Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old March 20th 14, 03:27 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Dec 2013
Posts: 96
Default A sign of dirty connectors?


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I'll try the card swap to see if I can detect any differences.


If you put a different card in the slot where the problem card goes, it
may or may not work - it isn't a given that all the slots on the
motherboard are the same. But you can at least judge the mechanical
condition of the connector that way. If you do this swap, do it with
*all* power to the mill shut off. (The different slots may have power
and ground on different pins...)

Unfortunately the board it plugs into is buried behind everything else
and will take a lot of time to remove.


That's usually how it is.

Looking at the connector contacts on the board I can see that some
have more obvious marks than others on them from the contacts in the
female connector. Hmmm.


They all should have some kind of mark, and it's normal for the marks to
vary a little. If most of the marks are obvious - dug into the copper/
gold somewhat, but a few of them you have to get out the 250 W lamp to
see the mark, then that's a clue.

Could failing caps be causing problems?


Possibly.

Could unplugging the board allow some caps to discharge which then
makes the alarm go away?


Kind of strange, but within the realm of possibility.

I'll try your folded paper cleaning strategy and report back.


OK. I will post to your new thread shortly as well.

Matt Roberds


Check the +5 volts to one of the LSTTL chips. If the 5 volt supply is
failing, it could be a power supply issue. Look up one of the 74LS chips for
what pins are Vcc (+5) and ground. For a 14 pin chip, ground is pin 7 and
Vcc (+5) is pin 14 usually. Track the voltage until it fails and note any
trend.

tm


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