MAI COMPANY CONFIDENTIAL FIELD INFORMATION BULLETIN
SERVICE GROUP(S): MINI MFG: BASIC FOUR
NACS TYPE(S): 4301 MFG. MODEL(S): 4300,4301,7250,7270
CATEGORY: VIDEO TERMINAL DESC: CLAMSHELL CASE
*** TABLE OF CONTENTS AS OF 01/28/92 ***
FIB 00001.General.Information.........................................10/15/86
FIB 00002.Logic to frame ground isolation.............................11/18/81
FIB 00003.Monitor parts information - Ball Brothers and C. Itoh.......02/25/82
FIB 00004.Troubleshooting Guide ......................................04/01/82
FIB 00005.Intermittant keyboard and display problems..................08/24/82
FIB 00006.7250 monitor control PCBA (MM731010)........................10/12/82
FIB 00007.Intermittent problems.......................................03/30/83
FIB 00008.7270 firmware must be level -039/40 if slave printer is atta10/11/83
FIB 00009.Replacement capacitor for C105 on MM732010 PCBA - 4250/70 te05/17/84
FIB 00010.Keyboard assemblies (MM733020)..............................07/13/84
FIB 00011.Complete monitor asm. no longer available - order separate p08/22/84
FIB 00012.Problem with mounting a different style of monitor PCBA.....07/24/85
FIB 00013.Field replacement of serial interface I/Cs..................08/30/85
FIB 00014.LOWER CASE OPTION INSTALLATION..............................07/10/87
FIB 00015.CRT SUBSTITUTION............................................02/03/88
FIB 00016.Keyboard Cleaning and Repair................................01/10/92
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------Table Of Contents Pg01 of 01
FIB 00001 10/15/86
*** General Information ***
14" Monochrome Video Terminal with adjustable baud rate up to 9600.
"Clamshell" type case with non-detachable keyboard.
4270 supports a slave printer, 4250 does not.
4250 has "long" Logic PCBA, 4270 has "short" Logic PCBA.
*** NACS MACHINE TYPES AND FEATURE NUMBERS ***
4270,4285,9748,9749
*** AVAILABLE DOCUMENTATION ***
Monitor Quick Reference Manual
4285 - Basic Four model 7250:
Video Display Terminal and Controller Service Manual - S-HDBK-235
4270 - Basic Four model 7270:
Model 7270 Video Display Terminal Service Manual - S-HDBK-226
*** AVAILABLE TRAINING ***
None
*** SPECIAL TOOLS ***
None
*** SPECIAL ADMINISTRATIVE PROCEEDURES ***
None
ORIGINATOR: J. ROGERS
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB001 Pg001
FIB 00002 11/18/81
*** Logic to frame ground isolation ***
FMK 09-304 has been released to prevent logic board damage on improperly
grounded VDT's. ICs may fail due to earth ground transient current.
Common symptom is the lack of communications between VDT and CPU. The
grounding requirements on the VDT are as follows:
a) Logic Ground and Chassis Ground must not be shorted together at the
terminal.
b) The CRT mounting frame is tied to Logic Ground.
c) The enclosure is tied to Chassis Ground.
d) The shield on the terminal cables must be connected to chassis ground
at both ends.
e) Chassis ground must be connected to earth ground thru the AC plug.
VDT's manufactured prior to 4/13/81 may not comply with all grounding
requirements.
Units affected are:
a) 7270 shipped before 4/13/81.
b) 7250 using Monitor type TVX 120 and with inside surface of the cover
painted with conductive coating (silver or copper colored) used as
EMI shield.
The installation of this FMK is mandatory on all units affected.
To determine if the FMK is required, inspect the units as follows:
a) Turn power off and remove AC plug from AC outlet.
b) Remove interface signal cables connected to logic board (J1 and J2).
c) Connect an ohmmeter to measure between chassis ground (screw holding
EMI filter) and logic board ground (logic board P5, Pin 10 from Power
Supply).
d) If ohmmeter reads open (greater than 100 k ohms) the FMK is not required.
e) If ohmmeter reads short (less than 100 k ohms) FMK must be installed.
