Saturday, 26-Sep-2020 22:52:25 BST
Help & FAQ
- Fault Finding
are normally five main areas that you need to check if your Z88
does not work. If the Z88 does not power up at all go to Dismantling your Z88,
but check the text below if it is sort of working before you get your screwdriver out.
sure that you follow the Inserting
RAM or ROM Cards Rules as the Z88 gets confused on what
size of memory it has if this has not been followed. Memory cards
sometimes do go faulty. If they do, you do not need to dismantle
the Z88 to fix them.
RAM or ROM Cards Rules
You can add more memory
(RAM packs) by following the INSERT RAM/ROM procedure, any time.
Whenever removing a RAM you need to do a Soft Reset. This will
clear the FAIL message and all your files that you may have stored.
You can add programs
(ROMs) by following the INSERT RAM/ROM procedure again any time.
- Turn the Z88 on
and go into INDEX.
- Open the card
flap at the front, push the card into a slot
- Shut the flap
You should try to
leave Slot 3 free for EPROMs as they can ONLY be used there.
You can use any of the Slots for RAMs or ROMs except if you put
a RAM in slot 3, your Z88 will use more battery power. I have
found that the following combination works best. Slot 1 RAM.
Slot 2 RAM/ROM. Slot 3 EPROM only. See Check
inserting any card, it is a good idea to check that your Z88
knows about it by selecting (<>CARD) while in the INDEX.
The display should
match what you have really got in the card slots. If this does
not match, you have found another problem.
Sometimes the EPROM
is not shown. See Header
FLASH, EPROM / ROM OR RAM Card
There are several sorts
of memory failure. They all make the Z88 behave badly.
There are two sorts
of mechanical failure.
The first sort gives
you unexplained "Memory stack overflow" or FAIL messages
at the top of the screen. The most common fault that causes this
is when the RAM card physically comes apart. You will notice
this when removing the card from the Z88. It may be a loose fit.
What you should find is that the RAM card is made up of two halves
and these are coming apart.
You can repair this
- Pressing the RAM
pack together and wrap a strip clear sticky tape (one inch wide)
around the outside the pack, near the connector. This should
force the RAM pack together and will make better contact with
the Z88 when plugged in again.
- Or using `SuperGlue'
around the edge of the pack and squeezing it shut. Remember not
to get your fingers stuck, as these are not required with the
The second sort is
that the Device just stops working due to the 'gold' contacts
The easiest way
of doing this is by sliding the card in and out of the connector a few
times. If this doesn't improve its performance use a very soft pencil
rubber and clean both the connector in the Z88 and the 'gold'
Be careful though,
There is not a lot of 'gold' used on the connector, it is only 'mechanical gold' and you might find that you
can clean it off altogether!
BBC BASIC Memory Test
The other type of
failure is when part of the memory doesn't act like memory. This
leads to inconsistent results when checking the size of the Ram
with (<> CARD). For example, you may have a 512K Ram card
in your Z88 but (<> CARD) reports that you only have 128K.
See Check Z88 Cards.
Running the BASIC
program while `tapping' the RAM pack will find this sort of error.
By downloading the
following BBC Basic program, you can test 32K, 128K 512K and
1MB Ram packs.
It is what is called
a destructive Ram Test which means that all the data that is
stored on the ram will be destroyed. So backup all your files
before using it. See Backing
Download the 4 files
zipped, (original instructions, two .CLI files (which do the
same thing) and the memory test software from here, and then
transfer them to your Z88 with a transfer program.
There are two ways
you can use this program.
- Just running the
BBC BASIC program (Ramcard.bas)
- Before using the
program you should save the program to EPROM as "RAMTEST.BAS"
and write the following BOOT.CLI to use with it.
to do the memory test,
do the following:-
- Back-up all your
- Take out the RAM
- Put in the EPROM
with the two files BOOT.CLI and RAMTEST.BAS in it.
- Do a Hard Reset.
- When you get the
Command line "Size of card to test? (in KBytes, Eg. 32,
128 etc.)" type in the number of K the ram card is.
- Put the Ram card
in Slot 1.
- Press the ENTER
key until you get the "Testing . . . " message.
- When the test
- Remove the EPROM
- Do another Hard
The other sort of
memory failure is where certain bits of memory suffer amnesia
when you are not reading or writing to the memory.
This is like when
you are just storing files in the RAM.
This fault can be
found with any program, (zCheck, Zip, Unzip (Z88 Forever) or
SqueeZ~88 (Rakewell)) that uses checksums on files. To use it
- Run the program
initially so that the checksums of the files are calculated.
If you are using SqueeZ~88 or Zip, squeeze/Zip a load of big
- Turn off the Z88
and leave it alone for about three to five days.
- Re-run the program
to see if the checksums of the files are different or unsqueeze/Unzip
all the files again. If they are, then the RAM where the file
was stored is faulty.
| Device fails to boot OZ in slot 1
sort of memory failure only occurs when you are booting the Z88 from
slot 1 and it just fails to boot. This is caused by a card select
fault, it is NOT the software.
