test-drb

test-drb@ccmp.vtda.org

101090 discussions

by p.gebhardt＠ymail.com

Hi Ben, >? I can't seem to find this anymore.? I have seen a few mentions that there is a "wrapper" installer that is necessary to install 7.2 on an ES47/ES80 >machine, and I'm hoping that it was archived or mirrored some place... Back then in 2016, I also looked for these images for my ES80 machine on the HP site and tried to find ftp mirrors, but all I found were broken links. I would be happy, too, if anybody has a copy of these installation sets. Cheers, Pierre

4 years, 1 month

VCF Swap Meet in Wall, NJ Sat, Feb 26 - Vintage Computers, Amateur Radio, TV, Radio, other Tech

by jeffrey＠vcfed.org

*The vintage Computer Federation will be having their 3rd swap meet.* *Saturday, February 26, 2022* *8AM to 2PM* *ADDRESS*: *Indoor swap Meet* InfoAge Science and History Museums (Camp Evans) 2201 Marconi Road, Wall, NJ 07719 Buildings 9010-D, 9032-A, 9001 *GPS location*: Google Maps <https://goo.gl/maps/YiEnhJAtffHTnfn8A> *Satellite Map*: *Street Map*: *EMAIL*: swapmeet at vcfed.org *PHONE*: 732-722-5015 *Flyer:* 2022-VCF-Swap-Meet-Flyer <https://vcfed.org/wp/wp-content/uploads/2022/02/VCF_Swap_Meet_2_26_2022_LQ_…> *Website*: https://vcfed.org/wp/vcf-swap-meet/ *VENDOR COST* is per space. First space is $20, each additional space is $10. This time it is an *indoor* swap meet. *Bring your own table!* Table isn?t required, but recommended. A space is considered a 6 by 3 foot area (the general size of a table). *Vendor setup at 7AM.* *FREE GENERAL ADMISSION!* *SEND PAYMENT TO*: paypal at vcfed.org (FRIENDS AND FAMILY OPTION) Write in the note section: [your name] VCF Swap Meet 2/26/2022 Number of spaces: *Click HERE for Swap Meet Vendor Signup* <https://docs.google.com/forms/d/e/1FAIpQLSfplnIROL-TTJ3qNkIo45mTelGNY3QCaFi…> * Reservation doesn?t guarantee sales. * The Vintage Computer Federation is only providing a space, vendors must bring their own tables. * In case of inclement weather, money paid will be refunded. * All items that you bring must be taken with you. No items are to be left behind. * Bathrooms on site * Limited food and drink options available. The same info can be found here: https://vcfed.org/wp/vcf-swap?meet <https://vcfed.org/wp/vcf-swap-meet> *EMAIL*: swapmeet at vcfed.org *AFTER THE SWAP MEET, COME VISIT OUR VCF MUSEUM @ INFOAGE!* We are open from 12PM to 5PM: https://vcfed.org/wp/vcf-museum The Vintage Computer Federation Museum is located nearby the swap meet and is part of InfoAge Science and History museums. InfoAge and VCF Museums are open every Saturday, Sunday and Wednesday from 12PM to 5PM InfoAge museums: infoage.org.

4 years, 1 month

Red Hat Linux 7.2 for Alpha

by ben＠huntsmans.net

Hi guys- Is anyone aware of an archive or mirror of HP / Compaq's Red Hat Linux 7.2 for Alpha download site: ftp://ftp2.compaq.com/pub/linux/RedHat/7.2-alpha/release-isos/ And the update site: ftp://ftp2.compaq.com/pub/linux/RedHat/7.2-alpha/updates/ I can't seem to find this anymore. I have seen a few mentions that there is a "wrapper" installer that is necessary to install 7.2 on an ES47/ES80 machine, and I'm hoping that it was archived or mirrored some place... Thanks in advance! -Ben

