Re: More switchmode power supply grief - Cisco IGS router
On Thu, Feb 03, 2022 at 06:06:10PM +, Peter Coghlan via cctalk wrote: > 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 :-( Does that PSU have a PWM controller IC, or is it built entirely from discretes? If there is an IC driving the chopper transistor then you may be able to get some clues about the likely characteristics of the transistor from the IC datasheet. Is it definitely a FET? Some, particularly older, designs used bipolar transistors there. As you say there is a fairly high likelihood that other components on the primary side will have blown up as well so you might be looking at a fairly extensive repair. Are there any other obscure, unmarked devices or is this the only one? p.
Re: Anyone know what an AM000076 (Dip 18) is?
If it's only got 18 pins (per the subject line) then I don't think it can be a 27S29. Based on the label my guess would have been a PAL/GAL of some kind, but I can't immediately think of any standard parts that would have had less than 20 pins there either... p. On Mon, Jun 01, 2020 at 02:55:03PM -0700, Ian Finder via cctalk wrote: > Thanks Bob- this is alongside the 27S29 parts- which are labeled as such, > but this question is about a part labeled AM76 (different than the > 27S29 which are clearly labeled). > Are you saying they're identical? > > On Mon, Jun 1, 2020 at 11:34 AM Bob Smith wrote: > > > 27S29 > > > > Abstract: AM27S28 Am27S28/27S29 > > Text: Am27S28/ 27S29 4,096-Bit (5 1 2 x 8 ) Bipolar PROM Am27S28/ > > 27S29 DISTINCTIVE CHARACTERISTICS · · · High Speed Highly reliable, > > ultra-fast programming Platinum-Silicide fuses High programming yield > > · · · Low-current PNP inputs High-current open-collector and > > three-state outputs Fast chip select GENERAL DESCRIPTION The > > Am27S28/29 (512-words by 8-bits) is a Schottky TTL Programmable > > Read-Only Memory (PROM). This device is available in both open > > collector (Am27S28) and three-state (Am27S29) output > > > > On Sun, May 31, 2020 at 7:35 PM Ian Finder via cctalk > > wrote: > > > > > > Title says all, > > > > > > Backing up all the programmable parts in the Apollo DN100 and the CPU > > board > > > has a few of these ceramic DIPs with the same Apollo P/N labels as the > > > Am27S29 and similar programmable parts. > > > > > > > > > Thanks > >
Re: "scsi bus continuously busy"
On Sat, May 02, 2020 at 10:22:02AM -0700, Alan Perry via cctalk wrote: > >sc0 at vme24d16 20 vec 0x40 > >sd0 at sc0 slave 0 > >si0: sc_cmd: scsi bus continuously busy > >sc0: resetting scsi bus > >sd1 at sc0 slave 1 Not that I know these particular devices, but is it at all possible one of the cables is in backwards? That sounds like the kind of behaviour you get with 50-pin SCSI if an IDC connector is upside down. But otherwise, this message presumably means the host controller is sensing BSY# asserted when it didn't expect it. So the first order of business would be to find out whether BSY# on the bus is genuinely low. If not, it must be a controller fault. If yes, disconnect the devices one at a time and see if the problem goes away. If it's still stuck low with no devices attached, the issue is either in the controller or termination. p.
Re: Apollo Ethernet EPROM mystery
On Thu, 2019-03-28 at 17:02 +, Phil Blundell via cctalk wrote: > I'll see if I can locate my unit later and confirm that. FWIW... https://photos.app.goo.gl/2mohWXwcdBS8uE9T9 p.
Re: Apollo Ethernet EPROM mystery
On Thu, 2019-03-28 at 09:43 -0700, Al Kossow via cctalk wrote: > Does anyone have a working Apollo 3C505 ISA ethernet board handy to look at? I have a 3c505 somewhere but I don't think it is an Apollo one. The Linux kernel configuration help message from that era read: tristate "Apollo 3c505 support" depends on NET_ETHERNET && APOLLO help Say Y or M here if your Apollo has a 3Com 3c505 ISA Ethernet card. If you don't have one made for Apollos, you can use one from a PC, except that your Apollo won't be able to boot from it (because the code in the ROM will be for a PC). which does indeed seem to imply that the Apollo units did have the boot PROM populated, and that the only difference between the Apollo and non-Apollo variants was the bits in that PROM. I don't think the Linux device driver had any mechanism for loading firmware into the card which would also suggest that it must have had an onboard firmware PROM as well. But I'll see if I can locate my unit later and confirm that. p.
