In fact, shown are the locations of all major
PC boards in the unit so that if you're talking to a Pioneer or Cinematronics
service person, you can speak intelligently about which board is which.
Continued on page 24.