Re: 9-Track 1/2 Tape Drive Recommendations?
On 08/23/2015 02:29 AM, jwsmobile wrote: There was an outfit here in Orange County, Ca that was a den of oddballs who actually like to write compilers and were good at that was called CSPI. In the 78-79 timeframe, Microdata bought a compiler for Cobol and Fortran from them with a really big check and helped them along the path of becoming a viable company. I do remember CSPI. Anyway, one of the things that Express was competing with were DEC systems and they benchmarked both the Fortran and the Cobol and outran DEC. Express was still a miserable failure for them, and they of course only made the one system design and never enhanced it. Someone with better knowledge about DEC can guess the 11 and OS. Anyway another thing they had to do was pass this test, and I suspect it is the one that Chuck refers to. If you were selling to the USG, it was definitely in your interest to pass the Naval COBOL Auditing tests. Grace Hopper was largely responsible for their development and it stems from a morass of vendor extensions and features and the individual interpretations of the CODASYL standard that could render compilers different as night and day. It was apparent that some sort of test of conformity to the standard was necessary. FORTRAN suffered from the same problem also. In particular, I recall a CDC extension that seemed innocent but resulted in ambiguous syntax--a definite no-no in the world of languages. The PSR was never solved, as it would have required a change in an existing language. Note that these tests are not benchmarks--they merely serve to make sure that the compiler and run-time actually do what they're supposed to--and not what somebody *thinks* they should do. So these tests are historically important. CSPI was bought up by or morphed into one of the outfits which sold Cobol compilers for the PC, but I don't know which one. If one looks on bitsavers at the front of the Microdata Express Cobol internal spec, it was prepared by CSPI, California Software Products, Inc. I think all major compiler producers had specifications of that nature--they were also written for operating systems. Paper first, code later... --Chuck
RE: RS-232 Tx / Rx monitoring LEDs?
-Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Brent Hilpert Sent: Sunday, August 23, 2015 3:07 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: RS-232 Tx / Rx monitoring LEDs? On 2015-Aug-22, at 11:55 PM, drlegendre . wrote: On Sun, Aug 23, 2015 at 1:17 AM, Chuck Guzis ccl...@sydex.com wrote: On 08/22/2015 10:23 PM, dwight wrote: I would think the reverse voltage sum of the diodes is enough. Different diodes also can handle different voltages. Since the sum of the forward voltages is enough to handle AC, I'd suspect the reverse voltages each would handle is quite small as well. The problem is when the current limiting is done with a resistor that in the forward direction drops a lot of voltage. The diode has to handle the voltage until breakdown when reversed. If the resistor was handling 1 Watts, with the right break down, the LED could be taking .5 Watts. This is more than most are designed for. ...and that's just the nub of it. The success of this depends largely on the consistent characteristics of every LED in the string. Since LEDs tend to fail short if submitted to overvoltage, I've often wondered if a spike in the AC supply would precipitate a cascade failure in the string. I've looked hard and there are no rectifier diodes in the string--just the LEDs themselves. Probably saves about 5 cents or so of manufacturing cost. I've also seen LED night lights from China that employ nothing more than a safety capacitor (usually about 104) in series with a resistor connected to two back-to-back LEDs, all across the AC line. I've wondered what the lifetime of such a setup is. --Chuck. I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? I doubt if any brief explanation here is going to the topic justice. Look up power factor or reactive power. FWIW: The impedance (capacitive reactance, Z=Xc=1/(2*pi*f*C) of the C does produce the desired voltage drop but the C also shifts the phase of the current relative to that of the V. To apply the power equation P=VI properly, you can't just multiply the RMS values together, you multiply the instantaneous values of the V I sine waves together through a cycle. You get a third sine wave, that for power. If V I are in phase, the power sine wave will all be in the positive region and is real power consumption. When they are out of phase, some portion of the power sine wave will be negative: a portion of the energy the C sucked down the line is being returned during each cycle. Yes, it does reduce energy consumption relative to a purely R solution. On a large scale, the power company doesn't like it because it unnecessarily adds to the currents circulating in the system, but then, this is from C which shifts the current in one direction, so it's doing some compensation for the inductive wall warts you have plugged in around the house, which as L shift the current in the other direction. --- Brent, that is an excellent explanation in just a few sentences. One quibble however. The power company does indeed like components that shift the current in the capacitive direction. Taken as a whole for the power grid, the power source sees the load as inductive because of all the industrial motors it powers, including the ones that exist in almost every home (washer, dryer, heating/air conditioning, mixer, disposal, etc.) Capacitor banks are frequently installed in large industrial operations to shift the inductive load more toward the capacitive power factor. This is because the power company, as you have implied, charges more for power that is current shifted away from zero %. I have even seen large motors installed in industrial situations that run continuously without load, because such motors appear as a capacitive load, and indeed are called 'rotary capacitors'. I recall one time when the CFO ordered such a motor turned off because it is wasting power. It took a little plain and fancy instruction by the engineer to let him know that it was actually saving the company money.
