AnyCPU
http://anycpu.org/forum/

EXPLODING MAX 232's
http://anycpu.org/forum/viewtopic.php?f=17&t=1104		 Page 1 of 1
Author:  oldben [ Fri Feb 09, 2024 5:40 am ]
Post subject:  EXPLODING MAX 232's
Max 232's have been around as the quick and dirty fix for RS232 lines with only a +5 volt supply.
With the last batch of MAX 232's or similar, they have been all crapping out. The only one working
is junk box MAX 3232 that I had kicking around. Are there any other ways to get +-12 from +5 volts
so I can use real RS232 chips, with low noise on the power supply?
Author:  DockLazy [ Fri Feb 09, 2024 6:24 am ]
Post subject:  Re: EXPLODING MAX 232's
Where are you getting them from? If it's from china you probably got something else.

Also what are you using RS232 for?
Author:  oldben [ Fri Feb 09, 2024 2:09 pm ]
Post subject:  Re: EXPLODING MAX 232's
DockLazy wrote:
Where are you getting them from? If it's from china you probably got something else.

Also what are you using RS232 for?


I got them off Amazon so I suspect China. It was one of them cases I needed it yesterday.
Digikey is fast shipping, but they don't carry TTL any more. In most cases I order from China
for all my parts off ebay, as shipping from Hong-Kong or Poland is cheap and know in general
what I need, like bypass caps and sockets and resistors.

For now I got a single rs232 port, connected to the PC acting as terminal and a paper
tape bootstrap loader.
(I need to get a REAL TTY :) )
Later I want add a serial printer, and a second port for downloading files to disk, in my case compact
flash.

For PCB boards, I use PCBWAY from China. It takes about a week to have the PCB made and shipped to
me. They have good service and DHL is about $25 (US) shipping plus $25 import tax to Canada.

It is Kicad that I hate, because of all the stupid metric footprints, or not having footprints for things like switches.
I miss the Austrailan PCB programs like Autotrax, that were simple to use and easy mechanical routing like
memory address lines to the cpu.

If the second ram card works, then I need to revise the mother board PCB using better swiches and 2 oz
copper. About 2.5 amps I suspect on the +5 volt line.
Author:  DockLazy [ Sat Feb 10, 2024 8:52 am ]
Post subject:  Re: EXPLODING MAX 232's
Yeah Digikey is a bit of a mess.

Mouser still has plenty available. I assume you mean LS as the 74xx series chips are pretty much all no longer in production.
Author:  drogon [ Sat Feb 10, 2024 5:42 pm ]
Post subject:  Re: EXPLODING MAX 232's
You could - at least to start with - use TTL Serial and one of the many TTL/USB serial adapters to get data to your PC.

This won't address the printer issue, but it would be a start.

And if the MAX devices continue to be a PITA then to address the printer issue, you could connect the printer serial port again with another TTL/USB adapter to your PC then there are USB/Serial adapters that will provide the correct +/- ~12v signals to a real RS232 device. I have used the Startech ones in the past with good results and they provide proper 9 and 25 pin models.

The issue then is how to plumb 2 USBs together on your PC - which is easy if you run Linux, there is a program called socat which lets you plumb things together. I used it myself a while back when I wanted to get my retro 65816 system taking to a real terminal - ttl serial to usb to my PC then a Startech usb -> 'real' RS232 to the terminal. It worked a treat.

-Gordon
Page 1 of 1 All times are UTC
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/