New Mac 512k owner (with a few queries)

CooperBox

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Nov 28, 2010
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Hi Guys,
I was recently given a Mac 512k which I'm told had been stored in a lockup for a number of years. No original box or software floppies, but do have the original keyboard and mouse.
First thing I noted was that the battery had been left in the compartment - and leaked! On removing it, one of the battery terminal lugs fell apart due to corrosion. (Photo 2 attached).
I've now removed both the logic and power board, both of which fortunately appear to be free from any battery spillage or contamination. Unfortunately the same can't be said for the metallic frame which the power board attaches to, as this has suffered from acid spillage and corrosion - most of which can probably be removed with the use of a wire brush. (Photos 3 & 4 attached).
I have also removed and disassembled the floppy drive, the disk-carriage mechanism of which had completely seized up. Nylon gears looked ok, and after a thorough cleaning and re-application of grease, gears & mechanism appear to now operate smoothly by hand. The floppy drive is a Sony, model OA-D34V-22 which I understand to be a 400k.
Regarding this drive, I note that on the motherboard the ROMs are marked:
"ROM-LO" "342-0221-A"
"ROM-HI" "342-0220-A"

- My 1st query: Is this floppy model OA-D34V-22 (400k) compatible with the 'A' suffix ROMs?
Reading MacTec68's excellent info provided in a previous thread (July 22/2015 #2), he advises that, "Earlier "-A" ROMs are only compatible with the "OA-D34V" drive." This would seem to suggest that floppy and ROM's on this Mac are incompatible. True?
-My 2nd query: The damaged battery holder is a Capetronic, model DS 1011. (Photo 1 attached). I can find no on-line reference to this part number. Any idea on where I can find an identical replacement, or a similar battery holder to suit?
-My 3rd query: After brush clean-up of the power-board metallic frame, what is the best way to further protect the surface prior to refitment?
Would greatly appreciate any comments on the above.
Cheers for now.

Battery Holder 1.jpg Batt lug.jpg Corrosion 1.jpg Corrosion 2.jpg
 

MacTech68

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Mar 16, 2008
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You know, I've just realized that MAYBE a panel-beater/vehicle body repairer might be able to use a sandblaster to rid you of the corrosion for a tiny fee.

Second, that's not the part number of the battery holder - and I'm trying to find it. IIRC, the originals were re-worked with a wire, and the battery contacts would come out of the holder, so at the very least, it MIGHT be possible to find a reasonably suitable battery contact replacement.

As for the ROMs, if that's what I noted, it is noted in the original Apple Tech data - but I don't recall if it's a major incompatibility or not. More to come (hopefully).

EDIT: Battery holder plastic part is a custom Apple mold. P/N 815-0727-B :(
The contacts are also stamped "Apple" and seem to be P/N 5046-06 (-ve terminal) and 5045-06 (+ve terminal). Whilst the plastic holder is reusable, the nearest type of contact I can find is not tall enough. You might be able to fashion something similar from thin steel and use short lengths of wire to solder the contacts to the PCB.
 
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CooperBox

macrumors 65816
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Nov 28, 2010
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Hi, your reply and thoughts were much appreciated.
Regarding the Apple mold P/N, having now removed the holder, I note is molded into the underside of the holder - mine happens to be 815-0727-D
Will take your advise and fabricate some contacts to suit.

Another good idea! I'm just off to my local panel-beater to get some advise on sand-blasting the contaminated frame.

Another question just comes to mind. I note that the powerboard P/N 630-0108 is stamped, 'For 120v operation, W12 MUST BE IN PLACE. For 240v operation W12 MUST BE REMOVED."
As I'm in Europe (where the Mac was previously purchased and used here - one assumes with 220-240v), my simple (albeit logical) mind expected to see no capacitor installed at the W12 - 120v board location. But there is one. Strange! :confused:
Again thanks for your input.
 
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MacTech68

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Mar 16, 2008
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I note that the powerboard P/N 630-0108 is stamped, 'For 120v operation, W12 MUST BE IN PLACE. For 240v operation W12 MUST BE REMOVED."
As I'm in Europe (where the Mac was previously purchased and used here - one assumes with 220-240v), my simple (albeit logical) mind expected to see no capacitor installed at the W12 - 120v board location. But there is one. Strange! :confused:
Again thanks for your input.
The W12 refers to a Wire jumper number 12. The 240V International boards have 4 large capacitors in that location, whereas the 120V Only boards have just two. The layout of the two boards is different, and even component references differ in their numbering.

So, you should have no wire at W12 for 240V operation, which in France is what you want.


630-0102 Mac 128K Analog 120v Compare.jpg


630-0108  240V W12 Compare.jpg
 

CooperBox

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Nov 28, 2010
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Ah, the wire jumper W12. All becomes clear. Many thanks for that.

My local panel-beater wasn't around today, so I spent a fair amount of time and especially elbow grease cleaning up the contaminated chassis. It's now looking pretty good. Will post additional photos on completion.
 

CooperBox

macrumors 65816
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Nov 28, 2010
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Hi,
Just an update for those who may be interested to know how my 512k reburb is progressing - especially MachTech68 who's advise and words of wisdom have been well noted.

Here's the 512k at receipt, and after clean-up of the case.

