Schematic diagrams

[stevep]

Does anyone know where to locate schematic diagrams for Compact Macs? Particularly need for an SE/30 logic board.

Or a list of what parts are referenced by board markings. Example what is "D1".

 

[Mac128]

A Google search turned this right up ... http://www.jagshouse.com/macplus.html

Tom Lee's repair manual has much of this detailed too ...

http://68kmla.org/files/

 

[wally]

...Example what is "D1".

Just for example, D1 and D2 are both diodes in the SOT-23 package, manufacturer's package marking 5D. Investigating this part marking code, http://www.tkb-4u.com/code/smdcode/smdcode5.php indicates that Zetex FMMD914, and Motorola MMBD914 both have the appropriate basing diagram. This is consistent with other knowledge I have about the 1N914 being used for this circuit area.

The anode of D1 is driven by the battery, the cathode goes to a feedthru to R27 underneath. The other side of current limiting R27/4.7K goes three places: C50, a .1 bypass to ground, the cathode of D2 (D2 anode goes to +5V) and to UK4-8, the RTC/PRAM power pin. D2 supplies +5 to the RTC/PRAM when the SE/30 is powered up. D1 supplies backup keep-alive current, but also keeps the battery from being charged by the +5V (minus one D2 diode drop) when the SE/30 is powered, so D1 must have low leakage to avoid an exciting electrochemical incident.

Some SE/30 logic board versions have C12/47uf16V nearby in position K2 as opposed to the more distant L1 location. If the SMT cap C12 at K2 leaks "goo", D1 can be bypassed by conductive corrosion product, and each time the SE/30 is used the battery can receive a trickle charge much larger than the miniscule leakage of a good D1. This can lead to an eventual battery breach and vile corrosion of uncertain chemical proportions.

If only battery liquid electolyte leaks, the MSDS indicates that subsequent reaction with atmospheric moisture forms HCL acid. On the other hand if the battery case breaches and Lithium metal is spread around, reaction with moisture can form alkaline hydroxides in addition (assuming an outright fire does not occur!). What dominates and where after a period of storage is uncertain, but cleanup might have to take into account both neutralization of acid and mechanical and/or chemical removal of hydroxide products from both battery and leaking SMT capacitor following the other previous discussions of capacitor goo corrosion cleanup. The battery holder might have to be removed to inspect/clean the many traces that cross under the battery, as it is not uncommon for capacitor goo alone to eat right thru the surface overcoat film.