Subject: Apple IIgs question..

From: David Holland <[email-masked]>
Date: Thu Jun 5 08:32:37 2003

Hi, all..

( Gee, I get to ask a legitimate classic comp question..  )

Anyways, I've a A2GS sitting here, that I've been beating myself over
the head with for about two days now.. (Yes, I'm stubborn) 

I've been trying to get ADT (serial) working between the GS, and my PC. 

I've gotten it to work just fine PC -> GS.  (I even had my PC type a
copy of Dos3.3/ADT/ADTgs in via the serial port at 300baud.) 

Anyways the stumper is in the GS -> PC direction.  Nothing works.  I've
tried the modem port on the GS, as well as 2 different super serial
cards. 

I finally got desperate enough to pull out a RS-232 break out box, and a
scope. (Plus a couple of dweebie basic programs)     What I find is the
Apple serial communications looks like its running at about +/- 4v. 
(This is on the builtin modem port.   I can't get a SSC to work either.)
(The waveform also appears to have a fair amount of ring on the voltage
swings, but that may be normal) 

I'm guessing that the +/-4volts isn't enough for my PC to recognize it. 

Question #1: 
Does anyone have any thoughts about my theory that the PSU is weak, or
suggestions where else to look? 

Question #2: 
Presuming question #1 is reasonable, schematics for a GS PSU?

Thanks, 

David

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From: Ian Primus <[email-masked]>
Date: Thu Jun 5 08:32:49 2003

Sounds like a weak PSU, I have had no trouble using ADT on a IIgs. How 
much stuff do you have connected to it? I know I have found that after 
two Unidisk 5.25's, two 3.5" drives, two Disk II's, a SCSI card, RAM 
expansion, etc, etc, it the computer sometimes can't get the juice to 
power drives, I/O, etc (especially those pesky Disk II's)... Try 
measuring voltages at the power supply, it should have the pinouts 
printed on it IIRC. If you want, I have a spare IIgs or two that you 
can have for a few bucks plus shipping. I also have IIe's and floppy 
drives as well, if you want.

Ian Primus
[email-masked]

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From: David Holland <[email-masked]>
Date: Thu Jun 5 08:32:54 2003

Hi, 

Wandered downstairs, and dug out my pile of parts. 
(and more importantly a spare ROM 01 system.)   My testing was on a ROM 03.

Thanks for the parts offers, I think I've enough parts now though.. 
(The wife eye's me evilly every time I drag out my parts pile anyways :-) )

I checked the voltages.   

The worst I saw as -10.2v (on what aledged to be the -12v pin) on the ROM03. 

The ROM 01's voltages were all pretty normal. 

There's nothing else plugged into the systems for the last couple of tests
I just ran.  This scope I have is fairly old, and probably not terribly
accurate, but about the best I've seen is +/- 4.9v.   

Neither the ROM 01, nor the ROM 03 will talk to the PC. 

At this point, I'm wondering if the IIgs's normal "serial" is on the 
low side of valid, and my PC's (mis)wired for the high side.   I'll 
try the serial ports on my Linux firewall.

Data sheet for the AM26LS30's on the thing doesn't make sense to me either
at this point.. but that's besides the point.. 

Anybody got a schematic for the whole GS?  :-)

David

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From: David Holland <[email-masked]>
Date: Thu Jun 5 08:32:57 2003

I now consider myself an idiot.  (again)

My 9 pin serial cable was not plugged in good.. 

It was plugged in just enough that I could transmit from the PC, but
not enough to received.

So, that's what those little thumbscrews are for.. 

<doh!>

We now return to our regularly scheduled programming. 

David

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From: Vintage Computer Festival <[email-masked]>
Date: Thu Jun 5 08:33:10 2003

> I'm guessing that the +/-4volts isn't enough for my PC to recognize it.

Have you tried a different cable?

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

 * Old computing resources for business and academia at www.VintageTech.com *

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From: David Holland <[email-masked]>
Date: Thu Jun 5 08:33:48 2003

> Have you tried a different cable?

Sorta.. Tried a different clue, (The one that had (a little) common 
sense attached) and found the cable 1/2 plugged in.  

:-]

David