[comp.sys.atari.st.tech] Need help with bad RS232 port

sytang@lamar.ColoState.EDU (Shoou-yu tang) (04/21/91)

 Hello:
 My 1040ST has a bad RS232 port and I'm trying to fix it, when nothing connected
 to the RS232 port it works fine. But when a working modem connected to the port
 the screen on the mono monitor got distored in some part. And the Uniterm would
 hung up the whole machine when try to dail out. 
 (NOTE: Uniterm and modem are working correct and has try with another ST with
 exact same configuration).
 Is it the 1488 or 1489 went bad? OR the Sound chip? Any hints?
 Thanks
 Tang
 sytang@lamar.colostate.edu

bjoern@drdhh.hanse.de (Bjoern Kriews) (04/25/91)

From article <14371@ccncsu.ColoState.EDU>, by sytang@lamar.ColoState.EDU (Shoou-yu tang):
>  My 1040ST has a bad RS232 port and I'm trying to fix it, when nothing connected
>  to the RS232 port it works fine. But when a working modem connected to the port
>  the screen on the mono monitor got distored in some part. And the Uniterm would
>  hung up the whole machine when try to dail out. 
>  (NOTE: Uniterm and modem are working correct and has try with another ST with
>  exact same configuration).
>  Is it the 1488 or 1489 went bad? OR the Sound chip? Any hints?

First guess: 1488 (output driver)

Anyway, the both 14xx are easier to replace than the YM-2149 and
cost nearly nothing.

Greetings, Bjoern


---
bjoern@drdhh.hanse.de = Bjoern Kriews / Stormsweg 6 / 2000 Hamburg 76 / FRG
"gaaga mahwe Bjoern urgl ufzae Turbo-C bnub"     (J. Willamowius)

nils@ooc.uva.nl (Nils Arbeitstein) (05/03/91)

the YM-2149 is NOT the only chip wich is controlling the rs232, the mfp
(68901) is also controlling it, and if that chip is broken, you're in trouble 
cause that chip costs twice as much as the YM-2149.

nils