test-drb July 2007

test-drb@ccmp.vtda.org

189 participants
323 discussions

by marvin＠west.net

> From: "Mike Hatch" <mike at brickfieldspark.org> > > I haven't heard anyone discuss this yet: what causes traces on some old > > PCBs to wrinkle and not others? My guess is a combination of suboptimal > > glue and wide temperature swings. > > > Caused by the hot air solder levelling process when a manufacturer skips a > process or has the process order slightly out. > The solder should only be deposited on the component pads, but some > manufacturers used to put the solder on before the silk screen, then level > the board. The solder melts during levelling and aggregates under the mask > forming the "wrinkles". > > It should be - silk screen, apply tin/lead to pads, level. > It can be - tin/lead, silk screen, mask, level. > but if its - apply tin/lead, silk screen, level - you get wrinkles. You seem to be implying that the wrinkles are a result of the PCB manufacturing process, and that is wrong; the wrinkles you are talking about occur during wave soldering at the assembly portion of the process. By going to SMOBC (Solder Mask Over Bare Copper), both the wrinkles and extra weight of solder picked up during the wave soldering process were eliminated. And of course, it was not a problem when the boards were hand soldered. The wrinkles are NOT caused by hot air leveling (that was my area of expertise when I was working as a field engineer installing/training/maintaining Gyrex Hot Air Levelers.) I know of no process or reason for putting soldermask over tin/lead and using Hot Air Leveling for the reflow process. Hot air leveling was mainly used for SMOBC boards. Solder gives a longer shelf life than the SealBrite coatings that were also fairly common a number of years ago, and thus Hot Air Leveling was also used on some boards without soldermask. The usual manufacturing process before hot air leveling was drill, electroless copper/copper plate, plating resist applied (either photographically or silkscreening), copper plate to desired thickness, tin/lead plate, strip resist, and etch. If the board was going to be hot air leveled, the tin/lead plating was chemically removed. Otherwise it went through a reflow process to alloy the tin/lead into solder before the soldermask was applied.

18 years, 2 months

Strange SCSI devices (was: Re: LISA)

by Arno_1983＠gmx.de

Ray Arachelian <ray at arachelian.com> wrote: > As as aside, there were lots of very strange things on SCSI busses back > in the day. Scanners were quite common, but there actually existed > printers, and even video cards on SCSI busses. :-) The SCSI video card > and ethernet card were useful for compact Macs that had a scsi port, but > no expansion slots. Not even to speak of some of the stuff the scientific camp came to use. I got two "Gradient DeskLAB" SCSI DSP boxen for audio I/O from a chair at University where they were used for speech recognition and synthesis in the context of an automatic phone-in train timetable information system. Unfortunately absolutely no documentation and/or software to go with them, not much about them in the web (except for some people stating they used them for diploma thesis and similar), so I'm looking for any information about them you could come up with. -- Arno Kletzander Studentische Hilfskraft Informatik Sammlung Erlangen www.iser.uni-erlangen.de Ist Ihr Browser Vista-kompatibel? Jetzt die neuesten Browser-Versionen downloaden: http://www.gmx.net/de/go/browser

18 years, 2 months

M9312 boot rom trade

by wacarder＠earthlink.net

I spent a little time yesterday going through my M9312 boot roms. I have a few spares for devices that I do not have, and I am looking for a few boot roms for devices that I do have. If anyone wants to trade or if you have the boot roms I need, contact me offlist at wacarder at usit.net. Spare ROMs that I have: 755A9 - RP02/03/04/05/06 RM02/03 757A9 - TU16 TE16 TM02/03 I am looking for these: 753A9 - RX01 811A9 - RX02 756A9 - RK05 760A9 - PC05 761A9 - TU60 758A9 - TU10 One other note: I found a few 'oddball' boot ROMs. By examining the contents of the ROMs, I determined that the mnemonics for them are DA and DN. Does anyone know what devices these are for? They are not listed in the M9312 technical reference. Thanks, Ashley Carder http://www.woffordwitch.com

