Re: SSC Failure - odd symptoms

[Zero dB <no@email.com>]

On Thu, 20 Aug 2009 19:51:32 +0200, Patrick Schaefer
<pa.schaefer@web.de> wrote:

>Zero dB schrieb:
>
>> It it possible for the SSC to fail in such a way that transfers won't
>> work, but the logic still does ?  I can "session" into the card and
>> get a responsive prompt, but can't transfer. 
>
>Sure. The 6551 may have failed, or the baud rate generation circuit. If 
>you dropped the card, the crystal may have broken.
>
>You can remove the 6551 from its socket and connect pin 10 to 12 with a 
>jumper wire. Then start Hyperterminal on the other side and see if you 
>get back what you're typing. If you see the remote echo, everything up 
>to the UART chip is ok.
>
>Testing the crystal requires an oscilloscope. However, for a quick test 
>you can just connect a working part in parallel. Usually a broken 
>crystal is broken in a way that it isn't present in the circuit at all 
>anymore.
>
>
>Patrick

Thanks to everyone for all of your help.  I really appreciate your
time.

I definitely am going to have to try to re-seat everything. I
attempted to be careful with the connectors cleanliness, and also
didn't use terribly high pressure, so everything is as-was, to my eye
anyway. Obviously something isn't as-was. 

Moments ago, I did just pop the 6551 out and jumped tx/rx (10/12) as
recommended by Patrick. I got as far as "IN#2" at which point it just
started spitting out paragraph sized blocks of solid cursors followed
by a back slash, then another paragraph sized set of blocks, ad
nauseum.   No chance to attempt anything past that. 

I'm certain it was in 10 & 12 with proper continuity, i checked the
dip pinouts on the schematic. tx & rx. 

Re-apply the 6551 and all is well logically, but still no transfers.

Sure sounds like a user error, doesn't it ?  So weird, I have been
working with rs232 quite awhile and am certain that is all ok. 

I will set forth with the reset/re-seat operation next........

any ideas on why tx-to-rx would cause such a fuss, patrick ?
again, it sounds like operator error but i triple checked the proper
pins 10 and 12. Simple enough, just 10 and 12 over from the dot
signifying pin 1. 

Hrmmmmmmm.

Taking a break, will try reassembly later. getting anxious and
frustrated. 

Jayson