ETX TECHNICAL TIPS Last updated: 14 January 2000

Meade PSU / P.C Serial Cable - hints from the U.K.

From: 	steve.jarman@lineone.net

Greetings  from  over the pond from the U.K.! You will be pleased  to
know that your site was a major influence of my recently purchased
ETX90EC.

I  would  like  to  clarify  the  set up for both the external power
supply,  and  the  P.C. serial cable, from a UK perspective. There is
obviously  lots of advice from the U.S., but alas the part numbers and
store  details  do  not apply over here. As an electronics engineer, I
decided  to  investigate  and pass on my findings. One common fault in
using  a  serial  cable  taken  from  a  telephone handset is that the
release  tab  on  the connector is cut off. This means that once it is
inserted in the Autostar, it is almost impossible to get it out!!!

NOTE: The usual disclaimers apply here!

Power Supply ===========

I currently use a UNIROSS PSU, fully regulated, and rated at 12V and 1A.
This  is  more  than enough for the MEADE ETX90, and is readily
available  here  in  the  UK  for  around 12 (Part number VN10, see
MAPLIN,  below).  Be sure to configure it for 12V, and use the 2.5mm
connector,  (the  RED  tipped  connector).  ENSURE  THAT  THE TIP IS
CONFIGURED FOR POSITIVE (else expect some smoke!)


Serial Cable ============

The  connector  that  fits  into  the Autostar is known as a 4C4P (4
connectors  in a body designed for 6). The 8C8P is commonly known as an
RJ45, used in computer LAN connections for example.

I  have  seen  some  postings that use an RJ11, with the edges filed
down,  which  seems to work. This is because it is a 4C6P connector,
i.e.  it  uses  4 individual connectors, in the width of a connector
designed for 6! That explains why it is too wide.

To cut this short, this is what you need here in the U.K. :-

1  x 4C4P connector part No. JW42 (about 0.39), 10 x metres of XR86
(0.41  per  metre  flat cable), 1 x RK61 (9way D connector), 1 x FP27
(Hood).

The  above  part  numbers  refer  to  MAPLIN,  (www.maplin.co.uk), the
biggest consumer electronics supplier here in the U.K.

Manufacture  the  cable  as per the other postings at Mike's ETX site,
but  the  4C4P connector is a little fiddly. Cut back precisely 4mm of
outer  insulation  from  the  flat  cable.  Insert  this into the 4C4P
connector, MAKING SURE NO WIRES ARE BENT OVER. Don't worry, it will go
in first time! If you do not have a crimping tool to hand, GENTLY push
the  4 gold contacts into the connector with long nosed pliers, one at a
time, until they are tight. Also, using a small screwdriver, push on the
small rectangle which sits over the main cable - this indents the
plastic  of  the  cover  into  the cable, and forms a primitive strain
relief.  If  you  do  have  a  crimping tool, this is done in one fell
swoop. Incidentally, the crimping tool from MAPLIN is around 6.00.

Once  you  have  soldered  the 9 way connector to the other end of the
cable,  check  the  cable using a multimeter or simple lamp & battery.
This took me around 5 minutes to make, and worked first time.

And  that's  it  !  one P.C. to Autostar cable for around 5.00!

Keep  up  the  good  work,  and  now  lets go outside and see if I can
actually SEE anything with it!!

Steve Jarman - Bexleyheath, Kent, England
  
mailto:steve.jarman@lineone.net

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