Navtel RS-232 breakout box

From: joe <rigdonj_at_intellistar.net>
Date: Mon Jul 9 20:08:37 2001

At 06:49 PM 7/9/01 +0100, you wrote:
> >
> > Tony,
> >
> > It must be something like that, I'll have to experiment with it. I
> > do have the "operator's instructions" for it do you want a copy? They
> > explain the controls but that's about all.
>
>Thanks for the offer, but I think I've figured out how to use it
>already... Or at least I can use the main features.
>
>
> >
> > FWIW I have a second box that doesn't do the self test. The display
> > and other indicators ont he bottom never come on. However the signal LEDs
> > seem to work ok. I guess I need to work on it when I have time.
>
>IIRC, the LEDs in the breakout box part are powered off the RS232 lines,
>like in a coventional breakout box. The controls/displays at the bottom
>of the panel are controlled by a little microcontroller system inside (I
>forget what the CPU is, it's either an 8085, or possibly an 8035, and yes
>I do know those are very different). There's also an EPROM containing the
>operating software, an 8155 RAM/IO chip, etc.


     It uses an 8085AH-2 that's programmed in BASIC. However there are two
Intersil ICs on the same board as the displays and I suspect that they're
the display drivers. I need to research them and see how they're
controlled. I suspect that either they're both bad or that something else
(the CPU?) is controlling them and not enabling them. They act exactly
like youhad turned off the display via the Display button except that they
won't turn back on. I have noticed that the CPU is generating it's own RTS
signal so it looks like the CPU is at least running.


>My guess is that you've got problems with the microcontroller system. The
>first thing to check is the inter-board connections. There are 3 PCBs in
>there, interconnected by solid-core ribbon cable. A single broken wire
>can cause all sorts of problems.
>
>Then see if the CPU is running, is it accessing the EPROM, etc. Oh, and
>of course check the +5V power line early on.

       I did. It's ok and it's generating the +/- 12 volts for the power
outlets on the front panel.


>I got mine cheap at a radio rally, not working. The processor and the
>8155 were both dead. Fortunately (and I am still wondering how this
>happened), the EPROM was good, so I could repair it.


      I picked both of mine up at a scrap place for free. I was lucky
enough to find the two AC wall-warts and operator's instructions at the
same time.

     BTW does your's have batteries in it? Mine don't but it would be nice
to add them.

    Joe


>-tony
Received on Mon Jul 09 2001 - 20:08:37 BST