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#1 2016-07-02 19:40:27

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 955
Website

LC 520/550 and Color Classic (Rom Slot Addition)

there is a spot to add a rom simm slot.. and that is fine and dandy
but there is some additional parts missing.

wondering what pads i should solder bridge to make this rom simm work?
right now it lights up, but the main board does not see it.

if you have any idea please let me know.


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#2 2016-07-02 20:56:52

uniserver
Member
From: Sf, Mi
Registered: 2014-05-15
Posts: 955
Website

Re: LC 520/550 and Color Classic (Rom Slot Addition)

I asked Warren (bomarc) the same question, but in regards to the the Color Classic because i knew he didn't have a LC520 or LC550 schematics to look at.
witch is missing the same parts but in different locations.

OK, first off, I am NOT an engineer, and 90% of what you said is total gibberish to ma, as I don't speak computese,  I don't even know where the power cord goes on one.  With this in mind, I took a look at the print, and found the unpopulated area you mentioned, and am going to assume you are wanting to replace the missing parts, no???   I also got a wild hair up my old wrinkled ass and went through my other Apple prints looking for a similar configuration, no no avail, so this is something new - - to me anyway.    The transistors are most likely simple switching types, and most likely surface mount bastards as well.  If so,  I would guess they would have used MMBT3904 for Q2 (top mark 1AM) and MMBT3906 for Q3 (top mark 2A).   I am to antiquated to mess with surface mount and would use their thru-hole counterparts, namely 2N3904, and 2N3906.  I have replaced these things by bending a tiny "L" at the ends of the leads, and carefully ( VERY VERY CAREFULLY) soldering these to the correct pads.    Basing on the SMD part looking at them with the single tit up, is bottom left tit - Base, Top tit collector, and bottom right tit - emitter.   Basing on the TO-92 package thru-hole looking at the flat face is Emitter, Base, Collector.   Of course, you kNOW all this already I trove.   
  As for the resistors, I don't know.  Usual rule of thumb is base bias resistor ten times collector load resistor, so using base bias resistor of 10K, the collector load would be 1K.  This thing uses a collector load on Q3 of two resistors to two different B+ levels, so   ??????????
   I would advise you to call Apple, but the we BOTH know what secretive shitwipes THEY are.  Find an engineer and present the problem to him for better results.


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#3 2016-07-02 23:52:37

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 955
Website

Re: LC 520/550 and Color Classic (Rom Slot Addition)

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#I Re-Cap √Mac √NeTX √Amiga Boards - A/B - PSU# (MacCaps.com)  Modern SCSI HD's - For Old Macs - Pre Cfg'd - 10k RPM! 73gb!! $50 + free shipping  -- Mac 128K Re-Ram kits (16 Chips) $35 + shipping, Floppy Issues?-> Bourns Filter Solution 128k - SE/30, $16 + shipping

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