Re: ADM 3a with no horizontal scan
> On Apr 8, 2016, at 11:59, Seth Morabito wrote: > One more observation: Two of the three +5V regulators cut out > when their input voltage exceeds about 11.5V. The input voltage > comes from a 9.4VAC winding on the primary transformer. Input ripple > is VERY low, maybe 200mV. So, I suspect those regulators need to be > replaced. Could they be going into thermal shutdown? I don't recall whether linear regulators from that era commonly had thermal shutdown features yet. -- Mark J. Blair, NF6X http://www.nf6x.net/
RE: really old test equip
On Fri, 8 Apr 2016, Cindy Croxton wrote: No sorry, I do not recall the manufacturer. Most of the boxes had grey pattern bases with black lids, but a few were brown pattern boxes with dark brown lids. Not very helpful, I know. I should have taken some pics! Cindy Hi Cindy, Actually somewhat helpful ;) We can probably rule out that they are Berry test sets ... those usually came in blue ... there were a few other third party vendors of trunk and station test sets ... names eluding me ... in addition to Western Electric itself. If the units are a "battleship gray" sort of color, that could suggest (though not guarantee) WECo manufacture. Given a bit more identifying information or a picture, I'd be happy to pass this along to a few phone collector lists that I'm on ... depending on what it is and what it costs, there's a chance some people there could be interested. Best, Sean
Re: Voltage regulator with alternate voltage source...
On 2016-Apr-08, at 11:58 AM, Bill Sudbrink wrote: > I don't know why I bothering to be coy about it... > > My unit here: > > http://wsudbrink.dyndns.org:8080/images/cyclops-latest/P4060005.JPG > http://wsudbrink.dyndns.org:8080/images/cyclops-latest/P4060006.JPG > > Actually, I'm further along than that, but I > don't have more recent photos. > > Original unit here: > > http://www.swtpc.com/mholley/PopularElectronics/Feb1975/PE_Feb_1975_pg30.jpg > > Schematic here: > > http://www.swtpc.com/mholley/PopularElectronics/Feb1975/PE_Feb_1975_pg28.jpg Well that's neat. I assembled the Cromemco kit version of the Cyclops ( https://en.wikipedia.org/wiki/Cromemco_Cyclops ) ca. 1976 for a friend with an IMSAI, and built the companion adapter to provide display on an oscilloscope, but I don't know that it was ever made to work. (The kit version presented an interface for a computer rather than the scope drive of the magazine article. Hopefully you're more successful with your unit. (I think you'll find the MC7805 there is indeed plastic not ceramic. Moto produced various power transistors and regulators in those packages (case 90 in Moto parlance) as well as a smaller version from the same plastic material) A 9V wall wart would probably do for the power supply, or remove the regulator and use a modern 5V switching wall wart (not that I wish to promote wall warts, but if they're on hand . . )
Re: Shipping big things across the atlantic.
Thanks everyone who replied. The seller stopped communicating with me so this time it's a no-go. But I'm sure there will be a next time :) /P On 04/01/2016 11:48 AM, Pontus Pihlgren wrote: Hi. I'm considering to ship an empty full height rack from the USA to Sweden. It is definitely something I wont find here so it might be worth the cost and effort. What are my options to get it here safely? If you have any experience I would greatly appreciate if you could share them. Thanks in advance, Pontus.
Re: Voltage regulator with alternate voltage source...
On 2016-Apr-08, at 11:27 AM, Mouse wrote: >> I archive all data sheets I run across and I found this information >> on both TI and Fairchild data sheets for the 78H05, LM340 and LM78XX >> devices - it is usually under a heading called Application Hints and >> for some reason Fairchild have removed these Hints from the sheets >> you quote. > >> In ALL cases the manufacturers caution that putting voltage to the >> output when the input is not powered CAN DAMAGE THE CHIP. > > I have the datasheet PDF for the On Semiconductor version, and I have > been unable to find anything of the sort in it. http://www.ti.com/lit/ds/symlink/lm340-n.pdf page 11 I suspect it would be OK if VIN and VOUT were shorted during the procedure (and VIN was otherwise open or has just a small cap to gnd) as that likely takes care of reverse current and reverse bias situations being set up on internal junctions, but one doesn't know for sure unless you examine the internal schematic adequately or test the device.
