[AZ-Observing] Re: Cable Gone Out

Regarding the Meade LX-series cables and electrical problems...

There are actually TWO types pf cables -- the one for the hand paddle, 
which uses a "standard" RJ11 telephone-type plug, with four connectors, 
and the second one, for connecting the DEC motor circuits to the base 
computer, which is a similar plug, but with two additional connectors.  
They are NOT interchangeable, and, amazingly enough, the smaller hand 
paddle cable WILL plug into the middle part of the DEC cable. This is 
NOT good, as it WILL burn out some components in the DEC motor circuits 
(possibly in the base computer !!)  I would not have believed that 
connection was possible, except that a friend of mine plugged in his 
spare hand paddle cable into the DEC motor circuit, with disasterous 
results!!  Furthermore -- the DEC cable would appear to be similar to a 
CAT5 / CAT6  type computer data cable... BUT -- it is of the 
"cross-over" circuit type -- the wiring reverses end-to-end at the 
connectors.  This is because there is a pass-through connector installed 
in the DEC fork arm, which requires the circuit reversal.

On the subject of making your own replacement cables.... unless you have 
LOTS of experience, AND the required (expensive!) crimping tools, I 
would not recommend trying it.  Another tool that is useful (but also 
expensive) is a cable checker box.  But this is not economical for a 
single replacement cable.

So far as I can determine, the LX-series hand paddle cable is wired the 
same as a standard RJ11 telephone handset cord -- so replacement cables 
of longer length, white insulation instead of black, etc. should work 
o.k. FOR THE HAND PADDLE. And these are widely available and economic.
The rotating connector gadgets available for telephone plugs are 
probably not a good idea, as they use cheap sliding contacts which are 
known to be "noisy" in phone service, and therefore probably not 
suitable for the hand paddle to computer circuits on the telescope.

FYI, the connector on the base computer for hooking up to a computer 
serial port -- the so-called RS-232 port -- is NOT 'standard" RS-232... 
Moreover, the circuit diagram for the series connection cable in the 
older version of the Meade manual is incorrect !  Also, that plug 
carries plus and minus 12 volts on the outer two pins - again, not 
standard, and very easy to short out!  BTW, any intermittent shorts or 
grounds on the 12VDC input WILL "kill" the computer in the base...There 
is no buffering or protective diodes on the power input circuits -- that 
means the accessories, such as the reticle light and the focus motor 
connector, are tied right onto that circuit, too!!

Much information on these subjects (and many others) is available on the 
MAPUG web pages:
http://www.mapug-astronomy.net/AstroDesigns/MAPUG/ArhvList.htm
Dr. Michael Covington has some suggestions about modifying the 12VDC 
input circuit (which I won't go into here; this is for the 
electronically experienced!):
http://www.covingtoninnovations.com/astro/powerinlet.html
...plus lots more tips:   
http://www.covingtoninnovations.com/astro/links.html

I cannot recommend buying parts from Radio Shack.... At most of the 
stores I have visited, their stock is very limited (compared to the olde 
days), and some of the components are not of the best quality -- you 
have to know what you are looking for... They do have many useful 
connector adapters, for say, audio and TV.  Lately my impression is that 
they are getting out of the hobby electronics business, and 
concentrating mainly on iPods and cell phones and accessories.  They 
have even dropped much of their inventory of TV and audio components....

It is fairly easy to order electronic components over the internet, or 
if you are in Phoenix and don't mind a cross-town drive, you can visit 
one of the Fry's Electronics stores -- they still carry a large 
selection of components.  Circuit Specialists in Mesa is a big player on 
the internet now... but the store on Country Club is not a walk-in shop 
anymore...  There used to be a couple of stores in west Phoenix that 
carried fairly broad lines of components...

FYI, my experience is primarily with the LX200 "classic" telescopes...
Cheers,
Gene Lucas
(17250)

Stan Gorodenski wrote:
> Thanks, Steve. Stan
> Steven Dodder wrote:
>   
>> My original reply was overquoted, so rejected.
>> What it said was, be careful with Radio Shack telephone plugs if you use 
>> one.  Be sure to check the polarity of the connectors.  I wrote a procedure 
>> for you, but if you're in contact with Gene, he can describe it for you.
>>
>>     
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