Re: HELP needed on a vocabulary problem ;-)
On Mon, 2019-03-18 at 13:03 +0100, GerardCJAT via cctalk wrote: > The TECHNICAL problem : I am repairing a not so old electric typewriter. > I need to replace what I call : a flexible printed circuit ( strip / ribbon / > what's the "correct" word ??? ) *** AND *** the associated connector > I searched Mouse, Digikey, Arrow, etc ... catalogues and find absolutly > nothing !! > > I think I DO NOT use the correct WORD(s) for my search. > > What are the "usual" words for the TWO items I describe ?? "FFC"/"FPC" and "FFC/FPC connector" possibly. Are these the sort of things you mean? https://uk.farnell.com/molex/15015-0423/cable-assy-23core-101-6mm-brown/dp/2096098?st=fpc https://uk.farnell.com/te-connectivity/1-1734248-9/fpc-connector-receptacle-19-position/dp/1846686?st=fpc%20connector p.
Re: Market improving for monitors?
On Fri, 2018-12-07 at 14:18 -0500, Paul Koning via cctalk wrote: > Does a plain LCD panel have delay? If not, what about a TV used as a > monitor? Depends what you mean by a "plain LCD panel". If you mean the glass itself, no, they generally scan synchronously to the input signal and don't have any appreciable delay. But all commercially-available LCD TVs and monitors have at least some input buffering which adds maybe 10ms-30ms of latency in most cases. One frame time at 60fps is 16ms, so if you wait for each picture to be completely scanned in over HDMI before you start scanning it out to the glass then that's going to set your minimum latency. And obviously if the input frame rate is less than 60fps it's possible that the latency may go up. TVs tend to have more picture processing than monitors, and also less market pressure for low latency. But there's very little technical difference between an LCD TV and an LCD monitor. p.
Re: Apple B CRT monitor popping and clicking
On Tue, 2018-04-03 at 21:07 +0100, Ian Frost via cctalk wrote: > > Recently booted up my B Powermac G3, all came up fine including the > 17” CRT monitor. However after a second or so, the > monitor gives a ‘popping’ sound and the image on the screen expands > then shrinks. This repeats every few seconds. > > I’m guessing the monitor is on the way out - but as this is a > complete B system - I wondered what the likely cause is? That sounds like some sort of problem with the EHT supply. If the picture is stable until the first pop and then it expands, that might suggest that the EHT voltage is dropping because of some sort of sudden spark discharge. Does the image also get dimmer/fainter at the same time? Can you see any evidence of arcing inside the monitor when this is happening? I guess it's not impossible that slightly-conductive dust might have built up inside the monitor somewhere to the point where the EHT insulation is compromised and it's flashing over. If that's the problem then a bit of a clean-up might be all it takes to fix it. Needless to say, be careful when cleaning around the EHT. Conversely, if the image was to get initially smaller and then suddenly expand with a "pop", that might suggest that the EHT supply regulation has gone wrong and the voltage is going too high. From what you've described though it doesn't sound as though that's what is happening. p.
Re: QSIC update - v6 Unix boots and runs
On Mon, 2018-01-29 at 16:06 -0500, David Bridgham via cctalk wrote: > For those of you who are following along with our QSIC project, today > we > booted v6 Unix successfully for the first time. We'd first tried > this a > week or two back but discovered that Unix does use partial block > reads > and writes after all and I hadn't implemented those yet. We're > running > this on an 11/23 using the QSIC with an SD card emulating a couple > RK05s. That sounds pretty awesome. Good job there! Do you know how hard it would be to take this design and make a UNIBUS version? I have an 11/34 languishing under the bench in my hardware lab and one of the principal reasons for the languishing is that I don't have any drives to go with it. p.
Re: ID board Dilog SU723A
On Mon, 2018-01-08 at 09:13 -0600, John Welch via cctech wrote: > Does anyone know this board? I think it may be a SCSI controller. I > cannot tell if it is Unibus or Qbus. According to: http://www.dilog.com/unibus.html it's: SU723A SCSI, TMSCP, 7drives, Quad Height. and (judging from the URL) it's presumably Unibus. hth p.
