thinfilm@uicsl.UUCP (03/12/86)
I have a USR password modem that I use to communicate from my home
computer with and have experienced some terrible problems with noise
whenever I attempt to communicate with the USR 2400 baud courier. I
would suspect the phones lines, but I communicate with 4 or 5 university
machines which generally use racal vadiac modems and have experience NO
errors at all (for many hours of transmission). The error rate I perceive
with the 2400 baud courier on the other end is 25% or so. If anyone else
has experienced this problem is there anything that can be done about it?
Do other modems have this trouble?
Paul Fons
{ihnp4,pur-ee}!uiucdcs!uicsl!thinfilmkg@elan.UUCP (Ken Greer) (03/17/86)
In article <7000017@uicsl>, thinfilm@uicsl.UUCP writes: > I have a USR password modem that I use to communicate from my home > computer with and have experienced some terrible problems with noise USR has a upgrade PROM (revision 243) which may fix the problem. Send "ATI0" to it to see your PROM revision number. USR will swap your old one with a new one for free.
radzy@calma.UUCP (Tim Radzykewycz) (03/18/86)
> I have a USR password modem that I use to communicate from my home >computer with and have experienced some terrible problems with noise >whenever I attempt to communicate with the USR 2400 baud courier. I >would suspect the phones lines, but I communicate with 4 or 5 university >machines which generally use racal vadiac modems and have experience NO >errors at all (for many hours of transmission). The error rate I perceive >with the 2400 baud courier on the other end is 25% or so. If anyone else >has experienced this problem is there anything that can be done about it? > Paul Fons > {ihnp4,pur-ee}!uiucdcs!uicsl!thinfilm I have several USR 2400s, and have found the following problem. There is one chip in the beast which causes several things to happen whenever it receives "some kind of" noise. The symptoms I see are that the modem *changes baud rate* from 2400 down to 1200 for a period lasting from 1/2 second to 2 seconds. I suspect the same thing is causing Paul's problem. I have isolated it down to one chip by opening a couple of modems and swapping several of the chips around. The chip in question is labelled "U100". Defective versions are also labelled "8440", while working versions are labelled "8438". I've had a terrible problem getting US Robotics to fix this problem. I sent the modem to them once, and had it returned in exactly the same condition (at which time I tried the chip swapping). After isolating the problem to a chip, I called US Robotics to get the chip swapped. They have had my call open for several months now, and whenever I call them I get some kind of story: 1 One of the people who is doing the shipping has been sick for the last week, and we're way behind schedule. 2 We're way understaffed, and have over 2 weeks of back work. 3 We don't have any of the part you need, and I don't know when we'll get them. I *strongly* recommend that people don't buy USR 2400 modems unless you can open the modem up and check that chip. If one has the chip described above, then the modem is broken. -- Tim (radzy) Radzykewycz, The Incredible Radical Cabbage. ARPA: calma!radzy@ucbvax.berkeley.edu GEnet: cc5vxa::cc5mxd::calma::radzy UUCP: {ucbvax,sun,csd-gould}!calma!radzy VOICE: "Hey! Radzy!"
roy@phri.UUCP (Roy Smith) (03/20/86)
In article <193@calma.UUCP> radzy@calma.UUCP (Tim Radzykewycz) writes: > >I have isolated it down to one chip by opening a couple of >modems and swapping several of the chips around. The chip in >question is labelled "U100". Defective versions are also labelled >"8440", while working versions are labelled "8438". I just opened one of our defective Couriers and found the U100 labeled 8438, so it looks like radzy@calma knows what he's talking about. What he doesn't mention, however, is how to open the frigging modem to see inside. After much frustration, and almost driving a screwdriver through my hand trying to pry the cover off, I finally discovered that the two screws which hold it together have their heads hidden by the rubber feet on the bottom in the rear. Just tear them off (they are glued on) to get at the screws. -- Roy Smith, {allegra,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016