4 years, 1 month

DECTape head problem

by go＠aerodesic.com

In debugging my DECtape interface lashup, I found that one of my head has two open windings.? Specifically, one channel has an open 'ground' with the other two lines apparently the full winding of the channel.? The second channel failing has no continuity between any of the three lines.? I have tested the other head and it has all the requisite continuity so I'm hoping I can at least get a single spindle running. Visual inspection of the head 'suggests' it might be caused by the age-old 'wire stress' of being captured within a polyester resin and then finally snapping due to internal stress.? I see lots of internal stress cracks on this head so I'm probably toast on this one. Are there documents on how the heads are made?? I.e. number of turns of number X wire; cap of X micros etc.? I'm not (yet) seriously entertaining the idea of rebuilding this head, but it looks pretty low tech.? These heads are Western Magnetic heads without a model number (only serial number 19976 - don't know the other head S/N as I haven't removed it yet.) And the look to be hand made... Has any ever attempted repair of one of these? -Gary

4 years, 1 month

Varian 620/L backplane netlist?

by mark.kahrs＠gmail.com

I realize this a rare bird indeed, but would anyone just happen to have a Varian 620/L backplane netlist hanging around? Unless I missed it, the schematics on bitsavers do *not* have it.

4 years, 1 month

AlphaServer ES47 partitioning

by ben＠huntsmans.net

Hey guys- Anyone on here know much about the Marvel boxes? I've had one for years but never had much time to fiddle with it. I'm looking at the partitioning features. In particular, the manual says: Hard partitions must be on 2P boundaries Tru64 only supports hard partitions However, I can confirm that you can definitely create a hard partition with a single CPU. This got me thinking, and I dug a little deeper into the MBM CLI. The manual seems to suggest that this is the case, but says that the operating system won't work correctly in that configuration. Anyone know why not? When you create a hard partition, you specify what type of subpartition the hard partition can contain. The manual says that only "soft" partitions are officially supported, but the CLI also allows you to create subpartitions of type "firm" and "semi-firm". Does anyone know what "firm" and "semi-firm" partitions do differently than soft partitions? And does Tru64 work with any of that, or is all of that OpenVMS-specific stuff? Also, on a side note, I don't suppose anyone here has a rail kit for an ES47 or ES80 they'd like to sell, or an I/O drawer... Many thanks in advance! -Ben

4 years, 1 month

More switchmode power supply grief - Cisco IGS router

by cctalk＠beyondthepale.ie

I have a Cisco IGS router which hasn't worked for a long time. When I was last using it several years ago, it occasionally crashed and restarted. This turned out to be due to a poor contact on a connection in the cable going from the output of the power supply to the main board. I cleaned the contact more than once but it was difficult to make it good enough to ensure reliability. When I switched it on more recently, it was completely dead, no LEDs, no fan noise, no anything. I put it in the naughty pile and it sat there for a few years before I got around to looking at it. Today I finally managed to check it out. The ceramic F4A mains input fuse beside the power switch on the back panel had blown. When I opened it up, I found a POWER-ONE MAP80-4000 power supply. The main chopper transistor labelled Q1 on the PCB is almost a dead short. It is a large plastic packaged FET mounted on a piece of aluminium which is in turn screwed to the case for heatsinking. Unfortunately, there are no markings on it so I have no idea what to replace it with :-( As Q1 is shorted across all three terminals, whatever drives it may be damaged too :-( After finding screw heads hidden under the label, I managed to extract the PCB from the case and found some corrosion underneath, possibly from leaking electrolytic capacitors :-( There are lots of data sheets available for this power supply on the web but they concentrate on the specifications for the unit and don't say anything about the components :-( There are also lots of people offering to sell power supplies like this for way more than I am interested in spending on this project :-( I could replace the power supply with a different one, however, I don't have anything to hand that will fit in the approx 5-6cm headroom :-( Anyone have any suggestions? Regards, Peter Coghlan.