RE: really old test equip
-Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Sean Caron Sent: Friday, April 08, 2016 4:42 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: really old test equip On Fri, 8 Apr 2016, Cindy Croxton wrote: > When I was at the recycler last week, I saw a lot of really OLD test > equipment. > Hi Cindy, Did you happen to catch the manufacturer on any of it? They sound a bit like trunk test sets ... I'm all covered myself, but I know of another list where folks might be interested, especially if they do SF signalling. Best, Sean No sorry, I do not recall the manufacturer. Most of the boxes had grey pattern bases with black lids, but a few were brown pattern boxes with dark brown lids. Not very helpful, I know. I should have taken some pics! Cindy --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Re: really old test equip
On Fri, 8 Apr 2016, Cindy Croxton wrote: When I was at the recycler last week, I saw a lot of really OLD test equipment. I started looking through it to see if there were things I could recognize, but the closest thing I could figure out was a 1940s telephone equipment tester. All of these were portable, with lids that closed with latches. Probably weighed abt 20-30 pounds each. Any cables that might have been needed to run the equipment was gone. If things like this are of interest in the $25 range, then I can pick some up next time I see them. Unfortunately I have no cell phone numbers for anyone in the DFW area to tell them to come and see the goodies while I am there, and they will not let strangers come in and poke around. I am (or was) an electronics tech, but most of the functions on these old test machines eluded me. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus Hi Cindy, Did you happen to catch the manufacturer on any of it? They sound a bit like trunk test sets ... I'm all covered myself, but I know of another list where folks might be interested, especially if they do SF signalling. Best, Sean
really old test equip
When I was at the recycler last week, I saw a lot of really OLD test equipment. I started looking through it to see if there were things I could recognize, but the closest thing I could figure out was a 1940s telephone equipment tester. All of these were portable, with lids that closed with latches. Probably weighed abt 20-30 pounds each. Any cables that might have been needed to run the equipment was gone. If things like this are of interest in the $25 range, then I can pick some up next time I see them. Unfortunately I have no cell phone numbers for anyone in the DFW area to tell them to come and see the goodies while I am there, and they will not let strangers come in and poke around. I am (or was) an electronics tech, but most of the functions on these old test machines eluded me. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
A tale of a chip and a socket
So I just had the incredibly amusing experience of managing to repair an -11/04 CPU by un-soldering a chip, putting in a socket, and putting _the same chip_ back in that socket! Before you go 'WTF?!?!', let me explain what happened. The CPU wouldn't run, and in poking around, I stumbled on the cause: all the registers would not 'take' 1's in the 0360 bits. Hmm, 4 contiguous bits - sounds like it might be a bad register file chip. But before I pulled it, I wanted to make sure it wasn't some other part of the data path - Mux, ALU, etc. So I put a DIP clip on the chip, whipped up a 3-instruction 'scope loop that would exercise it, and... while I was looking at it, the problem went away! WTF? So I pull the clip - and the problem comes back. Repeat. Clearly there's a bad connection in the chip, and the pressure of the clip is 'fixing' it. So I pull the chip, put in a socket (I always use sockets on repairs, I'm paranoid I'll overheat the parts - I don't mind living with an potential eventual bad contact from corrosion), and figure what the heck, let me see if fiddling with it fixed the bad connection - and sure enough, it now seems to work! And if it eventually fails, no problem - it's in a socket, I know where to go if the machine stops working, those P3101A's are rare and expensive, etc! :-) Noel
RE: Voltage regulator with alternate voltage source...
> > > 1) I have a 12 volt DC supply. 12 volts seems to be > > >within the VIN range for the 7805s whose data > > >sheets I've now read. Can I simply apply 12 volts? > > > > Yes, but that regulator might get mighty hot! I would > > not do this for fear of cooking the poor thing. > > That's what I figured to start with, before reading the > datasheets. If as your photos (in another message) suggest it will run OK from 8V with no heatsink on the 7805, then I would be pretty sure it will be OK at 12V if you bolt a reasonable heatsink to the regulator. Give it a smear of silicone grease, of course. -tony
Re: Why do good floppy disks go bad?
On 04/08/2016 12:11 PM, Tom Gardner wrote: > Sorry, to a EE they are all epoxies, but: Gorilla glue is an epoxy? News to me. Polyurethane is far from stable over the long term and exhibits hygroscopic properties: For example, vide: http://www.ptonline.com/knowledgecenter/Plastics-Drying/Resin-Types/Hygroscopic-VS-Non-Hygroscopic-Resins ...and many others. Floppy and tape binder also is somewhat of a witches' brew as it usually includes a fatty acid or some other substance for lubrication. As far as "stability", that's subjective. Most plastics will eventually degrade; some are worse than others. There's a big problem in the museum archiving business that not much, other than freezing seems to retard eventual decomposition of plastics. --Chuck
RE: Voltage regulator with alternate voltage source...