Inspect all 7250/7270 VDTs in your area and order the following FMK as
required:
MM NUMBER P/N DESCRIPTION
990015 FMK 09-304 VDT Logic Ground Isolation Kit
NOTE: Instances have been noted where the threaded inserts for the CRT
mounting brackets in the VDT enclosure cover make contact with
the conductive coating. If the FMK is required, prior to install-
ing the CRT assembly, verify that the threaded inserts which hold
the CRT mounting brackets (Figure 2, FMK 09-304) are electrically
isolated from the conductive coating. Use an Xacto knife to scrape
the coating from the case adjacent the insert as required to ensure
an open ohmmeter reading between the insert and the coating.
ORIGINATOR: J. RIPPL
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB002 Pg001
FIB 00003 02/25/82
*** Monitor parts information - Ball Brothers and C. Itoh ***
Basic Four Manufacturing is now using two different sources for the CRT
Monitor Assembly on 7270 VDT's. The new CRT Monitor Assembly is procured
from C.ITOH/3Q and consists of only 2 parts, the CRT/Yoke assembly and the
Monitor board. The High Voltage Transformer and vertical choke are now
mounted on the Monitor board.
C.ITOH/3Q
MM # P/N DESCRIPTION
732010 400369-010 PCBA, Monitor (3Q)
732000 906924-002 CRT/Yoke Assembly (3Q)
The original monitor is manufactured by Ball Bros. and consists of the
following parts:
BALL BROS. TV-120
MM # P/N DESCRIPTION
*731020 6-002-0895 PCBA Monitor TV-120
*731021 6-002-0935 PCBA Monitor TV-120
*731022 6-002-1064 PCBA Monitor TV-120
733130 6-003-0604 Flyback, TV-120
733140 6-003-0529 Choke, Vertical TV-120
733150 906924-001 CRT/Yoke Assembly
You can no longer order MM 733120, P/N 906659-001 TV120 CRT/Yoke, Monitor
PCBA, Flyback and Choke assembly (Ball Bros.). You must now order each
part needed for either source.
* These Ball Bros. Monitor PCBA's are interchangeable and the last
three numbers of the P/N are usually stamped near J101.
ORIGINATOR: H. MONTIJO
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB003 Pg001
FIB 00004 04/01/82
*** Troubleshooting Guide ***
The following is a brief guide to determining which part of the 7250/7270
Display is faulty when a problem exists in the field. The tests do not
account for all possible modes of failure but should isolate the faulty
part in the majority of cases.
PRELIMINARY:
1. Place VDT in Batch mode.
2. a. For 7250 turn on Katacana switch (S6 Sw7), turn on terminal and a
full display of block characters should appear on the screen.
b. For 7270 turn terminal on, push "Escape" key then "U" key then "H"
key. A full display of H's should appear on the screen. When
terminal is turned on, it will beep if the self test is successful
on the logic PCBA. A raster but no blanks (7250) or characters
(7270), check video drive signal.
LOGIC PCBA CHECK:
1. Turn terminal off, remove cables going to monitor PCBA at the logic
board (J3 and J8) turn on terminal.
2. At the 7 pin brown connector, use Pin 1 to ground the scope. (Pin 2
is the key and is missing.)
3. On brown connector the following digital signals should appear on the
scope:
a) Pin 3 - Horizontal drive is a +4V, 25 MSEC pulse every 65 seconds.
b) Pin 5 - Video drive is a +2V, 420 NSEC pulse every 500 NSEC. (Signal
varies with different characters displayed.
c) Pin 6 = Vertical drive is a +4 1/2V, 15.5 MSEC pulse every 16.5 MSEC
on 7250 and +4 1/2V, 16.3 MSEC pulse every 16.5 MSEC on 7270.
4. On the 5 Pin white connector there should be +15 VDC on pin 1 (pin 2 is
missing). If the +15 VDC is low or missing and can't be adjusted,
replace the power supply.
MONITOR CRT CHECK:
1. Turn terminal off. Re-connect J3 and J8. Repeat step 2. Clip scope
ground to CRT grounding spring. Set scope to .2V/div. and 20 us/div.
You should be able to trigger on the horizontal flyback pulses that
are radiated from the monitor PCBA as you bring the probe close to the
flyback cable. If not the monitor board or flyback transformer is
probably bad. If pulses exist continue to step 8.