4 years, 1 month

WTB: DEC VSXXX-AA Mouse or Compatible

by lists＠glitchwrks.com

All, I'm looking for a DEC VSXXX-AA "hockey puck" mouse or compatible for a VAXstation 3100. Thanks, Jonathan

4 years, 1 month

Vintage computers Swap-meets in Knoxville region

by peveep＠gmail.com

Between the 30th of March and the 20th of April. I am a computer collector from England and specialise on computer artefacts >from the 1940s to the 1970s. and would love to attend one of these when visiting my son in TN. Many thanks, peter vp

4 years, 1 month

TTL substitute for DTL

by cclist＠sydex.com

I've got a piece of gear here with a bad MC858P used as a bus driver--terminated in 220/330 ohms at the far end. Given that old DTL is a hit-or-miss proposition, I'm proposing to substitute a 7438 OC buffer. Pinout's the same, as is Vcc. Before I get out the soldering iron, any "don't do it" thoughts? --Chuck

4 years, 1 month

Wanted: Pinout IDT 49C402 PGA84

by holm＠freibergnet.de

Hi, I have 4 pcs. IDT49C402 Bit Slices, it is no problem to find a datasheet for that chip..but it is an problem to find the pinout for the PGA84 Package. In all Datasheets that I've found only DIP68, LCC/PLCC68 PGA68 and CERQUAD68 are listet.. Has anyone a databook newer than 1989 where the PGA84 Pinout is listed? TIA, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Goethestrasse 15, 09569 Oederan, USt-Id: DE253710583 info at tsht.de Fax +49 37292 709779 Tel +49 37292 709778 Mobil: 0172 8790 741

4 years, 1 month

PDP-11/34 CPU PROMS

by jnc＠mercury.lcs.mit.edu

> From: Warner Losh > Do those chips have ROM numbers on them? I have updated the: https://gunkies.org/wiki/KD11-E_CPU https://gunkies.org/wiki/KD11-EA_CPU articles with the DEC part numbers for the i) microcode and ii) instruction decode PROms. That's not all the PROMs on the Control card - there are effing bazillions of the damned things (I suspect they used them to reduce the amount of random logic, so the CPU'd fit on two boards) - but it's most of them. I have yet to triple-check them, so there might still be transcription error or two. > From: Rod Smallwood > I am sure somebody will come up with the actual images either the > original files or derived from what we have. I wouldn't be too sure of that; silence so far. I have reached out to Mike Douglas, to ask where the microcode dump on DeRamp came from: perhaps the originator can help with the missing bits. (Although perhaps I should ask Al K; BitSavers also has the dump, and it's older, so perhaps that copy came >from the originator.) > We have narrowed the problem down. > Its the instruction decode ROM's that are the issue. > The images of those are whats needed. All of them? Or is just one failed? I'm wondering if you've just had a single one lose a bit or two; that's somewhat common in old PROMs. The chip you reported as failing (E111) almost certainly couldn't have taken out an instruction decode PROM, it's nowhere near them. I ask because we have absolutely nothing on those PROM's contents. With the microcode PROMs, we at least have the contents in symbolic form (see pg. 15 of MP00082; alas, we don't seem to have the KD11-EA equivalent of Table 7-15 >from EK-FP11A-TM-002), but for all the instruction decode PROMs - nada. Absolutely nothing. But if they're _mostly_ there, with the partial contents, and a description of the failure mode (e.g. 'SETC doesn't set the C bit'), we might be able to work out what bit got dropped. Failing that, someone's going to have to volunteer to unsolder a set, and read them out - at least, I assume that's what would have to be done. Perhaps a logic analyzer could be attached to an instruction decode ROMwhile the CPU ran diagnostics, and eventually a complete readout of the contents accumulated. Noel