Re: RS-232 Tx / Rx monitoring LEDs?
On 2015-Aug-23, at 9:06 AM, Chuck Guzis wrote: On 08/23/2015 07:10 AM, dwight wrote: I've used the capacitor method to provide most of the drop in the past. I don't usually max out the LEDs at 20ma. I find there is little difference between 10 and 20ma. Yes, the 10 ( or 20ma ) is current flow through the capacitor. It is necessary to have some resistor in series as well to suppress line spikes. Another similar dirty trick back in the day was to run a 6SL7 dual-triode form the line using a 1.0 uF nonpolar capacitor in series with the line to provide a supply for the 500 ma 6.3 v heater and then use one of the triode sections as a half-wave rectifier. You thus had the other triode section for whatever stupid purpose. Of course, this was horrible abuse of the tube, particularly in the area of heater-cathode voltage ratings. It probably wouldn't work as well in 220VAC countries, but it worked well enough in the 120VAC ones. Those ubiquitous motion detectors for outdoor lights use capacitive dropping to supply the low voltage for the ICs and electronics. Cap and small R in series with the AC input to a bridge rectifier. Works out well in that the bridge rectifier permits current flow in both directions, which is necessary to get current flow through the cap (the cap has to charge and discharge).
RE: RS-232 Tx / Rx monitoring LEDs?
Those ubiquitous motion detectors for outdoor lights use capacitive dropping to supply the low voltage for the ICs and electronics. Cap and small R in series with the AC input to a bridge rectifier. Works out well in that the bridge rectifier permits current flow in both directions, which is necessary to get current flow through the cap (the cap has to charge and discharge). Over here that sort of circuit was common for the power supply for the control electronics in washing machines and the like. It may still be, I've not worked on anything that recent. -tony
Re: RS-232 Tx / Rx monitoring LEDs?
On 2015-Aug-23, at 9:54 AM, Steve Moulding wrote: -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Brent Hilpert Sent: Sunday, August 23, 2015 3:07 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: RS-232 Tx / Rx monitoring LEDs? On 2015-Aug-22, at 11:55 PM, drlegendre . wrote: On Sun, Aug 23, 2015 at 1:17 AM, Chuck Guzis ccl...@sydex.com wrote: On 08/22/2015 10:23 PM, dwight wrote: I would think the reverse voltage sum of the diodes is enough. Different diodes also can handle different voltages. Since the sum of the forward voltages is enough to handle AC, I'd suspect the reverse voltages each would handle is quite small as well. The problem is when the current limiting is done with a resistor that in the forward direction drops a lot of voltage. The diode has to handle the voltage until breakdown when reversed. If the resistor was handling 1 Watts, with the right break down, the LED could be taking .5 Watts. This is more than most are designed for. ...and that's just the nub of it. The success of this depends largely on the consistent characteristics of every LED in the string. Since LEDs tend to fail short if submitted to overvoltage, I've often wondered if a spike in the AC supply would precipitate a cascade failure in the string. I've looked hard and there are no rectifier diodes in the string--just the LEDs themselves. Probably saves about 5 cents or so of manufacturing cost. I've also seen LED night lights from China that employ nothing more than a safety capacitor (usually about 104) in series with a resistor connected to two back-to-back LEDs, all across the AC line. I've wondered what the lifetime of such a setup is. --Chuck. I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? I doubt if any brief explanation here is going to the topic justice. Look up power factor or reactive power. FWIW: The impedance (capacitive reactance, Z=Xc=1/(2*pi*f*C) of the C does produce the desired voltage drop but the C also shifts the phase of the current relative to that of the V. To apply the power equation P=VI properly, you can't just multiply the RMS values together, you multiply the instantaneous values of the V I sine waves together through a cycle. You get a third sine wave, that for power. If V I are in phase, the power sine wave will all be in the positive region and is real power consumption. When they are out of phase, some portion of the power sine wave will be negative: a portion of the energy the C sucked down the line is being returned during each cycle. Yes, it does reduce energy consumption relative to a purely R solution. On a large scale, the power company doesn't like it because it unnecessarily adds to the currents circulating in the system, but then, this is from C which shifts the current in one direction, so it's doing some compensation for the inductive wall warts you have plugged in around the house, which as L shift the current in the other direction. --- Brent, that is an excellent explanation in just a few sentences. One quibble however. The power company does indeed like components that shift the current in the capacitive direction. Taken as a whole for the power grid, the power source sees the load as inductive because of all the industrial motors it powers, including the ones that exist in almost every home (washer, dryer, heating/air conditioning, mixer, disposal, etc.) Capacitor banks are frequently installed in large industrial operations to shift the inductive load more toward the capacitive power factor. This is because the power company, as you have implied, charges more for power that is current shifted away from zero %. I have even seen large motors installed in industrial situations that run continuously without load, because such motors appear as a capacitive load, and indeed are called 'rotary capacitors'. I recall one time when the CFO ordered such a motor turned off because it is wasting power. It took a little plain and fancy instruction by the engineer to let him know that it was actually saving the company money. Sure, L shift predominates in the system, I was just speaking in general terms at that point. The power companies may be playing it both ways though: I was once told a story of a small mill or manufacturing co. and an electro-plating company situated next door to each other. But the mill was inductive (motors) and the electro-plating was effectively capacitive (not sure how that worked), so they pretty much cancelled each other out and weren't contributing to line losses for the power company. The power
Re: RS-232 Tx / Rx monitoring LEDs?
