💾 Archived View for mirrors.apple2.org.za › archive › apple.cabi.net › FAQs.and.INFO › CPUandMore › … captured on 2023-05-24 at 23:47:03.
⬅️ Previous capture (2023-01-29)
-=-=-=-=-=-=-
Path: blue.weeg.uiowa.edu!news.uiowa.edu!uunet!tcsi.tcs.com!agate!msuinfo!harbinger.cc.monash.edu.au!yarrina.connect.com.au!werple.apana.org.au!boombox.apana.org.au!tlp!peterm
From: peterm@tlp.apana.org.au (Peter Maloney)
Newsgroups: comp.sys.apple2
Subject: Re: IIe power supply problems
Message-ID: <JVg1Rc1w165w@tlp.apana.org.au>
Date: Fri, 02 Sep 94 16:53:18 PDT
References: <1994Aug31.162618.1101@sandia.gov>
Organization: The Lower Planes BBS
Lines: 45
kjhass@sandia.gov (Joe Hass) writes:
>
> Wizards of the Net:
>
> I'm trying to help a local elementary school keep their IIe's running and
> have found what appears to be a bad power supply.
>
> The machine will boot properly when it's warm but the power supply won't
> come up if it's cool. When it's cool the +5 output is at about 1.1V, the
> -5 is at about -1.1V and the +/- 12V outputs are proportionately low.
> Sometimes, if it's not too cool, the voltages will slowly rise and then
> the supply will suddenly come to life and be fine. I know it's the supply
> and not the motherboard because I've swapped them with another machine,
> and I've tried heating the supply alone with a hair dryer. Also, when the
> supply is cool but disconnected from the motherboard the positive voltages
> are about 1% above nominal and the negative voltages are about 10% more
> positive than nominal.
>
> I can't see any cold solder joints or obviously bad components. The
> machine is of 1985 vintage and the supply was made by Astech.
>
> Any diagnostic suggestions would be appreciated, as well as pointers to
> a low-cost vendor for a new supply. I'm an EE so I have a passing
> familiarity with switching power supplies, but I don't have the schematics
> for this guy.
>
> TIA,
> Joe
>
> --
> Joe Hass | library clever_sigs; | My opinions are my o
> kjhass@sandia.gov | use rock_and_roll.verses.ALL; | not Sandia's and
> Sandia National Labs | use lineprinter.art.ALL; | not the DOE's
Theis problem is usually caused by a failed capacitor (220uf/16V?)
that sits near the big power transistor. Test it by warming it up
before you power on.
Regds,
Peter M.
peterm@tlp.apana.org.au TLP - The only *REAL* A2 BBS in
Peter Maloney Melbourne
A2 Hardware Freak
Path: blue.weeg.uiowa.edu!news.uiowa.edu!hobbes.physics.uiowa.edu!math.ohio-state.edu!usc!bloom-beacon.mit.edu!senator-bedfellow.mit.edu!pbauer
From: pbauer@ATHENA.MIT.EDU (Paul H Bauer)
Newsgroups: comp.sys.apple2
Subject: Apple II Power Supplies
Date: 28 Nov 1994 04:09:04 GMT
Organization: Massachusetts Institute of Technology
Lines: 21
Message-ID: <3bbl50$2lj@senator-bedfellow.MIT.EDU>
NNTP-Posting-Host: puttanesca.mit.edu
For those of you that have had power supply problems!
This week-end I descided to clean up my work bench and either
repair or throw out a few AII power supplies I had in various states of
disrepair. I made an interesting discovery on two supplies, one an aztec
(?) unit, and the other a dead unit from a late model platinum 2e. The
supply from the platinum unit was dead. After checking almost all of the
semi-conductors and finding them good I finally started looking at the
resistors and found a 100k 1 watt
unit that kick starts the supply was open. Replacing this resistor fixed
the supply. I then looked at the aztec unit. This unit woul sometimes
start but most of the time it would not. I looked at the same resister
(R3) which is a 150k 1 watt resister. I changed this to a 100k 1 watt unit
and the supply works like a champ.
If you have a dead supply you might check these resisters as they
could be the culprit. The resister goes from the + rectified line side to
low voltage oscillator that drives the power switching transistor.
pbauer@mit.edu