512k Mac upgraded to Mac Plus?

[Leografix]

Today I' facing a rather unusual Mac which I won within a non-eBay auction. The front housing of that Mac clearly identifies it as the 700th 512k Mac manufactured within the 34th week of 1984 (regarding the aerial number decoder online) - the sticker and the front housing are definetly original meaning a possible "Plus" badging wasn't rubbed off that front housing which normally leaves clearly visible hints when removed.

But...

The back of the housing is definetly a "Plus" one as it carries a SCSI port (which to my informations is missing within a 512k). I haven't had the chance until now to fire up that machine with a Mac OS so I'm still lacking any further information. I aslo know that Apple once provided a "Plus" upgrade for the 512k which consisted of a "Plus" mainboard and "Plus" back housing exchange but the back housing sticker is missing (besides this the typical Apple logo / Macintosh 512k marking on the back housing is missing, too).

Now...

Are there any more details which I can have look on to determine if this Mac really is / was a 512k one? If the mainboard was exchanged I suppose that the tube and the board (not main board) aside the tube are still original but I do not know much about details there so any hint would be very welcome. I haven't opened this Mac but I will do to compare it's mainboard with the "Plus" one I already owned before.

Thanks a lot for any information from the Classic Pros in here!

J

 

[slomacuser]

As you figured out this is upgraded model ...

 

[Torbar]

From what I know about these upgrades, its everything from the 512k, except logic board and back case.

 

[Mac128]

From what I know about these upgrades, its everything from the 512k, except logic board and back case.

The disk drive will also have been upgraded to an 800K and there was an optional extended keyboard.

 

[Leografix]

Now after opening both machines it seems pretty clear that my 512k is an upgraded one. The tube and the board beside the tube are definetly from the 512k and so is the front housing; mainboard and backside housing is from that Plus upgrade which also contains the 800k floppy drive but not the extended keyboard.

One thing is still a bit strange: while my Plus shows all the signatures on the inside of the beige backside housing the "upgraded" backside housing from my 512k is missing these signatures and is held in black, it also misses any further engravings that my Plus shows but it is definetly a housing from Apple.

I think I will exchange the mainboards. My Plus has 4 MB RAM, the 512k/Plus just 1 MB. The Plus also faces the video dropouts which the 512k doesn´t show. So when I´m reanimating my old Plus webserver the 512k will be a bit more "special" for this job, I suppose

J

 

[MacG4]

how about some pics?

 

[Mac128]

Now after opening both machines it seems pretty clear that my 512k is an upgraded one.

It was always clear to us! LOL No 512K ever had a SCSI port.

One thing is still a bit strange: while my Plus shows all the signatures on the inside of the beige backside housing the "upgraded" backside housing from my 512k is missing these signatures and is held in black, it also misses any further engravings that my Plus shows but it is definetly a housing from Apple.

Not sure what you mean by "misses any further engravings".

As for the signatures, they persisted in some form through the SE/30. So for a beige Plus kit not to have them is quite odd. When you say "held in black", so you mean the metallic RF coating on the inside of the case is "black"? If so, I have seen compacts where the shielding coat is so thick it conceals the signatures, but if you look real closely you can still make out a few. I suppose the Plus case backs could have been manufactured at some of Apple's new international plants and as such used a new mold that did not have the signatures, though I have never heard of this.

I think I will exchange the mainboards. My Plus has 4 MB RAM, the 512k/Plus just 1 MB. The Plus also faces the video dropouts which the 512k doesn´t show. So when I´m reanimating my old Plus webserver the 512k will be a bit more "special" for this job, I suppose

If you are planning on using the 512K as a server, consider that the 512K analogue board is not as robust as the Plus board and therefore is subject to burning out faster, especially when left on continuously. You are better off repairing the Plus board and switching it to the 512K case if you prefer its design.

 

[Leografix]

I will ake some photos as soon as possible!

It was always clear to us! LOL No 512K ever had a SCSI port.

Well, some obscure online auction sellers are sometimes manipulating old stuff in order to achieve higher rates. Although not very "popular" it might have been possible that this Mac is a physically downgraded Plus with the faceplate from an "out of order" 512k. Plus Macs are much easier to find nowadays...

Not sure what you mean by "misses any further engravings".

For example: the small circle of production months stamp. European Macs sometimes bear special markings from some non-Apple companies that tested those machines in operating security aspects - but these markings are missing.

