Classic II schematic? RTC doesn't keep time across power shutdown

[howardc64]

Took apart my Classic II nearly 10 years ago for repairs. It had no sound and RTC didn't keep time across power shutdown. Back then I replaced all the chemical capacitors (a couple of lifted pads/traces with some wire repairs) along with a fresh battery. Sounds came back, but RTC still lost power across power shutdown. Left it that way for 10 years.

Decided to repair it again this weekend. Lithium Ion battery still had good Voltage (3.6V). Found some SE30 circuit diagrams for RTC power supply. Pretty simple circuit design from the backup battery end on the SE30, I'm guessing Classic II is same or pretty similar. However, I couldn't find the diode and resistor from the + circuit side of backup battery (D1+R27 in the following SE30 diagram)

http://museum.dyne.org/gallery/apple/stuff/mac/andreas.kann/SE30_P4.GIF

Does anyone have a Classic II schematic?

I did find the contact point between D2+C50, a friend suggest we can easily wire up a diode + resistor from battery + to this contact point.

 

[Paralel]

You can buy a Classic II schematic.

 

[mraroid]

I buy from Mouser Electronics.  You can buy one diode or a thousand.  They stock high voltage caps, any kind of resistors and many other componets.  They also do not charge you rip off shipping charges.  I am very happy with them:

http://www.mouser.com/

I think you will be able to find the diode and resistor that you need.

http://www.mouser.com/Search/Refine.aspx?Keyword=diode

and

http://www.mouser.com/Passive-Components/Resistors/_/N-5g9n/

It is sad that a Classic II schematic is not posted on line for free someplace....  It is not like Apple is selling them.  This stuff is so old, it is just us hobbyist now....  I moderate a forum on old time (1920s to 1960s) motion picture sound formats.  We post literature for free.  And if an engineer sometimes reverse engineers a old device, they post the schematic for free.  The thought behind this is the free exchange of information is best for all. But that is just us.... 

mraroid

 

[howardc64]

Thanks guys. And yes, am familiarwith mouser. Previously got a contactless angle sensor there to fix my Volvo's throttle position sensor

Did some more circuit board tracing and found what I think is the RTC (8 pin chip with small Apple logo next to the battery holder). Also found battery's 3.6V goes into a pin on this chip. I'll do some more tracing and reconstruct a schematic for this area Will post update soon. Here are some pics in case anyone is curious

https://picasaweb.google.com/lh/photo/-r5Tn8TkF6iILZ7C0DN1MtMTjNZETYmyPJy0liipFm0?feat=directlink

https://picasaweb.google.com/lh/photo/RdCiIj6u0lxmoUeGqEy4QdMTjNZETYmyPJy0liipFm0?feat=directlink

A=positive contact to the battery.

A-B on topside have continuity

B-C, C-D on underside of board have continuity, C-D is a resistor

D-E have continuity (flips from underside to top side of the board)

I can see 3.6V at pin 7 of the RTC with battery installed.

 

[Paralel]

...It is sad that a Classic II schematic is not posted on line for free someplace....  It is not like Apple is selling them.  This stuff is so old, it is just us hobbyist now....  I moderate a forum on old time (1920s to 1960s) motion picture sound formats.  We post literature for free.  And if an engineer sometimes reverse engineers a old device, they post the schematic for free.  The thought behind this is the free exchange of information is best for all. But that is just us....

I know the person selling the schematic, he had to pay quite a bit to get it done, de novo, by someone who had to document the hardware and connections by hand, piece by piece, trace by trace. Not an easy nor cheap thing to do. More power to people who can spend money and give stuff away for free. But, in general, it's asking alot for someone to do that.

 

[mraroid]

Thanks Parael for the added info.  I thought that the schematic was a "off the shelf" item by Apple.  Guess I was wrong.  Yea, I am all for paying someone if they did a lot of work on something....

 

[techknight]

Only apple authorized service centers could get them. 

 

[Instow]

Uniserver has schematics available ... $25 for the Classic II.

Here.