On 8/10/2019 4:57 AM, Dave Wade wrote: I bought the long cables off ebay, so they have to be good? Right? I think the short cables came from a hamfest. The cables can be fairly long, I remember interfacing a TU80 to an Emulex QT14 (maybe) and the DEC cables were round and about 15 feet long.? And it worked. It was too late last night to begin checking the long cables for continuity, so I fired off the email instead thinking it may be a termination problem. Is it possible for the IDC and Card edge connectors to be put on wrong?? You would want pin 1 to map to pin 1, and so on. Doug

On Sat, Aug 10, 2019 at 9:46 AM Douglas Taylor via cctech <cctech at classiccmp.org> wrote: If you build cables yourself without proper tools it might be easy to end up with bad results. It takes a fair amount of force to properly press a 50-pin connector on to a ribbon cable with even pressure. I picked up a used 3M Scotchflex 3316 manual hand press with locator plates for IDC and card edge connectors a few years back for a reasonable price. It made quick work of properly pressing 50-pin IDC connectors on to ribbon cables when I built some Pertec interface tape drive cables. I used some Amphenol Spectra-Strip Twist 'N' Flat ribbon cable and made a couple of cables that are about 8 feet long. I haven't had any problems using them between an Emulex QT13 controller and a Fujitsu M2444AC tape drive.

via house? Engineering is Same an field of Yes.. An electronics engineer... Dave G4UGM

It's funny how licensing bodies do not recognise computer engineers. I am a member if the IEEE, but since I first wrote to the local body in 1974 they have never recognised computer engineering as a discipline.? After twenty years of chip-level troubleshooting on DEC machines I spent twenty twenty-five years teaching college before retiring to my soon-to-be-restored collection of old kit. I ran into the then President of the provincial licensing association at an alumni event a few years ago and he laughed, saying they are still working on it! Meanwhile, computers run everything... cheers, Nigel Johnson On 11/08/2019 11:34, Jon Elson via cctalk wrote: -- Nigel Johnson MSc., MIEEE VE3ID/G4AJQ/VA3MCU Amateur Radio, the origin of the open-source concept! You can reach me by voice on Skype: TILBURY2591 If time travel ever will be possible, it already is. Ask me again yesterday This e-mail is not and cannot, by its nature, be confidential. En route from me to you, it will pass across the public Internet, easily readable by any number of system administrators along the way. Nigel Johnson <nw.johnson at ieee.org> Please consider the environment when deciding if you really need to print this message

Jon Elson via cctalk wrote: I very much agree with the U.S. philosophy with regards to school organization (i.e., a department or school? with general electrical engineering faculty, directly hosting a degree program in electrical engineering, with majors in either communications, power systems, computer engineering, and so on.? In the last few decades some departments in the U.S. have transitioned to names such as "Department of Electrical and Computer Engineering" (see e.g. http://www.ece.wisc.edu/ and https://www.ece.cornell.edu/ece, precisely the two universities where I studied in the U.S.). In Latin America, with some exceptions, it is common that each very specific program is hosted by one very specific department, thus there is one electronics engineering program linked to a department of electronics engineering and a different electrical engineering program with a department of electrical engineering. This is especially true in older, public universities.? The reason for this is petty:? resource management (i.e., handling of tuition, human resources and so on) was often done at the program level, so people preferred to have "their own turf" in the organization and this led to this kind of granularization. I do belong to a "Department of Electrical, Electronics and Computer Engineering" and I like it this way.? We do, however, host two differently-named undergraduate programs, called, you guessed it, Electrical Engineering and Electronics Engineering.? Nowadays many students are choosing to stay one or two more semesters and obtain the two degrees; this is possible because of the curricular design that we have in place. In the U.S., some of the first Electrical Engineering programs were created inside Physics departments and only later were the corresponding departments created. carlos.