When you say "held in black", so you mean the metallic RF coating on the inside of the case is "black"? If so, I have seen compacts where the shielding coat is so thick it conceals the signatures, but if you look real closely you can still make out a few."

The RF shielding foil just covers the back up to the top of the connection ports, it doesn't reach the top of the housing, so it doesn't cover the signatures in my Plus which are placed on the plastic housing itself and not on the shielding foil. It's the plastic housing itself which misses the beige color. To me it looks like this housing just got the paint's grounding on the inside but wasn't colored beige afterwards (I know that the beige color wasn't sprayed onto those housing parts, Apple colored the plastic itself - it's just a description to give You an imagination until my photos are made).

You are better off repairing the Plus board and switching it to the 512K case if you prefer its design.

As long as I don't know --- exactly --- what to fix where (I just heard something about Pin 1 re-soldering) I'm simply not able to fix my Plus

J

 

[Mac128]

Well, some obscure online auction sellers are sometimes manipulating old stuff in order to achieve higher rates. Although not very "popular" it might have been possible that this Mac is a physically downgraded Plus with the faceplate from an "out of order" 512k. Plus Macs are much easier to find nowadays...

Either way, the end result is the same. I guess there's no easy way to determine if a 512K was upgraded to or downgraded from a Plus.

European Macs sometimes bear special markings from some non-Apple companies that tested those machines in operating security aspects - but these markings are missing.

This too is something subject only to where the Mac Plus case back was manufactured and how Apple distributed the Plus upgrade kit. It is possible that the Plus case back and upgrades were not subject to the same government regulatory rules that a "whole" Mac was and in this event, "one-size-fits-all".

When you say "held in black", so you mean the metallic RF coating on the inside of the case is "black"? If so, I have seen compacts where the shielding coat is so thick it conceals the signatures, but if you look real closely you can still make out a few."

The RF shielding foil just covers the back up to the top of the connection ports, it doesn't reach the top of the housing, so it doesn't cover the signatures in my Plus which are placed on the plastic housing itself and not on the shielding foil. It's the plastic housing itself which misses the beige color. To me it looks like this housing just got the paint's grounding on the inside but wasn't colored beige afterwards (I know that the beige color wasn't sprayed onto those housing parts, Apple colored the plastic itself - it's just a description to give You an imagination until my photos are made).

I wasn't talking about the foil covering the ports. I was speaking specifically of the metallic paint which served to shield the entire case, which in every compact Mac I have ever seen is a dark gray or silver color. Some models have a much thicker coating than others and sometimes that paint is so thick it covers the signatures so that you don't know they are there. A photo will not improve the situation. I have never seen a compact Mac which was either missing the RF paint or had a beige layer painted over it, so I'm not sure what you are comparing it to – are you saying your other Mac Plus is missing the RF paint or uses a beige-coloured paint instead?

You are better off repairing the Plus board and switching it to the 512K case if you prefer its design.

As long as I don't know --- exactly --- what to fix where (I just heard something about Pin 1 re-soldering) I'm simply not able to fix my Plus

There are two types of Mac collectors. Those that use them and those that store them. Sadly if you intend to actually use your old Mac you are well advised to start learning how to repair it, or find someone locally you can pay to maintain them. They are not hard to maintain yourself once you've done some minimal education. Either way, if you start using the old 512K power supply in any regular way, it won't be long until you experience some kind of failure. Word to the wise ...

 

[Leografix]

There are two types of Mac collectors. Those that use them and those that store them.

I surely am a user (not only) of old Macs and if possible I repaired nearly every machine I own by myself (besides my G5 that leaked its cooling liquid for killing both CPUs).

Sadly if you intend to actually use your old Mac you are well advised to start learning how to repair it, or find someone locally you can pay to maintain them.

Again: I never dealt with CRTs before, nor with analogue boards of old Macs and before I´m searching for any good starting point in order to repair my Plus I´m trying to find helpful hints where ever I can. To be honest I´m no super-soldering-master and I´d really hate to blow my Plus just because of re-soldering something that didn´t need it.

J

 

[Charlieman]

If you need to repair the high voltage bits in a compact Mac, look around for a traditional TV repair man. If you are in education, try to find a friendly lab technician. People with old fashioned repair skills are often generous teachers, so you may get a free education as well as a competent repair.