> > First, a few quick "whys": > > 1) The 7805 is actually a Motorola MC7805CP, date >code 7308 with gold leads. Very hard to exactly >replace. Any reason why it would have to be an exact replacement? In any case, the behaviour of the 7805 if you apply a voltage to the output with the input floating may well depend on the manufacturer and even the date (some devices were improved over the years). Unless you have a 1973-or-so data sheet from Motorola, I don't think you know whether it will be damaged or not. [...] > 1) I have a 12 volt DC supply. 12 volts seems to be >within the VIN range for the 7805s whose data >sheets I've now read. Can I simply apply 12 volts? Yes, but... The power disipated in the 7805 will increase, in fact it will be more than doubled. To put it crudely, a linear regulator acts like an automatic variable resistor. I have no idea what current the load takes, let's call it I. If you supply 8V, then the power disipated in the 7805 is 3*I watts, if you supply 12V it's 7*I. This may or may not be a problem. > 2) Could I place a resistor in series between the 12V >supply and the 7805 to drop the voltage at the 7805 >to somewhere around 8? Yes. You need to know the maximum current the load will draw, which will be much the same as the current drawn from the PSU. Then just calculate the resistor to drop 4V at that current. If you can find one, you could probably use a 7808 to supply 8V to the unit from a 12V supply. Or a 7805 'jacked up' with a 3.3V zener diode (in series with the common lead to the extra 7805 only). My guess is that giving it 12V will be fine though. What is the device, and do you have any idea how much current it is going to draw? -tony
Re: Why do good floppy disks go bad?
> On Apr 8, 2016, at 3:11 PM, Tom Gardner wrote: > > Sorry, to a EE they are all epoxies, but: > > "BINDER: A polymer such as polyester-polyurethane used to bind magnetic > particles together and adhere them to the base film in the manufacturing of > magnetic media." > http://www.fujifilmusa.com/shared/bin/Magnetic_Media_Terminology.pdf > > "Polyester polyurethane is the workhorse of polyurethane films. It offers > excellent strength and long-term stability" > http://www.apiusa.com/polyesterpolyure.html > > I think properly cured all binders used are pretty stable. That may be, but if so, there are some big name vendors who do not know "properly". paul
Re: Why do good floppy disks go bad?
>> Entropy: Could the rust on the cookie be de-oxidizing, and turning back int$ > No. If that were true, iron ore would spontaneously turn into iron. Unfort$ Anyone keep their floppies in a hydrogen (or, more generally, reducing) atmosphere? (Cue xkcd #1426. :-) /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTMLmo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
RE: Why do good floppy disks go bad?
Sorry, to a EE they are all epoxies, but: "BINDER: A polymer such as polyester-polyurethane used to bind magnetic particles together and adhere them to the base film in the manufacturing of magnetic media." http://www.fujifilmusa.com/shared/bin/Magnetic_Media_Terminology.pdf "Polyester polyurethane is the workhorse of polyurethane films. It offers excellent strength and long-term stability" http://www.apiusa.com/polyesterpolyure.html I think properly cured all binders used are pretty stable. Tom -Original Message- From: Chuck Guzis [mailto:ccl...@sydex.com] Sent: Thursday, April 07, 2016 10:47 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: Why do good floppy disks go bad? On 04/07/2016 10:06 PM, Tom Gardner wrote: > And it's not likely the binder, fully cured epoxies are also very > stable. Note disks do not have the tension problem that tape has. There, I have to respectfully disagree. Floppy disks do not use an epoxy binder, but usually a polyurethane-based one. (Most are proprietary formulations). Hard disk coatings usually use an epoxy-phenolic binder, but they're not on a flexible substrate. Polyurethane isn't forever and tends to be somewhat hygroscopic. --Chuck
Re: ADM 3a with no horizontal scan
* On Fri, Apr 08, 2016 at 02:33:25PM -0400, Mouse wrote: > > Today, for whatever reason, my Variac was turned down to 110V, and I > > didn't notice. I turned on the ADM 3a, and... it's fine. [...] > > Fascinating! > > I have trouble imagining what sort of fault could cause those symptoms. > I would have agreed with whoever (tony, I think) said that if you have > HV then the horizontal scan is almost certainly operating in some > sense, but this makes me doubt that. I have trouble coming up with a > failure mode in that design that could kill the horizontal scan but not > the HV based on the power supply input voltage, so there is probably > something very unusual in there. It IS odd. One more observation: Two of the three +5V regulators cut out when their input voltage exceeds about 11.5V. The input voltage comes from a 9.4VAC winding on the primary transformer. Input ripple is VERY low, maybe 200mV. So, I suspect those regulators need to be replaced. I'm sure it needs to be recapped, too, so I'll do that before I investigate too much furtther. -Seth -- Seth Morabito s...@loomcom.com
RE: Voltage regulator with alternate voltage source...
