I-Robot Mathbox problem

I guess it's time to change the subject line now that the switching power
supply works.

Thanks Tim. I had tested all of the math prom sumchecks using my eprom
programmer. They all seem to test out fine.
I'm pretty sure my problem has something to do with the Mathbox clock.
MBCLK looks like a mess to me.

One of the first things I noticed was there was no output on the 245
buffers at 2L and 2K. I'm getting a proper signal on pin 1, but pin 19 is
stuck high for some reason, which is labeled /EXTDEN.
http://games.rossiters.com/manuals/IROBOT_5A.jpg

I traced that signal back to the 74LS00 at 9B. I'm seeing input signals on
pins 4 and 5 but nothing on pin 6 so I replaced that chip but I'm still
having the same problem. http://games.rossiters.com/manuals/IROBOT_4B.jpg

The signal on pin 5 of 9B looks really strange. So I've been tracing that
back into the circuit a little further, but I haven't been able to find the
problem yet. I've been using a logic comparator to find potential problems
but nothing yet. http://games.rossiters.com/manuals/IROBOT_5B.jpg
Perhaps I have a bad socket somewhere.

I'm in Spain at the momement so I haven't been able to check in the last
few days, but if you have any interesting tips I can think about while I'm
enjoying the beach that would be great. :)

Matt

On Tue, 5 Aug 2008 18:34:16 +0000 (GMT+00:00), teeray
<teeray@earthlink.net> wrote:
> 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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>>>>> chris@westnet.com
>>>>
>>>
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Received on Sat Aug 9 01:10:46 2008