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APPLEBOX basic page about the used Powersupplies |
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| What are some good general Apple II power supply fix tries? Apple II power supplies can often be repaired. The bother involved varies considerably with the cause of malfunction. Note: The following refers more or less directly to II+ and IIe supplies; however, many of the ideas will work with the IIgs power supply as well. Note: Unless otherwise indicated, power should be turned OFF. A Short Open the case and check inside for indications of Coke spills, debris, etc.. If everything looks okay, continue on. If not clean away the mess; it could be causing a short. After cleaning (and drying), turn ON the power to see if the problem is fixed. Pull all cards from Slots and turn ON power. If the machine 'comes alive' one or more of your cards may have a short or may have been cross-socketed. Clean the contacts on each card (e.g. with alcohol). With power OFF, replug a card (be sure to line-up card and Slot contacts) and turn ON power. Do this for each card. If a card causes the machine to fail, it is, probably messed up. If no card produces a failure the original problem was, likely, a card which was not properly inserted. Bad Power Cord Unplug and replug the power cord at the point where it connects to the IIe. Turn ON power. Try wiggling the power cord. If the Power Supply comes ON at any time, try substituting a power cord from a known-working IIe. If this fixes the problem, you can be pretty sure that the problem was a power cord with a broken wire. Poor Power Supply Connector Connection Unplug and re-plug the Power Supply cable to the motherboard. Turn ON power. If the machine seems to respond, or responds when the connector is wiggled, you probably have a dirty or loose connection. Clean the power supply plug and socket with an alcohol swab. Using longnosed pliers slightly re-crimp the 'holes' on the socket (or, insert a jeweler's screwdriver into the space between each hole and the plastic casing and twist). The idea is to restore a firm grip for all contacts. Another possibility is a loose or broken socket solder connection to the motherboard. The repair is to remove the motherboard and re-solder the connections to the socket. Bad Switch It is fairly easy to identify a bad switch-- it will, usually, not snap cleanly into position, feel crunchy, and/or have a burn spot. The repair is to replace the switch with some AC power switch that will fit. Or, you can permanently connect the switched lines and add an in-line switch to the power cord. Blown Fuse Some power supplies may have a fuse. Open the power supply. Look for a fuse mounted to the circuit board. If there is one, check it. An Ohm meter can be used to check for continuity if it is not obvious that the fuse is blown. If the fuse is blown, replace it. Bad "Globar" Element Look toward the end where the power cord is connected. Somewhere close to the place where wires from the switch go to the circuit board there should be a small disk-shaped component which is not a disk capacitor. Probably, it will be black with no markings. This is a "globar" resistor. Check it to be sure that it is not cracked and that both leads are really connected to the disk. If the globar element is broken or if a lead has popped off, you will need to get a replacement from an electronics supply shop. (Tell the shop person where the globar resistor comes from and describe its size.) Blown Electrolytic Capacitor(s) On the end of the circuit board near the Switch are some relatively la shrink-wrapped grey or light-green covers on which there are markings). Usually, they are the same size and have the same uF value and Voltage rating. One (or more) of these may be obviously blown or may just show some slime near the base. If you find something like this, the suspect capacitor should be replaced by one of the same (or slightly larger) uF value with the same (or larger) Voltage rating. Size and shape are, also, important in order to get a good fit. When removing the bad cap, be sure to mark the "+" side on the board-- use the markings on the cap's cover to identify the "+" side. Install the replacement cap with its "+" lead in the marked hole. Note: Also see the fix in the next Q&A and the C7 fix discussion in Q&A 012. Messed-up or 'Dirty' Adjustment The power supply may have a mini-potentiometer mounted on the circuit board for fine-tuning voltage output. Usually, it will be somewhere near the end opposite the Switch and will have a slotted plastic 'knob'. If there is such an adjustment, mark its current position and, then, turn it back and forth. (If you have some Radio Shack, etc. 'Circuit Cleaner', into the mini-pot first is a good idea.) Set the adjustment a bit to one side of the original setting and plug in the power supply. If it now seems to work the problem was a 'dirty' voltage adjustment control. Check the voltage on the +5V line with a meter and adjust it to 5 Volts. (Note: no output due to a dirty adjustment control seems unlikely. Incorrect output is more probable; and, this could cause a IIe to not work.) Beyond the above, you are, most likely, looking at a bombed electrolytic capacitor which is not obviously bad, a blown resistor (which may be easier to spot), or a blown main power transistor (the big silvery thing mounted on a heatsink). Unless you enjoy more involved electronic testing and repair work, your best course is, probably, to get a replacement power supply. |