Heh, all you had to say was power factor and I've have understood. I suspected that was the case, but it seemed too easy.. Guess I'm too used to thinking in simple ohmic terms, with Watt Kirchhoff always looming large. Something told me that, in the end, there was no way around dealing with the E^2/R heat - anything else seemed like a thermodynamic cheat. On Sun, Aug 23, 2015 at 11:54 AM, Steve Moulding fti1...@xmission.com wrote: -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Brent Hilpert Sent: Sunday, August 23, 2015 3:07 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: RS-232 Tx / Rx monitoring LEDs? On 2015-Aug-22, at 11:55 PM, drlegendre . wrote: On Sun, Aug 23, 2015 at 1:17 AM, Chuck Guzis ccl...@sydex.com wrote: On 08/22/2015 10:23 PM, dwight wrote: I would think the reverse voltage sum of the diodes is enough. Different diodes also can handle different voltages. Since the sum of the forward voltages is enough to handle AC, I'd suspect the reverse voltages each would handle is quite small as well. The problem is when the current limiting is done with a resistor that in the forward direction drops a lot of voltage. The diode has to handle the voltage until breakdown when reversed. If the resistor was handling 1 Watts, with the right break down, the LED could be taking .5 Watts. This is more than most are designed for. ...and that's just the nub of it. The success of this depends largely on the consistent characteristics of every LED in the string. Since LEDs tend to fail short if submitted to overvoltage, I've often wondered if a spike in the AC supply would precipitate a cascade failure in the string. I've looked hard and there are no rectifier diodes in the string--just the LEDs themselves. Probably saves about 5 cents or so of manufacturing cost. I've also seen LED night lights from China that employ nothing more than a safety capacitor (usually about 104) in series with a resistor connected to two back-to-back LEDs, all across the AC line. I've wondered what the lifetime of such a setup is. --Chuck. I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? I doubt if any brief explanation here is going to the topic justice. Look up power factor or reactive power. FWIW: The impedance (capacitive reactance, Z=Xc=1/(2*pi*f*C) of the C does produce the desired voltage drop but the C also shifts the phase of the current relative to that of the V. To apply the power equation P=VI properly, you can't just multiply the RMS values together, you multiply the instantaneous values of the V I sine waves together through a cycle. You get a third sine wave, that for power. If V I are in phase, the power sine wave will all be in the positive region and is real power consumption. When they are out of phase, some portion of the power sine wave will be negative: a portion of the energy the C sucked down the line is being returned during each cycle. Yes, it does reduce energy consumption relative to a purely R solution. On a large scale, the power company doesn't like it because it unnecessarily adds to the currents circulating in the system, but then, this is from C which shifts the current in one direction, so it's doing some compensation for the inductive wall warts you have plugged in around the house, which as L shift the current in the other direction. --- Brent, that is an excellent explanation in just a few sentences. One quibble however. The power company does indeed like components that shift the current in the capacitive direction. Taken as a whole for the power grid, the power source sees the load as inductive because of all the industrial motors it powers, including the ones that exist in almost every home (washer, dryer, heating/air conditioning, mixer, disposal, etc.) Capacitor banks are frequently installed in large industrial operations to shift the inductive load more toward the capacitive power factor. This is because the power company, as you have implied, charges more for power that is current shifted away from zero %. I have even seen large motors installed in industrial situations that run continuously without load, because such motors appear as a capacitive load, and indeed are called 'rotary capacitors'. I recall one time when the CFO ordered such a motor turned off because it is wasting power. It took a little plain and fancy instruction by the engineer to let him know that it was actually saving the company money.
Re: RS-232 Tx / Rx monitoring LEDs?
On 08/22/2015 11:55 PM, drlegendre . wrote: I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? That's correct--but there's the matter of the voltage. Eventually, you'll see that the brightness of the LEDs will drop fairly rapidly before the thing is useless. A common dodge used by Chinese manufacturers. Saves a few components, doesn't it. --Chuck
Re: RS-232 Tx / Rx monitoring LEDs?
