[vcf-midatlantic] MAC with squashed screen

Ian Primus ian.primus.ccmp at gmail.com
Thu Apr 28 08:36:08 EDT 2016


Just reread the description of the fault on your site - I'd gotten the
impression it was always squashed like that the first time I looked at
it. If it's intermittent (i.e., you can hit it and it pops back), it's
probably just a bad solder joint. Resolder Q1 and Q2, and nearby
components, as well as the yoke connector. If it starts out bad and
gets better as it heats up, or starts good and gets worse as it heats
up, and hitting it doesn't affect it, then, it's definitely one of
those caps.

-Ian

On Thu, Apr 28, 2016 at 8:12 AM, william degnan via vcf-midatlantic
<vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
> thanks.
> b
>
> On Thu, Apr 28, 2016 at 8:09 AM, Ian Primus via vcf-midatlantic <
> vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>
>> Kind of covered - in my class on CRT monitor repair, I mentioned
>> vertical problems like this, and in my old Mac class, I went over some
>> of the basics there, but, didn't specifically get to this as it
>> relates to Macs. It's hard to cram that much information into a one
>> hour class - I had to move rather quickly.
>>
>> The 128 uses a pair of discrete transistors for it's vertical driver.
>> One of the caps in that circuit has failed/is failing. I'm guessing
>> it's C6. Failing that, it's either C5 or C11. While you're in there,
>> be sure to resolder the yoke connector, it's a very common point for
>> cold solder joints (will cause total loss of deflection)
>>
>> -Ian
>>
>> On Thu, Apr 28, 2016 at 7:57 AM, william degnan via vcf-midatlantic
>> <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>> > I am thinking about working to repair the display on my '84 MAC,
>> > occasionally the horizontal is "squashed" although for now it recovers.
>> > Was this covered in any VCF E classes this or last year?
>> >
>> > http://vintagecomputer.net/browse_thread.cfm?id=95
>> >
>> > I assume there are a few places on the web that describe MAC repairs like
>> > these, but any comments as to what to target are welcome and will save me
>> > some time.
>> >
>> > b
>> >
>> > --
>> > @ BillDeg:
>> > Web: vintagecomputer.net
>> > Twitter: @billdeg <https://twitter.com/billdeg>
>> > Youtube: @billdeg <https://www.youtube.com/user/billdeg>
>> > Unauthorized Bio <http://www.vintagecomputer.net/readme.cfm>
>>
>
>
>
> --
> @ BillDeg:
> Web: vintagecomputer.net
> Twitter: @billdeg <https://twitter.com/billdeg>
> Youtube: @billdeg <https://www.youtube.com/user/billdeg>
> Unauthorized Bio <http://www.vintagecomputer.net/readme.cfm>



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