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i baught an old APPLE - MAC PLUS computer . i pluged it to 230 v ac .
nothing happened .
so i opened the cover . i saw the fuse inside it had burst . so i
changed a onw 5 amp fuse . and i powdered it ON . i saw spark of fire
in POWDER/SWEEP board . and again the new fuse had burst . i think
some component had burst too. so please give me an idea to repaire
it . OR give me the circuit ,so that i can verify it...

 

[James Sweet]

i baught an old APPLE - MAC PLUS computer . i pluged it to 230 v ac .
nothing happened .
so i opened the cover . i saw the fuse inside it had burst . so i
changed a onw 5 amp fuse . and i powdered it ON . i saw spark of fire
in POWDER/SWEEP board . and again the new fuse had burst . i think
some component had burst too. so please give me an idea to repaire
it . OR give me the circuit ,so that i can verify it...

Isn't 5A a bit large for the fuse? You may have caused further damage by
installing too large a fuse.

These are not difficult machines to work on, just use standard switchmode
power supply troubleshooting procedures to track down defective components.
You likely have a shorted rectifier or chopper transistor on the input side
of the power supply. They're notorious for cooking flyback transformers as
well.

 

[Geoffrey S. Mendelson]

Are you sure it was a 230 volt model? If it had been imported from the U.S.
it was 120 volt only.

Look for Larry Pina's book "Macintosh Upgrade and Repair Secrets".

Where are you, I can lend you the tools and books, but I expect you are
not nearyby.

Geoff.

 

[James Sweet]

Many years since I used to fix these.

But some ideas, BP cap on the video,LM??? chip in the video, GI??? diode
in the video, Mis-jumped 120v, dead EHT ,(the little ones would blow, and
were replaced by a physically larger unit that was also used in the SE
which lasted.These faults were so common that you could buy kits of parts
to fix them for the 128k,512k,plus and SE, of which I am sure I still have
a few.

If you have, or know where I can get one of the flybacks for these that
would be cool, I realized I have a 512 kicking around with a bad one, last
one I bought was over a decade ago and the place is out of business now.

 

[Andrew]

Are you sure it was a 230 volt model? If it had been imported from the U.S.
it was 120 volt only.

Look for Larry Pina's book "Macintosh Upgrade and Repair Secrets".

Where are you, I can lend you the tools and books, but I expect you are
not nearyby.

Geoff.

Many years since I used to fix these.

But some ideas, BP cap on the video,LM??? chip in the video, GI??? diode
in the video, Mis-jumped 120v, dead EHT ,(the little ones would blow,
and were replaced by a physically larger unit that was also used in the
SE which lasted.These faults were so common that you could buy kits of
parts to fix them for the 128k,512k,plus and SE, of which I am sure I
still have a few.

regards Andrew

 

[Geoffrey S. Mendelson]

But some ideas, BP cap on the video,LM??? chip in the video, GI??? diode
in the video, Mis-jumped 120v, dead EHT ,(the little ones would blow,
and were replaced by a physically larger unit that was also used in the
SE which lasted.These faults were so common that you could buy kits of
parts to fix them for the 128k,512k,plus and SE, of which I am sure I
still have a few.

The SE flyback transformer also had a built in drain to remove any
remaining charge on the CRT anode.

Geoff.