I don't know why I bothering to be coy about it... My unit here: http://wsudbrink.dyndns.org:8080/images/cyclops-latest/P4060005.JPG http://wsudbrink.dyndns.org:8080/images/cyclops-latest/P4060006.JPG Actually, I'm further along than that, but I don't have more recent photos. Original unit here: http://www.swtpc.com/mholley/PopularElectronics/Feb1975/PE_Feb_1975_pg30.jpg Schematic here: http://www.swtpc.com/mholley/PopularElectronics/Feb1975/PE_Feb_1975_pg28.jpg Bill
RE: Voltage regulator with alternate voltage source...
William Donzelli wrote: > > 1) The 7805 is actually a Motorola MC7805CP, date > >code 7308 with gold leads. Very hard to exactly > >replace. > > Is that the big flat plastic package with the wide > flat leads? Nope, purple ceramic. The heat transfer plate is gold plated too. > > 1) I have a 12 volt DC supply. 12 volts seems to be > >within the VIN range for the 7805s whose data > >sheets I've now read. Can I simply apply 12 volts? > > Yes, but that regulator might get mighty hot! I would > not do this for fear of cooking the poor thing. That's what I figured to start with, before reading the datasheets. > > 2) Could I place a resistor in series between the 12V > >supply and the 7805 to drop the voltage at the 7805 > >to somewhere around 8? > > Yes, you could do this. Pick an appropriate power resistor, > or use a big wirewound rheostat. At this point, I think I'll just wait till Monday and work on other things. > > 3) If I was to "tack on" a jumper between VIN and VOUT, > >would that protect the 7805 and allow me to power the > >circuit with 5 volts? > > I would not do this at all. I didn't think so. Bill
Re: Voltage regulator with alternate voltage source...
Silly question, but then I'm feeling silly today: Why not just connect the output and input of the 7805 together and power from the normal +8 line with your +5 supply? --Chuck
Re: Voltage regulator with alternate voltage source...
> 1) The 7805 is actually a Motorola MC7805CP, date >code 7308 with gold leads. Very hard to exactly >replace. Is that the big flat plastic package with the wide flat leads? I might have a few of those around, but I agree, not an easy variant to find. > 1) I have a 12 volt DC supply. 12 volts seems to be >within the VIN range for the 7805s whose data >sheets I've now read. Can I simply apply 12 volts? Yes, but that regulator might get mighty hot! I would not do this for fear of cooking the poor thing. > 2) Could I place a resistor in series between the 12V >supply and the 7805 to drop the voltage at the 7805 >to somewhere around 8? Yes, you could do this. Pick an appropriate power resistor, or use a big wirewound rheostat. > 3) If I was to "tack on" a jumper between VIN and VOUT, >would that protect the 7805 and allow me to power the >circuit with 5 volts? I would not do this at all. -- Will
Re: ADM 3a with no horizontal scan
> Today, for whatever reason, my Variac was turned down to 110V, and I > didn't notice. I turned on the ADM 3a, and... it's fine. [...] Fascinating! I have trouble imagining what sort of fault could cause those symptoms. I would have agreed with whoever (tony, I think) said that if you have HV then the horizontal scan is almost certainly operating in some sense, but this makes me doubt that. I have trouble coming up with a failure mode in that design that could kill the horizontal scan but not the HV based on the power supply input voltage, so there is probably something very unusual in there. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTMLmo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
Re: Voltage regulator with alternate voltage source...
> I archive all data sheets I run across and I found this information > on both TI and Fairchild data sheets for the 78H05, LM340 and LM78XX > devices - it is usually under a heading called Application Hints and > for some reason Fairchild have removed these Hints from the sheets > you quote. > In ALL cases the manufacturers caution that putting voltage to the > output when the input is not powered CAN DAMAGE THE CHIP. I have the datasheet PDF for the On Semiconductor version, and I have been unable to find anything of the sort in it. Whether On was sloppy when writing their documetnation or whether some manufacturer's devices are safe or whether I just missed something, I don't know. But, when dealing with a device of unknown provenance, it does seem clear you're better off not powering the output side if the input side has a low-impedance path to ground. (Powering the output with the input disconnected appears to be a completely different thing; I have trouble imagining a design that would be damaged by that.) /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTMLmo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
RE: Voltage regulator with alternate voltage source...
