[TenTec] More on Orion Serial port trouble

[Martin Sole]

Hi,

 

Many thanks for the replies that suggested a serial driver chip failure
could well be the problem. This is U600 on the DSP board located behind the
front panel. I have investigated and indeed found that I can see the
incoming RS232 from the PC and the output TTL data going to the CPU. I could
also see TTL coming from the CPU at the input of the chip but no RS232 on
the output of the chip. So I tend to think the chip has failed.

 

In my Orion U600 is marked as an ADM232AARN. Data on the AD site says it is
a MAX232 equivalent and the schematic identifies U600 as a MAX232. My local
parts shop does not have the AD232AARN but did have MAX232CSE in SO16 narrow
format. I purchased 3. Having fitted the chip nothing works! No TTL to the
CPU or RS232 to the PC so now I am wondering if the chi is really an
equivalent or if I need to do something else. I did note that the supply on
pin 16 was about 4.8 volts with the chip removed but only about 3.8 volts
with the chip fitted, though that was the same for the AD device too. I did
not check the 10 volt charge pump pins.

 

So what to do? Should I try another device? I've cleaned the board and can
see no fractures or bridges under magnification. DO I really need the AD
device? Any ideas?

 

Thanks

 

Martin, HS0ZED