On 08/23/2015 07:10 AM, dwight wrote: I've used the capacitor method to provide most of the drop in the past. I don't usually max out the LEDs at 20ma. I find there is little difference between 10 and 20ma. Yes, the 10 ( or 20ma ) is current flow through the capacitor. It is necessary to have some resistor in series as well to suppress line spikes. Another similar dirty trick back in the day was to run a 6SL7 dual-triode form the line using a 1.0 uF nonpolar capacitor in series with the line to provide a supply for the 500 ma 6.3 v heater and then use one of the triode sections as a half-wave rectifier. You thus had the other triode section for whatever stupid purpose. Of course, this was horrible abuse of the tube, particularly in the area of heater-cathode voltage ratings. It probably wouldn't work as well in 220VAC countries, but it worked well enough in the 120VAC ones. --Chuck
RE: VT100 preventative maintenance?
... [1] In the UK we call all CRT elecrodes after the control grid (first grid) 'anodes' which makes sense as they are run +ve wrt the cathode. So does a UK tetrode have one grid and two anodes? Or is there one terminology for CRTs and a different one for other tubes? The second. A Tetrode over here has 2 grids (control grid and screen grid [1]) and one anode. A pentode has 3 grids (control, screen, supressor) [1] An old name for a tetrode or pentode over here is a 'Screen grid valve' Some early valves had type codes which clearly came from this For example there was a 'AC/SG' which was an indirectly heated (the 'AC' part, meaning the heater could run on AC) tetrode (the 'SG' part). I have an old Cossor MVS/PEN valve. That stands for 'Metalised' (meaning there is a conductive coating on the outside of the glass envelope for shielding), Variable Mu (non-linear, so amplification depends on grid bias) Screengrid (a tetrode or pentode) and the 'PEN' part means it really is a Pentode. Also note that we use the term 'valve' for diodes, triodes, etc, but 'tube' for CRTs, nixie tubes, dekatrons, voltage stabilisers, probably trochotrons, etc. There seems to be no obvious reason for what is a 'valve' and what is a 'tube'. -tony paul
Re: 9-Track 1/2 Tape Drive Recommendations?
There was an outfit here in Orange County, Ca that was a den of oddballs who actually like to write compilers and were good at that was called CSPI. In the 78-79 timeframe, Microdata bought a compiler for Cobol and Fortran from them with a really big check and helped them along the path of becoming a viable company. They then had a fellow as a contracter, Mas Okano, who also contracted for Olivetti for a long time and for CSPI maintain it as the Express system was sold to Olivetti and transferring into one of their main systems. I think Mas was there till the mid 90s, but CSPI went out of the picture. Anyway, one of the things that Express was competing with were DEC systems and they benchmarked both the Fortran and the Cobol and outran DEC. Express was still a miserable failure for them, and they of course only made the one system design and never enhanced it. Someone with better knowledge about DEC can guess the 11 and OS. Anyway another thing they had to do was pass this test, and I suspect it is the one that Chuck refers to. CSPI was bought up by or morphed into one of the outfits which sold Cobol compilers for the PC, but I don't know which one. If one looks on bitsavers at the front of the Microdata Express Cobol internal spec, it was prepared by CSPI, California Software Products, Inc. Unfortunatly, it is really just the compiler spec, and doesn't have what I know were in other documents, the requirements for the spec. It is a good writeup of the internals of a compiler if anyone is interested. I believe both Fortran and Cobol used the technique of compiling to the intermediate target MOM then on to machine code, enabling them to sell the compiler to other vendors. Microdata paid for the first one though in 79 I also think they had the tests and ran them for Microdata and submitted the results as the tests were very involved. thanks Jim On 8/22/2015 6:31 PM, Chuck Guzis wrote: On 08/22/2015 02:14 PM, Al Kossow wrote: No, I haven't the faintest idea where you would even find a copy today. I did find a reference to the CCVS suite of tests for sequential I/O: http://oai.dtic.mil/oai/oai?verb=getRecordmetadataPrefix=htmlidentifier=ADA019757 TOG lists the 1985 suite as the standard validation for COBOL, but the link goes to NCC and thence to a 404. One used to be able to get such stuff from the USDOC, but I doubt that they would know what you were talking about today. I suspect that there's a reel of tape somewhere with the damned things on it. --Chuck
RE: RS-232 Tx / Rx monitoring LEDs?
I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? Yes, the capacitor passes 20mA. But unlike a resistor the voltage drop across a capacitor is not in phase with the current. For a pure capacitor, it is out of phase by 90 degrees. For a pure inductor, BTW, it is 90 degrees out in the oposite direction. Now, if you consider the power at any instant, it is, indeed the product of the voltage and current at that instant. For a resistor, this is alwas positive, so if you add up all the instantaneous powers over a full cycle (mathematically, this is integration, of cource), the total power consumed is positive. But for a capacitor, sometimes the instantaneous power is negative, in effect the capacitor is supplying energy back to the circuit. And if you integrate that over a full cycle, you end up with zero. Intuitively : With a resistor, voltage and current are either both positive or both negative, so the product is positive. With a capacitor, due to that phase shift, there are 4 regions to consider : V +ve., I +ve; V +ve, I -ve; V -ve, I -ve; V -ve, I+ve. The first and third of those give a +ve power, the second and fourth a -ve power and they exactly cancel out. It turns out that the power in an AC circuit can be calcualted as the product of the RMS voltage, RMS current and the cosine of the phase angle between them. The RMS values are the ones normally quotes (115V mains had an RMS value of 115V). The cosine(phase) term is known as the 'power factor', and is probably the thing to look up in a book on AC electric circuits. -tony
Re: RS-232 Tx / Rx monitoring LEDs?