18 years, 2 months

[lisaem] LisaEm 1.0.0 Released

by ray＠arachelian.com

LisaEm 1.0.0 has been released. Download is available at http://lisaem.sunder.net/downloads.html as usual. ------------------------------------------------------------------------------ Lisa Emulator Change History http://lisaem.sunder.net/ ------------------------------------------------------------------------------ 2007.07.06 - Display color balancing to remove fuzziness. 2007.07.05 - LisaConfig bugs found - overwriting date information with garbage on save of preferences. - corrected a bug preventing the grabbing of the host time and date. Found that MacWorks locks up when date is invalid. 2007.07.04 - LisaEm documentation completion 2007.07.03 - Testing various opcodes to locate scroll bar arrow bug in LOS not found, but eliminated shift/rotate opcodes. 2007.07.01 - regression testing to locate MacWorks bug - not found yet, high probability that it lives somewhere inside the C++ code. 2007.06.30 - added Mac OS trap symbol printing for A-Line traps for tracelog 2007.06.29 - fixed inability to detect no-floppy from Lisa boot ROM - fixed entry to Service mode - not perfect, need to attempt to boot from bad profile. - fixed tracelog bugs (hardcoded /log/lisaem-output)

18 years, 2 months

Altair Kits

by gstreet＠indy.net

Hello All, Regarding the Altair 8800 repro kit: An unsolicited plug -- This kit is of the highest quality. Because of my ridiculous commute schedules, I can only work on my kit sporatically. I missed my big chance to build one in 1975, and I when I saw this kit, I vowed not to miss it again. It's been a long time coming, but it was worth the wait. I love this kit!!! Kudos to Grant! Regards, Robert Greenstreet

18 years, 2 months

Old Modems and Telephony switches

by Peter.Coghlan＠EUROKOM.IE

> >I've got a lead on some four-wire and X.25 ("frame relay"?) stuff from University and just yesterday I got my second ADSL modem. What would it take to set up or "simulate" their counterpart (DSLAM?) at home? > Hi Arno, I've got some X.25 equipment which needs a good home. I have two Satelcom switches, two Dec DEMSB routers and two 4-wire NTUs ("baseband modems?") plus a few cables and manuals. The switches power up and can be configured from a console terminal but have problems retaining their configuration over a power off. This is probably due to a problem with the internal PCB mounted batteries which I have had to replace previously. One of them has a push-on connector from the power supply replaced by a soldered connection where the connector had overheated. The NTUs also power up and appear to work. I haven't tried the DEMSBs. Normally the NTUs are clocked from the telephone exchange end but it is possible to change the links in one to get it to generate a clock internally so that the two can talk to each other over a 4 wire crossover cable. At least, I can get all the LEDS to illuminate. I don't know enough about X.25 etc to get any further than that. Let me know if you are interested. However, I am located in Dublin, Ireland so I am not sure how it would be possible to get the stuff to you if you do want it. Regards, Peter Coghlan.

18 years, 2 months

cctalk Digest, Vol 47, Issue 12, Message 3 - Trace wrinkles

by mike＠brickfieldspark.org

> Message: 3 > Date: Fri, 6 Jul 2007 11:39:56 -0700 (PDT) > From: David Griffith <dgriffi at cs.csubak.edu> > Subject: trace wrinkles > > I haven't heard anyone discuss this yet: what causes traces on some old > PCBs to wrinkle and not others? My guess is a combination of suboptimal > glue and wide temperature swings. > Caused by the hot air solder levelling process when a manufacturer skips a process or has the process order slightly out. The solder should only be deposited on the component pads, but some manufacturers used to put the solder on before the silk screen, then level the board. The solder melts during levelling and aggregates under the mask forming the "wrinkles". It should be - silk screen, apply tin/lead to pads, level. It can be - tin/lead, silk screen, mask, level. but if its - apply tin/lead, silk screen, level - you get wrinkles. Wrinkles became less prevalent as tin/lead material costs went up, does not happen now as tin/lead here (UK) is banned except for special applications.

