Re: Pertec Interface Cable Length
On 8/11/19 8:51 PM, Douglas Taylor via cctech wrote: > > The TC02 is an Emulex TS11 emulation for pertec interface tape drives. > The J1 and J2 are sort of standard terminology, don't know why. 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
Re: Pertec Interface Cable Length
On 8/11/2019 10:44 PM, Chuck Guzis via cctech wrote: On 8/11/19 6:00 PM, Douglas Taylor 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? TC02? The DECtape controller? Sorry, I must be dense; I'm not following. --Chuck The TC02 is an Emulex TS11 emulation for pertec interface tape drives. The J1 and J2 are sort of standard terminology, don't know why.
Re: Pertec Interface Cable Length
On 8/11/19 6:00 PM, Douglas Taylor 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? TC02? The DECtape controller? Sorry, I must be dense; I'm not following. --Chuck
Re: Pertec Interface Cable Length
On 8/11/2019 7:01 PM, Jon Elson via cctech wrote: On 08/11/2019 11:11 AM, W2HX via cctech wrote: I seem to remember they were ribbon cables with each odd/even pair twisted which probably meant one active and one ground twisted together. Or differential pairs. No, both Pertec unformatted and Pertec formatted interfaces were TTL single-ended. Jon 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
Re: Pertec Interface Cable Length
On 08/11/2019 11:11 AM, W2HX via cctech wrote: I seem to remember they were ribbon cables with each odd/even pair twisted which probably meant one active and one ground twisted together. Or differential pairs. No, both Pertec unformatted and Pertec formatted interfaces were TTL single-ended. Jon
Re: Removing PVA (Was: ADM-3A question)
On 8/11/19 2:21 PM, Warner Losh wrote: On Sun, Aug 11, 2019, 11:29 AM Alan Perry via cctech mailto:cctech@classiccmp.org>> wrote: On 8/11/19 6:58 AM, Charles via cctech wrote: > Anyway. I did a bit more Googling and discovered that plain water > dissolves the PVA goop just fine. No need to use a lot of expensive > alcohol which seems to be a less effective solvent anyway! Last Christmas, I removed the old PVA from a DEC VR201 for a Rainbow 100. On the advice of a website that I found, I bought butyl acetate and a long needle syringe for injecting it deep into the PVA. However, after I removed the seal around the glass/tube, the glass practically fell off and most of the PVA came off in a sheet. I had some electronics grade isopropyl alcohol around anyway and I used that to do a final clean of everything before reassembly and reseal. What did you replace the PVA with? Nothing. Air. I think it was here that someone told me that a small CRT like the VR201 doesn't need PVA filling the gap for implosion protection. alan Warner So, if anyone in the Seattle area needs a bottle of butyl acetate ... alan
Re: Pertec Interface Cable Length
On 8/11/19 9:11 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 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
Removing PVA (Was: ADM-3A question)
On 8/11/19 6:58 AM, Charles via cctech wrote: Anyway. I did a bit more Googling and discovered that plain water dissolves the PVA goop just fine. No need to use a lot of expensive alcohol which seems to be a less effective solvent anyway! Last Christmas, I removed the old PVA from a DEC VR201 for a Rainbow 100. On the advice of a website that I found, I bought butyl acetate and a long needle syringe for injecting it deep into the PVA. However, after I removed the seal around the glass/tube, the glass practically fell off and most of the PVA came off in a sheet. I had some electronics grade isopropyl alcohol around anyway and I used that to do a final clean of everything before reassembly and reseal. So, if anyone in the Seattle area needs a bottle of butyl acetate ... alan
Re: Pertec Interface Cable Length
>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. That is because a) you had the proper termination in place and b) the signalling speed of the interface was slow enough to cope (you were probably within spec). > I seem to remember they were ribbon cables with each odd/even pair twisted which probably meant one active and one ground twisted together. Or differential pairs. 73 Eugene W2HX From: cctech on behalf of Bill Gunshannon via cctech Sent: Sunday, August 11, 2019 9:59 AM To: cctech@classiccmp.org Subject: Re: Pertec Interface Cable Length On 8/11/19 9:07 AM, W2HX via cctech wrote: >> Would folding the > excess cable up and covering with anti-static plastic help? > > unlikely. The typical problem is that the longer the cable, the higher the > capacitance of the transmission line. Therefore you get a lot of problems > with rising and trailing edges of the signals which can cause all kinds of > problems if not terminated correctly. I agree with the previous suggestion > to make sure all termination is in place. If you can also place a scope on > one of the lines (with high impedance probe) you can see what the edges look > like. 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. > > From: cctech on behalf of Douglas Taylor via > cctech > Sent: Sunday, August 11, 2019 12:33 AM > To: Jon Elson; On-Topic Posts > Subject: Re: Pertec Interface Cable Length > > On 8/10/2019 1:56 PM, Jon Elson wrote: >> On 08/09/2019 11:05 PM, Douglas Taylor via cctech wrote: >>> I have a question about cable length - any electrical engineers in >>> the house? >>> >>> Connected a Qualstar 1260 tape drive to an Emulex TC02 qbus tape >>> controller in a pdp-11/53. The interface is pertec with 2 50 pin >>> cables. >>> >>> When I use a pair of short flat ribbon cables, 18 and 30 inches each, >>> it works. Under RT11 I can INIT, Copy, DUMP, do a Directory. >>> >>> It doesn't work when I use a pair of 5 foot long flat ribbon cables. >>> Are they too long? Do I need twisted pair type of cable? Is it >>> possibly a termination problem? >>> >> I have used cables about 20 feet long without trouble. The 2 50-pin >> cables is the Pertec formatted interface, which is really forgiving. >> Does you drive have terminators in both ends of the cable (both at the >> TC02 end and the drive end)? >> Now, I will mention that I have ONLY used twisted-pair ribbon cables >> with both flavors of interface, never straight ribbon cable. >> >> Jon >> >> > 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? 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
