Millipede continuous beeping

Bullwinkle

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OK.. this is getting frustrating! A week ago, I was getting 3 beeps...i got some RAM (2101s) and replaced the bank of 4 surrounding and including M2 (which was the faulty one according to the beeps), the board has worked perfectly since. Tonight, I noticed that I had a direction on the trackball that was not responding very well. I knew the trackball needed attention so I pulled it and replaced the bearings and sanded off the crap from the roller. I then put the trackball back into the cab, powered it up and now I get a repeating beep..never stops..just keeps going. Screen shows a verticle staggered line of dots.

Any ideas what this might be?
 
my buddy falcon has a centipede that was doing all kinds of crazy krap, turns out 5v was low even when maxxed out..

tirns out the power cord was dropping ac voltage into the cab therefor causing low power out of the power suplies etc..


not saying thats what it is, but i would check your ac power in and dc power outputs first...

on the reverse, if the power supply has a bad transistor and is feeding like 6-7 volts to the board, that could be smoking your rams too..

check the obious and lets see if you dont just get lucky..
 
OK..guess my luck ran out :/ ... replaced the cord with no change. Here's a pic of the video output (remember there is a continous beep along with this output:

pede_error.jpg


Here's a link to a youtube video of it. Not much different, but has the sound:

http://www.youtube.com/watch?v=voAFJ1nMeKQ

After reading a few posts on millipede issues, it sounded like a POKEY issue. I swapped the two around hoping that maybe it would still give an error, but a different error... but still gives the exact same video and audio..no difference.

My board voltages at the test points are:

+5 = +4.92
+12 = +11.87
+22 = +22.98
-22 = -23.41

Any suggestions are greatly appreciated
 
Voltages sound fine. Try replacing the 6502. Also try gently flexing the board around the ROMs. Longshot, but you never know. It might be time to send it in.
 
Bit_Slicer..don't think I didn't have you in mind!! :D I am going to test it in another millipede tomorrow (grabbing a few POKEY chips from a few centipede boards to try... I'll grab a 6502 and try that too)

I did stick a different set of 8 RAM chips in there (pulled the 2101-2's that gave me the above picture and put in another set (2101-1's) ...the beeping is still there but the stuff on the screen is different. Tried a 3rd set I got from Riptor (I believe they are 9342s which worked for a week and a half prior to this happening) and I get the little staticy vertical line down the middle of the monitor, but nothing else.. I know those were much faster but were compatible. I figure the speed of the different chips causes the difference in what is displayed... would that be accurate?

If this doesn't work tomorrow... I'll most likely have to send it to you. I'll be pm'ing you shortly to get and idea as to what the costs are.

Thanks,

Tom
 
I bet you've got a bad driver chip between the playfield RAM and the CPU somewhere. The change in performance with the change in SRAM speed is a good indication.
 
bit_slicer...From the way you said that, I assume there are more than one that it could be? what are the locations of the possible driver issue? if there aren't too many, I may just replace them myself, if there are a slew of them, I most likely will just send it to you. I enjoy troubleshooting, so I'd like to try myself first if there are only a few possibilities, course, I dont have a logic probe or any other testing devices other than a multi meter, so I don't want to have to socket my entire board :) (then again, any chip swaps after socketing the whole board will be a breeze! :D)

thanks,

Tom
 
Well I don't have the schem in front of me, but it could be either address and/or data paths between the cpu and playfield RAM. Take a look at both paths and see what's in the way. It could also be a control line issue (ie. read/write). Really it is impossible to say without having it on the bench and hooking up the analyzer and scope. Yeah you're probably up against replacing a half-dozen chips or more with the shotgun approach. :(
 
well... half dozen chips shotgun approach wouldnt bother me as long as I know the correct ones...and that's the thing. I'll take a look at it to see if I can ID them, if not, it'll be coming your way!

Thanks,

Tom

EDIT: At first glance, it looks as though 2E, 2F between the first bank of RAM and 4E, 4F, 4G, & 4H between CPU and 2nd bank of ram. Admittedly I didn't trace them all, but just looking at a few, those locations seem to be the general areas of interest. I will definitely make sure before pulling them (provided I can pull them from another board..maybe centipede).

Maybe I'll get lucky and it'll be the cpu or pokeys... I'll know in a few hours on that front... but judging by your responses, its not likely.
 
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I would suspect the 2114 rams at 2E & 2F first, if the test runs the cpu is most likely good, if the first ram fails the board will give one beep and then reset to test and continue that pattern with a single beep.
Dick
 
I would suspect the 2114 rams at 2E & 2F first, if the test runs the cpu is most likely good, if the first ram fails the board will give one beep and then reset to test and continue that pattern with a single beep.
Dick

Not getting to the test, the beeping and the screen posted above starts immediately upon power-on (see the link to the video for the beeping sound...I don't believe it's a RAM error (at least not one that's covered in the manual)

I did put another CPU and a couple of POKEYs in but to no avail. Will work on extracting a few 2114s from a centipede parts board to test out. Thanks for the suggestion Dick. Any other ideas, please feel free to post.

EDIT:

No go on the 2114s (at least the ones from the centipede parts board didnt fix the issue.)

Bit_slicer... pm coming your way!!
 
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Found this old post, having the same issue. Did this get fixed? Any ideas? Thx
 
Thx but the board is working in my other cabinet.


Ah. If that's the case, check your big blue.

Measure the AC voltage on the 10.3V DC test point on the AR. (Yes, measure the AC on the DC test point.) If it's more than 500mV AC, your big blue is bad and needs to be replaced.

When there is too much AC on the power supply, the board won't boot.
 
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