2. Turn terminal off. Remove CRT socket connector about 1/10" to expose
CRT pins yet still maintain contact with the connector. Connect scope
ground to grounding spring and repeat step 2. Verify the following
voltages:
Cathode Yellow wire 25VPP signal, approximately
Brightness White wire 0 to -60V (controlled by brightness pot)
Focus Orange wire 250V approximately 95 - 250V
Contrast Red wire 125V approximately on 7270 & 350V on 7250
Filament Brown Wire 12V (or if filament glows)
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB004 Pg001
If these voltages are present, replace the CRT. If one or more is bad,
replace the monitor board.
ORIGINATOR: J. RIPPL
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB004 Pg002
FIB 00005 08/24/82
*** Intermittant keyboard and display problems ***
Intermittent keyboard and display problems (such as key repeat errors
and jittering display) on the 7250/7270 VDT have, in some instances,
been traced to loose mounting hardware for capacitors C2 and C4 on the
Voltage Regulator PCBA (MM730020, P/N 902130-000).
Prior to replacing this unit on a service call, verify that the capacitor
mounting screws are tight. Also make this a check point on installation
of replacement assemblies.
ORIGINATOR: J. RIPPL
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB005 Pg001
FIB 00006 10/12/82
*** 7250 monitor control PCBA (MM731010) ***
Subject PCB's have been replaced to correct problems of jittery screen
and/or screens shrinking. In many cases the PCB was not the cause of
the problem. The real cause was oxide build-up on the connectors on the
video board or the plug on the power supply. Replacing the PCB may cure
the problem for a short while because the connectors have been disturbed.
Before replacing the PCB for above problems clean and tighten contacts on
these connectors.
ORIGINATOR: DOUG WOODWARD
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB006 Pg001
FIB 00007 03/30/83
*** Intermittent problems ***
SYMPTOM: VDT screen appears to have expanded characters on left side
only. Left side extends past left margin. Right side appears
normal. Rapping VDT or flexing cables may cause problem to
go away or return.
CAUSE: Several monitor boards have been found with a defective solder
joint on J-104 pin 1. This is monitor board MM731020. J-104 is
the 7 pin white connector and pin 1 is the end where the brown
wire is plugged. To repair, resolder the pin. This would also
be a good time to examine the other solder joints for defects.
ORIGINATOR: JOHN GEORGE
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB007 Pg001
FIB 00008 10/11/83
*** 7270 firmware must be level -039/40 if slave printer is attached ***
Printers slaved on the model 7270 (Sorbus Type 4270) VDT may experience
data integrity problems resulting in lost data, duplicated data or printer
errors reported through Business Basic (Level 4 and Level 8).
All terminals with slaved printers, regardless of printer type, must have
the -039/40 firmware to minimize slaved printer errors. The firmware may
be ordered as listed below if required:
Location 8E: Prom 165009-039, ICN YY009072, Prom, WP Printer Support
Location 8F: Prom 165009-040, ICN YY009073, Prom, WP Printer Support
ORIGINATOR: J. RIPPL
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB008 Pg001
FIB 00009 05/17/84
*** Replacement capacitor for C105 on MM732010 PCBA - 4250/70 terminal ***
The C. Itoh Monitor PCBA (MM732010) has a chronic problem with horizontal
"jitter" of the video caused by leakage of capacitor C105. Sorbus had used
the wrong type replacement which caused shifting of the video image to the
right after warm-up. The incorrect capacitor was a very small square orange
ceramic device. Its characteristics were the same as C104 rather than
opposite as the design required. (Both increased in capacitance with a
temperature increase.)
A substitute was found which seems to give satisfactory results. For all
future use in position C105, use Sorbus part number HR002302, described
as follows:
MANUFACTURER AND TYPE DESCRIPTION
SPRAGUE "PACER" 192P Axial, Tubular Mylar .022 mFd. 80 Volt
Since this is an axial-lead device, it must be mounted at a right-angle
to the PCB, and one lead insulated with TEFLON or other insulating tubing.