On 2015-Aug-22, at 11:55 PM, drlegendre . wrote: On Sun, Aug 23, 2015 at 1:17 AM, Chuck Guzis ccl...@sydex.com wrote: On 08/22/2015 10:23 PM, dwight wrote: I would think the reverse voltage sum of the diodes is enough. Different diodes also can handle different voltages. Since the sum of the forward voltages is enough to handle AC, I'd suspect the reverse voltages each would handle is quite small as well. The problem is when the current limiting is done with a resistor that in the forward direction drops a lot of voltage. The diode has to handle the voltage until breakdown when reversed. If the resistor was handling 1 Watts, with the right break down, the LED could be taking .5 Watts. This is more than most are designed for. ...and that's just the nub of it. The success of this depends largely on the consistent characteristics of every LED in the string. Since LEDs tend to fail short if submitted to overvoltage, I've often wondered if a spike in the AC supply would precipitate a cascade failure in the string. I've looked hard and there are no rectifier diodes in the string--just the LEDs themselves. Probably saves about 5 cents or so of manufacturing cost. I've also seen LED night lights from China that employ nothing more than a safety capacitor (usually about 104) in series with a resistor connected to two back-to-back LEDs, all across the AC line. I've wondered what the lifetime of such a setup is. --Chuck. I've also seen C-R series voltage dropping circuits, here there. Correct me if I'm wrong, but doesn't the series cap dissipate power just as it would, were it a series resistor? I mean, if the LED is passing 20mA, the cap is also doing 20mA - and at whatever the Vdrop is. Right? If not, why? I doubt if any brief explanation here is going to the topic justice. Look up power factor or reactive power. FWIW: The impedance (capacitive reactance, Z=Xc=1/(2*pi*f*C) of the C does produce the desired voltage drop but the C also shifts the phase of the current relative to that of the V. To apply the power equation P=VI properly, you can't just multiply the RMS values together, you multiply the instantaneous values of the V I sine waves together through a cycle. You get a third sine wave, that for power. If V I are in phase, the power sine wave will all be in the positive region and is real power consumption. When they are out of phase, some portion of the power sine wave will be negative: a portion of the energy the C sucked down the line is being returned during each cycle. Yes, it does reduce energy consumption relative to a purely R solution. On a large scale, the power company doesn't like it because it unnecessarily adds to the currents circulating in the system, but then, this is from C which shifts the current in one direction, so it's doing some compensation for the inductive wall warts you have plugged in around the house, which as L shift the current in the other direction.
Re: Silent 785 docs?
On Sun, Aug 23, 2015 at 3:50 AM, Jay West jw...@classiccmp.org wrote: Glen wrote... - Is that the one you rescued from somewhere in LA? Was wondering if you were able to successfully manage that. - Nope. That was an 800 series KSR. I still want that, but the business trip I was hoping to use to justify it never materialized. Still looking for someone in NO to pick up and ship, or at least hold for me. The 785 I have had for decades. I think it came out of a rescue I did with Guy in Oklahoma. It doesn't look like the Terminals wiki have any info on the 785: http://terminals.classiccmp.org/wiki/index.php/Category:TI Perhaps you could create one? -- Regards, Torfinn Ingolfsen
Reversed Electrolytics redux
On 8/22/2015 2:41 PM, Jay Jaeger wrote: Unfortunately, bearings did not help the floppy drive, so now I am busy taking the floppy power supply I got with my FD 100-8, making sure it is up to spec to use with the Shugart (and correcting that if needs be), and making it safer (mains fuse, switch) and more fault tolerant (fuse in the 24V line, at least) and making sure all of the mains connected innards are not exposed. Just about done with that. The +24V and -7 to -16V are in spec, but the +5V (which, curiously for a 1A supply, does NOT use a simple 3 terminal regulator) is a tad high, at 5.35V. I may just change it to use a three terminal unit. Well, just found another reversed electrolytic - but this time the original fault was not my own. I decided to trace out this floppy supply I have had for decades (back in my original Altair days), that I got from the same guy from whom I purchased my Siemens FDD 100-8, and discovered that the electrolytic on the unregulated -7 to -16 V was reversed - installed BACKWARDS. That capacitor is now in reform school. ;) Also, I now know why the +5 V is high. It has a UA 7805 3 terminal regulator serving as a voltage reference for a TIP-3055 so the supply can provide more current. That 7805 has a forward biased diode between the center terminal and ground, thus raising the output voltage by right around 0.5v. I expect I will leave it alone. The same design is used for the +24V, which comes out at 24.2V. So, odds are that this supply could drive two floppy drives. JRJ JRJ
Re: RS-232 Tx / Rx monitoring LEDs?
