Re: Need some help with an Atari Switching Power Supply

Test all of the 82137 math proms and
check the Battlezone Mathbox for a better understanding.
It's on a aux board by it's self.

Tim

-----Original Message-----
>From: Matt Rossiter <matt@rossiters.com>
>Sent: Jul 26, 2008 3:14 AM
>To: rasterlist@vectorlist.org
>Subject: Re: RASTER: 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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>>>
>>
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Received on Tue Aug 5 14:34:21 2008