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Power Supplies & Cooling 001- What's the pinout and load specs for the IIgs Power Supply? 002- Are the power supplies for the ][+ and IIe interchangeable? 003- What are the output capabilities of GS and IIe power supplies? 004- Can I use a 'generic' surplus power supply in my Apple II? 005- How do fatter leads reduce noise on the +5V & +12V lines? 006- Is there any more that can be done to eliminate glitches? 007- Is there a power supply upgrade kit for the Apple IIgs? 008- What kind of internal fan can I install in an Apple IIgs? 009- Why do so few GS power supplies have a fan installed? 010- What are some good Apple II power supply fix tries? 011- Some of our classroom IIe's don't work at all. Is there a fix? 012- Why does my Apple IIe often fail to turn on?! 013- What does a rapid chirping noise on a GS power supply mean? 014- How do I fix a nearly dead GS power supply? 015- What is a "Buggie Power Supply"? 016- Do I need the metal shielding in my GS case? 017- My System Saver IIgs has gotten very noisy. How can I fix it? 018- My System Saver IIgs panel feels springy? Is there a problem? 019- Can an overloaded power supply affect IIgs sound? 001- Does anyone have pinout and current ratings info for the Apple IIgs Power Supply? 7 - 5 Volts 0.25 Amps 6 -12 Volts 0.25 Amps 5 +12 Volts 1.0 Amps 4 + 5 Volts 4.0 Amps 3 --nc-- 2 GND 1 GND The Power Supply connector pins are numbered as above. When you are sitting in front of the computer, pin 1 is nearest you. (i.e. pin 7 is nearest to the back of the motherboard). ____________________________ 002- Are the power supplies for the ][+ and IIe interchangeable? Yes. The plugs are the same and the ratings are the same and they look alike. Aside from, possibly, needing to add mounting holes for particular models, you should be able to swap ][+ and IIe power supplies whenever you wish. ---------------------------- 003- Could someone compare the output capabilities of the GS and IIe power supplies? Okay. This is from information presented in GS and IIe manuals: PS Connector Output Max. Output Current Pin# (GS/IIe) Volts (GS/IIe) 7/6 - 5 V 0.25 Amps /0.25 Amps 6/5 -12 V 0.25 Amps /0.25 Amps 5/4 +12 V 1.00 Amps /1.50 Amps 4/3 + 5 V 4.00 Amps /2.50 Amps 2/2 GND 1/1 GND ---------------------------- 004- Can I use a 'generic' surplus power supply in my Apple II? Sure. Check out the power supplies listed in the MPJA, JDR, Jameco, and similar catalogs. Mainly, you are looking for a relatively compact switching power supply which fits the following guidelines: 1- all four Voltages (+/- 5V and +/- 12V) are available* 2- the power supply can be fitted into your Apple II 3- the +5 Volt output is rated at 5-10 Amps 4- the +12 Volt output is rated at 1.5-3 Amps 5- price is no more than $25 * Except for PC power supplies, good four-output models with a -5V output seem to be rare. You can add a simple -5V regulator circuit to the -12V output to obtain -5V. As more and more new surplus power supplies are dumped, part of your shopping challenge is finding one which is _small_ enough to work well with the Apple II. This explains the price guideline. If a unit costs more than $20, the odds are pretty good that it's too big physically or electrically. Too big electrically? In general, power supplies need to be loaded in order to do a good job of regulation. A 25-Amp output which is called upon to deliver 1 or 2 Amps is more likely to exhibit problems with feedback and regulation than were it asked to deliver, say, 5 or 6 Amps. An Apple II with a few power-sucking Slot cards will work fine with many PC power supplies; a base system with no cards could have problems adequately loading some PC supplies. Your best choice for an in-the-case replacement is likely to be some $10-$15 unit rated at a total of less than 125 watts which was originally designed to power a printer, monitor, or portable PC. Probably, it will be "open frame" with no case, switch, fan, or power cord. Installing a power supply unit-- i.e. one not specifically designed for the Apple II-- inside your Apple II can involve a fair amount of work. fixing up a way to mount the On/Off switch and AC cord socket in the usual power supply opening in the back of the case. (Mounting the stuff on a small plastic panel set into the opening worked fine.) The power supply board itself mounted nicely on spacers in the space provided for the standard PS. Once the AC and various DC lines were connected, the new PS came on-line without a hitch. Our II+ hasn't had any power supply problems since. ____________________________ 005- Could you please explain how adding thicker wire will decrease noise on the +5V and +12V lines? I received and installed my new "Heavy Duty" A2 power supply and get the same results with my Second Sight board as before-- it still locks up the computer on boot-up. The leads coming from most Apple II power supplies have a low resistance-- much less than 1 Ohm. (Thanks to Michael Mahon for driving home this point!) Even so, as a user piles on peripherals and the current load increases, a wire lead's resistance may prove to be too high to allow maintaining proper operating voltages and low system noise-- e.g. you routinely get "FATAL SYSTEM" errors. A good indicator of power problems is a noticeable drop in voltage on the +5V line as measured on the motherboard. Instead of the 4.9V - 5.0V typical for a light load, it will be 4.7V or lower. Measurements and experiments with standard IIgs power supplies indicate that the actual DC voltage drop through the 18 gauge +5V and Ground leads is only (approximately) a total of 0.04V at 3Amps, which is what a moderately "loaded" IIgs system will draw. The explanation for getting a drop of 0.2V - 0.4V or greater appears to be power supply regulation error. Some standard (and "heavy duty") Apple II power supplies with 18 gauge leads will hold at-motherboard voltage to around 4.9V at 3-4 Amps and some won't. It is easy to see that a system designed to work at 5 Volts will eventually begin to malfunction as the available voltage drops by half a volt or more. In fact, any actual computer system would be likely to experience crashes long before the average, measured at-motherboard voltage got down to 4.5 Volts. A voltmeter reading at the motherboard does not show instantaneous spike or "noise" voltages. Each time a circuit switches, there is a change in current drain. Quite a few circuits are switched with each main system clock transition; so, the change in current can be substantial at 1 x and 2 x main clock frequency. Other events, like turning ON a disk drive, can also produce brief up or down shifts in current drain. Either way, you have brief changes in voltage across the power supply and its leads. The brief voltage changes are called "spikes" because they are VERY brief. The larger the current shift and the greater the effective resistance of the power supply plus its leads, the higher the spike voltage generated. Since these spikes are in series with the circuits connected to the PS and since they are difficult to eliminate via bypass capacitors, they propagate throughout the system. Even worse, as current draw increases and spike voltage increases, atmotherboard supply voltage decreases. So, you have a 'double whammy': the lowered supply voltage reduces IC noise immunity just when you need it most. At some point, noise spikes appear which cause latches, memory IC's, etc. to switch state. If the latch is on a RAMfast, you may get a disk read error. If a memory chip is affected, data will be corrupted, program instructions may change, ....; in short, your computer is likely to malfunction. All of which is bad enough; but, there may be another negative affect when noticeable system noise appears 'across' the power supply. How many csa2 posts complain about GS power supplies that crater "for no reason" after just a couple months? How many users seem to be on eternal quests for a solution to PS woes? Reducing the noise may significantly extend the life of your Apple II power supply. Power supplies with noticeable regulation error often benefit greatly from heavier leads, especially for +5V and Ground. Reducing the actual drop through the lines reduces the resulting error; and, at-motherboard voltage is back to 4.8V or better under high loads. The heavier leads also reduce noise. Whether or not tighter regulating power supplies benefit significantly from swapping in heavier leads is an open question. At high switching frequencies the power supply's leads will have a higher effective resistance and the spike voltages appearing across the power supply output will be larger. If you notice otherwise 'mysterious' system glitches despite having a good, solid looking power supply and/or that power supplies tend to crater when connected to your Apple II, swapping in heavier leads may be a good idea. Our current GS power supply is the one which came with the computer when it was purchased in the Fall of 1986. Yes, our GS was plugged into a System Saver IIgs fairly early on; but, then, line deglitchers have been a nearly universal accessory since the mid-1980's. The main difference between our power supply and the piles of blown units is that fattened +5V, Ground, and +12V leads were added back when we upgraded to an accelerator board. Despite having also added a Focus Hard Card drive, RamFAST SCSI interface, and a couple other boards, system crashes are very rare-- perhaps one every 8-10 sessions (and those usually relate to a fault in the software). The 'bottom line' is that, so long as the power supply is not actually defective, real world experience supports fattening at least the +5V and Ground power supply leads as a major step in curing crashes due to system noise. (See also Marvin Miller's