Vertical Line On A Mac Plus Screen
Date: Fri, 27 Nov 1998 11:17:14 +0000 To: Classic Posts <firstname.lastname@example.org> From: Rebecca and Rowland <email@example.com> Subject: Re: MacPlus: Vertical white line inc 128/512/Plus upgrade info >From: EDRIZER@aol.com >Date: Thu, 19 Nov 1998 17:01:09 EST >To: firstname.lastname@example.org >Subject: MacPlus: Vertical white line > >I remember this topic from several months back, but I wasn't paying attention. >My Mac Plus suddenly lost its picture. I now have only a vertical line >running down the middle of the screen. What's the solution? I'm not *certain*, but Larry Pina's `Macintosh repair and upgrade secrets', Hayden Books, ISBN 0-672-48452-8 says that the cause is most likely a fault with L2, C1, and/or J1 - these are the reference numbers on the PCB. (L2 = inductor, C1 = capacitor, J1 = connector) Likely faults are component failure (in the case of C1), or cracked solder joints. If you replace C1, you need to get a 3.9 micro farad *unpolarised* *high frequency* capacitor, with a 100V rating. Make utterly certain that the replacement part is suitable for high frequency use - most electrolytic capacitors aren't. Get this bit wrong and you might well end up looking at the wreckage of an exploded capacitor in the near future. I've also heard that the flyback transformer has been known to fail and produce this symptom. If you're going to be doing component-level repairs, it's as well to replace as many electrolytic capacitors as possible, because they'll all be near or past the end of their lives by now. In particular, replace the following parts, using capacitors rated for at least 105 degree C and high frequency operation. The rest of this email applies to the original 128K thin Mac, the 512K and Ke, and the Mac Plus. In the follow parts lists, do check the values I've written down against what's on the PCB. If the capacitance value on your PCB differs from what I've typed here, assume I've made a mistake. The voltage and temperature ratings are supposed to be higher than what's fitted - they make for longer life. I am at the moment half-way through this upgrade procedure myself - I've got to get a few more bits before I can switch on and re-adjust everything myself. I've supplied part numbers for suitable parts (where I could find them) from RS,a global industrial electronics supplier <http://www/rs-components.com/rs> (uF = micro farad, or x 10^-6 F) Part numbers for US Mac Plus/512K/128K: C1 3.9 uF 100V C3 220 uF 35V RS 394-872 C24 2200 uF 25V RS 394-844 C25 1000 uF 25V RS 394-838 C26 1000 uF 25V RS 394-838 C29 2200 uF 25V RS 394-844 C30 220 uF 35V RS 394-872 C31 1000 uF 25V RS 394-838 Part numbers for international Mac Plus/512K/128K: C1 3.9 uF 100V C3 220 uF 35V RS 394-872 C24 2200 uF 25V RS 394-844 C27 2200 uF 25V RS 394-844 C28 1000 uF 35V RS 394-917 C30 2200 uF 25V RS 394-844 C31 1000 uF 25V RS 394-838 C32 2200 uF 25V RS 394-844 have a look at C33 and C36 (int. board) or C33 and C37 (US board). These are a pair of 250V 470pF suppressor capacitors which suffer abuse from mains spikes - mine were cracked so I replaced them - this got rid of some nasty arcing in my Plus's mains switch that used to occur each time I switched off. You *must* use 250V Class Y capacitors for this job, such as a Rifa PME 217 Y, RS 210 594. If in doubt, assume the capacitors you have are unsuitable. It's also worth replacing (US and international board refs): CR20 and CR21 with 45V-100V 10A Schottky barrier diodes suitable part: MBR1045 10A 45V RS 642-250 CR1 and CR5 with 400-600V 5A fast rectifiers (150ns or less if possible) suitable part: STTB506D 600V 5A 95ns RS 217-8420 and finally... `Mac repair and upgrade secrets' says that the zener diodes on the analogue board are inclined to drop out of spec. It's worth replacing them: International board: CR15 6.2V 500mW zener BZX79 series suitable RS 283-671 CR17 6.2V 500mW zener BZX79 series suitable RS 283-671 CR18 6.2V 500mW zener BZX79 series suitable RS 283-671 US board: CR15 6.2V 500mW zener BZX79 series suitable RS 283-671 CR18 12V 5W zener 1N5349B suitable RS 850-338 CR19 6.2V 500mW zener BZX79 series suitable RS 283-671 If you do replace all these parts, you'll need to adjust the power supply voltage and re-align the video circuitry - I've not got this far yet, so I can't be much use. Spec for the PS voltages is: +5V +4.85V to +5.15V +12V +11.90V to +12.80V -5V -5.25V to -4.75V -12V -13.00V to -11.30V All the adjustment knobs are marked on the cover for the analogue board, so it shouldn't be impossible to work things out. Getting access to the various PS voltages is tricker - the connector on the logic board (from the analogue board) has three of them: Pin number 1 White (video) 2 Empty (key) 3 Orange (hor sync) 4 Yellow (speaker) 5 Green (vert sync) 6 Blue +5V 7 Violet (ground) 8 Red -12V 9 Orange (ground) 10 Yellow +12V 11 Green +4.5V battery Now then... I've done an honest job with the stuff above, but mistakes do happen - if anyone who reads this is in the slightest doubt about *anything*, don't do it, and ask me about it. <insert standard disclaimer> Rowland.
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