Re: Which Dec Emulation is the MOST useful and Versatile?
On Fri, 2017-10-27 at 13:38 -0700, Brent Hilpert via cctalk wrote: > I wonder if they were just trying to draw an analogy between the > inherent dynamic operation requirements of magnetic logic and the > dynamic operation requirements of some (many?) NMOS designs (not > really inherent to NMOS). On the subject of NMOS dynamic logic, someone recently pointed out a paragraph in the technical manual for a 1990s ARM2-based computer which warned of dire consequences, including possibly destruction of the chipset, if the circuitry was left powered with the clock stopped for more than a second or two. Obviously if the clock is stopped for more than a few hundred microseconds then the logic will start to lose its marbles and the system will need a reset to recover. But I don't think I've previously heard any suggestion that dynamic logic ICs would actually be damaged or destroyed under these circumstances. I can just about imagine that there might be some situation where an invalid internal state would result in a short circuit between power and ground, but that's just supposition really. Anybody know of a case where something bad has actually happened? p.
Re: Fujitsu M2235S
On Mon, 2017-10-23 at 20:14 -0500, Jules Richardson via cctalk wrote: > There appears to be a photo of the internals here, if that helps at > all: > > http://museum.ipsj.or.jp/computer/device/magnetic_disk/images/0011_03 > _l.jpg > > ... it's a little small, so hard to tell what's going on for sure! I > don't > see any obvious locking mechanism, though. > > There's a Fujitsu M2333KS on ebay - item # 182218376023 - which > appears to > be quite similar in layout. That one appears to have some form of > positioner / track 0 sensor accessible from outside the HDA if the > logic > board is removed - is that true of the 2235 too? Yes, the stepper motor and track 0 sensor is external and, as you say, you can get at it with the logic board removed (or, to a lesser extent, though the side of the chassis with the logic board still in situ). I took the lid off the chamber in the end and confirmed that there was no latch and the head assembly itself was free to move. It seemed that the stepper motor itself was the bit that was stuck. So, emboldened with the knowledge that I probably wasn't about to snap the positioner arm off, I gave it a rather more enthusiastic shove from outside and it now does move a bit. I was able to recover the data from the first 26 cylinders but it won't seek beyond track 25 for some reason, possibly just more mechanical resistance inside the stepper. There doesn't seem to be anywhere obvious to add lubrication so I suppose I will just have to try a bit more force and hope that this frees it up! Phil
Re: Cleaning and Restoring a Badly Corroded PSU
On Mon, 2017-10-23 at 21:45 +0100, Rob Jarratt via cctalk wrote: > I am now looking at the H7826 PSU that came with a TURBOchannel > Extender. It > looks like there may have been capacitor leakage and some heatsinks > will > need to be replaced. I have posted pictures here: > > > > https://robs-old-computers.com/2017/10/23/corroded-h7826-power-supply > / Maybe the photos don't do justice to the full horror but it doesn't look all that bad from what you've posted. The heatsinks do look a bit corroded but, if they are aluminium (which I would guess they are from the photos) then this might just be dampness rather than anything more sinister. Aluminium does tend to rot a bit in prolonged contact with water, and if it is also in contact with steel then you get an electrolytic reaction which can be fairly ruinous. I doubt the heatsinks are a standard part you can buy off the shelf. They have a bit of a custom look about them. But, unless you are worried about authenticity of those parts, a standard heatsink from Farnell etc will work just fine. If you do want the authentic article then you might need to get some replacements machined. As for cleaning the board, given that it seems to be relatively low- tech I would probably be fairly comfortable putting it in the dishwasher on a shortish cycle. Then give it a bit of a rinse with deionised water and let it dry out. The caps don't look obviously leaky, and (unlike batteries) it doesn't seem to be common for capacitors to ooze their electrolyte without fairly evident physical distress. But replacing them is probably a good plan anyway! p.