ORIGINATOR: JOHN VANDERHEYDEN
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB009 Pg001
FIB 00010 07/13/84
*** Keyboard assemblies (MM733020) ***
The malfunction of one key is the major failure of most keyboard
assemblies. The individual key may be sticking, not functioning at all,
or bouncing (which may cause a multiple of characters to appear on the
screen).
To replace an individual key in a keyboard assembly, proceed as follows:
1. Remove AC power from VDT.
2. Remove or raise VDT cover.
3. Remove keyboard assembly from VDT.
4. Place keyboard assembly upside down on a workable surface. Remove
the 16 small Phillips-head screws which secure the keyboard to the
keyboard PCB.
5. Inspect and clean contact areas (use isopropyl alcohol) on the
keyboard PCB.
6. Remove key top (by pulling upward) of faulty key on keyboard. Be
sure to retain the key spring (YY008921) which is underneath the
key top.
NOTE: The Space Bar and Motor Bar I each have an extra plastic
retainer. The Space Bar retainer must be removed from
underneath the keyboard before the key top can be removed.
The Motor Bar I retainer is underneath the key cap and must
be removed before the key stem can be replaced.
7. Remove key stem (YY002934) by pushing in on retainers and then
pulling up from keyboard plate.
NOTE: The Mode key cannot be replaced as it uses a different type
of key stem for the locking mechanism.
8. Install new key stem by pushing it into the keyboard plate and make
sure that the retainers lock under the keyboard plate.
a. Be sure high side of key stem is facing the front of the
keyboard.
NOTE: Motor Bar I key is the only key stem that mounts sideways
with the high side of the key stem towards the right side
of the keyboard.
9. Reverse the above procedures to re-install the keyboard assembly
and test all keys, along with faulty key, for proper operation.
ORIGINATOR: JOHN O'BRIEN
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB010 Pg001
FIB 00011 08/22/84
*** Complete monitor asm. no longer available - order separate parts ***
Monitor Assembly MM733120 will no longer be spared in the field. It
has been split into three different parts. VDT's equipped with C. Itoh
monitors, part numbers are:
MM732000 12" CRT
MM732010 PCBA, MONITOR (C. ITOH)
MM732020 YOKE (C. ITOH)
VDT's equipped with Ball Brothers monitors, part numbers are:
MM732000 12" CRT
MM731020 PCBA MONITOR (BALL BROS.)
MM731030 YOKE (BALL BROS.)
ORIGINATOR: J. BUSCAGLIA
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB011 Pg001
FIB 00012 07/24/85
*** Problem with mounting a different style of monitor PCBA ***
PROBLEM: Replacing a Monitor Assembly (MM732000) may cause problems due
to differences in mounting brackets.
SOLUTION: If the removed monitor is a C. Itoh brand, order two each of
the brackets listed below to ensure proper mounting for a Ball
brand.
YY006470 902124-000 Bracket, CRT (Ball) Monitor Mount
ORIGINATOR: J. RIPPL
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB012 Pg001
FIB 00013 08/30/85
*** Field replacement of serial interface I/Cs ***
Problem: All controller boards with 1488 and 1489 chips frequently fails
during an electrical storm.
Solution: These boards can be repaired in the field by replacing the chips
that are on the IC sockets. Order the chips and keep them in
your tool bags and replace them when one of the channels are not
functioning.
The IC chip inventory control numbers are as follows:
1. OR999398 IC, 1488L
2. YY003599 IC, 1489
The following are the boards that have the 1488/1489 on IC sockets:
1. MM081018 901706 PCBA, 1 Channel Controller Board 13XX
2. MM081019 901708 PCBA, 4 Channel Controller Board 13XX
3. MM081020 901420 PCBA, 8 Channel Controller Board 13XX
4. MM361000 903271-001 PCBA, Tritel Logic Board
5. MM362070 903300-003 PCBA, Whisper Logic Board
6. MM531011 903441-002 PCBA, CMB 2000
7. MM531040 903390-001 PCBA, 4-Way Controller 2000
8. MM720010 901810 PCBA, 7230 Logic Board 7230
9. MM730010 901990-001 PCBA, 7250 Logic Board 7250
10. MM741020 903260-001 PCBA, 7270 Logic Board 7270
11. MM780010 903373-001 PCBA, EVDT Logic Board EVDT
12. MM780150 903462-001 PCBA, EDT Logic Board EDT
13. MM821020 903242-001 PCBA, 8 Channel Controller Board 13XX
14. MM831061 903149-002 PCBA, 1345 Accessory Board 13XX
15. MM871010 903179-003 PCBA, CPM/VDM Board MDT
ORIGINATOR: E. Unten
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB013 Pg001
FIB 00014 07/10/87
*** LOWER CASE OPTION INSTALLATION ***
SYMPTOM/TEXT: INSTRUCTIONS TO INSTALL THE LOWER CASE OPTION ON 7250 OR 7270
TERMINALS.
