[Premium-Rx] Racal A6A1 Board Setup Help Needed

[Claus Hanke]

Hi Guy,
I checked both manuals, GM and GM-3, and it is not possible to mix the boards.
So, if you have a remote for the GM-3 (UART 8251) you cannot use it with the
GM CPU board (3 EPROMs and 3850 CPU). The pining between the boards
 used by the GM and GM-3 versions are different. The GM-3 CPU is a Z80
(1 EPROM). The UART on the GM remote board is a IM6402 or compatible.
That would explain that the receiver is not working anymore. Pin 2 - GM is the
RESET (active low) and MI (active low) for GM-3. I'm just guessing, but maybe
the CPU is always in RESET mode.
Anyhow the two versions are not compatible, so check what versions you have.
Hope that helps.
Claus

Guy Atkins wrote:

> Hi Shaun,
>
> I made the changes to my A6A1 board to match Andy's description, but no
> success yet. I'll have to give your suggestion a try, which is basically
> John Kolb's comments (make sure of the RXD and TXD pins).
>
> I got to reading the documentation of Vradio's 6790 documentation, and saw a
> comment about removing LINK 1 on the A6A2 CPU board to enable remote
> operation. I removed the link, but it resulted in a fully locked-up receiver
> with only partial information showing on the display. Ack!  The BITE test
> wouldn't even function. I replaced the link, but the radio was still
> locked-up. Uh-oh... !  However, I waited a few minutes and powered on again,
> and this time the receiver control was back to normal.
>
> This episode got me to looking closely at the boards in my receiver, and I
> realized that I have a "GM-01" CPU board ( with 9666 software) and Remote
> board, and my manual is for a "GM-3" version of the receiver. This appears
> to be a newer board pair, with 1 EEPROM rather than 3 on the CPU board. The
> illustrations in the manual are different for both boards.
>
> So, still no luck with the remote control of the RA6790GM, but I'm wondering
> if the diagram for RS232 link settings on the A6A1 (GM-3) is different from
> the earlier board I have? This board was already configured as shown at the
> Vradio page ( http://vradio.home.att.net/Racal_6790.htm )
>
> There are so many variables here it's hard to know what to tackle first.
>
> Guy
>
> -----Original Message-----
> From: Shaun Merrigan [mailto:smerriga at compusmart.ab.ca]
> Sent: Friday, February 20, 2004 7:22 PM
> To: Guy Atkins
> Subject: RE: [Premium-Rx] Racal A6A1 Board Setup Help Needed
>
> Guy,
>
> I had a similar problem with a 6790 that refused all attempts to
> communicate with it. I solved it by swapping the RXD and TXD pins.
>
> Shaun Merrigan
>
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