First, a few quick "whys": 1) The 7805 is actually a Motorola MC7805CP, date code 7308 with gold leads. Very hard to exactly replace. 2) As per the design of the unit, the 7805 is soldered to the foil side of a single sided, copper clad circuit board with no through hole plating. Lifting the traces seems like a significant possibility that I don't want to risk. 3) I'm still waiting for the components to build the 8 volt power supply. Hopefully they will arrive Monday. 4) No, one thing missing from my bench, that I've never really needed up to now, is a good adjustable DC supply. My have to ask for one for Christmas. Three thoughts have come to me since my original post. 1) I have a 12 volt DC supply. 12 volts seems to be within the VIN range for the 7805s whose data sheets I've now read. Can I simply apply 12 volts? 2) Could I place a resistor in series between the 12V supply and the 7805 to drop the voltage at the 7805 to somewhere around 8? 3) If I was to "tack on" a jumper between VIN and VOUT, would that protect the 7805 and allow me to power the circuit with 5 volts? Thank You, Bill S.
Re: Voltage regulator with alternate voltage source...
Keep in mind that "not powered" and "open" are very different things. What do the data sheets say? I will admit that this is all careening towards the academic at this point... -- Will On Fri, Apr 8, 2016 at 1:31 PM, John Robertson wrote: > On 04/08/2016 8:54 AM, wulfman wrote: >> >> https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf >> >> http://www.ti.com/lit/ds/symlink/lm78l05.pdf ( page 8 gives you the >> internals for a low power version ) >> >> Nothing in the data sheet saying you cant apply voltage to the output. >> >> As per the low power version circuit diagram i cant see how you can do >> any damage to it >> I was not able to find an internal diagram for the higher power version >> but >> i am sure its close to the same circuit just larger pass transistors. >> >> I took a new regulator and measured the output pin to ground with my >> trusty ohmmeter >> on the diode setting and had no reading. If you think about it the >> output on the regulator is a pass transistor >> and the output to ground will be in effect a diode that will not allow >> current to pass from output to ground. >> >> >> My last comment still stands. i doubt you will cause any ill effects to >> your regulator. >> >> >> I personally have done this to some old arcade boards with no ill effects. >> >> >> On 4/7/2016 6:08 PM, drlegendre . wrote: >>> >>> "...if you leave the unregulated rail _unattached_ and put +5 >>> switcher straight onto the regulated +5 rail..." >>> >>> My error, I read that as "attached". >>> >>> In any event, just lift both the 7805 IN and OUT pins, and then supply >>> known-solid +5DC between the OUT and GND pads on the board. >>> >>> No, you can't feed the IN pin with +5V, for as others have mentioned, >>> the 7805 has a minimum dropout of 2V or so. >>> >>> On Thu, Apr 7, 2016 at 4:03 PM, William Donzelli >>> wrote: >>> Per his description, the 7805's input will be open. It will not try to source any current, as it will have none to give. I suppose there might be a little leakage. -- Will On Thu, Apr 7, 2016 at 4:58 PM, drlegendre . wrote: > I archive all data sheets I run across and I found this information on both > TI and Fairchild data sheets for the 78H05, LM340 and LM78XX devices - it is > usually under a heading called Application Hints and for some reason > Fairchild have removed these Hints from the sheets you quote. > > In ALL cases the manufacturers caution that putting voltage to the output > when the input is not powered CAN DAMAGE THE CHIP. > > The sheets I have appear to be a bit hard to find so here are my archived > copies: > > http://www.flippers.com/pdfs/LM340_LM78XX_National_2003.pdf (page 11) > > http://www.flippers.com/pdfs/LM78H05A_Fairchild.pdf (page 4) > > So, yes, you can get away with it for a short time, but you are stressing > the regulator outside its design limits and that will shorten its life. > > John :-#(# > > -- > John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 > Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames) > www.flippers.com > "Old pinballers never die, they just flip out" >
Re: Voltage regulator with alternate voltage source...