This failure may not be detected when OZ is running as OZ is managing
which card it is selecting. When you boot from slot 1, OZ is not
running the individual card's hardware needs to select the card.
The normal conclusion is that you may have the fault with the card in
slot 1, but this is not true, it could be any of them, you need to take
all your other cards out and see if the fault persists. Unfortunately,
all the other tests - Flashtest and the memory test will not detect
this fault as they are running under OZ which hides the fault.
the display is cracked this is easy to replace but it is the
most expensive item in the Z88. Symptoms are obvious. Cracked
or broken glass, with oozing chemicals coming out of the display.
Do not allow these chemicals to have contact with your skin.
They cause cancer.
The Z88 can work for
a while before it becomes difficult to switch it On/Off with
the Shift keys. Most problems like this are caused by the conductive
rubber layer underneath the keyboard becoming removed. Keys like
the cursor, delete and Shift keys, are the first to go.
I have read several
interesting things that Z88 users have done to repair the keyboard.
By far the best thing to do is to replace both the rubber mat
and membrane simultaneously but failing this you can try the
- Clean the membrane
with a soft pencil rubber where the keys make contact.
- Carefully clean the
underside of the keys but make sure you don't remove any more
of the conductive rubber coating that is used.
Unfortunately we do
not have any UK rubber keyboards or membranes left. You can fit
a foreign keymat instead.
You can get problems
if the case becomes damaged internally, due to the Z88 being
dropped. This can lead to short circuits occurring, rattling
from inside the Z88. See Case Damage.
There are two versions
of the case. The UK and most of the European cases are just made
out of black plastic.
The USA version has
the same plastic case from the outside but the inside is coated
with a metallic finish. This improves the radio interference
immunity so that the Z88 complies with the FCC regulations.
Both have the same
label on the back of the Z88 saying `Certified to comply with
Class B limits Part 15 of FCC rules, ' so how can you tell
If you look into an
empty card slot (where the RAMs and EPROMs are fitted), you should
see either a black or a silver inside.
There are several
parts that make up the complete case for the Z88. These are listed,
with possible fault symptoms.
The Display is the
heaviest item in the Z88 and the least supported. Check that
the four pillars that the display fits onto are still standing,
with the rubber washers.
Check the plastic
battery lugs (the bit that supports the springs). They sometimes
get broken resulting in the Z88 not working on batteries or worst
still shorting out the power supply.
The plastic lug behind
the plastic leg often gets broken. The effect of this is that
the leg always wants to flop down as there is nothing to hold
it up when the leg is put away. This item can be replaced without
dismantling your Z88.
This also gives support
to the display. Check that the four flat side supports for the
display are still intact. You can often tell if they are not
there by noticing a broken plastic ridge where it was.
Normally, when the
card flap is opened (with the Z88 turned on) the display goes
out. This is because it operates a switch to let the operating
system know that there are changes ahead.
If the display does
not go out, then the card flap or the support from the "Reaction
plate" is broken and should be replaced.
Although better RFI
protection is achieved the metallic covering inside the case
can lead to short circuits between the electronics and the case.
This usually manifests itself after the Z88 has been reassembled.
Underneath the printed
circuit board there is normally an insulated mat. This can get
punctured by IC pins on the board. The solution is to cut all
those pins off close to the board.
The other way shorts
can occur is through the keyboard reaction plate. You should
try to establish where the short is taking place, (easier said
than done) and scrape the offending metallic part off the plastic
making sure that no metallic bits fall anywhere near the electronics.
Shorts can also occur
while you are plugging in the Mains Adapter.
These fall off and
can be easily replaced. Do not use SUPERGLUE on the front feet.
You might need to get to the screws underneath them.
To change any of these
parts yourself see Dismantling
This is not an area
for the weak hearted Z88 user. If the Z88 appears to work and
then does unexplained things, the printed circuit board may be
faulty. Usually if they go wrong they show themselves within
the year's guaranty period.
A good test here is
to twist the Z88 longways. If the display goes out and comes
on again or the fault occurs, some components may have `dry joints.'
You can also check
as this can reveal some electronics faults.
You can check the
power consumption of your Z88. This can show up problems with
either the keyboard or electronics.
All you need are the
- An ammeter which
can measure up to 300 mA.
- A double sided
blank printed circuit board.
- Some wire and
- Two crocodile
Cut the printed circuit
board so that it will fit between the batteries in the Z88. Solder
two bits of wire on each side of the printed circuit board. Fasten
the crocodile clips to the other end of the wires.
To measure the current
do the following:-
- Connect the crocodile
clips to the probes of the ammeter.
- Place the printed
circuit board between two batteries that you can get to (with
the cover off).
- Check that the
ammeter is measuring some current. If it isn't then you need
to check why not quickly, since your Z88 will be starved of power
and will die.
