test-drb April 2008

test-drb@ccmp.vtda.org

196 participants
307 discussions

Schematics and description of an acoustic memory (1k byte, Display terminal, 1969)

by pichotjm＠free.fr

Hi,If there are some electronic enginneers here, they may be interested by this descritption of an alphanumeric display terminal using acoutic delay lines. (used in european TV sets)This display terminal was designed in 1969, and uses 32 TV delay lines as memory! The memory size is 16 rows of 80 characters coded in 6 bit ascii: 1280 words (6 bits)If you are interested, have a look there: http://pichotjm.free.fr/DisplayDL/DisplayDLus.htmlYou will find the complete set of schematics and deep explanations. Remember, in that time, there are no micro-processor, neither RAM chips! Only few gates (or, and, nand, JK flip-flop,...) Sorry, i have no photos of the terminal.As you can read, i have a poor english, you can help me in correcting the text.Have a good trip in 1969.Jean-Marie PICHOT

17 years

looking for replacement parts - 74S01, 74S73, 2518, 2533

by grant＠stockly.com

At 09:58 PM 4/13/2008, you wrote: >It was recently asserted here that TTL parts aren't hard to find, but >I'm having a heck of a time finding the 74S01 and 74S73. > >As far as I can tell from the data sheets, the 74S103 is functionally >and pin-compatible with the 74S73, but a little faster. I wouldn't mind >substituting that, but it doesn't seem any easier to find. > >The 74S03 and 74S107 are non-pin-compatible replacements for the 74S01 >and 74S73, but I'd much prefer to stick with pin-compatible parts. Unicorn Electronics can get all of those ICs, but you'll have to order a minimum quantity. http://www.unicornelectronics.com/prod.htm

17 years

looking for replacement parts - 74S01, 74S73, 2518, 2533

by eric＠brouhaha.com

It was recently asserted here that TTL parts aren't hard to find, but I'm having a heck of a time finding the 74S01 and 74S73. As far as I can tell from the data sheets, the 74S103 is functionally and pin-compatible with the 74S73, but a little faster. I wouldn't mind substituting that, but it doesn't seem any easier to find. The 74S03 and 74S107 are non-pin-compatible replacements for the 74S01 and 74S73, but I'd much prefer to stick with pin-compatible parts. I'm also looking for the 2518 and 2533 shift registers. The 2518 is a hex 32-bit static shift register, and the 2533 is a 1024-bit static (not dynamic!) shift register. The original parts were Signetics, but I don't mind using other sources: Signetics 2518 2533 TI TMS3122 TMS3133 Fairchild 3349 3533 National - MM5058 GI - 2533 AMD - Am2833 Eric

17 years

modern switching power supply faults

by rescue＠hawkmountain.net

I have two Dell switchers out of P4 based 1U servers. The first one has a failure in the startup circuit... pressing the power button will lead to a flash of the power light... and that's it. The second one failed spectacularly.... There is a wire wound power resistor (5W15RJ) near the AC input... it cooked... and I do mean cooked. It came out in pieces (with almost no effort), melted the nearby capacitor and a nearby relay. It also did a pretty good job of puckering/burning the PCB (but not bad enough it could not be used). I suspected maybe shorted primary full wave rectifier... but I used the DVM on diode test and got what I'd expect. Oddly, despite there being a fuse on the primary side... it's still good... it wasn't taken out. That resistor got hot hot hot. Could that resistor have failed on it's own ? I suspect something further down the circuit must have a problem. I'd be happy if I could make one power supply out of the two. These are not simple supplies however. While much of the switching transistors, regulators, bridge rectifiers, capacitors and the usual fair in a switcher are pretty readily identified, there is a 6" x 1" "brain" board (I'll call it that as it has adjustment pots, the ps fan circuit, quite a # of surface mount components on both side of it, and it interfaces with the main PCB with 34 connections. These are Dell W5916 supplies. Unsure who really makes these for Dell, only other marking is Model: HP-U280EF3. Both these supplies had been cycled 4 times on/off the mains due to a power failure (power fail, generator cycled on, power restored, generator cycled off, repeat process one more time) within a few minutes of each other. The first one was dead immediately after this (the one that has a problem in the start circuit (or a monitor/etc is shutting it down when it detects a problem during turn on). The second one failed almost two weeks after. I know this isn't particularly classic... but I know that there are those out there much wiser than me in switchmode power supplies. So lets pretend it is 2014 that way the supplies will be 10 years old :-).... -- Curt