Case Before.jpg Case After .jpg

Battery holder before & after repair. (New contact tongue fabricated & installed).

Battery Holdert Before.jpg Battery Holder After.jpg

Chassis on removal (heavy oxidation due to battery leakage).


Chassis After1 .jpg

Chassis Before 2.jpg Chassis After 2.jpg

Front cover before & after lots of elbow-grease.

P1080194.JPG Case Front After.jpg

A suivre......
 

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CooperBox

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Nov 28, 2010
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Wow, is that chassis the same one after sand-blasting?
Hi,
No, I decided to do it the hard (manual) way. Started with a wire brush to remove residual rust deposits. Then emery cloth, followed by a powered wire brush. Needless to say, all that took some time. A quick blast of metal silver spray from an aerosol provided the final finish. It came up nicer than I imagined.
Of course when finally re-assembled, I have no idea if the screen will spring to life, as the serviceability of the graphics and power-board, CRT and floppy-drive is unknown. But I'll be happy just knowing that it's generally in better shape, and been saved from the trash (as it was destined).
Few more photos to follow.....
 

CooperBox

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Nov 28, 2010
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The floppy drive was in one hell of a state. Plastic gears however were in excellent shape. The mechanical linkage was seized-up solid, and took multiple applications of WD40, followed by 48 hrs to dry after a final clean. It was as if someone had lubricated with Araldite instead of grease, but I understand that's the problem with the original grease that was used at the time. I applied a light silicon grease on the linkage (for better or worse).

Floppy overhaul.jpg Parts Assy.jpg

Now looking forward to getting everything back inside the box, and pressing the ON switch. :)
 

CooperBox

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Nov 28, 2010
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Just been giving these components a last look-over before re-installing. And just as well I did; found a major fault on the mother-board. Must take some photos for further discussion, but now being coaxed out of my workplace to join in some seasonal cheer. Will update you asap.
Cheers, :)
 

CooperBox

macrumors 65816
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Nov 28, 2010
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This is the condition seen on the motherboard with the aid of a x4 magnifier. The component marked Filter.

Mboard Filter 1.jpg


Mboard Filter 2.jpg

Same component on rear of board.

Mboard Filter rear 1.jpg

Mboard Filter rear 2.jpg


Looking at other photos of the same motherboard 630-0118 posted elsewhere, I note that their are 3 similar Filters marked CRL844L 115-0002, whereby on this board there are 2 only, plus the dissimilar problematic one shown, which surely has been installed by an unqualified person.
Any thoughts/comments on this please?
 

MacTech68

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Mar 16, 2008
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I wouldn't worry about the component itself, having obviously been replaced at some point.

These filters do fail and can cause problems with internal and external floppy drives and mouse.

The only real problem I can see is the potential discontinuity on one pin, the one I've marked with the arrow. If you can trace the track that goes to that pin to another component and check for continuity from the filter's pin to the other component then it's probably going to be fine.

If you find the floppy drive or your mouse gives permanent problems, then you may need to have this reworked. By the looks of it, at least 3 tracks have been broken but only one looks suspect from the photos you've provided.

Mboard Filter discontinuity annot.jpg


EDIT:

Checking on it, pin 3 and 4 of this filter handle the Printer Port and Floppy port respectively. Below is an annotated pic showing which pins end up where.

Mboard Filter trace annot.jpg
 
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CooperBox

macrumors 65816
Original poster
Nov 28, 2010
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France - between Ricard & Absinthe
I wouldn't worry about the component itself, having obviously been replaced at some point.

These filters do fail and can cause problems with internal and external floppy drives and mouse.

The only real problem I can see is the potential discontinuity on one pin, the one I've marked with the arrow. If you can trace the track that goes to that pin to another component and check for continuity from the filter's pin to the other component then it's probably going to be fine.

If you find the floppy drive or your mouse gives permanent problems, then you may need to have this reworked. By the looks of it, at least 3 tracks have been broken but only one looks suspect from the photos you've provided.

View attachment 607623

EDIT:

Checking on it, pin 3 and 4 of this filter handle the Printer Port and Floppy port respectively. Below is an annotated pic showing which pins end up where.

View attachment 607712
Many thanks for these comments and guidance. Hopefully this weekend I'll get the time to check out continuity from the pins indicated.
Methinks this filter will eventually get changed out, as now knowing the condition, and being obsessed with top quality, I could never leave it 'as-is', and probably wouldn't even sleep soundly until completed!
I've done a fairly detailed web search for Mobo Filter CRL8448L and Filter 115-0002 which returned nothing positive. Is there some other technical name or reference in order to procure this particular filter?

512k Mbo Filter.JPG
 

MacTech68

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Mar 16, 2008
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Australia, Perth
A few manufacturers were used, but the easiest to find these days is the Bourns "4120R-601-250/201".

If you're going to replace it, there appears to be another broken track on the top of the board, on Pin 2 of the filter.
 
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CooperBox

macrumors 65816
Original poster
Nov 28, 2010
1,275
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France - between Ricard & Absinthe
MacTech68, that information is just what I wanted. Thank you.
I had indeed noticed another defective track, and will ensure all the above is taken into consideration during rectification.
Again, I really appreciate your interest in this.
Cheers.
 
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