On 08/22/2015 10:23 PM, dwight wrote: I would think the reverse voltage sum of the diodes is enough. Different diodes also can handle different voltages. Since the sum of the forward voltages is enough to handle AC, I'd suspect the reverse voltages each would handle is quite small as well. The problem is when the current limiting is done with a resistor that in the forward direction drops a lot of voltage. The diode has to handle the voltage until breakdown when reversed. If the resistor was handling 1 Watts, with the right break down, the LED could be taking .5 Watts. This is more than most are designed for. ...and that's just the nub of it. The success of this depends largely on the consistent characteristics of every LED in the string. Since LEDs tend to fail short if submitted to overvoltage, I've often wondered if a spike in the AC supply would precipitate a cascade failure in the string. I've looked hard and there are no rectifier diodes in the string--just the LEDs themselves. Probably saves about 5 cents or so of manufacturing cost. I've also seen LED night lights from China that employ nothing more than a safety capacitor (usually about 104) in series with a resistor connected to two back-to-back LEDs, all across the AC line. I've wondered what the lifetime of such a setup is. --Chuck.
SA-800/801 saga continues / schematic request
Anyone out there have: 1) The Schematic for the newer SA-800/SA-701 board part number 25229.1 ? (It might also go by 25228 or 27121). The SA-800 maintenance manual on bitsavers from Feb 78 describes the original discrete board (such as I have on my Altos in the SA-800s) and an LSI-based board which is apparently earlier than the one in my SA-801 drives - the parts layout does not match the layout on these newer boards. 2) A source for Shugart ASICs, particularly 16270-1 ? And the saga to date: As you may recall, one SA-800 on my Altos was misbehaving. I decided to swap in an SA-801 I had from a Data Systems DSD-440 (a two drive cabinet with 2xSA-801, power supply, and controller intended to talk, I think to a Q-Bus controller...). Anyway, that blew the fuse on my Altos on the second track of a floppy test, but (IIRC), the Altos was not damaged. Call this drive X. I then decided to swap in the second SA-801 from the DSD-440. That also blew the fuse on the Altos, and this time the power supply was damaged. Call this drive Y (The Altos power supply has since been repaired - that saga was recorded earlier. ;) ). Replacing the bearings on the problem SA-800 did not help appreciably with its wobble problem. (The spindle shaft is still a possibility, I suppose, along with a damaged clamping frame). Today's news: Having gotten my 20+ year-old home-built floppy supply all fixed up and fused and load tested, I was still a little hesitant to apply it to either of these drives X and Y. So, I disconnected X and Y, and checked out the power supply on the Data Systems DSD-440 Except that the +5V is low, at 4.5V, the supplies seemed OK, in particular, the +24V was fine. So I tested the +24V under load, and it held 24V to 3A (and more, I am sure). When I connect up drive X, the +24V series pass transistor gets very warm and the +24V drops to around +8.5V (regardless of whether or not the stepper motor leads are connected). On the circuit board, a Shugart ASIC 16270-1 gets quite hot, and is clearly dead. This chip is labeled WR/CHNL in an SA-850 schematic, and is listed in the Shugart spares catalog as IC, Write Channel. It is indeed fed from the +24V line on pin 15, and connects to the erase and center tap terminals on the head. [I have not measured the head to see if it was damaged - nope not]. I expect that if I pull that chip, the board will not overload the +24V supply. When I connect up drive Y, the +24V series pass transistor on the power supply gets very hot, but nothing on the circuit board gets hot at all, and the +24V drops to 0. The board measures as a dead short with an ohmmeter (even X shows *some* resistance). The stepper driver IC, a standard part UNL2074 (quad darlington power transistors in a 14-pin DIP no less) has a suspicious bump on its head, so I will probably start by pulling it and see what changes (I hope that is it), and if that is the issue, I will also check the voltage clamping diodes in the output circuit and the stepper windings and the 7404 that drives it to make sure it wasn't collateral damage. I expect regardless of the cause, the dead short will be not *too* difficult to find and correct. So, now the saga of the Altos power supply is fully understood. It was the second drive from the DSD-440 that actually killed it. Fortunately, the DSD-440 power supply was apparently robust enough to put up with the abuse. With a little luck, I can make one whole SA-801 out of the pair (focusing on Y since I have no source for that 16270 ASIC), and then use the mechanism of X with the board from the Altos SA-800 to make a working SA-800 for the Altos. JRJ
Indianapolis: More classic computing equipment than I can shake a stick at.