4 years, 1 month

PDP-11/34 CPU PROMS

by jnc＠mercury.lcs.mit.edu

>>> On Tue, Feb 8, 2022 at 6:18 PM Rod Smallwood wrote: >>> On the M8266 CPU control board a defective 7404 (E111) has killed a >>> bunch of the PROMs holding the microcode. That's pretty astonishing; I've heard of PROMs dropping bits over time, but I'm a bit amazed to hear of a failure in a TTL gate (the 74S04 is a hex inverter; its gates are on pg. 7 of the M8266 prints - they produce uPC03-08) taking out a bunch of other gates connected to it. >> On Tue, Feb 8, 2022 at 7:04 PM Warner Losh <imp at bsdimp.com> wrote: >> I found >> https://deramp.com/downloads/mfe_archive/011-Digital%20Equipment%20Corporat… >> which has the source code... >> >> But I couldn't find the tools to use these files to create microcode >> images. Actually, the "m8266_ucode.v.txt" there seems to actually be the program that produced the symbolic dump (which is also available at: http://www.bitsavers.org/pdf/dec/pdp11/1134/m8266_ucode.out.txt) It looks like the program is in VHDL or something like that, but it doesn't seem to have the actual microcode (was it stored/defined in another VHDL file?); that raises the question of where the actual microcode that it was dumping was. It might be worth inquiring of Mike Douglas (he runs the DeRamp site) to find out where the files in "mfe_archive" came from; perhaps the source has, or knows of, the file which "m8266_ucode.out.txt" was a symbolic dump of - maybe >from a complete KD11-EA simulation in VHDL? If that's not possible,it would be trivial to extract the PROM contents (well, partial contents - see below) from the "m8266_ucode.out.txt" file; each uword entry starts with the lines: ***** PDP-11/34a micro code word for MPC = 000 ***** (MSB is left, indented fields generated by expansion ROMs) micro word........ = 0000 0111 1100 0000 1100 1000 1010 0001 0000 0000 1110 0000 from ROM: E105 E103 E104 E100 E98 E97 E99 E106 E107 E108 E109 E110 The address of each uword is the "MPC = xxx" line; the contents of the 12 PROMs, at that address, are given on the "micro word........ = " line (the PROMs are 4 bits wide). If someone explained what format they needed as input for burning new PROMs, I could easily (like an hour) write a small portable program (using StdIO only, so it could be compiled and run on _anything_) that read that file in, and spat out the 12 PROM files. (Most of the dump could be ignored - all the data that's needed is in that one line.) BUT (and this is why it would be good to get back to the source of that file), that's not a complete M8266 ucode PROM dump. The KD11-EA has a uword address space 1 bit larger than the KD11-E - almost certainly to support floating point instructions; the KD11-EA adds 'uPC 09' (although looking its source at the top of pg. 7 of the prints, I don't quite grok how it is generated - maybe it's fed back through J2 from the FP11-A when one is plugged in). Anyway, uword addresses run up to 02000 in the KD11-EA, and the last uword in that dump is 0777. Interestingly, according to the flow charts of the 'basic' KD11-E/EA ucode in the prints (indexed and annotated here: https://gunkies.org/wiki/KD11-E/EA_microcode in full), they stop at 0757 - but the dump (in "m8266_ucode.out.txt") contains uwords that are 'supposed' to be blank (per the flow charts), as well as above 0757. So that dump must have been prepared from a copy of the 'new' KD11-EA PROMs - the ones including the floating point ucode. (Note that the FP11-A _also_ contains ucode, intended to control the stuff on the FP11-A; but the floating point instructions _also_ use the KD11-A for some stuff - e.g. fetching operands from main memory. Only the ucode address space is shared.) > From: Warner Losh > There's a small chance that the tools.tar.gz link on > http://www.ak6dn.com/PDP-11/M9312/ has these, but that's for a > different module so who knows. Right, a _completely_ different card - a boot PROM, not a CPU; totally un-related - and by a different person (Don North). But just for completeness, I looked in "tools.tar.gz", and it's just bootstrap PROM stuff. Noel

4 years, 1 month

Retro Chip Tester Pro, done!

by wh.sudbrink＠verizon.net

You may recall that, a few weeks ago, I requested parts help (shopping baskets) for the Retro Chip Tester Pro that I got for Christmas. Well, today's mail brought the last few parts and I have finished and tested it. Wow! The only thing that it doesn't do is slice bread. It's great. I've put up a few pictures here: http://wsudbrink.dyndns.org:8080/images/RCTPro/ I got the 4008 and 1702 adapters with it, but I'm pretty sure that I will get the rest over the next month or so. This is the latest HW version with the latest release software. Bill S. PS: Thanks to everyone that helped with parts. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

