Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!usc!snorkelwacker!apple!apple.com!alexr
From: alexr@apple.com (Alexander M. Rosenberg)
Newsgroups: comp.sys.mac.comm
Subject: Re: U N C L E ! !
Message-ID: <10173@goofy.Apple.COM>
Date: 12 Sep 90 17:11:38 GMT
Sender: usenet@Apple.COM
Organization: Hacker's Anonymous
Lines: 35
References:<69723.26E9C6F7@cmhgate.FIDONET.ORG> <3431@syma.sussex.ac.uk>

In article <3431@syma.sussex.ac.uk> paulr@syma.sussex.ac.uk (Paul T 
Russell) writes:
> On at least one of the modems I notice a crackling from the speaker
> at switch on, which sounds like it might be a capacitor breaking down
> or some such.
> 
> When I get a spare moment I'll pull one apart and see if I can do
> anything with it. I believe there is some sort of piggy back
> modem module in there so I guess I could try swapping those around.

Your problem is probably a bad power supply. The speaker is driven 
directly by the 65C112 processor in the modem. Switching the "piggy back 
modem module" will probably not help. This module is the modem tranceiver 
chip set, and your symptoms don't suggust this to be the problem.

If you insist on doing it yourself (and it seems you must) then I'd check 
the voltage coming out of the power supply. If the supply isn't supplying 
enough, then everything will seem to work, but transmissions will be slow 
and full of errors, and any of the "failure" modes you described can 
happen.

We had a problem similar to this where one of our test modem's power 
supply had gone bad, and we spent two days trying to figure out if it's 
poor transmission performance could be attributed to a particular fax 
machine. (This involved me running around from building to building and 
using every fax machine Apple owns, not just the ones we had been using in 
our lab. After we figured it out, the hardware engineers checked the power
supply and decided that it was an isolated case.)

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