GS WorldView article: "I Did the IIgs PS Mod, and the glitches are gone!" at http://apple2.org.za/gswv/a2zine/Sel/IdidThePSmod.html .) ____________________________ 006- Fattening my GS's power supply leads greatly reduced system crashes. Is there any more that can be done to eliminate glitches? Yes. There is another weak link in the power delivery 'chain': the motherboard circuit traces supplying power to Slot boards are fairly skimpy, especially on ROM-01 boards. A heavy power user, such as a soupedup Transwarp accelerator board, in Slot 7 can produce significant noise up and down the entire Slot 'backplane'. The cure is to remove the motherboard and tack on #18 - #16 gauge jumper leads. (See Question 007 for details.) ---------------------------- 007- Does anyone here remember the Mac SE upgrade kit that included 18-ga wire, a bunch of new caps and other fun stuff, that increased the computer's amperage and allowed more upgrades, also fixed many problems? Is there a power supply upgrade kit for the Apple IIgs that someone has constructed? Okay; here is your very own A2-2000 On-Line Power Supply Mods Kit! Swapping-in fat leads is, technically speaking, a pretty simple job. You pop out the power supply, open it, unsolder old +5, +12, and Ground leads, solder in the new leads, close and replace the power supply. The tricky part is what hackers call the "mechanics". First, #12 or #14 gauge wire is not very flexible. Getting stranded wire (instead of solid) helps. Probably, #14 gauge is more than fat enough for all three leads. One case where #12 or #10 gauge may be worth the extra trouble is the +5V lead. Use wires colored the same as those you replace. On the standard connector, the first two leads are Ground. Almost always, these are black. Next, there is a space, then, in order +5, +12, -12, -5. Depending on the bother involved, you can unwedge the wire bundle where it passes through the supply case and remove the three old wires (+5V, +12V, and one Ground wire). Or, you can just cut away each old lead. Leave the -5V and -12V leads and one Ground lead alone. Getting to the PS circuit board involves some work. After removing the mounting bolts, you will have to scooch up the board in order to get to the bottom side. This will be easier if the wire bundle has been unwedged. Another hurdle is soldering to the circuit board. Once the old leads and excess solder are removed, you will probably find that the holes are too small! A jeweler's screwdriver makes a good hand drill for enlarging holes. (Drill from the circuit side. Be careful not to tear or dislodge the printed circuit.) The new leads should be routed through the unused fan slots. (If a fan is attached, remove it. It's in the wrong place to do much good in cooling your GS.) Note: If you have a fan mounted to the PS and you wish to keep it, then, it will be necessary to enlarge the original cable exit hole. A sheet metal "munching" tool should let you do this without having to entirely remove the PS circuit board. (Just be sure to catch all of the munched pieces!) When routing the leads be careful not to place a twisting force on a lead where it is soldered to the circuit board. To get to each spronger (contact) in the plug, press on it through the slot on the side near the wire end. This pushes up a small retaining tab so that pulling on the attached lead will pull out the spronger. Cut off the old lead, clean the end, and solder on the new lead. Press the spronger back into the plug. To avoid mixups, it's best to complete the process for each lead before doing the next. When plugging in the power supply, take time to shape and arrange the wires to minimize stress on the motherboard. Motherboard Mod Fatter +5, +12, and Ground leads should protect you power supply and reduce circuit noise. If audio noise in your stereo card output and/or system bombing due to noise glitches were problems, they may be eliminated. A lot depends upon which cards you've installed, which slots they are in, and whether your IIgs is a ROM-01 or ROM-03. The motherboard circuit traces supplying power to each Slot are fairly skimpy, especially on ROM-01 boards. A heavy power user in Slot 7 can produce significant noise up and down the entire Slot 'backplane'. The cure is to remove the motherboard and run leads to a couple Slots ... First, flip over the motherboard and get oriented. Below is a quickie sketch showing the Power Connector points as well as key power pins for a Slot. The view is from the _Bottom_ with the _Back_ of the motherboard facing you: Bottom of Motherboard Power Connector Socket Slot X GND +12V (pin 50) X X (pin 1) X GND X X . X +5V . X +12V . X -12V X -5V X X GND (pin 26) X X (pin 25) +5V .... Ground Plane Area (plug shields, etc. connected here) .... | |______________ Back Edge of Motherboard _________________________ Motherboard Mod Fatter +5, +12, and Ground leads should protect you power supply and reduce circuit noise. If audio noise in your stereo card output and/or system bombing due to noise glitches were problems, they may be eliminated. A lot depends upon which cards you've