Re: Fujitsu M2235S
No, that was what I was thinking of with the "some sort of latch" comment. Where is the head lock? Thanks Phil On Mon, 2017-10-23 at 10:19 -0500, Tom Uban wrote: > I assume you've released the head lock? > > On 10/21/17 1:31 PM, Phil Blundell via cctalk wrote: > > Anybody familiar with the internals of these disks? I have one > > here > > which seems to have the positioner stuck at track zero. I'm not > > sure > > whether it's likely to be just a bit sticky and in need of some > > assistance or whether there is some sort of latch involved, and I > > am a > > bit reluctant to just pull the lid off the chamber to find out. > > > > Thanks > > > > Phil > > > > > >
Fujitsu M2235S
Anybody familiar with the internals of these disks? I have one here which seems to have the positioner stuck at track zero. I'm not sure whether it's likely to be just a bit sticky and in need of some assistance or whether there is some sort of latch involved, and I am a bit reluctant to just pull the lid off the chamber to find out. Thanks Phil
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Thu, 2017-10-05 at 11:50 -0700, Chuck Guzis via cctalk wrote: > > What I found curious was the CDC manual that called SCSI "SASI > subset". > To me that says that SASI was the more elaborate protocol and SCSI > initially picked and chose from it. I think that's just bad/ambiguous wording and the intended meaning was "SCSI (but only the parts that are in SASI)" as distinct from "SCSI (all parts)". p.
Re: The origin of the phrases ATA and IDE [WAS:RE: formatting MFM drives on a IBM PC]
On Tue, 2017-10-03 at 18:56 +0100, Pete Turnbull via cctalk wrote: > So there's clear proof that at least three companies in the UK were > using the term IDE before (or at least by) 1990. I never heard it > called anything else in that timeframe. That pretty much matches my recollection also. The earliest use I can find of the "AT Attachment" terminology is the X3T9 project proposal from late 1990 which eventually led to the formation of the X3T10 group: http://www.t10.org/ftp/x3t9.2/document.90/90-058r2.txt p.
Re: formatting MFM drives on a IBM PC
On Tue, 2017-09-26 at 14:19 -0400, Ethan via cctalk wrote: > I don't know if it's a good idea to low level format a drive or not. Low-level formatting (which, at the time, was just called "formatting") used to be quite a routine operation on ST-506 MFM and RLL hard disks. They usually came completely blank from the factory and you had to format them according to whatever sector layout and interleave your particular controller wanted before they were usable. Once the drive was formatted you then had to run a separate process to lay out an actual filesystem. For MFM controllers on ISA cards I think the formatter was usually in the BIOS. For separate MFM controllers with a SCSI interface (Xebec S1410 kind of things) you used the FORMAT UNIT command. Newer ATA/SCSI drives with integrated electronics tended to come preformatted and there often wasn't any way to execute a low-level format even if you wanted to. At about the same time they started using embedded servo data on the disk itself for head positioning which made it impossible to do a low-level format in the field. I can't immediately think of any class of device on which attempting to execute a low-level format would be an actively bad idea (apart from destroying your data of course). On older ones it would work, on newer ones the drive would refuse the command, but in neither case is there likely to be any bad consequence. Was there a time in the middle when something bad would happen? p.
Re: 2.11BSD on two RL02 drives? Probably not, but...
On Fri, 2017-08-04 at 15:04 -0400, Noel Chiappa via cctalk wrote: > > And this path allowed us to get rolling without having to go through > the PC-board fab cycle... (including the complexity of doing boards > with gold fingers). Just as an aside on that, I doubt you really need the hard gold fingers on a prototype board. You do need something to stop the copper from tarnishing, and hard gold is almost certainly the most durable option, but I can't think of any obvious reason that an ENIG or immersion silver finish wouldn't work just fine on the fingers for a moderate number of insertions. Not that I've ever actually built a Unibus card though so perhaps there is some complexity or something especially hostile about the sockets that I'm not realising. p.
Re: 2.11BSD on two RL02 drives? Probably not, but...
On Fri, 2017-08-04 at 09:17 -0800, David Bridgham via cctalk wrote: > So my question is: do industrial SD cards exist? Yes they do. Most of the big card manufacturers have an "industrial" range, for example: https://www.sandisk.co.uk/oem-design/industrial/industrial-cards There are also specialist vendors who offer SLC cards. For example: https://swissbit.com/products/nand-flash-products/cards/sd-memory-cards / You can buy the Swissbit cards at Farnell. I'm not sure if the Sandisk industrial ones are easily available in small quantities. Phil
Re: 2.11BSD on two RL02 drives? Probably not, but...