17 years

OK, now this is impossible (11/23+ and RL02-RLV12 problem)

by bob＠jfcl.com

I have this 11/23+ system with an RL02 drive and the RLV12 controller that won't boot XXDP. Attempting to boot XXDP v2.5 either halts at 000154 during the initial boot, or gives ?RD ERR messages from XXDP. The behavior is a little random - sometimes it halts at 154, sometimes you'll get a few ?RD ERRs and then it'll lock up, and sometimes you'll get far enough to get an actual prompt from the XXDP monitor, but even then you can't run anything. You just get more RD ERRs. OK, I know - bad drive or bad pack, right? Well, I've tried two different RL02 drives and two different XXDP packs with the same results. Better yet, I've connected one of those RL02 drives to another -11 (this time a 11/04 w/RL11) and that same drive with those same packs boots and runs with no complaints. The drive even passes all the ZRL??? diagnostics and ZRLM?? can scan the entire pack and finds no bad sectors. Better yet, I have another RL02 pack with RSX-11M v3.5 and that boots and runs on the 11/23 with the same RL02 and RLV12 with no apparent problems. Now that's really impossible - the same drive that won't boot XXDP will boot RSX? How can this be? It almost seems like it has to be a software problem with XXDP, but XXDP obviously works on a 11/23 and the RLV12/RL02. Is there some strange hardware compatibility or ECO issue with the RLV12 or the 11/23+? Is there something XXDP does with the drive that RSX doesn't? I'd run diagnostics on the RL subsystem, but I don't really have any other load path for XXDP on this system. I did pare the system down until there are only three cards in the backplane - CPU, memory and RLV12. No joy. And just on a whim I tried a different cable for the RL02 - still no joy. Thanks much, Bob Armstrong

17 years

Mac Plus ozone?

by cclist＠sydex.com

Date: Sun, 13 Apr 2008 09:32:36 -0400 > From: "Curtis H. Wilbar Jr." I believe the proper name for the water-based colloidal graphite suspension used to coat CRT surfaces is "aquadag". "Dag" is probably just a shortened form. Aquadag paint for repair should still be available. Some old HOTs (horizontal output transformers/flyback transformer) in CRT HV supplies develop cracks in the potting material with age and sometimes expose the connection of the winding to the HV anode lead. This can cause a corona discharge and the ozone smell. There can also be arcing from the HV lead to the chassis. A lights-out inspection will sometimes yield the telltale purple glow of corona discharge. Often, the discharge can be heard by young ears as a "hissing" sound. Good old red glyptal HV dope is the most commonly prescribed cure for insulation failures. I think GC still sells the stuff. Cheers, Chuck

17 years

Bay Area collection viewing?

by wdonzelli＠gmail.com

Once again, this year I will be in the Bay Area for a few days, basically most of the week of the 4th of May. In the past, a couple of computer collectors opened their doors to me and did a show and tell. Once again, thank you much. So, does anyone else want to show of their machines to an East Coast weenie? Remember, bigger is better. Microcomputers are only shims for real computers. Computers with big blue skins are extra cool. Old is good. Let me know as soon as possible. I will have some email access as I cross the country, but I always like to have things planned out before I leave my driveway. -- Will

17 years

govliq: HP-1000 (Mechanicsburg, PA)

by legalize＠xmission.com

<http://cgi.govliquidation.com/auction/view?id=1675504&convertTo=USD> Buried in a giant lot of other stuff, 17 pallets, 7000 lbs. -- "The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download <http://www.xmission.com/~legalize/book/download/index.html> Legalize Adulthood! <http://blogs.xmission.com/legalize/>

17 years

pcmcia gpib on govliquidation

by Tim＠Rikers.org

Is there any way to contact those who win an auction on govliquidation? If I read this right, this auction includes approximately 24 pcmcia GB-IP interface cards and cables: http://cgi.govliquidation.com/auction/view?id=1654940 It also includes a ton of other things I don't want. I'd love to get my hands on 2 of those pcmcia card+cables. I don't want to even consider shipping the rest of the lot from Mechanicsburg, PA though. -- Tim Riker - http://Rikers.org/ - TimR at Debian.org Embedded Linux Technologist - http://eLinux.org/ BZFlag maintainer - http://BZFlag.org/ - for fun! ????????u poo? ??n??u??s ?no? u? 8-??n ?u???? s?

17 years

Help with ICL power supply fault (Farnell SMPS)

by john_a_s2004＠hotmail.com

Hi, I have an ICL PC2 CP/M box (like this: http://www.old-computers.com/museum/computer.asp?c=752) which has a faulty PSU, I am hoping someone here can advise me. The PSU is a Farnell N100/F4190 SMPS, looks like a high quality unit with nice screw terminals for mains in and DC out. When fired up with 240V AC and a dummy load the output voltages are: 12V output=1.1V 5V output=2.3V -12V output=-5.9V The other worrying thing is it is also drawing 100W power (measured with a one of those plug in mains meters from Maplin), whilst the dummy load is around 20W (split between +12V and +5V). I've checked all the capacitors with multimeter and ESR meter, and all seem fine, and none are bulging or obviously overheating, DC resistance on each of the output connections to ground is around 60 ohm. I couldn't find a short so I don't know where all the power is going to, I suspect there is some protection circuit kicking in? I don't have a circuit diagram, so my first plea does any one have one please? The circuit has few ICs, and mostly transistors. There is a CA339E quad comparator chip, and a IL201 opto isolator (I'll try and check these), but no nice single IC controller. My current strategy is to apply +5V to the comparator chip and apply voltages to the output to try and see some feedback, and also apply 50V DC to the input in the hope this is enough to start up the oscillator (I think this is a small group of transistors, resistors and small capacitors near a small torial transformer, which then feeds to the main conversion transformer). Any suggestions gratefully received, Thanks, John _________________________________________________________________ Get Hotmail on your mobile. Text MSN to 63463 now! http://mobile.uk.msn.com/pc/mail.aspx

17 years

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test-drb April 2008