Re: [techtoolslist] Fluke 6800 POD resets when testing UUT...

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Well, duh...(sorry couldn't resist ;-). I use machined pin sockets or
double wipe in all our repairs...and Atari/Bally/Williams from that period
generally get new CPU sockets as a matter of course....BEFORE I try fixing
the board..sorry not to contribute to your nightmares.

Yeah, not one of the better designed MPUs - Williams blanking is nice, when
it works.

At least you have power - I suspect a lot of our friends are without.

John :-#)#

At 03:29 AM 15/08/2003 -0500, Rodger Boots wrote:

>Please reassure me that you got rid of the Atari gold-plated CPU and ROM
>sockets if the ICs weren't also gold plated. Had more than one of these
>have problems because of different metal combinations, almost all were
>Atari games. The Atari pinball that had this mix would flake out, but if
>the CPU was removed and reinserted it would run fine for 1-2 weeks then
>crap out again. The last time it died it turned on ALL the solenoids
>first (Atari can do this, unlike Bally). The solenoids shorted which
>overloaded the drivers, which then shorted. The high current blew the
>emitters open in the drivers, but the collector/base shorts then put the
>full solenoid power into the driver ICs. They blew and sent the power
>back into all the addressable latches, which passed it back into
>everything on the address and data busses.
>
>A full set of very expensive solenoids (some were rotary), about 22 ICs,
>and a full set of driver transistors later it was back running. The
>sockets got replaced and never caused another problem. Oddly enough the
>only things on the buss that DIDN'T blow were the ROMs and 6800.
>
>So PLEASE tell me you replaced the sockets so I don't start having
>nightmares again.
>
>
>John Robertson wrote:
>
>>I don't know if anyone else has had this happen, but I was fixing an
>>Atari pinball MPU and my 6800 pod would give timeout errors and reboot
>>the pod to the default display of "Fluke 9000 Ready".
>>
>>Found a number of interesting causes - first the 6800 uses both phase 1 &
>>2 clocks, and phase 2 was noisy. Fixed that...
>>
>>So far so good...still got the pod rebooting itself...strange. Unplugged
>>the interconnect cable between the MPU and the Lamp/Audio AUX board and
>>the pod worked perfectly (found additional faults on MPU RAM). Plugged
>>the AUX cable back in - down went the pod. Even gave messages of self
>>test etc flickeringly fast as the base would then reset. None of the
>>lines connect directly to the address or data bus to the AUX board, but
>>there is a filtered A1 and A2 that feed back to the CPU - weird, check
>>the schematic! However if I put the AUX cable on sideways so not all
>>contacts engage the board will work until I get near the A/1 end (the
>>A1/2 are at the K end of the plug - long since connected) at which point
>>the pod craps out again. Pull out scope. Check Audio output lines - they
>>are noisy...find bad latch IC for one Address line for the Audio PROM.
>>Now the board works fine with the AUX cable plugged in.
>>
>>I believe the noisy Audio lines were cross-talking with the two address
>>lines and this was enough to load down the CPU and shut it down.
>>
>>Moral of the story? Don't assume that just because something isn't
>>connected to the Address/DATA bus that it can't take the UUT down!
>>
>>(UUT = Unit Under Test)
>>
>>John :-#)#
>
>
>
>

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Received on Fri Aug 15 10:36:14 2003