installed, which slots they are in, and whether your IIgs is a ROM-01 or ROM-03. The motherboard circuit traces supplying power to each Slot are fairly skimpy, especially on ROM-01 boards. A heavy power user in Slot 7 can produce significant noise up and down the entire Slot 'backplane'. The cure is to remove the motherboard and run leads to a couple Slots ... First, flip over the motherboard and get oriented. Below is a quickie sketch showing the Power Connector points as well as key power pins for a Slot. The view is from the _Bottom_ with the _Back_ of the motherboard facing you: Bottom of Motherboard Power Connector Socket Slot X GND +12V (pin 50) X X (pin 1) X GND X X . X +5V . X +12V . X -12V X -5V X X GND (pin 26) X X (pin 25) +5V .... Ground Plane Area (plug shields, etc. connected here) .... | |______________ Back Edge of Motherboard _________________________ A good way to make sure you know what's where is to use an Ohm meter to check Resistance from pin 26 (GND) to a metal plug shield near the back of the motherboard. (Set your meter to Ohms X1. Touch one meter lead to pin 26 and the other to a metal plug shield. Resistance should read nearly zero. Reverse the leads and repeat the check. Again, Resistance should read nearly zero.) Repeat the check for R between pin 26 and the GND points on the Power Connector socket. R should be nearly zero. Using a marker pen or white-out, mark pin 26 (GND) on Slots 3 and 7. Also mark the GND points of the Power Connector socket. GND: On the bottom side of the motherboard, connect a Black #16 gauge wire from one of the Ground points of the Power Connector socket to the Ground plane area near the back of the motherboard. Run a short Black #16 gauge wire from pin 26 of Slot 3 to the Ground plane; run a short Black #16 gauge wire from pin 26 of Slot 7 to the Ground plane. (You may need to scrape through green insulating lacquer to solder to the Ground plane area.) +5V: On the bottom side of the motherboard, connect two #16 gauge Red wires to the +5V point of the Power Connector socket. Connect the other end of one +5V Red wire to pin 25 of Slot 3; connect the other end of the second +5V Red wire to pin 25 of Slot 7. +12V: If you have any cards which are likely to draw heavily on the +12V line, then, on the bottom side of the motherboard, run a #18 gauge White wire from the +12V point of the Power Connector socket to pin 50 of the Slot in which the card is normally located. Otherwise, just run an #18 gauge White wire from the +12V point of the Power Connector socket to pin 50 of Slot 7. Check your connections. One quick check is that the GND and +5V wiring to Slots 3 and 7 should be Black, Red (moving left to right) and Slots 3 and 7 should 'look the same'. Any +12V wire should be on the same side of the Slot (i.e. the same column of pins) as GND. None of the wires should be connected to a middle pin on any Slot. Notes: 1. All wires are insulated. 2. When cutting wires, allow enough slack to permit routing each wire. You want to avoid having a wire rest against pointy connections on the motherboard. Route wires away from motherboard mounting holes and around places where the bottom of the case supports the motherboard. 3. The case's bottom and back metal shields are something of a shorting hazard. Replacing the motherboard is much easier if these shields are popped out and ditched. Once everything checks out, replace the motherboard taking care that no wires are caught between a support point and the motherboard. ____________________________ 008- I would like to install an internal fan in an Apple IIgs. I pulled a good looking fan from an old PC power supply. It is an NMB "FLOW MAX" rated: DC +12V @0.14 Amps. Is this fan okay? How do I connect it? The voltage rating is fine, the amperage level should be fine as well. You can connect the fan to the two-pin connector near the back left side of the motherboard. The pinout for the "Fan connector" is +12V and Ground. The +12 is the pin closest to the powersupply, or the pin on the left if you are facing the GS motherboard from the front end. Most fan wires are color coded, so the red wire goes to power and black to ground. ____________________________ 009- Why do so few GS power supplies have a fan installed? Most users depend upon System Saver GS to handle cooling because the GS case is not designed to take advantage of an internal fan. With a fan mounted on the power supply, you can, mainly, blow air around inside the case. The fan is not much good for drawing in cool air from outside or pushing hot air out. Another problem is noise-- both the kind produced by a fan when its bearings begin to go and electrical noise which degrades the quality of sound output. The fan uses the +12V pins which are needed for simple installation of a popular sound digitizer card. A fan mounted on the PS case could prevent plugging long circuit boards into Slot 1 and, possibly, Slot 2. Perhaps, as Charles Plater seems to suggest, there is some reason for an internal fan. Mounted on the power supply (which is the only place a mounting point is available), a fan could blow some air into