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Macintosh LC 475

ironborn65

Well-known member
1661509122073.png
I immediately removed the terrible battery connector.
It needs recapping, it found there is leaking already but strangely it is working, HD spins with not weird noises
MacOS system 8.0.
1661509141992.png
 

pfuentes69

Well-known member
Nice machine. It's the one I use the most. Always on my desk.

I guess that thing connected to the battery holder is a coin cell wrapped in duct tape, right?
 

cheesestraws

Well-known member
Agreed with both @MrFahrenheit and @pfuentes69—the 475 is probably one of the best 68k macs for hobby purposes. It's robust, compact, easy to work on, not rare and pretty fast. I love the LC case(s) and form factor.
 

Jockelill

Well-known member
Love the 475! I have two of them, works great! You can trim it to 33Mhz by modifying a few resistors:

"There are four resistor pads used in this modification. Surface mount (SMT) resistors are placed in these pads to pull "low" or "high". The pads are in sets of two, so you need to have a resistor on one of the first two and one of the second two. The resistors are either 300k Ohms (301) or 4.7k Ohms (472). They are the "0805" surface mount package.


R22 (low) R21(high) R25(low) R24(high)

301 --- 301 --- low, low 20MHz

--- 472 301 --- high, low 25MHz

301 --- --- 472 low, high 33MHz

--- 472 --- 472 high, high 40MHz


If you monitor Pin 6 of U17, you will get the following:


low, low 9.982MHz so 19.964MHz

high, low 12.377MHz so 24.754MHz

low, high 16.425MHz so 32.85MHz

high, high 19.964MHz so 39.928MHz"

40MHz creates other issues, so don't bother :).
 

Phipli

Well-known member
If you overclock, you can try adding a simple heatsink. Use silicone thermal glue to stick something like a 40x40 heatsink on the processor.

The fan in mine was really loud so I took it out, turned it upside down, peeled back the label and put a small amount (like, two tiny drops) of sewing machine silicone oil in the hub... quiet as a mouse now :)



 
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pfuentes69

Well-known member
I did some mods too to my LC475,,,
- Full 68040
- OC to 33MHz
- VRAM upgraded to 1MB
- Quieter fan and fan speed controller
- PDS Ethernet card
- RASCSI

It's so fun to tinker with this machine!
 

ironborn65

Well-known member
thanks you all mates.
I was not aware of the resistor swap to OC, I'll have some fun with it.
(I did it for my 3 LC III though with success)
I'll add a PSD Ethernet card.
The PSU is ok but I was wondering if to replace the capacitors to extend his life
MacOS 8 is not something I like, but I'll keep it
 

ironborn65

Well-known member
I'm asking you here because I do not fine a suitable thread in the forums.
Which liquid do you use to clear motherboards with ultrasonic cleaners?
 

pfuentes69

Well-known member
The PSU is ok but I was wondering if to replace the capacitors to extend his life
I had to recap a couple of these and I'd say it's a must at some point.
Did you open it to see how's inside? (specially on the bottom side of the PCB, where the cap goo trends to go)
 

ironborn65

Well-known member
I read it's not recommended to use IPA with ultrasonic cleaners, "vapours could ignite" if in a non properly ventilated room...
 

ironborn65

Well-known member
I had to recap a couple of these and I'd say it's a must at some point.
Did you open it to see how's inside? (specially on the bottom side of the PCB, where the cap goo trends to go)
yes, they do not look domed and I see not sign of leaking ... but I'll to the "upgrade"
 

joshc

Well-known member
I read it's not recommended to use IPA with ultrasonic cleaners, "vapours could ignite" if in a non properly ventilated room...
I believe this is correct, IPA is not the correct stuff to use in an ultrasonic cleaner. However, I don't know exactly what is as I don't have one.
 

ironborn65

Well-known member
Recapped, I run out of tantalum caps, it's ok tough
Successfully overclocked to 33MHz :)
Are these heat sinks enough?
which VRAM SIMMS should I look for for an upgrade?
I have 832x624 256 colors

1661618692163.png
 

Phipli

Well-known member
Recapped, I run out of tantalum caps, it's ok tough
Successfully overclocked to 33MHz :)
Are these heat sinks enough?
which VRAM SIMMS should I look for for an upgrade?
I have 832x624 256 colors

View attachment 45646
:)

They're cute, but I'd try to find a bigger heatsink! With heatsinks it is all about surface area.

For VRAM I'd start by browsing eBay, but Siliconinsider makes very pretty new ones if you're interested.
 
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