Weird problem, random led behavior and sound

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rv0
 
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Weird problem, random led behavior and sound

Post by rv0 »

I bought a x0x recently, worked fine.
I got out the cpu because I was going to place the cpu-mod board, but left it for a week.

When I tried a week later, no luck. So I put in original cpu again.. Result is random led action, a sound every now and then.
I think, when measuring voltage on cpu, that the 5V line drops every now and then, resulting in a crash.
I checked flatcables, resoldered the socket, measured every single line around the cpu for continuity, no luck.

I'm out of options here, any suggestions?

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mmm
 
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Re: Weird problem, random led behavior and sound

Post by mmm »

Did you check the voltage on the IOboard? Perhaps it's something in the vicinity of the 7805? (Or perhaps the 7805 itself?)

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rv0
 
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Re: Weird problem, random led behavior and sound

Post by rv0 »

Did checks on the IO-board as per the build manual
All voltages were spot on, perfect.

Will recheck the 7805, but I think the problem is further down.

Sokkan
 
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Re: Weird problem, random led behavior and sound

Post by Sokkan »

Make sure the CPU is firmly set in the socket. I once "fixed" a x0xb0x with random problems by pressing hard on the CPU making it snap in place... :-)

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mmm
 
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Re: Weird problem, random led behavior and sound

Post by mmm »

darffader wrote:Did checks on the IO-board as per the build manual
All voltages were spot on, perfect.

Will recheck the 7805, but I think the problem is further down.
Do you have access to an oscilloscope? Perhaps it is a clock problem.

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rv0
 
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Re: Weird problem, random led behavior and sound

Post by rv0 »

Not really..

I doubt its a clock issue though, since the cpu mod board that I tried has it's own XTAL

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rv0
 
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Re: Weird problem, random led behavior and sound

Post by rv0 »

Any voltages/stuff I can measure on the main board with a multimeter?

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mmm
 
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Re: Weird problem, random led behavior and sound

Post by mmm »

I'm not sure what could cause such a behaviour. The digital side is pretty robust and straightforward.

The problem with measuring with a multimeter is that it won't catch very short dropouts. So if the +5V are ok it could be a number of other things. What about the Reset circuit - is that one solid?

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rv0
 
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Re: Weird problem, random led behavior and sound

Post by rv0 »

Meanwhile, I finally managed to get in touch with the person I bought it from and sent it back (under warranty)

Will post back here what the problem was. Thanks for the help!

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