Recapped 840AV still acting… ODD.

[gsteemso]

As you may have seen in my post in the Compact Macs subforum, a friend helped me recap two Macs over the past few months. The Classic II was a dismal failure, but the 840AV seems to work… Sort of. It tends to freeze up when I tell it to shut down. That’s under a freshly installed OS 8.1. I’m going to be installing 7.6.1 on the second HD; with any luck that will work better. Also, a previously working (i.e. a few months ago before the recap began) AAUI adapter seems to have jammed my network somehow. I don’t understand that at all; does anyone have any troubleshooting tips?

 

[uniserver]

did you wash that 840av board after the re-cap?

that cap goo has to be wash out from under all the ic's

It needs a hot water Wash with soap,  scrub,  hot water rinse,  air compressor dry.

 

[gsteemso]

…Ah. Drat. That probably explains a lot. OK, I guess I know what my next working evening is going to involve.

 

[lopaka1998]

You might also want to check the replaced caps for shorts between the two sides. 

 

[gsteemso]

I think it may actually have been a PRAM issue. For the past few weeks it’s been working perfectly, without my ever having had time to do anything to it. It probably helps that this board had next to no cap goo on it to begin with; the recapping was largely preëmptive maintenance. (By all accounts, if you wait until a Q840av dies it usually is then too late.)

I may have identified a minor issue relating to the caps, or not. The microphone (these machines use the PlainTalk variety, with the extra-long plug to supply power) is extremely insensitive, producing very, very faint audio even when shouted into. I’m not sure whether my mic has given up the ghost or one of the caps just didn’t “take.” Anyone got any clue which cap I should be looking at to see?

 

[beachycove]

I have found a high rate of failure among the oldest plaintalk microphones (I have a box full of them for some reason, and many are dead). So the problem might not be in the Quadra. Can you try the microphone in something else?

 

[beachycove]

Also, one place on the Q840av logic board where capacitor goop really wreaks havoc is near the molex power connector.

 

[gsteemso]

Alas, nothing else I have will accept a PlainTalk mic. There must presumably be some way to test for voltage as I shout into it unplugged, but I don’t have any idea what it’s SUPPOSED to do there. Also, what voltage is it expecting on the supply contact?

 

[aladds]

5 volts.

Half way down this page: http://whitefiles.org/b1_s/1_free_guides/fg1mt/pgs/h13d.htm

 

[gsteemso]

Ah, thanks for finding that! Interesting reading there.