Path: news1.icaen!news.uiowa.edu!news.physics.uiowa.edu!math.ohio-state.edu!news.cis.ohio-state.edu!newsfeed.berkeley.edu!cyclone.swbell.net!typhoon01.swbell.net.POSTED!not-for-mail Message-ID: <370BA2FC.CE633107@swbell.net> From: Rubywand Reply-To: rubywand@swbell.net X-Mailer: Mozilla 4.51 [en] (Win95; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.sys.apple2 Subject: Re: //e power supply References: <3704c09f.22344937@news.zipworld.com.au> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 170 Date: Wed, 07 Apr 1999 13:25:00 -0500 NNTP-Posting-Host: 207.193.9.84 X-Complaints-To: abuse@swbell.net X-Trace: typhoon01.swbell.net 923509360 207.193.9.84 (Wed, 07 Apr 1999 11:22:40 PDT) NNTP-Posting-Date: Wed, 07 Apr 1999 11:22:40 PDT Organization: SBC Internet Services Xref: news1.icaen comp.sys.apple2:146657 Jlogo writes ... > > Just recently one of my Platinum //e's power supplies appears to have > failed. When I switched on my //e the system responded normally but > after I turned it off then turned it on again (rather quickly - maybe > this caused the problem?) it no longer shows any power on indicator > from the front keyboard. Is it possible that the power supply is > overloaded or short-circuited?. > > BTW, The power supply is a silver coloured one and looks very similar > to the IIgs one. I just wish these power supplies were'nt so flaky - > this is the second //e power supply that I've used which quit working. .... Here is some information which may help ... >> 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. 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 long-nosed 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 resister comes from and describe its size.) Blown Electrolytic Capacitor(s) On the end of the circuit board near the Switch are some relatively large electrolytic capacitors (typically these are tubular aluminum things with 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 C7 fix discussion in next Question. 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 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. ____________________________ From: O Aaland 012- My Apple IIe 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. ---------------------------- From: Stephen Shaw 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. ---------------------------- From: Jeff Allen 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. .... << Rubywand