Anyone who's passing through, or lives near Indianapolis, feel free to give me a shout to set up a time to peruse what I have. I have amassed enough machines to take on their own gravitational pull. Most are in various states of disrepair, in need of attention, but quite a few still work or don't need much work to be functional. A number of machines I intend on keeping for their neat factor (like an Olivetti M20) but might be persuaded to part with. Apple (bunch of IIc's, IIe's, IIgs's) Macintosh (40 or so compact Macs - 512, Plus, SE, 'splodey-battery-SE/30's -, a big 'ol stack of 68k and PPC desktops, PowerBooks, a stack of DuoDock II's) Kaypro (maybe 6?) Osborne Compaq Portables (luggable and plasma) Epson QX-10 (2 machines, 1 monitor, pretty certain I have the Valdocs disk somewhere) IBM (5150's, 5160's, and a 5170 with box, and a few monitors) Wang (PC S1-2 with keyboard/monitor(s)) Franklin 8000 with keyboard A few 386/486 machines ADM 3A terminal (doesn't power on, but it's cute) Amiga 2000HD (boots, but I don't have a keyboard or mouse, and the floppy drives continuously seek) Amiga 500 (untested, no power supply) C64's (definitely for parts!) and some drives Tandy 1000 EX (untested) NeXT 21 Color Monitor (too huge and heavy for me to keep, I'll be happy with a VGA converter when I find one) And probably a few other things I'm forgetting about. Price-wise, basically make me an offer. Scrap metal prices are fine with me for a lot of machines so long as they're not actually getting scrapped (hence the post here!). If you're looking for something specific, let me know and I'll see what I have. Thanks! Kind regards, -Maxx
Re: Indianapolis: More classic computing equipment than I can shake a stick at.
On Aug 23, 2015, at 13:52, Maxx Wood max...@gmail.com wrote: Amiga 2000HD (boots, but I don't have a keyboard or mouse, and the floppy drives continuously seek) If you're referring to a 1-track click each second, then that's normal for an Amiga. It's part of the disk change detection routine. There were lots of noclick utilities that patched the code to seek in one direction rather than back and forth, so that the clicking would stop once the heads reached the track 0 sensor. -- Mark J. Blair, NF6X n...@nf6x.net http://www.nf6x.net/
Re: Indianapolis: More classic computing equipment than I can shake a stick at.
Would you willing to ship the A500 up to Michigan? I'd give you a few bucks for it as a spare unit for the one I've got. Best, Sean On Sun, Aug 23, 2015 at 4:52 PM, Maxx Wood max...@gmail.com wrote: Anyone who's passing through, or lives near Indianapolis, feel free to give me a shout to set up a time to peruse what I have. I have amassed enough machines to take on their own gravitational pull. Most are in various states of disrepair, in need of attention, but quite a few still work or don't need much work to be functional. A number of machines I intend on keeping for their neat factor (like an Olivetti M20) but might be persuaded to part with. Apple (bunch of IIc's, IIe's, IIgs's) Macintosh (40 or so compact Macs - 512, Plus, SE, 'splodey-battery-SE/30's -, a big 'ol stack of 68k and PPC desktops, PowerBooks, a stack of DuoDock II's) Kaypro (maybe 6?) Osborne Compaq Portables (luggable and plasma) Epson QX-10 (2 machines, 1 monitor, pretty certain I have the Valdocs disk somewhere) IBM (5150's, 5160's, and a 5170 with box, and a few monitors) Wang (PC S1-2 with keyboard/monitor(s)) Franklin 8000 with keyboard A few 386/486 machines ADM 3A terminal (doesn't power on, but it's cute) Amiga 2000HD (boots, but I don't have a keyboard or mouse, and the floppy drives continuously seek) Amiga 500 (untested, no power supply) C64's (definitely for parts!) and some drives Tandy 1000 EX (untested) NeXT 21 Color Monitor (too huge and heavy for me to keep, I'll be happy with a VGA converter when I find one) And probably a few other things I'm forgetting about. Price-wise, basically make me an offer. Scrap metal prices are fine with me for a lot of machines so long as they're not actually getting scrapped (hence the post here!). If you're looking for something specific, let me know and I'll see what I have. Thanks! Kind regards, -Maxx
Re: Indianapolis: More classic computing equipment than I can shake a stick at.