4 years, 1 month

DECTape head problem

by amp1ron＠gmail.com

> So it sermsdectape heads are special. I don?t think Dec would have the desire to make them internally so they probably contractef with a company already set up to do that. Who were the big tape head manufacturers at that time? Does anyone know? A photo of the back of a TU56 DECtape head can be seen at https://www.pdp8online.com/tu56/pics/head_label.shtml?small . The head has a label on it that reads: Western Magnetics Glendale Calif. Record 7282 I've never seen a TU56 in person and have no idea if they have separate read, write, and erase heads or some other combo. The "Record" notation on the above head's label hints to me this might be a write head. I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml . -- Ron

4 years, 1 month

DECTape head problem

by michael.99.thompson＠gmail.com

> > > Date: Tue, 8 Feb 2022 20:55:31 +0000 > From: Wayne S <Wayne.Sudol at hotmail.com> > Subject: Re: DECTape head problem > > So it serms dectape heads are special. I don?t think Dec would have the > desire to make them internally so they probably contractef with a company > already set up to do that. Who were the big tape head manufacturers at that > time? Does anyone know? > We have one from Applied Magnetics Corporation, maybe the one in Goleta, CA. -- Michael Thompson

4 years, 1 month

DECTape head problem

by go＠ao-cs.com

On 2/8/22 14:14, Wayne S via cctech wrote: > Searched a lille bit for Western Magnetics. Here?s a site that has some surplus heads, even a western magnetics onebut probably not the correct one. There is a corporate charter record for Western Magnetics in Minnesota dated 1964. Maybe this is the same company. There?s also a tape head from Michigan Magnetics. Maybe a merged company? > > https://www.surplussales.com/Equipment/magnetic-tape.html > > > Sent from my iPhone > > On Feb 8, 2022, at 13:05, Ron Pool via cctech <cctech at classiccmp.org> wrote: > > ? > So it sermsdectape heads are special. I don?t think Dec would have the desire to make them internally so they probably contractef with a company already set up to do that. Who were the big tape head manufacturers at that time? Does anyone know? > > A photo of the back of a TU56 DECtape head can be seen at https://www.pdp8online.com/tu56/pics/head_label.shtml?small . > The head has a label on it that reads: > Western Magnetics > Glendale Calif. > Record > 7282 > > I've never seen a TU56 in person and have no idea if they have separate read, write, and erase heads or some other combo. The "Record" notation on the above head's label hints to me this might be a write head. > > I found that and other DECtape photos at https://www.pdp8online.com/tu56/tu56.shtml . > > -- Ron > > Thanks.? Hadn't seen the Minnesota information.? Found some references but not actual company info.? Did find a reference somewhere it Canada, but I couldn't tell if it was original or successor company.? At any rate, no web presence nor telephone numbers found (yet.) I've dealt with the SurplusSales (of Nebraska) many times.? His prices are usually pretty high (not obscene, but just not 'surplus' prices I'm used to.)? However, he is a first-rate dealer and when he says something is so, you can count on it.? Never had problem with anything I was willing to *PAY* for.? I scanned the list you provided and found only a few 'digital' devices, unfortunately.? I suspect from 7 and 9 track mag tape drives.? I will scan his site and send him a ping so he'll be on? the lookout. -Gary

4 years, 1 month

PDP-11/34 CPU PROMS

by rodsmallwood52＠btinternet.com

Hi ???????? Jerry Walker and I have an 11/34 under restoration. We have run into a bit of a problem. On the M8266 CPU control board a defective 7404 (E111) has killed a bunch of the PROMs holding the microcode. Does anybody have or can get images of the PROMs on this board so replacement devices an be programmed. Rod

4 years, 1 month

Need 8mm or DLT-II tape?

by van.snyder＠sbcglobal.net

I have many 8mm tapes. A few are new. First comers get new ones. I have a few 8mm cleaning cassettes I have about a dozen DLT-II tapes. I have a Quantum DLT-II drive with wide SCSI LVD/SE interface I have some Ultrium LTO fibre-channel SCSI drives that were removed >from a tape-mounting robot several years ago. I never used them in my computers. The mounting bracket for one was modified to have an internal power supply -- which might be inadequate. ?I have one LTO tape. I have a 5.25" floppy drive. Yours for the price of shipping, or local pickup OK. Van Snyder van.snyder at sbcglobal.net La Crescenta, CA