Re: Pertec Interface Cable Length
On 8/11/19 9:07 AM, W2HX via cctech wrote: >> Would folding the > excess cable up and covering with anti-static plastic help? > > unlikely. The typical problem is that the longer the cable, the higher the > capacitance of the transmission line. Therefore you get a lot of problems > with rising and trailing edges of the signals which can cause all kinds of > problems if not terminated correctly. I agree with the previous suggestion > to make sure all termination is in place. If you can also place a scope on > one of the lines (with high impedance probe) you can see what the edges look > like. 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. > > From: cctech on behalf of Douglas Taylor via > cctech > Sent: Sunday, August 11, 2019 12:33 AM > To: Jon Elson; On-Topic Posts > Subject: Re: Pertec Interface Cable Length > > On 8/10/2019 1:56 PM, Jon Elson wrote: >> On 08/09/2019 11:05 PM, Douglas Taylor via cctech wrote: >>> I have a question about cable length - any electrical engineers in >>> the house? >>> >>> Connected a Qualstar 1260 tape drive to an Emulex TC02 qbus tape >>> controller in a pdp-11/53. The interface is pertec with 2 50 pin >>> cables. >>> >>> When I use a pair of short flat ribbon cables, 18 and 30 inches each, >>> it works. Under RT11 I can INIT, Copy, DUMP, do a Directory. >>> >>> It doesn't work when I use a pair of 5 foot long flat ribbon cables. >>> Are they too long? Do I need twisted pair type of cable? Is it >>> possibly a termination problem? >>> >> I have used cables about 20 feet long without trouble. The 2 50-pin >> cables is the Pertec formatted interface, which is really forgiving. >> Does you drive have terminators in both ends of the cable (both at the >> TC02 end and the drive end)? >> Now, I will mention that I have ONLY used twisted-pair ribbon cables >> with both flavors of interface, never straight ribbon cable. >> >> Jon >> >> > 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? 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
Re: DEC VT20 boot device
The VT20 design team was, iirc, John Kirk for the video, and me for the Unibus interface in the first version. The one with the slick one shown here, http://bitsavers.org/pdf/dec/terminal/vt20/vt20_2.jpg The /05 based package was after my time, I don't remember much about how it was deployed. The boot device called using the boot strap board was variable, and I don't recall anything beyond an RK05 based system (booting the RK) for the versions in the lab on 1-2 in the mill. It was for the Typeset 11 team, and then the TypeSet.DecSet team/Product line. bob On Sat, Aug 10, 2019 at 2:56 PM Paul Birkel via cctech wrote: > > The DEC VT20 terminal apparently included a PDP-11/05 with a direct mapped > character display and was intended for text editing and typesetting. It > seems to have been followed by the VT21, and then VT71/VT72, all three based > on an LSI-11 (KD11-F). There's a real lack of documentation about these > online, although the VT72 does have a print set. > > > > Apparently the VT20 used the M792-YK as its bootstrap; the Field Guide is > silent regarding the boot device and M792 documentation stops earlier in the > series of variants. > > > > According to the VT72 print set, it used the MRV11-VC (M9942-YC; described > in the Field Guide as a "bootstrap/diagnostic module") for its bootstrap but > is also silent regarding the boot device. In interestingly, the Field Guide > also describes a MRV11-AA (M7942-TB) as a "M7942 with VT52 emulator, VT71 > bootstrap". > > > > For async. communications the VT20 used a DL11-B (M7800 (EIA)). the VT72 a > DLV11-F (M8028). > > > > Looking in a DEC "Options and Modules" listing I see VT20 bundles including > Typeset-11 and DECset-11, and it appears that the VT20 could be configured > with two displays & serial lines in a single 11/05. > > > > So . is the boot device in these systems the remote host via the serial > line? What protocol would that have been? Something native to Typeset-11 > and DECset-11? > > > > paul >
Re: DEC VT20 boot device
> On Aug 10, 2019, at 2:56 PM, Paul Birkel via cctech > wrote: > > The DEC VT20 terminal apparently included a PDP-11/05 with a direct mapped > character display and was intended for text editing and typesetting. It > seems to have been followed by the VT21, and then VT71/VT72, all three based > on an LSI-11 (KD11-F). There's a real lack of documentation about these > online, although the VT72 does have a print set. > ... > Looking in a DEC "Options and Modules" listing I see VT20 bundles including > Typeset-11 and DECset-11, and it appears that the VT20 could be configured > with two displays & serial lines in a single 11/05. > > So . is the boot device in these systems the remote host via the serial > line? What protocol would that have been? Something native to Typeset-11 > and DECset-11? I've never heard of DECset-11, but I worked on Typeset-11 1978-1980. The VT71 was the standard high end terminal for that system. I saw a VT20 sitting in a corner of our lab, but it was collecting dust and I never saw it operate, or connected to anything. As far as I know, no trace of Typeset-11 or TMS-11 (same software pretty much, ported to a stripped-down IAS instead of RSX-11/D) have been preserved. It seems plausible that the download protocol would be DDCMP MOP mode, since that was a standard protocol supported by DEC for this purpose. But it could have been something custom as well -- it's not something I was ever exposed to. Yes, as far as I know the 11/05 controller for the VT20 could drive two independent displays. The VT71 had a single display, the control processor was built into the terminal case. I'm fairly sure the VT71 software was derived from that of the VT20, but just how close they were I do not know. paul
Re: Pertec Interface Cable Length
On Sat, Aug 10, 2019 at 9:46 AM Douglas Taylor via cctech 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 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.