the power supply. Supposedly, this could extend power supply life. Still, many users have 11 year-old GS's with original power supplies which continue to work fine with no internal fan. Basically, a PS-mounted fan in a GS appears to be the cure for a problem which has yet to be discovered. ---------------------------- 011- Some of our classroom IIe's don't work at all. There is no beep and nothing on the monitor. Do the power supplies need to be replaced? Maybe not. My experience with a couple Australian Platinum //e's indicates that you may be able to repair the power supplies. The power supply in the //e's I fixed is made by Dyna Comp, Inc. for Apple, model no: 699-0136. Ratings are as follows: Input 240V/50Hz, Output +5V/4A, +12V/1A, -5V/.25A, -12V/.25A. Measuring the voltages on the //e motherboard I get +5V= +1.3V, +12V= +2.8V, -5V= -4.3V. If I disconnect the power supply connector from the motherboard and switch it back on, I measure the correct voltages on the connector. The fault is caused by one or two failed 1uF 35V 85deg small electrolytics. The location of each is as follows: o- 103mm (4.1") from the back, and 27mm (1") from the left of the circuit board o- 163mm (6.4") from the back, and 10mm (0.4") from the left of the circuit board. I checked each of the ones I removed. they measured less than .05uF. The fix is to replace each capacitor with a 1uF 35V or higher rated electrolytic-- if there is no "+" indication on the circuit board, mark the plus side before removing the old capacitor. I used 1uF 50V 85deg as that's what was in my parts bin. (You may need to clean up some gunk leaked onto the board by the old capacitors.) ---------------------------- These are called "kickstart capacitors" in switched mode power supply (SMPS) technology circuit descriptions. If you ever get an SMPS in with tripping or low output voltage or amperage, change all small value electrolytic capacitors (below 330uF and 35v) with high temperature capacitors (105 degree centigrade). ____________________________ 012- My Apple IIe usually fails to turn on! I have to turn its power switch on and off several times and sometimes wait a long time before it finally powers up! If the power supply you are working on is an ASTEC brand the most common problem is the 10V 220 uf capacitor located about 1 inch to the rear and left of the transformer. I find this to be the cause in about 80 pecent of the ones I repair. Use a 25V 220uf capacitor as a replacement and chances are real good that it will not fail again. ---------------------------- If you open the power supply up (WITH THE MAINS PLUG OUT!) you will find a capacitor C7 near the transformer in the middle of the printed circuit board (a 220 uF 16V capacitor if I remember correctly) change it for a 220uF 25V 85 degree Centigrade rated capacitor and it should clear the problem up. ---------------------------- I've been trying to fix several dead Apple II power supplies from a local school and have managed to bring back one from the dead now. The fix was to replace the 10V, 220uF electrolytic cap with a new one. (I used a 35V piece). Assuming that the board markings are useful, this was C7, on an Astec board with the datecode "T8312" on it. I'm curious if anyone else that has replaced that cap has noticed any browning of the pc board where the leads enter from that 27ohm 2W 'R4' beast. .... ---------------------------- Very interesting! A bad C7 would screw up the regulator's feedback voltage. Even better, Jeff Allen's observation of the heat spot on the PCB seems to indicate that heat from the nearby 27 Ohm power resistor is responsible for shortening C7's life. If there is some way to eliminate this hot spot-- e.g. using a 10W resistor, perhaps with a heatsink attached, or mounting the resistor on the power supply's metal case-- many II+ and IIe power supply crashes might be prevented. ____________________________ 013- To my horror, this morning when I flipped my GS ON it emitted a rapid chirping noise (maybe 8-10 times a second) and refused to start!? The chirping usually means that the PS load-detect circuit thinks that the load is too great (i.e. that it draws too much current) or that there is an 'open' in a major output line (i.e. that there is, practically, no load at all). This can mean that the power supply is bombing and, so, almost any load is too great. It may, however, mean that a short has developed on the motherboard or on a Slot. It can, also, mean that a break has developed somewhere in the +5V line or at the connection of the connector to the motherboard. One test is to unplug the power supply, remove it, and do some load tests. (Note: If the PS has a slotted adjustment pot, mark its position and, then, turn it back and forth in case it has become stuck at a dead spot on the control.) If you open the power supply up (WITH THE MAINS PLUG OUT!) you will find a capacitor C7 near the transformer in the middle of the printed circuit board (a 220 uF 16V capacitor if I remember correctly) change it for a 220uF 25V 85 degree Centigrade rated capacitor and it should clear the problem