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#1 2017-09-02 00:03:41

Grant2053
Member
Registered: 2017-09-02
Posts: 2

Mac Plus stuck in boot loop pls halp.

https://youtu.be/t3tY_zbAnyM

Here is a video of what its doing.
Already hit the usual suspects like the caps and stuff. At a dead end.

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#2 2017-09-03 13:17:35

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 237

Re: Mac Plus stuck in boot loop pls halp.

try dufferent ram?  clean ram contacts in sockets?  It loops so fast like a ram check going on.  The tones with no start up are listed on most classic mac repair guides as its the first test. 

A typical Macintosh hardware initialization consists of the following events:
1. Power is applied to the system.
2. The power supply establishes the appropriate voltage levels required by
the system.
3. ThesevoltagelevelstypicallyaremonitoredbyoneoftheSonysoundinte-
grated circuits on the logic board. I f the levels are acceptable, a reset sig-
nal is then generated by this IC.
4. Thisresetsignalforcesthecentralprocessingunit(CPU),mathcoproces-
sor (FPU), primary logic ICs, expansion cards, and other internal devices to come to a known state.
5. The reset signal is withdrawn.
6. The CPU obtains the reset vector (typically four eight-bit words), which
begins at memory address 0000 0000 (hexadecimal). A ROM overlay address map then is used by the memory decode and control circuitry to map the standard memory locations to a ROM address. The CPU goes to the reset vector memory address, which is now mapped to ROM.
7. Special program code called the Macintosh reset handler (MRH) is exe- cuted. The MRH remaps ROM and RAM to their respective locations.
8. The MRH initiates the P.O.S.T. sequence.
If your Macintosh fails any portion of the initialization, it appears to be dead. Refer to the general troubleshooting portion of this book for possible remedies.

Detailed P.o.s.T.
As I mentioned, the MRH initiates the P.O.S.T. stage of the startup sequence. This is done in conjunction with a special low-level routine called the Start Man- ager. The P.O.S.T. begins by testing ROM and other critical circuitry on the logic board. If all is well, the machine emits a medium-pitched (soft) startup chord that sounds like Bong! If an error is encountered at this point, the machine appears to be dead or emits a short, harsh error cord. This may be followed by a four-tone test cord. The harsh cord is most important because it indicates a serious hardware prob- lem, such as an IC failure on the logic board.
It could also be a stuck programmer switch on a Macintosh 11-family computer.
Next, the system memory is tested, which can take a considerable amount of time in older Macintosh computers with upgraded memory configurations. You can bypass this test by holding down the mouse button when you tum your computer on.
I f the machine fails the memory test, you are greeted with either a medium- pitched error chord, with or without the four-tone test chord, or a medium- and/or high-pitched error chord, with or without the four-tone test chord.
Typical error chord sequence (the Death March)
When an error occurs during P.O.S.T. startup, the typical sequence of chords produced is as follows:
1. Normal, medium-pitched soft chord.
2. One of three error chords: short and harsh, medium, or medium followed
by high. These chords are the most critical.
3. A four-tone test chord (from low to high).
It's important to note that older Macintosh computers won't give you an audi- ble error chord when an error occurs. For instance, if a Mac Plus or Macintosh SE has a RAM failure, it would be unusual to get audible tones. Instead you typically face the infamous Sad Mac, one of four startup icons that we discuss next.

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#3 2017-09-03 15:09:46

Grant2053
Member
Registered: 2017-09-02
Posts: 2

Re: Mac Plus stuck in boot loop pls halp.

I already tried that but will try again, any other ideas as to what could be causing it?

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#4 2017-09-04 17:04:49

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 237

Re: Mac Plus stuck in boot loop pls halp.

If it isnt ram, the rom may be suspect next.

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