Author Topic: need help finding NEC part  (Read 2236 times)

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Offline KTP

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need help finding NEC part
« on: January 26, 2011, 10:05:05 pm »
Hi guys,

I was tinkering around with an Adept EXC standalone controller for robot linear modules, trying to communicate with it via RS232.  I built the correct cable for the teach port and I have it spitting out the startup information to a pc terminal program, but I can't managed to send any commands to it.  The command 8F is supposed to put it in teach mode but it does nothing.  I am guessing the problem is the RS232 receiver chip is blown (could have gotten static zapped by previous owner(s) ).  I took off the cover and see that the 9 pin serial port leads to a NEC chip part number D4711AC.   This is a 20 pin narrow DIP chip surrounded by four 22uF caps.  I did some searching and finally found a data sheet from NEC for a uPD4711B, which I am pretty sure is the same part.  I can't seem to find any supplier of this part or a drop in replacement from Maxim or ST or someone.  Anyone just happen to know of one offhand?
 

Offline KTP

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Re: need help finding NEC part
« Reply #1 on: January 26, 2011, 10:38:58 pm »

Ok, I used my trusty Rigol to determine that indeed the transmissions from the computer terminal program RS232 are not making it through the NEC D4711AC chip from pin 13 to pin 8.  When I send a char I can see a burst at pin 13 and I see nada at pin 8.  Diagnosis, blown chip.  Now, the question is, exactly how obsolete and hard to find is this part?  I guess I could hack in a daughterboard with a Maxim chip...ugly.

Here is the data sheet I found:

 

Offline mikeselectricstuff

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Re: need help finding NEC part
« Reply #2 on: January 26, 2011, 11:03:24 pm »
Probably easiest to just bodge in a more available RS232 transceiver than hunt down an obscure one. If you want it neat, put a SMD trasceiver on a DIP carrier PCB.
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Offline KTP

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Re: need help finding NEC part
« Reply #3 on: January 26, 2011, 11:27:36 pm »
Probably easiest to just bodge in a more available RS232 transceiver than hunt down an obscure one. If you want it neat, put a SMD trasceiver on a DIP carrier PCB.


Ya, I agree with you.  I found an old board that has a 14 pin Max1489 on it.  Since 3/4 of the NEC chip is still working, I could just dead bug glue this 1489 on top of the old chip and carefully cut the offending receiver line leg of the NEC chip and bypass that buffer with the 1489.  Hopefully nobody will peek inside and see the nastiness.
 


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