Stuck channels on a 16550A

Dec 06, 2006 3 Replies
H

I have a 16550A with several stuck channels. One of them is always stuck hi and two other stuck low. I checks the cables on another card and they work fine. When I boot the 16500B into diagnostic mode, the card passes all self diagnostics and it shows that all channels are changing, but when rebooted in to normal mode, the hi channel always shows hi even if I short it to ground. This leads me to believe that the problem is somewhere before the sampling ICs. How likely is it that one of the 1DX5-001 has gone bad? Does the self-diag test these? Is there any part you would suggest I troubleshoot first? Does anyone else have a 16550A with stuck channels that they are willing to sell for parts? Or any known good 1DX5-001 [P]LCC parts?



Thanks,



Harout S. Hedeshian snipped-for-privacy@hedeshian.net



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H

UPDATE: I jumped the bad channel (always showing hi) to the input channel on another pod that one showed hi as well. If I check the voltage on a normal channel with my voltmeter, I get 0 volts. But the stuck channel shows 1.4 volts all the time. Jumpering that channel to ground accomplishes nothing. It is bit #3 on pod 1, does anyone know which chip to check?

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UPDATE: I traced the bad channel back to the corresponding 1DX5-001 chip. I swapped those two with known working ones from another pod. Sure enough the bad channel showed up on the pod I switched it to. I moved the chips around such that pods 1-4 are working but 5 and 6 currently have bad channels. SO... Does anyone have a 16550A that has at least two good pods that they are willing to pawn off? OR does anyone have 4 DX5-001 chips?

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