Author Topic: Serial Port Repair (MAX232)  (Read 1189 times)

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Offline SirWhy

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Serial Port Repair (MAX232)
« on: August 15, 2015, 01:46:33 am »
I think for something to be repaired it has to work in the first place right?

Anyway, I have a Replica 1 from Briel Computers that I built a few years back but the serial port has never worked on it. Now that I have a shiny new Rigol DS1054z, I flt it was time to track down the issue. A look at the schematic and it seems to me that the MAX232 on the board isn't functioning correctly. I measured the voltages from pins 2 and 6 with respect to ground and they read 4.73V and 0.1V respectively. I don't know a lot about the 232, but looking at the datasheet, this is definitely not right.

Now I'm just wondering if its a simple job of lifting out the old MAX232 and replacing it, or if the caps/other parts of the circuit are the problem? I've tried to post this on the Briel Computers forum, but you need approval to post and Vince seems to have gone AWOL.

Hopefully you fine people can help! Thanks
 

Offline bookaboo

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Re: Serial Port Repair (MAX232)
« Reply #1 on: August 15, 2015, 01:52:49 am »
I'd change the caps too on the very off chance they are faulty, time and cost is negligible to change both chip and caps. I would check that there's nothing pulling on the RS232 or TTL lines pulling the supply rails up/down (bend the pins), also check you have a nice clean supply in to start with.
 

Offline SirWhy

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Re: Serial Port Repair (MAX232)
« Reply #2 on: August 16, 2015, 12:27:57 am »
Checked the supply and the voltage rails, all clean, nothing unusual. Will just replace all the caps and the MAX232. I'll put them in with my next component order. Thanks
 


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