On 8/10/2019 1:56 PM, Jon Elson wrote: I haven't checked to see if there are terminators (Arnold the Terminator) on either end.? I did check the long cables for continuity and found no problems.? It may be an EMI problem. Would folding the excess cable up and covering with anti-static plastic help? Doug

On 8/11/19 9:07 AM, W2HX via cctech wrote: All of my Pertec tape drives (in the past) were located in a differentrack from the actual computer so the cables were always over 10' long and usually close to if not 20'. Never had a problem. I seem to remember they were ribbon cables with each odd/even pair twisted which probably meant one active and one ground twisted together. I don't remember there being any specific termination like you see on things like SCSI disks or RL Disks. But then, it has been a long time since I had my last Pertec Tape Drive. Only 9-track I have today is SCSI. bill ' bill

On 8/11/19 9:11 AM, W2HX via cctech wrote: I stand by my commentary re Qualstar 1xxx drives. They're not up to the task of driving long cables. Who has one such drive with 10' cables operating correctly? Until someone comes up with actual experience with said drives, we're just guessing. I note that my 1260S does have the capability to be used as a Pertec interface drive. I suppose I could re-cable from one of my other drives and test it, but at this stage, I hardly see the point. --Chuck

On 8/11/2019 7:01 PM, Jon Elson via cctech wrote: I just looked at the TC02 and the Qualstar, there are termination resistor packs on each.? The Qualstar has a bunch of 74LS240 IC's near the J1 and J2 pertec interface cables.? The TC02 has a bunch of 74LS374 chips near the J1 and J2 connectors. This is where the electrical engineer could help.? How do you determine how long a cable the 74LS240 can drive? Doug

On Sun, Aug 11, 2019 at 7:44 PM Chuck Guzis via cctech <cctech at classiccmp.org> wrote: I assume TC02 here refers to an Emulex TC02, a Q-Bus Pertec interface tape controller which emulates a TS11 tape controller. http://www.bitsavers.org/pdf/emulex/TC0251002-G_TC02tech_Jul85.pdf

On 8/11/19 8:51 PM, Douglas Taylor via cctech wrote: Ah, the *Emulex* TC02. You had me going there--DEC also has a DECtape controller called the TC02. Looking at the TC02, there are 374s to latch data coming from the Qualstar and use the termination packs, but there are also 7438s driving the lines from the TC02 to the Qualstar. Those have no terminators. The TC02 reference manual says that you get run lines up to 30 feet long between the TC02 and formatter. My point is that the driver technology for the Qualstar (i.e. read data and status) is inappropriate for long cable runs. The spec calls for 48 ma OC drivers. --Chuck

On 8/12/19 8:11 AM, Douglas Taylor via cctech wrote: If you needed to cobble something up suitable for long cable driving, you could work up the correct pertec driver interface to sit between the Qualstar interface board and the cable and install it in the 1260 case--there's plenty of room without the SCSI interface PCB. The big problem with the 1260 is that it doesn't move the tape fast enough for reliable operation at the 6250 GCR setting; operation at 1600 PE is just passable. But it's a drive that's portable and that is an advantage, especially to us older folk. Another possible option would be to replace the Qualstar LS240 drivers with TI 74BCT756 open-collector drivers (same pinout) with 64 ma drive capability. That probably would be the harder option, as it would entail removing the soldered-in LS240s. FWIW, Chuck

Another consideration with the TC02 is the small buffer. I don't know what tape speed your drive runs at, but we lost a lot of sales to Dilog because of buffer overflow on some of the faster CDC dirves.? When we came out with the TC03, it had a larger buffer to handle this. cheers, Nigel Johnson On 12/08/2019 11:13, Jon Elson via cctech wrote: -- Nigel Johnson MSc., MIEEE VE3ID/G4AJQ/VA3MCU Amateur Radio, the origin of the open-source concept! You can reach me by voice on Skype: TILBURY2591 If time travel ever will be possible, it already is. Ask me again yesterday This e-mail is not and cannot, by its nature, be confidential. En route from me to you, it will pass across the public Internet, easily readable by any number of system administrators along the way. Nigel Johnson <nw.johnson at ieee.org> Please consider the environment when deciding if you really need to print this message