- Now you can do
different things with your Z88, like turning it ON and take notes
of the different readings.
Consumption Table to compare your results.
is all around us. It does irreparable damage to low current electronic
circuits, such as those used in the Z88. It can be also responsible
for the Z88 doing a Soft
Reset when you are inserting the Mains
If you are a person
that experiences electric shocks when grabbing metalling objects
you need to take several precautions when plugging the mains
adapter in or Dismantling
To get rid of static
electricity, the object is to get all the parts that you are
working with to the same voltage. This is normally done in the
household by using the earth pin. As more items are made of plastic,
you never get the chance to return to earth during the day. Here
are a few tips that may help you.
If you are Dismantling Your Z88 you
should EARTH yourself and then the Z88 (by touching the metal
part around the RS-232 serial port) before you start any work.
Both feet in a bucket of salty water connected to the radiator
may be going a bit too far. Remove all insulating materials like
nylon and rubber soles.
Z88 TEST SOFTWARE
Your Z88 comes with a year's
guarantee. This is invalidated once you open the Z88.
You should, if your
Z88 is within the warranty period get in touch with your Z88
dealer before dismantling it.
If your Z88 is outside
the guarantee period or its origin is questionable, then here
is your chance to see what is inside.
Back-up your Z88.
See Backing up Files.
Read the Static
Get a Philips
screwdriver that fits the screws of the Z88
Taking it all to
You do not need to
take the Z88 all to pieces to replace certain items. These points
will be highlighted with what you can do there. Otherwise, just
You should take care
with the display unit as this is fragile and will move about
after the screws have been removed.
Remove any RAMs,
ROMs or EPROMs from the card slots.
Place the Z88
face down on a soft cloth larger than the Z88 like a towel.
Remove the two
square front rubber feet. This should reveal two screws.
The keyboard may be checked first by removing the FIVE screws below it. Remove the keyboard, by carefully hinging it
upwards from the rubber feet end. Part of the keyboard is under the top case but it can be slid out carefully. Disconnect the two flat plastic connectors by pulling them out from the main board. The Z88 can be tested again at this point by inserting the batteries and giving the Z88 a Hard Reset to see if it boots up. If it does, you have a keyboard fault.
This is the
point where you can Change Keyboard, or change the Card Flap, if not - continue ...
Move the Serial
No. label under the plastic leg to a different place. This will
reveal another screw.
You should now
see the remaining SIX of the ELEVEN screws. Undo them all and keep them in a safe place.
They are all the same type.
Get hold of the
Z88 by the top and bottom case, roughly level with the power
socket hole and the Serial Port socket and turn it over, gripping
hard to keep it together. Remember, you have just taken out the
screws. There is nothing holding it together now.
the top case where the display is.
display unit from the main board.
Remove the display
unit. NOTE PUT THIS IN A SAFE PLACE. IT IS FRAGILE AND THE MOST
EXPENSIVE PART TO REPLACE.
Remove the batteries.
Remove the battery
clips from the plastic lugs
Take the Serial
Port connector out of the plastic moulding.
the main board from the bottom case.
You should now have
the Z88 all in bits.
Putting it back
This is the reverse
of the above with the following points.
Now that everything
is out, why not clean the inside of the case, the display unit
and the keyboard.
Check for Case Damage.
If you have taken
the batteries out, put them back in after the Z88 has been assembled.
the keyboard, take care not to bend the membrane connectors.
Lay them on the resistors and push them up into the connector
with your finger.
Check that the
Z88 works (with the Mains Adapter if the batteries have been
removed) before putting in the ELEVEN screws. That will save
you taking them all out again if it doesn't work.
Check that the
leg from the Reaction Plate is holding the Card Flap correctly.
Make sure that
the wires to the battery clips do not get trapped between the
top case and keyboard.
Use the same thread
in the plastic case that was created before by just using the
weight of the screwdriver on the screw whilst turning it anti-clockwise.
When the screw drops into the start of the thread, you can then
tighten it up.
Do NOT do the
screws up too tightly. It is easy to damage the thread in the
Do not move the
Serial No. label back over the screw hole. Leave it where you
moved it to.
is one of the most common causes for problems.
There are three parts
of this assembly.
- The Keyboard Mat
- The Keyboard Membrane
- The Reaction Plate
(which is the plastic rectangle that the rubber mat wraps around
and goes over the printed circuit board below.)
Normally only two
parts need to be replaced. The mat and membrane. To assemble
these, do the following:-
- Clean the existing
- Make sure that
you have the three parts the right way round. There is only one
way that make's sense.
- Push the three
rubber grommets through the membrane and the reaction plate.
A small screwdriver or a pair of tweezers will help here.
- Push the keyboard
mat around the outside of the reaction plate.
- Use SuperGlue
or strong adhesive tape to stick the keyboard mat to the reaction
plate along the front edge.
- Wait until the
glue has set before installing the keyboard to the Z88.
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