4 years, 1 month

DECTape head problem

by paulkoning＠comcast.net

> On Feb 8, 2022, at 5:14 PM, Wayne S via cctech <cctech at classiccmp.org> wrote: > > Searched a lille bit for Western Magnetics. Here?s a site that has some surplus heads, even a western magnetics onebut probably not the correct one. There is a corporate charter record for Western Magnetics in Minnesota dated 1964. Maybe this is the same company. There?s also a tape head from Michigan Magnetics. Maybe a merged company? > > https://www.surplussales.com/Equipment/magnetic-tape.html Those all look like audio heads, nothing even vaguely resembling a DECtape head. paul

4 years, 1 month

Anyone live in Minneapolis?

by jnc＠mercury.lcs.mit.edu

> From: Steve at oldcomputers.net > There are some vintage tablets in Minneapolis (Eden Prarire) that would > like, but the seller will not ship. > Any help? When dealing with eBaiters who can't/won't ship, I have had good luck with PakMail (http://www.pakmail.com/); for a usually reasonable fee, they will go pick something up, package it properly, and ship it. In my experience with them, the shipping cost may not have been the absolute lowest possible I could have secured had I been on the spot, looking around, but.. I wasn't on the spot, looking around. And they went to the person's house, picked the thing up, and shipped it. Noel

4 years, 1 month

Anyone live in Minneapolis?

by steve＠oldcomputers.net

There are some vintage tablets in Minneapolis (Eden Prarire) that would like, but the seller will not ship. Any help? You will have to pay, pick up, and ship. I would do it for you! Thanks- Steve in CA

4 years, 1 month

DECTape head problem

by paulkoning＠comcast.net

> On Feb 8, 2022, at 2:53 PM, Wayne S via cctech <cctech at classiccmp.org> wrote: > > Since so many audio tape players and computer magtape units were made it would stand to reason that there has to be a stash somewhere of tape heads and it?s just a matter of finding where they are. > Are there any part numbers on the dectape heads? The schematics are bound to show DEC part numbers, but how those translate into supplier part numbers is anyone's guess. Or perhaps they were made internaly by DEC? In any case, DECtape heads are unusual. Computer tapes are normally 1/2 inch wide (a few old tape drives had different widths, like the 14 track 1 inch CDC tape). But DECtape and LINCtape are 3/4 inches wide, with 10 head positions. Audio tapes are unlikely to be helpful; consumer reel to reel tape is 2 tracks (interleaved for when you flip over the reel?) 1/4 inch; professional decks might have 8 tracks or more on 1/2 or 1 or 2 inch wide tape, but I don't remember ever seeing 3/4 inch wide audio or instrumentation heads. paul

4 years, 1 month

DECTape head problem

by go＠ao-cs.com

On 2/7/22 12:48, Marc Howard via cctech wrote: > The problem would be the non-standard track size and number of tracks. > However if at least one of the head's paired tracks is good you could > potentially cut the drive current in half and double the read amplitude and > just use one track for the affected channel. > > Marc > > On Mon, Feb 7, 2022 at 12:33 PM Wayne S via cctech <cctech at classiccmp.org> > wrote: > >> I?ve often wondered if the tape heads from consumer tape devices such as >> cassette or 4-8 track tape players could be used or be made to be used as >> replacements. Anybody ever try that? >> >> Sent from my iPhone >> >>> On Feb 7, 2022, at 11:51, Michael Thompson via cctech < >> cctech at classiccmp.org> wrote: Further, the DECTape had various track-to-track spacing.? Between the the Mark track and the first data track on both edges, the spacing is at a little less than twice that between the mark and timing tracks or between each set of data tracks.? Put a different way, the track spacing is: T.M..D.D.D.D.D.D..M.T The magnetic poles of each head is roughly 1mm wide with about .8 mm spacing heads? The '..' in the above means there is about 1.4mm spacing (between 'M and D' and 'D and M', for example - the measurements are crude, so I could be off 20% or more.) I've searched the documents I have (many from bitsavers) and haven't yet spied a specification for the head design.? I suppose if I could determine the head 'gap' and knowing the magnetic flux required of the tape (with proper margins) and knowing the stated impedance of the head and drive current, I could figure out how many turns of some size wire is required (looks to be at least as small as #40). Back when I was a bit younger and less experienced (and didn't know it was impossible,) I actually 'repaired' (for some definition of 'repair') an old 1/4 inch tape head.? But all I did was pull some wire off the coil and delicately soldered a tap to this wire.? It worked ok for a couple of years but was obviously failed again from rough handling.? Fortunately it was 'easy' since there wasn't a bunch of clear epoxy in the way ;-)? I'm not sure today I would have the temerity to even try. Hoping one will show up someday and I can make a deal as to complete my unit. Thanks to all who have replied. -Gary