On 04/08/2016 8:54 AM, wulfman wrote: https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf http://www.ti.com/lit/ds/symlink/lm78l05.pdf ( page 8 gives you the internals for a low power version ) Nothing in the data sheet saying you cant apply voltage to the output. As per the low power version circuit diagram i cant see how you can do any damage to it I was not able to find an internal diagram for the higher power version but i am sure its close to the same circuit just larger pass transistors. I took a new regulator and measured the output pin to ground with my trusty ohmmeter on the diode setting and had no reading. If you think about it the output on the regulator is a pass transistor and the output to ground will be in effect a diode that will not allow current to pass from output to ground. My last comment still stands. i doubt you will cause any ill effects to your regulator. I personally have done this to some old arcade boards with no ill effects. On 4/7/2016 6:08 PM, drlegendre . wrote: "...if you leave the unregulated rail _unattached_ and put +5 switcher straight onto the regulated +5 rail..." My error, I read that as "attached". In any event, just lift both the 7805 IN and OUT pins, and then supply known-solid +5DC between the OUT and GND pads on the board. No, you can't feed the IN pin with +5V, for as others have mentioned, the 7805 has a minimum dropout of 2V or so. On Thu, Apr 7, 2016 at 4:03 PM, William Donzelli wrote: Per his description, the 7805's input will be open. It will not try to source any current, as it will have none to give. I suppose there might be a little leakage. -- Will On Thu, Apr 7, 2016 at 4:58 PM, drlegendre . wrote: I archive all data sheets I run across and I found this information on both TI and Fairchild data sheets for the 78H05, LM340 and LM78XX devices - it is usually under a heading called Application Hints and for some reason Fairchild have removed these Hints from the sheets you quote. In ALL cases the manufacturers caution that putting voltage to the output when the input is not powered CAN DAMAGE THE CHIP. The sheets I have appear to be a bit hard to find so here are my archived copies: http://www.flippers.com/pdfs/LM340_LM78XX_National_2003.pdf (page 11) http://www.flippers.com/pdfs/LM78H05A_Fairchild.pdf (page 4) So, yes, you can get away with it for a short time, but you are stressing the regulator outside its design limits and that will shorten its life. John :-#(# -- John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames) www.flippers.com "Old pinballers never die, they just flip out"
Re: ADM 3a with no horizontal scan
OK, I made a very interesting discovery today. When I'm working on a project on my workbench, I normally have it plugged into a Variac. This ADM 3a is no exception. I bring up voltage slowly on any unknown old electronics, and then let it sit at our normal wall voltage - which currently reads 121V. Today, for whatever reason, my Variac was turned down to 110V, and I didn't notice. I turned on the ADM 3a, and... it's fine. It beeped, it has a cursor, and scan looks perfect. I turned the Variac slowly up to 121V, and at around 118V the 3a goes nuts and loses horizontal scan, I just get the vertical line. So, some part is really marginal, and I need to figure out which one it is. What fun! -Seth
RE: Dumb terminals for daily use today; failure scenarios
> If one were to use a dumb CRT terminal from the early '70s regularly in > this day and age, would it be more prone to hardware failure than if it > were kept in storage or just kept to look at but powered off? If you never turn it on, how will you know if the hardware has failed? More seriiously, I suspect the flyback transformer will fail more quickly if it is used. And the CRT will lose emission. BUT Even if that happens, the outside appearance will be unchanged. You will still be abe to keep it to look at. And if it is kept unpowered it will fail in the end. So my suggestion is to enjoy it now, fix it while you can, and if the worst happens just look at it. -tony
Dumb terminals for daily use today; failure scenarios
If one were to use a dumb CRT terminal from the early '70s regularly in this day and age, would it be more prone to hardware failure than if it were kept in storage or just kept to look at but powered off? -- Eric Christopherson
Re: Voltage regulator with alternate voltage source...
https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf http://www.ti.com/lit/ds/symlink/lm78l05.pdf ( page 8 gives you the internals for a low power version ) Nothing in the data sheet saying you cant apply voltage to the output. As per the low power version circuit diagram i cant see how you can do any damage to it I was not able to find an internal diagram for the higher power version but i am sure its close to the same circuit just larger pass transistors. I took a new regulator and measured the output pin to ground with my trusty ohmmeter on the diode setting and had no reading. If you think about it the output on the regulator is a pass transistor and the output to ground will be in effect a diode that will not allow current to pass from output to ground. My last comment still stands. i doubt you will cause any ill effects to your regulator. I personally have done this to some old arcade boards with no ill effects. On 4/7/2016 6:08 PM, drlegendre . wrote: > "...if you leave the unregulated rail _unattached_ and put +5 > switcher straight onto the regulated +5 rail..." > > My error, I read that as "attached". > > In any event, just lift both the 7805 IN and OUT pins, and then supply > known-solid +5DC between the OUT and GND pads on the board. > > No, you can't feed the IN pin with +5V, for as others have mentioned, > the 7805 has a minimum dropout of 2V or so. > > On Thu, Apr 7, 2016 at 4:03 PM, William Donzelli > wrote: > >> Per his description, the 7805's input will be open. It will not try to >> source any current, as it will have none to give. >> >> I suppose there might be a little leakage. >> >> -- >> Will >> >> On Thu, Apr 7, 2016 at 4:58 PM, drlegendre . wrote: >> -- The contents of this e-mail and any attachments are intended solely for the use of the named addressee(s) and may contain confidential and/or privileged information. Any unauthorized use, copying, disclosure, or distribution of the contents of this e-mail is strictly prohibited by the sender and may be unlawful. If you are not the intended recipient, please notify the sender immediately and delete this e-mail.