18 years, 2 months

trace wrinkles

by n8uhn＠yahoo.com

Hi All, i find it interesting that no one has mentioned the peel and press method of pcb making. some boards are not etched and placed in a chemical bath. instead the board starts as a copperless plate and the traces are on a sheet that carries the traces like a rub on transfer. the sheet has a protective layer that is removed and then the sheet is lay'ed on the blank pcb and pressed or rolled or vacuum pressure is applied. then the holes are drilled. after years of exposure to heat and air or even a bad transfer to start with, the traces "bubble" and wrinkle. i have not seen too many computer boards or cards made this way but alot of consumer audio and cb or marine two way radio's are made with this style of pcb and are a real pain to repair. when the trace is heated to replace a bad component, it wants to lift very quickly. my guess is that the peel and press way is cheaper then a real etched board. Bill ____________________________________________________________________________________Ready for the edge of your seat? Check out tonight's top picks on Yahoo! TV. http://tv.yahoo.com/

18 years, 2 months

TTL homebrew CPUs

by ed＠ed-thelen.org

Wakkkyness is not dead. "The Madscientist Builds a Processor" http://madscientistroom.org/table/mippy/ is the tale of a *second* electronics project, the first was a one chip TTL counter. Randy thought that was not hard, why not try a computer? He learned: - add lotsa capacitors between +5v and gnd, all over - ground can jump up and bite ya (a ground plane is a good thing) - and a lot of other practical stuff but crashed on, and finally succeeded :-))) Ed "Pops" Thelen

18 years, 2 months

TTL homebrew CPUs

by ajp166＠bellatlantic.net

> >Subject: Re: TTL homebrew CPUs > From: woodelf <bfranchuk at jetnet.ab.ca> > Date: Sun, 08 Jul 2007 16:06:02 -0600 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >Allison wrote: > >> If I were to do a TTL design right now I'd use 32Kx8 >> (or larger) parts even if the word size were 9 or 11 bits >> as they are cheap and easy to use and the unused excess bits >> are no real loss. >11 Bits ??? What uses that? Nothing I know of but theres no reason in the world to say that could not be done. >> Maybe because every time I did TTL or slice design I wasn't >> trying to make a period machine or be faithful I was doing >> some sacrelige but I was having fun and the expereince was >> no less because the memory, logic used or terminal was >> way out of period. > >If this your hobby , the main thing is to have fun. Roger that! ;) > >> Heck the guy that did the Apollo AGC has a hats off to me as >> he did in TTL something conceived as RTL with minimal data. >> If anything not only was a working machine a significant >> accomplishment but the information about it he dug up, made >> visible to public and preserved along the way speaks to >> great work. > >That was great work. I admire just finding all the data. That was a easter egg hunt if there ever was one. >> >> For those that try and or succeed to build a PISC >> (Pitiful Instruction Set Computer) or a VSC (Very >> Simple Computer) they are contributing a lot to the >> science and history of computing. After all there >> are many old (really old) machine preserved and sitting >> that most of us have not the first idea how to power >> up and program. Those that do it get my attention for >> their efforts. > >The Kenback 1 and the 6800 replica's that come >up is great work too. I wish I could get him >to do my cpu from my hen scratched schematics. >Now the biggest problem I have is do I want >Single Instruction or not with my minimal front >panel? Is that used that often that it needed? >Ben alias woolelf I have only done one front pannel, it was as much or more work than the CPU. It's all the wires and as I like to call it "drillin and blastin". So generally I try to avoid that or do a very minimal one for debug rather than show. The choice of what to build is always tough as there are so many choices. In the end I started with very simple state machines and microprogrammed controllers and gradually decided what capability was missing and how best to achieve it based on what I knew and had done. Whats funny is it's easier to design a slower wide word (32 or more bits) machine (lots of the same stuff repeated) than faster narrow word (8bit) machine. Then you get into variable word length or fixed, single address or multiple, register or memory based, microcode or random logic control, CISC or RISC. In the end whatever is built you're not going to be condemmed as at least it was built. >PS. How are IRQ's handeled when single stepping? Slowly. ;) Single stepping would just mean if there was an INT pending you would see all the steps and the adress changes involved. Or as I was told once, "Your the engineer, what do you want it to do?". Allison > > >

18 years, 2 months

← Newer
1
...
19
20
21
22
23
24
25
...
33
Older →

Jump to page:

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

test-drb July 2007