4 years, 1 month

DECTape head problem

by bitwiz＠12bitsbest.com

I wonder if there are any professional audio multi-track recorders that match the tape width, number of tracks and tack pitch and have the necessary frequency response. On 2/7/2022 3:05 PM, Marc Howard via cctech wrote: > 8 track tapes use 1/4" wide tape. Most 8 track units use heads with only > two tracks implemented. There was a stepper solenoid that moved the head > down (or up after all 4 stereo programs were played). Growing up in the > 60s you never forget things like listening to In-A-Gadda-Da_Vida fade in > the middle of the drum solo and a loud "klunk-klunk" sound and the song > resuming. > > Some true 8 track heads were made for mastering pre-recorded tapes and > maybe for consumer recorders. > > Marc > > > On Mon, Feb 7, 2022 at 12:51 PM Michael Thompson via cctech < > cctech at classiccmp.org> wrote: > >> DECtapes have 5x redundant tracks. If you could find an 8-track head that >> had the same track pitch, and maybe track width, you could read the tape >> but lose redundancy on the Mark and Timing tracks. That probably would not >> work with a marginal DECtape. >> >> On Mon, Feb 7, 2022 at 3:33 PM Wayne S <wayne.sudol at hotmail.com> wrote: >> >>> I?ve often wondered if the tape heads from consumer tape devices such as >>> cassette or 4-8 track tape players could be used or be made to be used as >>> replacements. Anybody ever try that? >>> >>> Sent from my iPhone >>> >>>> On Feb 7, 2022, at 11:51, Michael Thompson via cctech < >>> cctech at classiccmp.org> wrote: >>>> ? >>>>> >>>>> From: Gary Oliver <go at aerodesic.com> >>>>> Subject: DECTape head problem >>>>> >>>>> In debugging my DECtape interface lashup, I found that one of my head >>>>> has two open windings.? Specifically, one channel has an open 'ground' >>>>> with the other two lines apparently the full winding of the channel.? >>>>> The second channel failing has no continuity between any of the three >>>>> lines.? I have tested the other head and it has all the requisite >>>>> continuity so I'm hoping I can at least get a single spindle running. >>>>> >>>>> Has any ever attempted repair of one of these? >>>>> >>>>> -Gary >>>>> >>>> At the Rhode Island Computer Museum we found several DECtape heads on >>> TU55 >>>> and TU56 drives with open connections. A volunteer got one head X-Rayed >>> so >>>> we could see the solder joints between the tiny wires for the head >> coils, >>>> and the larger twinax wires that go to the relay board. We couldn't see >>> any >>>> damage to the wires or solder joints. >>>> >>>> We tried heating the potting material to soften it, and digging it out >> to >>>> get to the solder joints. While digging at the potting material you >> can't >>>> see the tiny wires, so they will likely get damaged. >>>> >>>> We considered using a solvent to remove the potting material, but >> thought >>>> that it would eat the enamel off the head coil wires and damage them >>> beyond >>>> repair. >>>> >>>> So far we haven't found a way to repair the heads. >>>> >>>> Michael Thompson >> >> -- >> Michael Thompson >>

4 years, 1 month

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1999

1998

1997

test-drb