Re: VCF Europe, April 30th - May 1st, Munich + registration for VCF Berlin
That's pretty nearly what it says. I'd tweak it as follows. paul > On Apr 8, 2016, at 8:42 AM, R SMALLWOOD wrote: > > >> > historische Computer und Rechentechnik> > The Vintage Computing - Berlin (VCFB) is an event for collectors of old > computers and calculators. ...an exhibition about historic computers and computation technology. > >> > und der Spaß daran vermittelt werden. ? > There are exhibits, lectures and workshops to show what the Vintage Computer > has to offer and the fun to be had. ...to show the hobby and the fun to be had. > >> Ziel des VCFBs ist es, den Erhalt und die Pflege historischer Computer und >> anderer (E)DV-Gerätschaften zu fördern und das Interesse an "überflüssiger" >> Hard- und Software zu wecken. >> >> The objective of the VCF-B is to encourage the collection and restoration of >> old computers and other equipment by those with just a passing interest. ... other IT equipment, and to stimulate interest in "redundant" hardware and software. > >> Unter die Inhalte des VCFBs fallen nicht nur historische Computer, sondern >> z.B. auch historische Betriebssysteme, Software, Programmiersprachen, >> Netzwerktechnik und andere Geräte, die rechnen, wie z.B. historische >> Taschenrechner und Rechenmaschinen. > Included in the range of items covered by VCF-B are not only old computers > but office machines, Software, Programming Languages, Networking and other > equipment including pocket and office calculators. ...not only historic computers, but for example also historic operating systems ...
RE: ADM 3a with no horizontal scan
> > This particular 3a has no horizontal scan. None at all. I just get a > vertical line down the center of the screen. First thing I checked was > the horizontal deflector on the yoke, which seems secure. I am going to assume this is a conventional design, I would be very surprised if not. In which case, to get anything on the screen the horizontal output stage must be working, as the CRT electrode voltages come from the flyback transformer. Normally the horizontal deflection yoke is capacitively coupled to the horizontal output stage (often straight off the collector of the transistor). There may be a width control inductor and a horizontal linearity inductor in series too. So it's about 4 components (yoke winding, the 2 inductors, the coupling capacitor) and the interconnections to check. If the coils (yoke and inductors) show DC continuity then most likely they are OK and in any case you would get some deflection. Most likely, actually, is the coupling capacitor. It will be non-polarised (maybe plastic film, maybe a reversable electrolytic) and a fair voltage rating. They do fail... -tony
Re: Space Travel (was Re: Data General Nova Star Trek)
On Fri, Apr 08, 2016 at 05:33:43AM -0700, Charles Anthony wrote: > > http://www.chdickman.com/pdp8/spacewar/ built his own VC8/I for his PDP-8 > and runs the PDP-8 version of space war on it. He lists the IOT > instructions for the VC8/I; they are similar to the 338. Ohh, that looks very doable, I already have the Posibus interface. This goes on my neverending TODO-list. /P
Re: Pinging Joe Rigdon
Yo, When I lived in Florida, I would see Joe several times a year. Since I moved 10 years ago, we have lost contact. His wife Sherry, daughter Amy, and Son Adam, do have facebook profiles. Just do a search for "Rigdon Oviedo" (Florida) and you can find some links to those family members but nothing for Joe. I got a feeling something bad must have happened to Joe :-( There is a name I haven’t heard in a *LONG* time. Zane -- Steve Robertson stee...@ccvn.com
Re: VCF Europe, April 30th - May 1st, Munich + registration for VCF Berlin
The Vintage Computing - Berlin (VCFB) is an event for collectors of old computers and calculators. From : stuebera...@yahoo.de Date : 06/04/2016 - 23:56 (GMTDT) To : cctalk@classiccmp.org Subject : VCF Europe, April 30th - May 1st, Munich + registration for VCF Berlin Hi list, the 17th edition of VCF Europe[0] is coming soon! It will take place on April 30th and May 1st in Munich, Germany. Please be aware that the information on the English version of the website might be outdated or less detailed than on the German page, but Google Translate will help. Also the registration for VCF Berlin[1] in October is open now. We are looking for speakers, workshop instructors and exhibitors, both for the regular exhibition and this year's special exhibition on computers and languages. It will be open for visitors on Sunday, 2nd and Monday, 3rd of October, as the 3rd October is a public holiday in Germany, but we are thinking about inviting people to build up on Friday already and using Saturday, 1st of October as a day just for the participants and the community. This way there would be more time to talk and see the other exhibitions. Maybe we could even offer advanced workshops on Saturday. Come and visit us! Ping me if you need a place to stay. Regards, Anke [0] http://vcfe.org/E/index.html [1] http://vcfb.de/2016/index.html.en