up. ---------------------------- I've been trying to fix several dead Apple II power supplies from a local school and have managed to bring back one from the dead now. The fix was to replace the 10V, 220uF electrolytic cap with a new one. (I used a 35V piece). Assuming that the board markings are useful, this was C7, on an Astec board with the datecode "T8312" on it. I'm curious if anyone else that has replaced that cap has noticed any browning of the pc board where the leads enter from that 27ohm 2W 'R4' beast. .... ---------------------------- Very interesting! A bad C7 would screw up the regulator's feedback voltage. Even better, Jeff Allen's observation of the heat spot on the PCB seems to indicate that heat from the nearby 27 Ohm power resistor is responsible for shortening C7's life. If there is some way to eliminate this hot spot-- e.g. using a 10W resistor, perhaps with a heatsink attached, or mounting the resistor on the power supply's metal case-- many II+ and IIe power supply crashes might be prevented. ____________________________ 013- To my horror, this morning when I flipped my GS ON it emitted a rapid chirping noise (maybe 8-10 times a second) and refused to start!? The chirping usually means that the PS load-detect circuit thinks that the load is too great (i.e. that it draws too much current) or that there is an 'open' in a major output line (i.e. that there is, practically, no load at all). This can mean that the power supply is bombing and, so, almost any load is too great. It may, however, mean that a short has developed on the motherboard or on a Slot. It can, also, mean that a break has developed somewhere in the +5V line or at the connection of the connector to the motherboard. One test is to unplug the power supply, remove it, and do some load tests. (Note: If the PS has a slotted adjustment pot, mark its position and, then, turn it back and forth in case it has become stuck at a dead spot on the control.) If the PS can deliver +5V with a 3 Ohm power resistor connected across the +5V and Ground lines, +12V with a 15 Ohm power resistor connected across the +12V and Ground lines, and correct Voltage for -12V and -5V lines into, say, 100 Ohm resistors, then the PS is likely to be okay. If the PS starts to chirp when even small loads are applied (e.g. 10 Ohms across the +5V output), then it has one or more bad components or is badly off-adjustment. If it has an adjustment, try cleaning the control and retry the load tests after a small change in the adjustment setting. If the chirping persists, replacing the unit with a new A2 power supply, a module from Jameco, etc. or a Buggie external PS may be the easiest cure. ____________________________ 014- My GS power supply seems to be nearly dead! The only odd looking symptom so far is that one of the big electrolytic capacitors near the power input side is at 260 volt & the other is at 30 volt?! There is a 100k bias resistor in the front end of the inverter. If this resistor is broken, loose, or otherwise 'open' you will get the symptoms described. Replace the resistor and both capacitors should be at the same voltage ( approx 140 volt) and within the 200 volt working rating of the capacitors. This should fix the power supply. ____________________________ 015- What is a "Buggie Power Supply"? It is an external power supply, usually a surplus PC unit, which connects to the Apple II via a heavy-duty cable. My IBM-style power supplies generate the same voltages (+5v, +12v, - 12v, -5v) as those required by the Apple II. But IBM-style power supplies deliver 150-200 watts of power, more than twice the weak output of the standard 60 watt Apple II power supply. Thus, problems associated with weak power (screen freezeups, crashes) in the Apple can be reduced or eliminated by using an IBM power supply on the Apple. With a strong IBM power supply, you can fill all your interface card slots or add extra disk drives without overloading the power source. Recently, I have offered these power supplies for Apple II: IBM 150 watt power supply, soldered to 5 ft cable; choice of either IIgs or IIe plug. $27.00 plus $5.00 UPS shipping ($8.00 shipping to Canada) Cable-only: connects to IBM power supply at power-points P8, P9, and Molex- 4. Allows you to connect the IBM power supply you already own to an Apple II (Specify whether IIgs or IIe plug is needed). $14.00 plus $3.00 priority mail; To Canada: US$4.00. Above cables made with heavy duty wires (AWG-18, with 600v insulation; color-coded. All power supplies and cables thoroughly pre-tested prior to shipping.) 