@#%!^ Why is all this posted a full year after I leave Indianapolis and move to Belgium!? :D LOLOL I will ask my local contacts. On Sun, Aug 23, 2015 at 10:52 PM, Maxx Wood max...@gmail.com wrote: Anyone who's passing through, or lives near Indianapolis, feel free to give me a shout to set up a time to peruse what I have. I have amassed enough machines to take on their own gravitational pull. Most are in various states of disrepair, in need of attention, but quite a few still work or don't need much work to be functional. A number of machines I intend on keeping for their neat factor (like an Olivetti M20) but might be persuaded to part with. Apple (bunch of IIc's, IIe's, IIgs's) Macintosh (40 or so compact Macs - 512, Plus, SE, 'splodey-battery-SE/30's -, a big 'ol stack of 68k and PPC desktops, PowerBooks, a stack of DuoDock II's) Kaypro (maybe 6?) Osborne Compaq Portables (luggable and plasma) Epson QX-10 (2 machines, 1 monitor, pretty certain I have the Valdocs disk somewhere) IBM (5150's, 5160's, and a 5170 with box, and a few monitors) Wang (PC S1-2 with keyboard/monitor(s)) Franklin 8000 with keyboard A few 386/486 machines ADM 3A terminal (doesn't power on, but it's cute) Amiga 2000HD (boots, but I don't have a keyboard or mouse, and the floppy drives continuously seek) Amiga 500 (untested, no power supply) C64's (definitely for parts!) and some drives Tandy 1000 EX (untested) NeXT 21 Color Monitor (too huge and heavy for me to keep, I'll be happy with a VGA converter when I find one) And probably a few other things I'm forgetting about. Price-wise, basically make me an offer. Scrap metal prices are fine with me for a lot of machines so long as they're not actually getting scrapped (hence the post here!). If you're looking for something specific, let me know and I'll see what I have. Thanks! Kind regards, -Maxx -- -Jon +32 0 486 260 686
RE: De-yellowing
I can believe that the effect is only temporary--the action simply cannot go any deeper than a few microns. All of which goes to show that if you want a more permanent color, there's always paint. I have equipment that's made from high-density polyurethane foam (no special dies or forms needed for injection molding) finished with a coat of paint that's more than 30 years old. It looks as good as the day it was delivered. Chuck, I can tell you from personal experience that repainting does not work well. One, matching the color is nearly impossible. You can get pretty darn close but not exact. Two, the paint quality is never as good. Three, the feel is different - this one is hard to explain: it just doesn't feel smooth and slick but rough and scratchy. I have tried different brands of paint, gloss, non-gloss, sealant, etc to no avail. I can make it look good especially from a few feet away but in practice you can easily tell it has been painted. Just my two cents. -Ali
Re: Indianapolis: More classic computing equipment than I can shake a stick at.
A! Neat to know - that's exactly what it's doing. :) On 08/23/2015 06:32 PM, Mark J. Blair wrote: On Aug 23, 2015, at 13:52, Maxx Wood max...@gmail.com wrote: Amiga 2000HD (boots, but I don't have a keyboard or mouse, and the floppy drives continuously seek) If you're referring to a 1-track click each second, then that's normal for an Amiga. It's part of the disk change detection routine. There were lots of noclick utilities that patched the code to seek in one direction rather than back and forth, so that the clicking would stop once the heads reached the track 0 sensor.
Re: Indianapolis: More classic computing equipment than I can shake a stick at.
On 8/23/2015 1:52 PM, Maxx Wood wrote: Compaq Portables (luggable and plasma) I'm interested in Portable III's and floppy media for them. Let me know what you might have working and otherwise. thanks Jim
FS: PDP-11/55
Hi all, I have a PDP-11/55 for sale (Ottawa, Ontario, Canada). Bids open until 2015 09 15, buyer to arrange shipping, I will have it wrapped and ready to go. Please visit: www.krten.com/~rk/museum/index.html For pictures, detailed inventory and contact info. Sealed bids via eamil please. Winner will be notified 2015 09 16, machine will be ready to ship same day. Must be shipped / picked up no later than 2015 10 09. Sold AS-IS / where is, untested, unpowered since received. Comes with H960 rack and 2 side panels. Cheers, -RK -- Robert Krten Visit me at http://www.ironkrten.com
FS: PDP-11/55
Hi all, I have a PDP-11/55 for sale (Ottawa, Ontario, Canada). Bids open until 2015 09 15, buyer to arrange shipping, I will have it wrapped and ready to go. Please visit: www.krten.com/~rk/museum/index.html For pictures, detailed inventory and contact info. Sealed bids via eamil please. Winner will be notified 2015 09 16, machine will be ready to ship same day. Must be shipped / picked up no later than 2015 10 09. Sold AS-IS / where is, untested, unpowered since received. Comes with H960 rack and 2 side panels. Cheers, -RK -- Robert Krten Visit me at http://www.ironkrten.com
Re: De-yellowing
On 08/23/2015 09:53 PM, Ali wrote: I can tell you from personal experience that repainting does not work well. One, matching the color is nearly impossible. You can get pretty darn close but not exact. Two, the paint quality is never as good. Three, the feel is different - this one is hard to explain: it just doesn't feel smooth and slick but rough and scratchy. I have tried different brands of paint, gloss, non-gloss, sealant, etc to no avail. I can make it look good especially from a few feet away but in practice you can easily tell it has been painted. Just my two cents. Hi Ali, If you're talking about rattle-can painting, I can believe that. But there's painting using professional spray gear, as well as powder-coating. Rattle-can was never intended as anything but an any idiot can do it proposition. If that weren't the case, we'd all be painting our cars using a spray can. Regardless, if I read the conservation lists correctly, plastic is eventually doomed. No one seems to know how to stabilize it. I recall an Apple color monitor that sat on a table and, without being powered on or otherwise disturbed, would shed a bit of itself every now and then... Just my own .02, Chuck
