test-drb December 2015

test-drb@ccmp.vtda.org

191 participants
268 discussions

Piggybacking 74LS logic chips to confirm a suspected fault

by jonas＠otter.se

>> -----Oorspronkelijk bericht----- >> Van: cctalk [mailto:cctalk-bounces at classiccmp.org] Namens Terry Stewart >> Verzonden: dinsdag 22 december 2015 21:50 >> Aan: General Discussion: On-Topic and Off-Topic Posts >> Onderwerp: Piggybacking 74LS logic chips to confirm a suspected fault >> >> Hi, >> >> I've written up my recent third Apple II repair, this time an Apple IIe. >> http://www.classic-computers.org.nz/blog/2015-12-22-appleiIIe-no-video.htm >> >> One interesting aspect of this repair is that piggy-backing a logic chip helped >> confirm a faulty one. I'd only ever used this technique with RAM. >> I'm sure it only works if the chip has a particular type of fault, but it worked this >> time for me. >> >> Terry (Tez) > > I use a HP 10529A logic comparator on regular basis for fault finding in ttl circuits. > It compares a reference chip with the CUT (Chip under test;) it's a very nice diagnostic tool. > It's a bit like piggy backing just a little more sophisticated :0 > > -Rik In my experience, the type of socket you used is quite unreliable and will tend to develop bad contacts. There is a reason they are cheap... I would use a turned pin type socket instead, e g an Augat socket. They will not let you down. More expensive, but considering the work involved in replacing a socket and the risk of messing up the PCB, the cost is negligible. Jonas

8 years, 11 months

More Manuals

by radiotest＠juno.com

BAMA is probably the best known site for old test equipment and amateur radio manuals, followed by Ebaman. Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA http://plymouthcolony.net/starcity/radios/index.html

8 years, 12 months

IBM channel-attached DASD emulation

by jnc＠mercury.lcs.mit.edu

> From: Guy Sotomayor > It's typical of most of the vintage gear. Folks save the CPUs and ditch > the peripherals. It's not entirely sloth and stupidity, though. Disk drives in particular (usually the biggest issue in this area) are complex precision machinery that operate at very high speeds, etc, and working on them is a formidable job, and requires specialized parts which are, in general, no longer available. > I think the biggest problem is that there isn't a spec per-se on > Massbus. A lot of reverse engineering will be required to make it work > properly in all cases. If it were done, though, that would be wonderful, especially for people with PDP-11/70's; the UNIBUS on those machines is reputedly the slowest of any PDP-11, so having mass storage on the MASSBUS is really necessary for good performance. (Apologies for my -11 centrism in an IBM-focused thread... :-) But finding the connectors (and probably the cables too) is going to be a cast-iron nightmare. Maybe we could settle on an alternative (the way I think we should switch to pairs of dual cards with Berg/DuPont headers, with standard flat cables between them, to replace the now-unobtainable BC11-A's - DEC showed this works, with the M9014/M9042..) Noel

8 years, 12 months

The best spreadsheet / database program for Commodore 64?

by tulsamike3434＠gmail.com

Is there anything like Appleworks 1.0 for the commodore 64? if so could you be kind enough to give me the name of the program? I have searched but have found nothing of any value. I just would like a checkbool ledger and a savings spreadsheet.

8 years, 12 months

Looking for 3COM 3C905-TX Drivers

by robert.jarratt＠ntlworld.com

Not too long ago I picked up a DEC Venturis FX 5120. It contains a 3COM 3C905-TX network card. There are some sites around the web that purport to have drivers for this card, but I am very wary of downloading anything from these sites. Does anyone happen to have drivers for this card? I am not sure what OSs this card was supported on, so any drivers at all would be appreciated. Thanks Rob

8 years, 12 months

More Manuals

by wrcooke＠wrcooke.net

Hi all, I just signed up today and haven't been admitted to the group, so I couldn't reply to the appropriate message. But, in browsing through recent messages I saw the one with a link to loads of manuals. My first thought was that if that was interesting, this one would be too. Manuals for tons of old test equipment. http://bama.edebris.com/manuals/ Will

8 years, 12 months

PDP-12 Restoration at the RICM

by michael.99.thompson＠gmail.com

Lots more work on the PDP-12 at the RICM. We got an RS-232 console board and baud rate generator from Vincent and now have both serial ports working. Warren modified Kyle's SerialDisk and we booted OS/8 from an emulated RK05 on the second serial port. We fixed one of the bus interface boards in the DW8E Omnibus expansion chassis, and connected the RX8E/RX02. We were able to boot OS/8 from an RX01 diskette. We replaced an M160 flip-chip and now the EAE instructions work. We replaced an M103 flip-chip and the KW12 clock works. This system is new enough that ECO EM12-0055 for the KW12 was installed when it was built. This means that the KW12 Maindecs earlier than D8CD will not work. We cleaned up the PC04 paper tape reader/punch and connected it to the PC8E. The punch works OK, but the reader does not always step correctly and does not read the tape correctly. Fixing this will be the next project. Once we get the PC04 working the next project will be the RK8E/RK05. Out of frustration we set aside fixing the TC12 LINCtape controller. We see spikes on data track #3 that corrupt the data. We swapped the TU56 for a known good TU55, swapped the data/control cable, and swapped every flip-chip that is related to data track #3. Nothing has eliminated the spikes. The only part that we have not swapped is the backplane wiring between the data cable and the G882 flip-chips. Warren has a plan to temporarily replace that. We found that the maintenance prints that came with the system do not include ECO EM12-0055. Does anyone have a set of KW12 prints that include ECO EM12-0055? -- Michael Thompson

8 years, 12 months

Massive document depository

by j＠ckrubin.us

This was shared on the TekScopes mailing list - http://bee.mif.pg.gda.pl/ciasteczkowypotwor/ "Massive" is an understatement. Jack

8 years, 12 months

Piggybacking 74LS logic chips to confirm a suspected fault

by terry＠webweavers.co.nz

Hi, I've written up my recent third Apple II repair, this time an Apple IIe. http://www.classic-computers.org.nz/blog/2015-12-22-appleiIIe-no-video.htm One interesting aspect of this repair is that piggy-backing a logic chip helped confirm a faulty one. I'd only ever used this technique with RAM. I'm sure it only works if the chip has a particular type of fault, but it worked this time for me. Terry (Tez)

8 years, 12 months

EAI TR-10 Patch Plugs

by dave.g4ugm＠gmail.com

Folks, I own an EAI TR-10 analog computer which sadly came without any patch cables and accessories. Normally this wouldn't be a problem, BUT the TR-10 comes with special resistive plugs which go at the ends of the patch leads. These have a 4mm plug and socket with a 10k or 100k resistor in between. I can't figure out a way to easily fabricate replacements. I can easily obtain 4mm plugs and sockets, and solder a resistor between them, but when I try and mount them on a short rigid tube all my efforts fail. The plug and socket need to be twisted in opposite directions and any soldered joint just fails. Any usggestions? Does any one have some of these and if so how are they constructed? Dave Wade G4UGM

8 years, 12 months

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test-drb December 2015