Re: Space Travel (was Re: Data General Nova Star Trek)
On Thu, Apr 7, 2016 at 9:35 PM, Pontus Pihlgren wrote: > On Thu, Apr 07, 2016 at 04:08:42PM -0700, Charles Anthony wrote: > > > > I have some code that does an X-11 emulation of the Atari Tempest vector > > graphics display; I'm thinking of wedging it into the simh PDP8 code to > > emulate the 338 and PDP-1 displays. > > > > That woyld be fun :) I could perhaps be used for future PDP-12 > and LINC emulators as well. > > I have read just a little about the 338. I believe it is more or > less a dedicated PDP-8. Can you say how it compares with other > vector displas, such as VC8E? > That is my understanding as well. I haven't actually ever seen any of these beasts; I'm just doing on documentation that I can find, so I am very likely wrong on some points. There is a 338 programming manual at https://archive.org/stream/bitsavers_decpdp8gragmgOct66_2439011/DEC-08-G61B-D_338pgmg_Oct66#page/n0/mode/2up with a the display list opcodes. The VC8E programming is discussed at http://homepage.cs.uiowa.edu/~jones/pdp8/man/vc8e.html. The VC8E has about 8 IO commands, and uses 12 bit coordinates.The commands boil down to set X, set Y and set intensity to 0 or 1. The 338 uses 13bit coordinates; the display has 10 bit resolution. The 338 has scaling, 8 intensity levels, delta move, character ROM, and a 36 page programming manual. There is a description of the VR14/VC8E at http://www.pdp8.net/vr14/vr14info.shtml.; it describes the VC8e as 50K dots per second ont the VR14 monitor, and the 338 as 300K DPS, and mentions that the 338 had a character ROM. http://www.chdickman.com/pdp8/spacewar/ built his own VC8/I for his PDP-8 and runs the PDP-8 version of space war on it. He lists the IOT instructions for the VC8/I; they are similar to the 338. -- Charles
Re: ADM 3a with no horizontal scan
> > I've been on a tear trying to resurrect old projects here, and next on > the list is an ADM 3a. > > This particular 3a has no horizontal scan. None at all. I just get a > vertical line down the center of the screen. First thing I checked was > the horizontal deflector on the yoke, which seems secure. > > Before I go diving into the schematics, I figured I'd ask here: Is > this a common failure mode? Has anyone else experienced no horizontal > scan on a 3a? Any tips on where to look first? > I have an ADM 5 (which might have the same monitor circuit) which did something like this but the vertical line faded out after a while. There was a bad joint on the little driver transformer just ahead of the horizontal output transistor. I guess the joint was managing to make intermittent contact allowing EHT to be generated and the CRT capacitance to be charged up for a while. If your vertical line is not fading out, EHT is being generated which rules out pretty much everthing (unless it's an unusual monitor circuit) except the scan coils (unlikely), connections to the scan coils and any correction components in series with the scan coils. Regards, Peter Coghlan.
Re: Voltage regulator with alternate voltage source...
On 04/07/2016 4:41 PM, William Donzelli wrote:
Does this warning assume that there is something on Vin, and not open?
With a quick look at the internal schematic of an old-school 7805, it
seems like what Bill suggests (leaving Vin open) will not actually do
much.
--
Will
This warning is for someone who is thinking of adding a large filter
capacitor (>10ufd) on the output of the 78XX device and the manufacturer
is warning against this. Typically the reason is when the input power
drops below 2VDC above the ouput (power removed) then the device can
conduct backwards to ground - if you provide enough current it will
probably self destruct.
To me it is simple, the manufacturer says don't do it as you will damage
the device. That is enough for me. If you want to check the internal die
design you can see why this is so.
John :-#(#
On Thu, Apr 7, 2016 at 7:23 PM, John Robertson wrote:
On 04/07/2016 2:18 PM, Bill Sudbrink wrote:
drlegendre wrote:
Not saying it's going to smoke-out, but it does
seem like a wonky thing to do.
I disagree about "wonky" let me try with more
diagram and less English:
(+8)
|
VIN|ceramic cap
|-][-
___| |
| 7805 |--GROUND
|
| |
VOUT|(+5) |
| |
___| |
| LOAD |---|
+8 is not currently available (no pun intended).
I would like to test LOAD without removing 7805
as it is soldered in place. Is damage to 7805
likely if alternative regulated current is applied
at (+5) and (+8) is left open?
Bill S.
Yes, you can damage the 7805 - READ the data sheets...
Raising the Output Voltage above the Input Voltage:
Since the output of the device does not sink current, forcing
LM340/LM78MXX Series 3-Terminal Positive Regulators LM340/LM78MXX Series
3-Terminal Positive Regulators
the output high can cause damage to internal low current paths in a manner
similar to that just described in the “Short- ing the Regulator Input”
section.
LM340/LM78MXX Series 3-Terminal Positive Regulato John :-#(#
