Re: Need some help with an Atari Switching Power Supply

I fixed the RAM problem. It turned out to be because of one of the ribbon
connectors I made. I think a small, small sliver of wire got under the
ribbon connector and was shorting a couple of pins. So that's now
resolved.

I have one last problem. I'm getting Mathbox errors. It's showing
'timeout C'

Apparently there are 4 different functions - Y, P, R, or C. I'm a little
lost on this one.

* Question 1:
Is anyone able to explain the four functions so that perhaps I can narrow
the problem down?
I tried looking at the Mame source code for some clues.
http://mamedev.org/source/src/mame/machine/irobot.c.html

The four 2901 bit slice processors should be fine. I swapped in new ones
to be sure. I will check the proms and look at all the signals on a scope.

The manual also says "To aid in troubleshooting the mathbox circuit, the
mathbox can be pulsed to provide an oscilloscope sync signal. Press the
Start 2 button to pulse the mathbox. Connect the oscilloscope sync input
to pin 10 on the integrated circuit at location 9L on the CPU PCB. Press
the FIRE button to stop the pulse mode."

* Question 2:
Is there a document somewhere that elaborates on this process? Can anyone
explain how to use this procedure and what to look for?

Thanks,

Matt

On Fri, 25 Jul 2008 01:38:31 -0700, Matt Rossiter <matt@rossiters.com>
wrote:
> A little more update. The crackly interferance sound was due to a bad
> plastic insulator which wasn't doing a very good job keeping a metal
screw
> from making contact with the metal heatsink on one of the switching
> transistors Q2. This also was causing the occasional shocks when I
> touched
> the coin door frame, also the power supply would shutdown when I
connected
> the ground lead of my oscilloscope to it. So I installed a tightly
fitted
> plastic screw. Now the power supply is working solid 100%. I'm getting
a
> nice even +5volts. Note to self, use plastic screws from now on.
>
> I'm still getting a RAM error message C0 W11 at address 2001. I don't
> believe it's actually the ram, I believe its further down the data lines.

> So I need to trace that bugger out. Once I have that done, I,Robot will
> be
> working 100%
>
> Matt
>
> On Mon, 21 Jul 2008 23:39:46 -0700, Matt Rossiter <matt@rossiters.com>
> wrote:
>> Here's an update on the I,Robot power supply. I put in the new FEP16CTA
>> part and now the power supply works fine. The game and monitor come up
>> fine. So if anyone is trying to fix their I,Robot power supply - the
>> schematics have that part number wrong. Whoever worked on this before
> me
>> put in the wrong part and probably gave up.
>>
>> The regulator is regulating at 5.4 volts. Perhaps I need to look at the
>> sense line? When I measure from ground to the speakers I'm getting
> around
>> -36volts. I'm getting alot of crackly hiss through the speakers.
> Almost
>> sounds like radio interference. I'm supposed to be getting around -31.5
>> volts so I'm thinking that might be why. I don't think it's just a bad
>> volume potentiometer.
>>
>> Other than that, I'm still waiting for my order of ram chips to come in.
>
>> The screen is all full of dots and is reporting a bad ram.
>>
>> Almost there! :)
>>
>> Matt
>>
>>
>> On Fri, 18 Jul 2008 15:17:56 +0000 (GMT+00:00), teeray
>> <teeray@earthlink.net> wrote:
>>>
>>> Check and make sure the grounds for the speakers are not connected
>>> to any other ground or metal object.
>>> The speaker ground is at -31.5 Volts.
>>> Treat it just like it was a power wire.
>>> No bare spots, etc.
>>>
>>> Tim
>>>
>>>
>>>
>>> On Jul 17, 2008 2:08 AM, Matt Rossiter
>>> Wrote:
>>>>
>>>>This is just a little update. When I removed L6 the +5v came up just
>>> fine
>>>>and the regulator didn't shut down.
>>>>http://games.rossiters.com/manuals/IR-PS2-1.jpg
>>>>So the problem is definitely in the audio section of the board. I'm
>>> still
>>>>trying to find where the problem is. I've replaced the audio amps and
>>> some
>>>>of the capacitors. I can't find any bad resistors. There seems to be
>>> loose
>>>>a ground somewhere because if I touch something metal like the coin
> door
>>>>frame or the power switch I can feel a slight tingle of electricity.
>> Not
>>> a
>>>>huge shock, but enough to be a little uncomfortable. I'm wondering if
>>> that
>>>>might have something to do with it.
>>>>
>>>>The boards seem to work fine with the ribbon connectors I made. It's
>>>>reporting a bad ram, but I'm not going to keep powering the boards up
>>> until
>>>>I resolve this loose ground issue.
>>>>
>>>>Matt
>>>>
>>>
>>
>
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Received on Fri Jul 25 23:14:50 2008