On Fri, 2017-08-04 at 07:20 -0700, Al Kossow via cctalk wrote: > > Can you actually buy SATA PHYs in small quantities now > or even SATA to PATA bridges? I can't think of anybody who makes discrete SATA PHYs, and there isn't a standardized interface for the other side of the PHY so I suspect there would probably be no market for a chip like that. Commodity FPGAs with 3Gbps SERDES channels are fairly readily available and I think you could probably build a SATA interface in one of those without too much trouble. It probably would not be very cheap though, and there would be hassle involved in implementing the SATA stack. Alternatively, there are ASSPs like TI's TUSB9260, which is actually intended for use as a USB-to-SATA bridge but could probably be bent into implementing PATA using its digital GPIOs. It costs $6.44 from Mouser at quantity 1. Phil
Re: 2.11BSD on two RL02 drives? Probably not, but...
On Fri, 2017-08-04 at 08:53 -0400, Noel Chiappa via cctalk wrote: > > But are SD cards really that unreliable? It depends on exactly how you measure "reliable". There are a few different things going on, and it differs from one SD card to another. Firstly, there are multiple types of flash memory that can be used for the underlying storage. The flash cells can be either SLC, MLC or TLC in decreasing order of cost per bit but also in decreasing order of robustness. An SLC cell might tolerate 100,000 erase/write cycles, whereas an MLC cell might fail after only 10,000 and a TLC cell might be worn out after 3,000. The act of reading from a flash cell also disturbs the charge in nearby cells: this effect is not particularly significant for SLC, which you can generally read without restriction, but on MLC and TLC the controller needs to keep track of how many times it has read from a particular block and periodically re-write the data to refresh it otherwise it will eventually become corrupt. And finally, the charge in flash cells does eventually leak away: for MLC and TLC cards your data may disappear over a timescale of months to a few years. Consumer-grade cards will almost always use MLC flash, or possibly TLC at higher capacity levels. SLC cards are available but typically they are the "industrial grade" ones and are only available in smaller capacities. Secondly, there are many different controller ICs and the behaviour of the controller has a significant effect on how well the card works overall. Some controllers are better than others at managing bad blocks and bit errors in the flash. Some deal better than others with unexpected power failures. Some deal better than others with the "read disturb" effect. Some deal better than others with random access, particularly random writes: it's fairly common for the cheaper consumer cards to only have enough buffer space for one output file to be open at a time, and if you start trying to write multiple files in parallel to different areas of the card then the write buffer will start thrashing and performance will be dismal. It's also worth remembering that most consumer-grade cards are used in a way that is not a very close match to a disk emulator. Cameras (including cameras in phones) are generally writing a relatively small number of fairly large files. They seldom read, and they virtually never modify a file in place. Also, because all SD cards come preformatted as either FAT or exFAT, the pattern of accesses that the host will make to the filesystem is somewhat predictable and some controller ICs are specifically optimised for this. All the above said, although it probably is true that the average consumer-grade SD card is significantly less robust than the average SATA SSD that you can buy today, and probably also less robust than the average spinning hard disk, I suspect they are probably not all that much less reliable than the average 1980s or 1990s-era hard disk. Personally I would be quite happy to use an SD card to emulate mass storage in a classic computer, and in fact I was thinking just this morning about buying one of the scsi2sd boards for that very purpose. If you are going to be using it in an application that sees frequent writes then I would try to get an SLC card, or failing that a low- capacity MLC one. But otherwise, I would just make sure I had a backup and live with the possibility that the card might need replacing after a couple of years. Phil
Re: Free to a good home, VAXstation 3100 M38, memory errors
On Sun, 2017-05-21 at 10:08 +0100, Aaron Jackson via cctalk wrote: > I won't post it again to avoid spamming people, but just one reminder > to > say that the below still available. I did have some interest from > abroad > but shipping would be far too expensive and difficult. I'd be interested if you can arrange shipping to Cambridge at a reasonable cost. (I will pay for it of course.) Or if you can box it up and let me know the size and weight, I could get a courier to come and collect. Let me know. Thanks Phil
