kruger@16bits.dec.com.UUCP (10/30/87)
About the differences in the A-500 parallel port -- it probably can't be powered because the 500 can't deliver the power. That power supply is wimpy, and it running on the edge. Can any C-A engineer verify this? dov p.s.Apologies for the odd format -- we at Digital get our net news mailed to us.
grr@cbmvax.UUCP (George Robbins) (10/30/87)
In article <11998@decwrl.DEC.COM> kruger@16bits.dec.com (Digital Drills: When analog bits won't do) writes: > About the differences in the A-500 parallel port -- it probably can't be > powered because the 500 can't deliver the power. That power supply is wimpy, > and it running on the edge. Can any C-A engineer verify this? This sounds like a "have you stopped beating your wife" question to me. The power supply for the A500 is fairly conservatively rated. It is certainly not "on the line". Most of the problems we've seen have been mechanical in nature - pieces that don't stay where they should when you drop the thing. The reason that we didn't put hundereds of amps of 5 volts on the parallel connector was that we wanted it to be safe to plug in any device attached to an IBM printer cable. The IBM parallel connector has *NO* 5 volts on it, and no spare pins to put it on. -- George Robbins - now working for, uucp: {ihnp4|rutgers|allegra}!cbmvax!grr but no way officially representing arpa: out to lunch... Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
bryce@hoser.berkeley.edu (Bryce Nesbitt) (11/02/87)
In article <2662@cbmvax.UUCP> grr@cbmvax.UUCP (George Robbins) writes: >In article <11998@decwrl.DEC.COM> kruger@16bits.dec.com () writes: >> That power supply is wimpy, >> and it running on the edge. > >The power supply for the A500 is fairly conservatively rated. It is certainly >not "on the line". Most of the problems we've seen have been mechanical in >nature - pieces that don't stay where they should when you drop the thing. One thing George did not mention was ventilation. The power supply case is such that leaving it on a nice insulating carpet could contribute to bad news. The manual does not have a warning about this. Or perhaphs I should say that it does not have a *WARNING*. While I'm picking nits at that manual, it says nothing about static or pluging the computer brick in first, so you have a discharge path. Now if only the power switch was on the side of the brick that the *computer* end of the cable exits :-(. >The reason that we didn't put hundereds of amps of 5 volts on the parallel >connector was that we wanted it to be safe to plug in any device attached >to an IBM printer cable. Sigh. In my mind I is an indication of the ultimate failure of the expansion scheme that so many things hang off the serial and parallel ports. However as general purpose cheap I/O hooks it's hard to beat a bi-directional parallel port *with power*. Even with the limited +5 on ATUOFDXT dealers need to be careful in selecting cables to avoid bad Ring Indicator problems. :-( (Is that cable "Amiga certified"? :-) |\ /| . Ack! (NAK, SOH, EOT) {o O} . bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce (") U "You can count how many seeds are in an Apple, but not how many Apples are in a seed." -Ken Kesey