200 watt power supplies occasionally available at $3.00 extra cost, but an extra 3-4 weeks must be allowed. Eight page illustrated instruction manual sent with each order; also the manual is available on self-booting text-file disk. Faster service! During the past month, users have had to wait 2-3 weeks from payment to shipment. More power supplies have arrived, and I have ordered the cable components in larger quantities, so through the remainder of the summer I expect to ship the orders within 4-7 days. Steve Buggie buggie@unm.edu 200 College Rd. (505) 863-7504 office Gallup NM 87301 (505) 863-2390 home ____________________________ 016- Does the metal R/TV interference shielding in my GS case matter? I've done some testing. The Radio/TV interference shielding mattered, at least for all the people around in my former dorm. ---------------------------- My tests were done in a separate dwelling (i.e. not an apartment, dorm, etc.) and focused upon effects in our 'Computer Room'. Turning ON the GS produces some interference with or without shielding and the level seems to be the same. One problem with R/TV interference is that its level and kind is dependent upon many factors. For example, I can get virtually complete elimination of GS-produced Radio station interference by simply turning ON a printer connected to our PC! Each user will have to weigh the trade-offs for his/her situation. Removing the shielding eliminates a dust trap and improves air flow. It is easier to pass cables through case slots; and, if you need to remove the motherboard (to make repairs, add Slot jumpers, etc.), removing the bottom shield removes a shorting hazard when the board is re-installed. If you remove the lid and do not like the way Radio or TV reception is affected, leave the shielding alone. If the result is acceptable, scrap the shielding. ____________________________ 017- My System Saver IIgs has gotten really noisy. How can I fix it? It may be that the fan inside the unit is showing wear. The good news is that replacing the fan is an easy and rewarding task. I knew my fan was starting to die when it sounded like it was wheezing during spin-up. The fan, a Sprite model SU2C7, uses sleave bearings, whose lifespan is determined by the lubricating oil supply in the bearings. When enough of the oil evaporates, metal will grind against metal resulting in heat and resistance that cause the fan to quickly lock-up. Better quality fans use ball-bearings, but Kensington apparently used the cheapest component available. Even among the models with sleave bearings, the SU2C7 is the least capable. It can only move 18 cubic feet of air a minute (half what a typical PC fan moves) and has a 55,000 hour rating. In looking for a replacement for my dying fan, I chose to use a better model. The Sprite model SU2B1 has the same dimensions as the SU2C7 used in the System Saver and is readily available from Digi-Key corporation. It uses ball bearings for long life (the fan is rated for 73,000 hours) and can move 34 cubic feet of air a minute. The higher quality is readily apparent: the replacement is currently noticeably quieter than the original even though it is moving more air per minute. To replace the System Saver fan, first make sure the System Saver AC power cord is unplugged. Next, you will need to open the case. Opening the System Saver case involves removing eight screws. You can remove the foam weatherstriping along the periphery of the case to expose the screws OR you can poke through/around the foam at each screw hole. The screw access holes are arranged as shown in the following diagram (bottom view of the System Saver): Once inside, the fan can be removed by unplugging the power cord that connects it to the circuit board. A grounding wire that is attached by a screw must also be removed. The fan itself is held to the case by two screws. Once you remove the SU2C7, you can replace it with the SU2B1. Now mount everything back together again with the screws. Apply new foam mweatherstripping if necessary. The refurbished System Saver is now better than a factory new model! Notice the difference in sound: a quiet hum rather than a load rumble. If you have a lot of cards, you will notice that the inside of the IIGS is alot cooler too. An upgraded System Saver is a great way to counteract accelerator instability caused by heat. Sources and parts needed: 1) Part: Sprite model SU2B1 (Digi-Key Part No. CR103-ND) Source: Digi-Key Corp. (1-800-344-4536/www.digikey.com) Note: Check below for other fans that will work. 2) Part: Foam weatherstripping tape (3/8th inch width, 3/16th inch thick) Source: Home Depot (or a comparable hardware store) ---------------------------- The fan I removed from my System Saver IIgs is the Comaire-Rotron Sprite SU2C1-- 'C1, not 'C7. Actually, out of the case, it seems very quite. Much of the noise seems to be rattle from contact with the plastic case of the SS ... I put down some foam weatherstrip along fan-case contact points and that did the trick! I guess there was a bit of vibraction or something. The fan is stil audible, but only slightly from the air. ---------------------------- Below are specs, ordering numbers, and prices for several possible System Saver IIgs replacement fans. As you can see, the noise numbers for the sleeve bearing fan models originally used in System Saver IIgs are not bad. The catch is that the numbers are for new units before bearing wear begins to increase noise. If you replace your fan, a ball bearing model is recommended. Digi-Key 800-344-4539 Mouser 800-346-6873 Newark 800-463-9275 cfm = cubic feet per minute of air moved |
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