FIX: FOR 7250 - MUST HAVE LOGIC BOARD MM730010/901990 AT REV. AX7 OR ABOVE
- INSTALL IC PROM 165003-035 (MM737130) AT LOCATION 5A
- CLOSE SWITCH S6-6 AT LOCATION 11L (ENABLES LOWER CASE)
FOR 7270 - INSTALL IC PROM 165003-035 (MM737130) AT LOCATION 2D
- SET ON SWITCH 1 AT LOCATION 2H (ENABLES LOWER CASE)
ORIGINATOR: J. VANDER HEYDEN VIA SPENCER SCHWARTZ
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB014 Pg001
FIB 00015 02/03/88
*** CRT SUBSTITUTION ***
SYMPTOM/TEXT: CRT P/N MM732000 is being substituted with the following items:
MM783061/C12M40P31D-AR (CRT, 12" GRN C.ITOH)
YY017807/906977-001 (Left Mounting Bracket)
YY017808/906977-002 (Right Mounting Bracket)
Although the CRT it replaces had a white screen, this one is green and there
is no longer a white one available. The above items should all come together
in.the order, if you do not get the brackets by some oversight, they can be
ordered seperately. No hardware to mount the brackets to the CRT is supplied,
so.you will have to purchase it locally.
FIX:
ORIGINATOR: John Tank LOGON: 11DPS1
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB015 Pg001
FIB 00016 01/10/92
*** Keyboard Cleaning and Repair ***
Most of the keyboards sent back to Tustin for repair require only cleaning or
minor repair, procedures which can easily be accomplished in the field.
1. Cleaning and simple repair should be attempted on ALL keyboards at the field
level. This covers both "switch-type" keyboards, as well as "membrane-type".
Keyboards should be repaired on-site, and where this is not possible, brought
back to the office or stocking location and cleaned/repaired there.
In general, the keyboards can be repaired by disassembling them, blowing-out
or brushing off dust and debris, cleaning the PCBA using a foaming-type
window cleaner (like aerosol Windex), brightening contact points by rubbing
them with an eraser (Pink Pearl), and replacing any worn-out springs or pads
Even the newer-style membrane keyboards (such as the DT4315, PSx30, etc.)
usually fail because of dust or liquid contamination between the membrane
layers preventing a key from making contact. Disassembling these keyboards is
equally easy and the membranes can be cleaned by wiping them with a soft
cloth dampened with window cleaner.
2. Several hundred keyboard repair kits were distributed throughout the field
in the past. Replacement parts for these kits can be ordered through
Tustin, part numbers are as follows:
Parts for 7270, 4309, and 4312 keyboards.
Spring, Spacebar YY013799
Spring, Print Key, Clear, Escape YY012913
Spring, All Others YY012914
Pad (foam/foil for each key) YY006594
Screws (hold PCBA to Keyboard) YY019809
3. After cleaning the keyboard and attempting simple repair, if the keyboard is
still not working properly, return it to Tustin using the normal return
process.
4. MM810041 (Grey 4312 keyboard) and MM810036 (Putty 4312 keyboard) are
alternates for each other and should be treated as such. If you need the
opposite color, take the time to switch the keycaps and enclosure rather
than ordering another keyboard. (Estimated time of about 10 minutes to
switch everything).
5. Effective February 1, 1991, the field will not be able to Code A the 4309
and 4312 keyboards from Tustin (P/N MM783020, MM810036, MM810041).
ORIGINATOR: Norm Jones
VIDEO TERMINAL-BASIC FOUR-4300,4301,7250,7270-------FIB016 Pg001